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Aim Conifers are invasive species in many parts of the world, especially in the Southern Hemisphere. There are many introduced conifers in Europe, but their status as alien species is poorly documented. We conducted a comprehensive literature review to ascertain the extent to which alien conifers can be considered invasive. Location Europe. Methods We reviewed the historical record of alien conifer invasion in Europe (i.e. species with a native range outside the continental boundaries of Europe) by screening the DAISIE database and the ISI Web of Science. Results According to DAISIE, there are 54 alien conifer species in Europe. Pseudotsuga menziesii is the species recorded as naturalized in the most countries (12) and the UK is the country with the most naturalized species (18). Thirty-seven of these conifers have been studied, to some extent, in a total of 131 papers (212 records). Nevertheless, only a few papers have investigated aspects related to biological invasions. In fact, the species are not referred to as alien by the authors in more than half of the papers (66%). Twenty-five per cent of the papers have investigated plant traits, 46% are about biotic and abiotic factors influencing tree performance and 29% deal with ecological and economic impacts. Most papers are related to entomology, dealing with natural enemies affecting the alien conifers. Main conclusions Scientists have not yet perceived alien conifers in Europe as problematic species. Moreover, the low introduction effort, long lag-time since plantation and phylogenetic closeness between alien and native conifers are possible reasons for their low expansion in Europe to date. From a management point of view, careful observations of sites with alien conifers is necessary to watch for new invasions. From a scientific perspective, thorough analyses of the extent that introduction, rates of naturalization and biogeographical differences influence invasive spread between the two hemispheres will prove timely. [ABSTRACT FROM AUTHOR]

The atmospheric effects of precipitating electrons are not fully understood, and uncertainties are large for electrons with energies greater than ~30 keV. These electrons are underrepresented in modeling studies today, primarily because valid measurements of their precipitating spectral energy fluxes are lacking. This paper compares simulations from the Whole Atmosphere Community Climate Model (WACCM) that incorporated two different estimates of precipitating electron fluxes for electrons with energies greater than 30 keV. The estimates are both based on data from the Polar Orbiting Environmental Satellite Medium Energy Proton and Electron Detector (MEPED) instruments but differ in several significant ways. Most importantly, only one of the estimates includes both the 0° and 90° telescopes from the MEPED instrument. Comparisons are presented between the WACCM results and satellite observations poleward of 30°S during the austral winter of 2003, a period of significant energetic electron precipitation. Both of the model simulations forced with precipitating electrons with energies >30 keV match the observed descent of reactive odd nitrogen better than a baseline simulation that included auroral electrons, but no higher energy electrons. However, the simulation that included both telescopes shows substantially better agreement with observations, particularly at midlatitudes. The results indicate that including energies >30 keV and the full range of pitch angles to calculate precipitating electron fluxes is necessary for improving simulations of the atmospheric effects of energetic electron precipitation. Plain Language Summary: The study presented here investigates the effects from energetic electron precipitation (EEP) in the southern hemisphere winter of 2003. Electron precipitation is common during periods of enhanced geomagnetic activity and can create reactive nitrogen oxides and hydrogen oxides that can destroy ozone. Most global climate models currently do not include precipitating electrons with energies greater than 30 keV. To test whether this deficiency is important, this investigation compares observations with model simulations that included electrons with energies greater than 30 keV, as observed by the Medium Energy Proton and Electron Detector (MEPED) satellite instruments. In addition, one of the EEP data sets used in the simulations included data from just one of the telescopes on the MEPED instruments, whereas the other included data from both of the telescopes. We found that including both of the telescopes is important for capturing chemistry changes at polar and subpolar latitudes. The model simulation that only included only one of the telescopes showed significant improvement compared to a simulation with only low energy electrons. However, it did not perform as well as the model simulation that included both MEPED telescopes. This work is important because it shows that including energies >30 keV and the full range of precipitating electron pitch angles is necessary to show the impact electrons have on the atmosphere and provides an EEP data set for use in future model simulations. Key Points: Effects of energetic electron precipitation in southern hemisphere 2003 simulated with Whole Atmosphere Community Climate ModelSimulations of middle atmosphere chemistry improve significantly by including >30‐keV precipitating electronsIncluding the full range of pitch angles is necessary to capture precipitating electron impacts at subpolar latitudes [ABSTRACT FROM AUTHOR]

Comprehensive pattern of ionospheric troughs' location in winter for all local times, longitudes, high (HSA), and low (LSA) solar activity, in both hemispheres, is at first investigated. Statistical analysis based on a large dataset of Interkosmos‐19, CHAMP, and Kosmos‐900 satellites was performed for quiet geomagnetic conditions Kp = 1–3. Three troughs were considered: high‐latitude trough (HLT) located inside the auroral oval, main ionospheric trough (MIT) located equatorward from the auroral oval, that is, at subauroral latitudes, and mid‐latitude ring ionospheric trough (RIT). The main purpose was to study the formation of the troughs' diurnal pattern in different conditions. The main problem was to distinguish MIT from RIT and MIT from HLT. For this purpose, early morning hours (04–06 LT), late morning hours (07–10 LT), day, evening, and night conditions were examined. In the early morning sector, RIT was separated from MIT and eliminated from the dataset. In the late morning sector, MIT and HLT were first clearly divided, although only for HSA. During the day, in the Northern Hemisphere under all conditions, HLT is mainly observed, in the Southern Hemisphere at poorly lit longitudes only the daytime MIT, and at well‐lit longitudes only the HLT is observed. The division of MIT and HLT was carried out according to the (statistical) position of the equatorial boundary of the auroral oval precipitation. At night, longitudinal variations in the MIT position determine the asymmetry of the hemispheres. Thus, the occurrence and position of MIT and HLT depend on the hemisphere, longitude, and solar activity. Plain Language Summary: Dynamics of the ionization troughs determines the variation in a structure of the winter and equinoctial subauroral and auroral ionosphere. Unfortunately, many aspects of this dynamics are still poorly known, which does not allow creating an adequate model of the high‐latitude ionosphere. Such a model is necessary to describe the conditions for propagation of short radio waves. In the international reference model of the ionosphere IRI, the trough as a structure is absent; therefore, IRI poorly describes high latitudes. In this paper, for the first time, a comprehensive pattern of diurnal variations in the different troughs position in winter high‐latitude ionosphere is constructed. They are found to be highly dependent on hemisphere, longitude, and solar activity. The results of this work will be used to build an adequate model of the high‐latitude ionosphere, which is being now created in the Institute of Terrestrial Magnetism, Ionosphere, and Radio Wave Propagation of the Russian Academy of Sciences (IZMIRAN). Key Points: Comprehensive pattern of diurnal variations in winter ionospheric troughs' position in Northern and Southern hemispheres was obtainedStatistical analysis based on a large dataset of Interkosmos‐19, CHAMP, and Kosmos‐900 satellites was performedDiurnal variations in trough position depend strongly on solar activity, hemisphere, and longitude [ABSTRACT FROM AUTHOR]

This paper describes properties and behavior of magnetic reconnection and flux transfer events (FTEs) on the dayside magnetopause using the global hybrid‐Vlasov code Vlasiator. We investigate two simulation runs with and without a sunward (positive) Bx component of the interplanetary magnetic field (IMF) when the IMF is southward. The runs are two‐dimensional in real space in the noon‐midnight meridional (polar) plane and three‐dimensional in velocity space. Solar wind input parameters are identical in the two simulations with the exception that the IMF is purely southward in one but tilted 45° toward the Sun in the other. In the purely southward case (i.e., without Bx) the magnitude of the magnetosheath magnetic field component tangential to the magnetopause is larger than in the run with a sunward tilt. This is because the shock normal is perpendicular to the IMF at the equatorial plane, whereas in the other run the shock configuration is oblique and a smaller fraction of the total IMF strength is compressed at the shock crossing. Hence, the measured average and maximum reconnection rate are larger in the purely southward run. The run with tilted IMF also exhibits a north‐south asymmetry in the tangential magnetic field caused by the different angle between the IMF and the bow shock normal north and south of the equator. Greater north‐south asymmetries are seen in the FTE occurrence rate, size, and velocity as well; FTEs moving toward the Southern Hemisphere are larger in size and observed less frequently than FTEs in the Northern Hemisphere. Key Points: Sunward IMF tilt results in a smaller tangential field at the magnetopause, slowing dayside reconnectionSmaller tangential field results from a decrease in the IMF component that is shocked up at the bow shockA positive IMF Bx component introduces north‐south asymmetries, where fewer (but larger) FTEs appear on the Southern Hemisphere [ABSTRACT FROM AUTHOR]

We present a statistical investigation of the effects of interplanetary magnetic field (IMF) on hemispheric asymmetry in auroral currents. Nearly 6 years of magnetic field measurements from Swarm A and C satellites are analyzed. Bootstrap resampling is used to remove the difference in the number of samples and IMF conditions between the local seasons and the hemispheres. Currents are stronger in Northern Hemisphere (NH) than Southern Hemisphere (SH) for IMF By+ in NH (By− in SH) in most local seasons under both signs of IMF Bz. For By− in NH (By+ in SH), the hemispheric difference in currents is small except in local winter when currents in NH are stronger than in SH. During By+ and Bz+ in NH (By− and Bz+ in SH), the largest hemispheric asymmetry occurs in local winter and autumn, when the NH/SH ratio of field aligned current (FAC) is 1.18 ± 0.09 in winter and 1.17 ± 0.09 in autumn. During By+ and Bz− in NH (By− and Bz− in SH), the largest asymmetry is observed in local autumn with NH/SH ratio of 1.16 ± 0.07 for FAC. We also find an explicit By effect on auroral currents in a given hemisphere: on average By+ in NH and By− in SH causes larger currents than vice versa. The explicit By effect on divergence‐free current during IMF Bz+ is in very good agreement with the By effect on the cross polar cap potential from the Super Dual Auroral Radar Network dynamic model except at SH equinox and NH summer. Key Points: Hemispheric asymmetry in auroral currents is larger for interplanetary magnetic field (IMF) By+ in the Northern Hemisphere (NH) (By− in the Southern Hemisphere [SH]) than vice versa during both signs of IMF BzStrongest asymmetry occurs in local winter and autumn for By+ in the NH (By− in the SH) and IMF Bz+ with NH/SH field aligned current ratio of about 1.18IMF By+ in the NH and By− in the SH causes larger auroral currents than vice versa. Effect is stronger for IMF Bz+ than for IMF Bz− [ABSTRACT FROM AUTHOR]

We present a statistical investigation of the seasonal effect on hemispheric asymmetry in the auroral currents during low (Kp < 2) and high (Kp ≥ 2) geomagnetic activity. Five years of magnetic data from the Swarm satellites has been analyzed by applying the spherical elementary current system (SECS) method. Bootstrap resampling has been used to remove the seasonal differences between the hemispheres in the data set. In general, the currents are larger in the Northern Hemisphere (NH) than in the Southern Hemisphere (SH). Asymmetry is larger during low than high Kp and during local winter and local autumn than local summer and local spring. For all Kp conditions together, the NH/SH ratio for FACs in winter, autumn, spring, and summer are 1.17 ± 0.05, 1.14 ± 0.05, 1.07 ± 0.04, and 1.02 ± 0.04, respectively. The largest asymmetry is observed during low Kp in local winter, when the excess in the NH currents is 21 ± 5% in FAC, 14 ± 3% in curl‐free (CF) and 10 ± 3% in divergence‐free (DF) current. We also find that evening sector (13–24 MLT) contributes more to the high NH/SH ratio than the morning (01–12 MLT) sector. The physical mechanisms producing the hemispheric asymmetry are not presently understood. We calculated the solar‐induced ionospheric conductances during low Kp conditions from the IRI model. The model conductance NH/SH ratios are above 1 in autumn and spring, similar to the currents, but below 1 for winter, which is in contradiction with the currents. Therefore, we do not consider solar‐induced conductances as the main explanation for hemispheric asymmetry. Key Points: Hemispheric asymmetry in auroral currents is largest during local winter and local autumn and smallest during local summer and local springLow Kp conditions show the strongest asymmetry in local winter, with maximum NH/SH ratio of 1.21 for FAC and 1.10 for DF currentCurrents in the evening sector contribute more to the high NH/SH ratio than the morning sector [ABSTRACT FROM AUTHOR]

Seismic signals can be extracted from ambient noise wavefields by the correlation technique. Recently, a prominent P-type phase was observed from teleseismic noise correlations in the secondary microseism period band. The phase is named Pdmc in this paper, corresponding to its origin from the interference between the direct P waves transmitting through the deep mantle and the core (P and PKPab waves). We extract the phase by correlating noise records from two seismic networks in the Northern Hemisphere and locate the microseism sources that are efficient for the Pdmc construction in the South Pacific. We investigate the spatiotemporal links of the Pdmc signal with global oceanic waves and microseism sources. Interestingly, the correlation with wave height is higher in several regions surrounding the effective source region, rather than in the effective source region. The Pdmc amplitude is highly correlated with the power of the effective microseism sources. Also, it is apparently correlated with ineffective sources in the Southern Hemisphere and anticorrelated with sources in the Northern Hemisphere. We ascribe the correlation with the ineffective southern sources to the spatiotemporal interconnections of the southern sources. The anticorrelation with northern sources can be explained by the reverse seasonal patterns between the southern and northern sources and by that the northern sources impede the signal construction. The signal construction from noise correlations relies on the competition between the effective and ineffective sources, not just on the power of the effective sources. This principle should be valid in a general sense for noise-derived signals. [ABSTRACT FROM AUTHOR]

Enigmatic calcareous conical fossils have been known from marine Paleocene-Eocene sequences of New Zealand since the early 1870s. More recently, similar fossils have been recorded from both Late Cretaceous marine sequences of Western Australia, New Caledonia and Antarctica, and possibly from the Eocene of South America. The present paper extends the record to the late Cretaceous of New Caledonia. These remains are unlike any living taxa, and have been variously interpreted as molluscs (rudistid bivalves), cirripedes (stalked barnacles), annelids and inorganic structures. Assignation to the Cirripedia has been refuted by Buckeridge (1983, 1993), who proposed that the material would be better placed within the Cnidaria. We investigate this hypothesis in light of the New Caledonian material and by comparison with living gorgonians and pennatulaceans, and demonstrate that Waiparaconus is best placed within the Pennatulacea. Waiparaconus zelandicus varies in form somewhat, with 3 morphotypes defined and reinforced by geography. Comment is provided on the imperative to fit organic remains into known groups, with reflection on what may happen if taxa are left in insertae sedis. [ABSTRACT FROM AUTHOR]

Bioclimatology based vegetation classification models play an important role in the response of terrestrial ecosystems to global climate change. In this paper, three periods (1911-1940, 1941-1970 and 1971-2000) of Potential Natural Vegetation ( PNV) maps were created based on the CSCS (Comprehensive Sequential Classification System) model and the CRU_ TS 2.1 datasets. A model of the mean center was used to calculate the shift distance and direction for each broad vegetation category during the three periods. Results indicate that: (i) the area of tundra and alpine steppe and desert decreased by 5.1 and 5.5%, while the area of forest and grassland increased by 2.3 and 3.8% from 1911 to 2000 at global scale, respectively. However, there was a significant difference in the magnitude of area change in northern and southern hemispheres. And (ii) the tundra and alpine steppe, semi-desert, savanna, temperate forest and subtropical forest shifted towards the poles; the frigid desert and temperate humid grassland shifted towards the equator, while the warm desert shifted towards southwest, the tropical forest shifted towards southwest in the northern hemisphere and southeast in the southern hemisphere, and the steppe shifted towards northeast in the northern hemisphere and northwest in the southern hemisphere. The shift distance of the warm desert in the southern hemisphere was the largest among the 10 broad vegetation categories. [ABSTRACT FROM AUTHOR]

Please cite this paper as: Van Kerkhove et al. (2011) Epidemiologic and virologic assessment of the 2009 influenza A (H1N1) pandemic on selected temperate countries in the Southern Hemisphere: Argentina, Australia, Chile, New Zealand and South Africa. Influenza and Other Respiratory Viruses 5(6), e487-e498. Introduction and Setting Our analysis compares the most comprehensive epidemiologic and virologic surveillance data compiled to date for laboratory-confirmed H1N1pdm patients between 1 April 2009 - 31 January 2010 from five temperate countries in the Southern Hemisphere-Argentina, Australia, Chile, New Zealand, and South Africa. Objective We evaluate transmission dynamics, indicators of severity, and describe the co-circulation of H1N1pdm with seasonal influenza viruses. Results In the five countries, H1N1pdm became the predominant influenza strain within weeks of initial detection. South Africa was unique, first experiencing a seasonal H3N2 wave, followed by a distinct H1N1pdm wave. Compared with the 2007 and 2008 influenza seasons, the peak of influenza-like illness (ILI) activity in four of the five countries was 3-6 times higher with peak ILI consultation rates ranging from 35/1,000 consultations/week in Australia to 275/100,000 population/week in New Zealand. Transmission was similar in all countries with the reproductive rate ranging from 1.2-1.6. The median age of patients in all countries increased with increasing severity of disease, 4-14% of all hospitalized cases required critical care, and 26-68% of fatal patients were reported to have ≥1 chronic medical condition. Compared with seasonal influenza, there was a notable downward shift in age among severe cases with the highest population-based hospitalization rates among children <5 years old. National population-based mortality rates ranged from 0.8-1.5/100,000. Conclusions The difficulty experienced in tracking the progress of the pandemic globally, estimating its severity early on, and comparing information across countries argues for improved routine surveillance and standardization of investigative approaches and data reporting methods. [ABSTRACT FROM AUTHOR]

Please cite this paper as: McVernon et al. (2010) Absence of cross-reactive antibodies to influenza A (H1N1) 2009 before and after vaccination with 2009 Southern Hemisphere seasonal trivalent influenza vaccine in children aged 6 months-9 years: a prospective study. Influenza and Other Respiratory Viruses 5(1), 7-11. Early outbreaks of the pandemic influenza A (H1N1) 2009 virus predominantly involved young children, who fuelled transmission through spread in homes and schools. Seroprevalence studies conducted on stored serum collections indicated low levels of antibody to the novel strain in this age group, leading many to recommend priority immunisation of paediatric populations. In a prospective study, we sought evidence of cross-reactive antibodies to the pandemic virus in children who were naïve to seasonal influenza vaccines, at baseline and following two doses of the 2009 Southern Hemisphere trivalent influenza vaccine (TIV). Twenty children were recruited, with a median age of 4 years (interquartile range 3-5 years); all received two age appropriate doses of TIV. Paired sera were collected pre- and post-vaccination for the assessment of vaccine immunogenicity, using haemagglutination inhibition and microneutralisation assays against vaccine-related viruses and influenza A (H1N1) 2009. Robust responses to H3N2 were observed regardless of age or pre-vaccination titre, with 100% seroconversion. Fewer seroconverted to the seasonal H1N1 component. Only two children were weakly seropositive (HI titre 40) to the pandemic H1N1 strain at study entry, and none showed evidence of seroconversion by HI assay following TIV administration. Administration of 2009 Southern Hemisphere TIV did little to elicit cross-reactive antibodies to the pandemic H1N1 virus in children, in keeping with assay results on stored sera from studies of previous seasonal vaccines. Our findings support the recommendations for influenza A (H1N1) 2009 vaccination of children in preparation for the 2010 winter season. [ABSTRACT FROM AUTHOR]

An inverse method is used to investigate the global carbon cycle from the early Holocene (8 kyr BP) to the end of the pre-industrial period (0 kyr BP) in an improved version of the "green" McGill Paleoclimate Model (MPM). In this paper, we now take into account the vegetation-precipitation feedback and evaluate the terrestrial carbon cycle for the pre-industrial equilibrium. From our coupled transient simulation under orbital forcing, reconstructed (Taylor Dome) atmospheric CO2 forcing and a prescribed retreating Laurentide Ice Sheet (LIS), we find a decrease of 70 PgC in total carbon storage in the Sahara region (15°N to 30°N and 15°W to 50°E), which is caused by the desertification simulated in the green MPM. The above decrease is partially compensated by an increase of 40 PgC in total carbon storage in the Southern Hemisphere from 8 to 2 kyr BP. From an analysis of the total carbon stored under the ice sheet, we can infer that this carbon has negligible impact on atmospheric CO2 after 8 kyr BP. From our model results, we further conclude that the retreating LIS, together with the vegetation-albedo feedback, cause the global terrestrial carbon to increase from 8 to 6 kyr BP. The application of the inverse method suggests that the first 10 ppmv increase in atmospheric CO2 from 8 to 6 kyr BP comes from the ocean. Finally, in the model simulations, the total terrestrial carbon release from 6 to 0 kyr BP is about 68 to 95 PgC, which would produce about a 5 to 7 ppmv atmospheric CO2 increase, based on the calculation of Joos et al. (2004). Owing to our model limitation (there is no ocean carbon cycle), we cannot conclude whether the overall oceanic CO2 release from 8 to 0 kyr BP is due to outgassing related to SST changes or to calcite compensation as proposed by Broecker et al. (2001). [ABSTRACT FROM AUTHOR]

Geographic variation in tooth row counts among sand tiger sharks Carcharias taurus (Chondrichthyes), from the SW Atlantic, NW Atlantic and the East China Sea is analyzed in this paper. We found significant differences between sand tigers from the SW Atlantic (Southern Hemisphere population) and each of the other two (Northern Hemisphere) regions in the number of upper lateral tooth rows, and between individuals from the SW Atlantic and the East China Sea in the total number of upper tooth rows. Sand tiger sharks from the two Northern Hemisphere populations did not differ in any of the studied variables. Our results agree with comparisons of vertebral counts between sand tiger sharks from Southern and Northern Hemispheres. Both lines of evidence suggest that Southern and Northern Hemisphere populations of C. taurus were isolated to a larger extent than populations of the Northern Hemisphere. The fossil record of the genus Carcharias begins in the Early Cretaceous and C. taurus is certainly known since the Late Miocene. During the Miocene, the Tethys Sea separating northern and southern land masses was still present and it provided a continuous temperate shallow sea that could allow dispersal of sand tiger sharks along Northern Hemisphere seas. Independent observations on the distribution and evolutionary history of the genera Myripristis, Neoniphon, Sargocentron and Aphanius, and genetic studies on the temperate shark genus Mustelus that indicate a close relationship between the Indo-Pacific M. manazo and the Mediterranean M. asterias suggest that this hypothesis is plausible and deserves to be tested. [ABSTRACT FROM AUTHOR]

This paper reports for the first time the presence of helminths in the gut and coelomic cavity of Southern Hemisphere lampreys. Moreover, the records of Pelichnobothriurn and Hepatoivion in the lamprey Geotria ausiralis are also the first records of these helminth genera in any species of lamprey. A consideration of the literature on the parasites and feeding mechanisms of lampreys provides good evidence that those parasites which are found in adult lampreys but typically utilize arthropod intermediate hosts are obtained via the food ingested by the lamprey's host fish. [ABSTRACT FROM AUTHOR]

Planetary wave (PW) associated dynamical variability in the equatorial and extratropical middle atmosphere during the September 2019 Southern hemisphere minor sudden stratospheric warming (SSW) is investigated utilizing meteor radar wind observations from São João do Cariri (7.4°S, 36.5°W) and Cachoeira Paulista (22.7°S, 45°W) and reanalysis data. Signature of the mesospheric warming in conjunction with the stratospheric cooling is found at low latitudes. The strong westerly wind at low latitudes decelerates notably near 65 km at the onset of the warming episode, although no wind reversal is observed. The wind spectra reveal a prevalent quasi‐16‐day wave (Q16DW) prior to the SSW and existence of a quasi‐6‐day wave (Q6DW) after the warming event. Possible existence of barotropic/baroclinic instability in the low and mid latitude middle atmosphere may be responsible for exciting the Q6DW. Both traveling and stationary waves exhibit notable activities during the warming event. Although involvement of both zonal wavenumbers 1 and 2 PWs are found in the event, PW with zonal wavenumber 1 seems to play a vital role in preconditioning the same. Furthermore, significant latitudinal mixing of airmass between the tropics and high latitudes is evident in the potential vorticity map. The Eliassen‐Palm flux diagnosis shows the propagation of the Q6DW and Q16DW from mid to low latitudes during the warming event. Plain Language Summary: A minor but impactful sudden stratospheric warming event occurred in the Southern hemisphere during September 2019. This event is characterized by a marked deceleration of the zonal mean westerlies at polar stratosphere although no wind reversal is observed. Simultaneously, stratospheric temperature at high latitudes increases sharply by more than 25 K within a few days. During the same warming event, stratospheric cooling and mesospheric warming is found at the present low latitude stations. The wind spectra reveal a long period wave of about 16 days prior to the warming event in the stratosphere followed by a relatively shorter period wave (∼6 days) in the mesosphere. The 6‐day wave component is possibly excited due to the instability in the middle atmosphere at low and middle latitudes during the warming episodes. Both traveling and stationary large‐scale waves are supposed to play a vital role in preconditioning the warming event. There is also significant meridional air mass mixing during the warming days owing to possible planetary wave (PW) driven weakening of the zonal mean westerlies. The PW fluxes for both the aforementioned components are observed to propagate from high and mid to low latitudes during the warming event. Key Points: Both traveling and stationary planetary waves with zonal wavenumber 1 seem to play a salient role in pre‐conditioning the warming eventExisting instability is believed to support the growth of the quasi‐6‐day wave (Q6DW) in post warming intervalThe Q6DW and Q16DW are found to propagate from high and mid latitudes to low latitudes during the warming [ABSTRACT FROM AUTHOR]

Phylogeography is a young, vigorous and integrative field of study that uses genetic data to understand the history of populations. This field has recently expanded into many areas of biology and also into several historical disciplines of Earth sciences. In this review, I present a numerical synthesis of the phylogeography literature based on an examination of over 3000 articles published during the first 20 years of the field (i.e. from 1987 to 2006). Information from several topics needed to evaluate the progress, tendencies and deficiencies of the field is summarized for 10 major groups of organisms and at a global scale. The topics include the geography of phylogeographic surveys, comparative nature of studies, temporal scales and major environments investigated, and genetic markers used. I also identify disparities in research productivity between the developing and the developed world, and propose ways to reduce some of the challenges faced by phylogeographers from less affluent countries. Phylogeography has experienced explosive growth in recent years fuelled by developments in DNA technology, theory and statistical analysis. I argue that the intellectual maturation of the field will eventually depend not only on these recent developments, but also on syntheses of comparative information across different regions of the globe. For this to become a reality, many empirical phylogeographic surveys in regions of the Southern Hemisphere (and in developing countries of the Northern Hemisphere) are needed. I expect the information and views presented here will assist in promoting international collaborative work in phylogeography and in guiding research efforts at both regional and global levels. [ABSTRACT FROM AUTHOR]

Subtropical western boundary currents (WBCs) are often associated with hotspots of global warming, with certain WBC extension regions warming 3–4 times faster than the global mean. In the Southern Hemisphere, strong warming over the WBC extensions has been observed over the last few decades, with enhanced warming projected into the future. This amplified warming has primarily been linked to poleward intensification of the mid‐latitude westerly winds in the Southern Hemisphere. Changes in these winds are often thought of as being zonally symmetric; however, recent studies show that they contain strong zonal asymmetries in certain ocean basins. The importance of these zonal asymmetries for the Southern Ocean has not yet been investigated. In this study, we use an ocean‐sea‐ice model forced by prescribed atmospheric fields to quantify the contribution of projected zonally asymmetric atmospheric changes in generating future ocean warming and circulation changes in the subtropical WBC regions. We find that the zonally asymmetric component of atmospheric forcing, characterized by a pattern that is consistent across CMIP6 models, can explain more than 30% (>2°C) of the sea surface temperature (SST) warming found in the Tasman Sea and southern Australia region and a sizable fraction of warming in the Agulhas Current region. These changes in SST in both the Indian and Pacific basins are found to be primarily driven by increases in the advection of warm tropical water to the mid‐latitudes due to changes in the large‐scale subtropical ocean gyres, which in turn can largely be explained by changes in the mid‐latitude surface wind stress patterns. Plain Language Summary: Strong ocean currents are found on the western side of the ocean basins, which flow from the tropics toward the poles in both hemispheres. These western boundary currents (WBCs) have shown strong changes in the last few decades, which have resulted in amplified ocean warming in the poleward extensions of these boundary currents; these changes are projected to amplify further in the future. In the Southern Hemisphere, recent changes in the WBCs are thought to have been primarily driven by changes in the surface westerly winds that encircle Antarctica. These westerly winds are generally considered to be changing uniformly in all three ocean basins; however, recent studies have shown that there are strong regional variations both historically and in future projections. Here, we find that regional asymmetries in wind projections can account for about 30% of the projected warming in the Tasman Sea and the southern Australia region and a sizable fraction of warming in the Agulhas Current region. This amplified warming in the Indian and the Pacific Ocean basins is primarily driven by changes in ocean circulation. Key Points: Strong warming in the subtropical western boundary current extension regions is projected in the futureZonally asymmetric atmospheric changes can explain >30% of future warming in the south Australia region, driven by ocean circulation changesUnderstanding historical and future ocean changes require the use of regionally varying and not simply zonally symmetric wind forcing [ABSTRACT FROM AUTHOR]

Monthly lower stratosphere temperature anomalies in a layer centred about 70 hPa, from the MSU data set are analysed for the period 1979–1997. T-mode approach principal component analysis (PCA) is used in order to obtain the leading spatial anomaly patterns and their sequences of occurrence throughout the period under study. Five principal components (PCs) are significantly different from the spatial distribution of noisy data. The patterns given by the PC scores represent ten typical spatial anomaly patterns: five correspond to the direct mode, that is to say anomaly fields with the same sign as the PC score patterns, and five have the opposite sign. The first three PCs represent simple spatial temperature anomaly distributions, with zonal wave 0 to wave 2 wave structures. The following significant PCs, orders four and five, display a more complex spatial behaviour, with wave 3 wave structures. The first two PC's frequency distribution in time, given by the PC loadings time series, do not show noticeable changes throughout the period analysed. The remaining three PCs show changes in their frequency of occurrence that might be associated with the negative trends in the lower stratosphere temperature, as well as to the other different features observed in the real temperature anomaly time series for the grid points in the Southern Hemisphere. The latter are studied with the PCA in the S-mode approach in the companion paper (Compagnucci et al., 2001. International Journal of Climatology 21: 419–437). Copyright © 2001 Royal Meteorological Society [ABSTRACT FROM AUTHOR]

The local, regional, and global morphology of the ionospheric response of the March 2015 geomagnetic storm has been investigated by different studies. However, the spatio-temporal evolution of the drivers of the global ionospheric response to this storm has not yet been investigated, using multidata sources, in detail. Therefore, in this study drivers of the ionospheric response to the March 17-18, 2015 storm are investigated. Spatial and temporal variations of deposition of solar wind energy are found to be the cause for hemispherical asymmetry of the response of the ionosphere; the American-Canada-Greenland sector, Northern Hemisphere high-latitude ionosphere responded about 12 h earlier than the Southern Hemisphere (SH) high-latitude ionosphere, resulted from hemispherical energy imbalance as detected from Hemispherical Power. The positive ionospheric storm observed in the high-latitude regions is found to be due to solar wind energy deposition at high latitudes. Interestingly, it is found that the Northern hemisphere ionospheric positive storm shifted to the mid-latitude and disappeared there whereas the SH ionospheric positive storm shifted to mid-latitude and then farther to the low-latitude with time; this spatio-temporal evaluation of positive ionospheric storm is found to be due to the spatiotemporal enhancement of the O/N2 ratio. Also, the mid (Europe-African)and low (Brazilian) latitudes positive ionospheric storms prevailed due to prompt penetration electric fields, disturbance dynamo electric fields, and enhancement of the O/N2 ratio. Moreover, the negative ionospheric storm, observed at the NH high and mid-latitudes in the American and Asian sectors, is linked to the reduction of the O/N2 ratio. [ABSTRACT FROM AUTHOR]

An unusual sudden stratospheric warming (SSW) event occurred in the Southern Hemisphere in September 2019. Ground-based and satellite observations show the presence of transient eastward- and westward-propagating quasi-10 day planetary waves (Q10DWs) during the SSW. The planetary wave activity maximizes in the mesosphere and lower thermosphere region approximately 10 days after the SSW onset. Analysis indicates that the westward-propagating Q10DW with zonal wave number s = 1 is mainly symmetric about the equator, which is contrary to theory which predicts the presence of an antisymmetric normal mode for such planetary wave. Observations from microwave limb sounder and sounding of the atmosphere using broadband emission radiometry are combined with meteor radar wind measurements from Antarctica, providing a comprehensive view of Q10DW wave activity in the Southern Hemisphere during this SSW. Analysis suggests that the Q10DWs of various wavenumbers are potentially excited from nonlinear wave-wave interactions that also involve stationary planetary waves with s = 1 and s = 2. The Q10DWs are also found to couple the ionosphere with the neutral atmosphere. The timing of the quasi-10-day oscillations (Q10DOs) in the ionosphere are contemporaneous with the Q10DWs in the neutral atmosphere during a period of relatively low solar and geomagnetic activity, suggesting that the Q10DWs play a key role in driving the ionospheric Q10DOs during the Southern SSW event. This study provides observational evidence for coupling between the neutral atmosphere and ionosphere through the upward propagation of global scale planetary waves. [ABSTRACT FROM AUTHOR]

A sudden stratospheric warming (SSW) is an extremely rare event in the Southern Hemisphere (SH), but occurred in early September 2019. From the Antarctic meteor radar (MR) stations, Davis (68.6°S, 77.9°E) and King Sejong Station (62.2°S, 58.8°W), quasi 10-day oscillations were clearly observed in the zonal mesospheric winds before the central date (DOY 253) of the SSW. From the northern low-latitude Tirupati (13.6°N, 79.4°E) MR, a strong wave activity with a period of ~6 days was detected in the zonal winds right after the central date. This oscillation is also seen in the geopotential height measurements from the Microwave Limb Sounder (MLS) on board the Aura satellite near the Tirupati region. To elucidate the possible source of the quasi 6-day wave (Q6DW), we use a specified dynamics version of the Whole Atmosphere Community Climate Model (SD-WACCM) constrained by the reanalysis data from the surface to 50 km. The simulation results show that the amplitude of the westward and equatorward propagating Q6DW was enhanced after the SSW central date in the MLT region, and the Q6DW can be attributed to the baroclinic/barotropic instability in the SH high-latitude mesosphere where the divergence of Eliassen-Palm flux occurred. Thus, we suggest that the Q6DW activity observed by the Tirupati MR and MLS originated from the SH high-latitude mesospheric region. Both the observation and the simulation results clearly demonstrate that the 2019 SH SSW affected not only the high-latitude MLT region but also the low-latitude MLT region. [ABSTRACT FROM AUTHOR]

Ionospheric sporadic E layers are irregularities with enhanced plasma density which occur in the ionosphere E region. In the present work, we have focused on an interesting wavenumber 4(WN4) pattern of sporadic E layer based on the Constellation Observing System for Meteorology, Ionosphere and Climate radio occultation S4 indices observation. It is found that amplitude of WN4 pattern has a significant seasonal dependency with the maximum appearing in summer/autumn and minimum in winter. The seasonal variation of the WN4 pattern is basically consistent with the eastward propagating diurnal tide with zonal wavenumber 3 (DE3) tide features. Inconsistencies, mainly an anomalous weak amplitude during the summer in southern hemisphere and propagation direction (speed), are also found. By removing the zonal ion drift factor effect, WN4 pattern of sporadic E layers exhibits a closer relation with the DE3 tide with larger amplitude in the northern hemisphere and ~90° shift in longitude on average during autumn in the southern hemisphere. In general, it is reasonable to conclude that DE3 tide greatly contributes to this WN4 pattern of sporadic E layers. [ABSTRACT FROM AUTHOR]

We report new findings of total electron content (TEC) perturbations in the southern hemisphere at conjugate locations to the northern eclipse on August 21, 2017. We identified a persistent conjugate TEC depletion by 10%--15% during the eclipse time, elongating along magnetic latitudes with at least ~5° latitudinal width. As the Moon's shadow swept southward, this conjugate depletion moved northward and became most pronounced at lower magnetic latitudes (>-20°N). This depletion was coincident with a weakening of the southern crest of the equatorial ionization anomaly (EIA), while the northern EIA crest stayed almost undisturbed or was slightly enhanced. We suggest these conjugate perturbations were associated with dramatic eclipse initiated plasma pressure reductions in the flux tubes, with a large portion of shorter tubes located at low latitudes underneath the Moon's shadow. These short L-shell tubes intersect with the F region ionosphere at low and equatorial latitudes. The plasma pressure gradient was markedly skewed northward in the flux tubes at low and equatorial latitudes, as was the neutral pressure. These effects caused a general northward motion tendency for plasma within the flux tubes, and inhibited normal southward diffusion of equatorial fountain plasma into the southern EIA region. We also identified posteclipse ionospheric disturbances likely associated with the global propagation of eclipse-induced traveling atmospheric disturbances in alignment with the Moon's shadow moving direction. [ABSTRACT FROM AUTHOR]

Energy and momentum can be transferred from the magnetosphere to the ionosphere through field-aligned currents (FACs), which show seasonal variations due to seasonal variation of the ionospheric conductance. Using Magnetospheric Multiscale Mission observations, we investigate the characteristics of kinetic-scale (close to local ion inertial length) FACs in the plasma sheet boundary layer (PSBL), such as occurrence rate, magnitude, and carriers. The results show that: (1) the occurrence rates of FACs exhibit a trident distribution; they are also larger in the northern hemisphere than in the southern hemisphere, especially for the earthward FACs. (2) Distribution patterns vs. plasma β are different for the beam-type and the flow-type FACs. Flow-type FACs are observed closer to the central plasma sheet (higher β), and their occurrence rate decreases linearly toward the tail lobe (lower β), while the beamtype FACs are mainly and equally distributed within 0.1 < β < 1.0. (3) The magnitude of FACs shows little dependence on β, and generally increases closer to the Earth. (4) Occurrence rate and magnitude of FACs both increase during active periods, consistent with ionospheric observations. (5) The main carriers for FACs in the PSBL are thermal electrons, while cold electrons also contribute occasionally, especially during active periods. Hemispheric asymmetry of occurrence rate and dependence on geomagnetic activity of the kinetic-scale FACs in the PSBL are consistent with FACs at ionospheric altitudes. This fact demonstrates that kinetic-scale FACs are significant in magnetosphere-ionosphere coupling and illustrates the possible ionospheric feedback effects to the magnetosphere in the nightside. [ABSTRACT FROM AUTHOR]

We present an event of simultaneous observations of the northern and southern middle‐altitude polar cusps by the Polar spacecraft and Cluster fleet that occurred on 23 September 2004. We examine the possible asymmetries in the fields and plasma parameters, although the proximity of the equinox should limit these asymmetries. Ion sensors reveal two dispersions in both cusps, and data analysis leads to the conclusion that those dispersions are due to pulsed reconnection at a single X‐line, which runs along the subsolar magnetopause. While the electromagnetic and particle energy fluxes injected in both cusp are globally very similar, we report significant differences in ion dispersions, width of the low‐latitude boundary layer, and peak convection velocities. We ascribe these differences to the dipole tilt that introduces an asymmetry in the magnetosheath flow at the exterior cusps. Key Points: Data from Cluster and Polar show a symmetry in ion injections in the magnetospheric cuspsSignatures corresponding to a single reconnection line running along the subsolar magnetopause and pulsed reconnection are highlightedDifferences in convection velocities are found and ascribed to the effect of the tilt angle [ABSTRACT FROM AUTHOR]

The Mars Science Laboratory rover (Curiosity) has monitored the line‐of‐sight extinction within Gale Crater since mission sol 100 (16 November 2012, MY 31 Ls 208°) with Navcam and since mission sol 1,187 (8 December 2015, MY 33 Ls 79°) with the color imager, Mastcam. This work reports 1,375 sols (>2 MYs) of line‐of‐sight extinction monitoring within Gale Crater with Mastcam and updates the Navcam line‐of‐sight extinction record to sol 2,556 (15 October 2019, MY 35 Ls 93°). A cyclical pattern with one or more peaks in the dusty season (Ls∼180–360°) and a trough in the less‐dusty season (Ls∼0–180°) was observed with both imagers and the results from Mastcam red and Navcam agree well. Green and blue filter Mastcam data show generally lower extinction than in the red filter data. Extinction as a function of azimuth and elevation angle were investigated and the extinction as a function of azimuth was generally found to be smooth and thus the dust well‐mixed horizontally. The extinction as a function of elevation shows increased dust loading at lower elevations during dusty seasons, indicative of dust lifting from the base of the crater. Plain Language Summary: The Curiosity rover has been taking images of the northern rim of Gale Crater, Mars, since 100 Mars days after landing (16 November 2012) with its single‐color Navigational camera and since 1,187 Mars days after landing (8 December 2015) with the Mastcam full‐color camera. Using these images, we can infer how much dust there is between the rover and the edge of the crater. Over the course of the mission, the results from both cameras agree well, showing an increase in dust during the Southern Hemisphere summer and a drop in dust during the Southern Hemisphere winter. Looking at the mixing of dust inside Gale Crater, it appears that the dust is well‐mixed horizontally, but there is evidence of more dust closer to the crater floor in some seasons, which could mean that dust is being lifted off the crater floor. Key Points: 1,375 sols of Mastcam‐derived line‐of‐sight extinction within Gale Crater are presented along with updates to the Navcam extinction recordA cyclical pattern with one or more peaks in the dusty season and a trough in the less‐dusty season was observed with both camerasExtinction suggests increased dust loading at lower elevations during dusty seasons, indicative of lifting or external introduction of dust [ABSTRACT FROM AUTHOR]

A total solar eclipse occurred in the Southern Hemisphere on 2 July 2019 from approximately 17 to 22 UT. Its effect in the thermosphere over South America was imaged from geostationary orbit by NASA's Global-scale Observation of Limb and Disk (GOLD) instrument. GOLD observed a large brightness reduction (>80% around totality) in OI 135.6 nm and N2 LBH band emissions compared to baseline measurements made 2 days prior. In addition, a significant enhancement (with respect to the baseline) in the SO/N2 column density ratio (~80%) was observed within the eclipse's totality. This enhancement suggests that the eclipse induced compositional changes in the thermosphere. After the eclipse passed, a slight enhancement in SO/N2 column density ratio (~7%) was also seen around the totality path when compared to measurements before the eclipse. These observations are the first synoptic imaging measurements of an eclipse's thermospheric effects with the potential to drastically improve and test our understanding of how the thermosphere responds to rapid, localized changes in solar short wavelength radiation. [ABSTRACT FROM AUTHOR]

An abundance of evidence indicates that the tropics are expanding. Despite many attempts to decipher the cause, the underlying dynamical mechanism driving tropical expansion is still not entirely clear. Here, based on observations, multimodel simulations from the Coupled Model Intercomparison Project phase 5 (CMIP5) and purposefully designed numerical experiments, the variations and trends of the tropical width are explored from a regional perspective. We find that the width of the tropics closely follows the displacement of oceanic midlatitude meridional temperature gradients (MMTG). Under global warming, as a first‐order response, the subtropical ocean experiences more surface warming because of the mean Ekman convergence of anomalously warm water. The enhanced subtropical warming, which is partially independent of natural climate oscillations, such as the Pacific Decadal Oscillation, leads to poleward advance of the MMTG and drives the tropical expansion. Our results, supported by both observations and model simulations, imply that global warming may have already significantly contributed to the ongoing tropical expansion, especially over the ocean‐dominant Southern Hemisphere. Plain Language Summary: Both observations and climate simulations have shown that the edges of tropics and associated subtropical climate zone are shifting toward higher latitudes under climate change. The underlying dynamical mechanism driving this phenomenon that has puzzled the scientific community for more than a decade, however, is still not entirely clear. A number of investigations argued that the atmospheric processes, in the absence of the ocean dynamics, lead to the tropical expansion. For example, increasing greenhouse gases, decreasing ozone and increasing aerosols are suggested to be the dominant factors contributing to expanding the tropics. However, these investigations are mostly based on model simulations, and observations show a much more complex evolution of expanding tropics. By examining the tropical width individually over each ocean basin, in this study, we find that the width of the tropics closely follows the displacement of oceanic midlatitude meridional temperature gradients (MMTG). Under global warming, as a first‐order response, the subtropical convergence zone experiences more surface warming due to background convergence of surface water. Such warming induces poleward shift of the oceanic MMTG and drives the tropical expansion. Key Points: Evidence shows that the tropical width follows the displacement of midlatitude meridional temperature gradients (MMTG)Under global warming, the MMTG advance toward the poles due to enhanced subtropical ocean warmingPoleward advance of the MMTG shifts the edges of the tropics and subtropical climate zone toward poles [ABSTRACT FROM AUTHOR]

The strongest Southern Hemisphere minor sudden stratospheric warming (SSW) in the last 40 years occurred in September 2019 and resulted in unprecedented weakening of the stratospheric polar vortex. Ionospheric total electron content (TEC) observations are used to provide an overview of statistically significant anomalies in the low‐latitude ionosphere during this event. Quasi‐semidiurnal perturbations of TEC are observed in response to the SSW, similar to those seen during Northern Hemisphere SSWs. Analysis indicates the existence of quasi‐periodic oscillations in TEC in the crests of the equatorial ionization anomaly, with strong 5‐ to 6‐day and 2‐ to 3‐day periodicities. Ionospheric anomalies from the combined effects of multiple mechanisms exceed a factor of 2, comparable to the strongest anomalies associated with Northern Hemisphere SSWs. These results also indicate a remarkable longitudinal variation in the character and magnitude of variations that could be related to a modulation of the non‐migrating diurnal tide. Plain Language Summary: Sudden stratospheric warming, a large‐scale meteorological disturbance, has been associated with profound anomalies in the Earth atmosphere, from troposphere all the way to the upper thermosphere and ionosphere. During the last decade, numerous studies showed that Arctic sudden stratospheric warmings cause especially large anomalies in the low‐latitude ionosphere. However, it was not clear if similar ionospheric anomalies can be produced by Antarctic sudden stratospheric warming, mostly because Antarctic sudden stratospheric warmings are pretty rare. In this study, we provide an overview of ionospheric anomalies in total electron content observed in September 2019, when very strong sudden stratospheric warming developed over Antarctica. We conclude that Antarctic events produce even more dynamical changes in the ionosphere than Arctic events. We report for the first time large differences in the observed features at locations that are separated by only 30° in longitude. Our results indicate that stratospheric weather can strongly influence the state of the ionosphere not only during December–February period (winter in the Northern Hemisphere), but also during September (equinox conditions). Key Points: Minor Antarctic sudden stratospheric warming of September 2019 produces large ionospheric anomalies at low latitudesChanges of total electron content exceeding a factor of 2 are observedLarge longitudinal differences in total electron content response to Antarctic SSW are reported [ABSTRACT FROM AUTHOR]

The 2015 St. Patrick's Day geomagnetic storm caused numerous disturbances of the ionosphere, particularly, plasma irregularities, large‐scale traveling ionospheric disturbances, and equatorial ionization anomaly enhancement. This study for the first time quantifies the global‐scale impacts of the ionospheric disturbances on Global Positioning System (GPS) precise point positioning (PPP) solutions during this extreme space weather event by taking advantage of 5,500 + GNSS stations installed worldwide. The overall impact was more severe at high latitudes, while PPP degradation at low latitudes was associated with different types of ionospheric disturbances. Specifically, our results show that kinematic PPP solutions degraded following an intensified auroral particle precipitation during the storm's main phase (06–23 UT) when up to ~70% of the high‐latitude stations experienced degraded position solutions in the multimeter range at 16–18 UT. Around magnetic noon and midnight, the storm‐induced plasma irregularities caused notable PPP errors (>10 m) at high latitudes. Interhemispheric differences were observed with a more severe impact seen in the Southern Hemisphere, where PPP outage lasted for ~12 hr during the second main phase (12–23 UT). At low latitudes, post sunset equatorial plasma irregularities were suppressed across most longitudes, but large PPP errors (>2 m) associated with storm‐induced plasma bubbles were registered at the Indian sector at 14–18 UT. The storm‐induced equatorial ionization anomaly enhancement and large‐scale traveling ionospheric disturbances were responsible for the low‐latitude PPP degradation at dayside sectors. This study fills the research gap between physical and practical aspects of severe ionospheric storm effects. Key Points: Ionospheric disturbances caused high‐precision GPS positioning degradation on a global scale during the 2015 St. Patrick's Day stormAt high latitudes, severe position degradation was observed around magnetic noon and midnight coinciding with plasma irregularities zoneAt low latitudes, position errors were due to storm‐induced plasma bubbles, EIA enhancement, and traveling ionospheric disturbances [ABSTRACT FROM AUTHOR]

The global distribution and variations of the monthly mesopause temperature are presented during 2002–2019 covering the latitudes of 83°S to 83°N based on Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) observations. To investigate the long‐term trend and solar response of the mesopause temperature, a three‐component harmonic fit is first applied to remove the seasonal variation from the monthly temperature data series. Then a multiple linear regression model is performed to residual temperatures versus constant, linear trend, solar activity, and geomagnetic activity terms. In this study, the mesopause temperature shows a cooling trend through all latitudes ranging from ~0 to −0.14 K/year with a mean of −0.075 ± 0.043 K/year. The cooling trends in the Southern Hemisphere are stronger than those in the Northern Hemisphere. For high latitudes (60–80°), significant negative trends can be observed during nonsummertime, while no significant trends are found for summertime. The mesopause temperature shows apparent positive responses to solar activity through all latitudes ranging from 3.03 to 4.80 K per 100 solar flux units (sfu) with a mean of 3.99 ± 0.49 K per 100 sfu, which is more significant and stable in the Northern Hemisphere. There is a pronounced drop for mesopause height at polar latitudes, which reflects the shrinking effect at lower altitudes mainly caused by greenhouse gas cooling. We show that the length of the time interval analyzed strongly influences the results. Our results, obtained from 18‐year SABER observations, are expected to be a robust measure of the mesopause temperature variability. Key Points: The mesopause temperature during 2002–2019 shows a cooling trend through all latitudes ranging from ~0 to −0.14 K/yearThe mesopause temperature shows a positive response to solar activity through all latitudes ranging from 3.03 to 4.80 K per 100 sfuA sufficiently long time interval is necessary for such analyses [ABSTRACT FROM AUTHOR]

Direct measurement of mean vertical velocities in the mesosphere‐lower thermosphere (60–110 km) is not possible due to their small values. Here we derive vertical velocities using the divergence of the mean meridional wind over the Antarctic summer pole using MF radar wind measurements made at Davis Station (69°S, 78°E) between 1994 and 2018. Estimates of vertical velocity are restricted to a 21‐day period centered just after solstice when the equatorward wind reaches its maximum value of about 15 m s−1 at heights near 90 km. The Medium Frequency (MF) radar winds are calibrated against colocated meteor wind radar observations. Neutral densities required for the vertical wind calculations are obtained from zonally averaged temperature measurements obtained by the MLS instrument aboard the AURA satellite. The estimated vertical velocities have peak values varying between 2 and 6 cm s−1 with significant interannual variability. While the peak values do not show significant long‐term change, there is a long‐term decrease in the mean height of maximum winds of about 0.6 km per decade that is statistically significant. The interannual variability is linked to the date of transition in the stratospheric zonal circulation from winter eastward to summer westward flow. Meridional and vertical velocities are smaller and peak at lower altitudes during early transitions (20–30 days prior to solstice) than is the case for late transitions that occur at solstice or later. Key Points: Two decades of MF radar wind measurements are used to estimate vertical velocities in the austral summer mesosphereThe height of maximum vertical motion descends at about 0.6 km per decade, but without significant trends in maximum amplitudeInterannual variability in mesospheric motions is related to dynamic variability in the stratosphere [ABSTRACT FROM AUTHOR]

The southwestern Atlantic Ocean has one of the largest and most productive continental shelves of the southern hemisphere. Despite its relevance, its circulation patterns have been largely inferred from hydrographic observations and numerical models. Here we describe the variability of the shelf circulation based on the analysis of 11 months of multilevel currents measured by two bottom‐mounted acoustic Doppler current profilers deployed over the continental shelf at 39°S. The record‐length mean is 12 and 13 cm/s in the upper layer and decreases to 6 and 8 cm/s near the bottom, at the deployment nearer and further from the coast, respectively. The mean flow direction is toward the NE, following the orientation of the isobaths. Measurements at both sites show that the alongshore barotropic component accounts for 83% of the variability observed and are well correlated (0.86), suggesting a relatively uniform flow, which is presumably driven by large‐scale forcing. Indeed, large‐scale wind stress patterns dominate the temporal variability of the in situ currents and the passage of atmospheric fronts induces significant changes in the observed currents at all depths. We found that for 12% of the measurements the currents reverse the direction to the SW in response to these atmospheric patterns. Furthermore, the analysis of sea surface height reconstructed from bottom pressure measurements at both sites and from a coastal tide gauge reveals that the variability of the alongshore currents is driven by the cross‐shore pressure gradients generated by the alongshore wind stress. Key Points: Eleven months of in situ velocities at two sites of the Argentine continental shelf are analyzedThe barotropic component explains 83% of the total variance and the alongshore velocities at the two sites are highly correlated (0.86)Alongshore wind stress causes across‐shore pressure gradients that modify the alongshore currents [ABSTRACT FROM AUTHOR]

Based on the electron density, field‐aligned currents (FACs) and ion drift velocity data from the Swarm‐A satellite during 2013–2018, we investigate the features of the high‐latitude trough in the Southern Hemisphere. The results show that the high‐latitude trough in the Southern Hemisphere is a persistent postmidnight feature in winter. It is observed mainly in the eastern longitudes under low solar activity conditions and in a smaller longitudinal range under high solar activity conditions. The high‐latitude trough moves to higher latitudes at later local times, which is more obvious under low solar activity conditions. We also find that the features of FACs and ion drift velocity distribution in the high‐latitude trough region depend on longitude. In the longitude sector of 0°–70°E, the high‐latitude trough positions are always located at the poleward boundary of the downward FAC region, and collocated with the convection reversal boundary in the postmidnight region. In the longitude sector of 80°–130°E, the high‐latitude trough positions are located at the poleward boundary of the downward FAC region in the midnight region and at the strong westward or antisunward ion flow region in the postmidnight region. It is suggested that the high‐latitude trough formation and evolution is possibly associated with downward FACs, flow stagnation in the convection reversal boundary, and westward or antisunward ion flow. Plain Language Summary: Ionospheric troughs are depletions of the nighttime F region plasma density around the auroral and polar regions. The presence of the trough has a significant impact on the radio transmission. There are two types of troughs: the midlatitude trough and the high‐latitude trough. The midlatitude trough locates on the equatorward side of the auroral oval, and the high‐latitude trough locates within the auroral oval or polar cap. The features and formation mechanisms of the high‐latitude trough in the Southern Hemisphere are not yet clear. This study uses a new multiparameter data set gathered by the Swarm‐A satellite to find out the features and formation mechanisms of the high‐latitude trough in the Southern Hemisphere. We found that the high‐latitude trough in the Southern Hemisphere is a persistent postmidnight feature in winter. It is observed mainly in the eastern longitudes. The features of FACs and ion drift velocity distribution in the high‐latitude trough region depend on longitude. The formation and evolution of the high‐latitude trough is suggested to be associated with downward FACs, flow stagnation in the convection reversal boundary, and westward or antisunward ion flow. Key Points: The high‐latitude trough is a persistent postmidnight feature in winter in the Southern HemisphereThe high‐latitude trough is observed mainly in the eastern longitudesThere is a longitude dependence of features of FACs and ion drift velocity distribution in the high‐latitude trough region [ABSTRACT FROM AUTHOR]

Much theoretical and observational work has been devoted to studying the occurrence of F region polar cap patches in the Northern Hemisphere; considerably less work has been applied to the Southern Hemisphere. In recent years, the Madrigal database of mappings of total electron content (TEC) has improved in Southern Hemisphere coverage, to the point that we can now carry out a study of patch frequency and occurrence. We find that Southern Hemisphere patch occurrence is very similar to that of the Northern Hemisphere with a half‐year offset, plus an offset in universal time of approximately 12 hr. This is further supported by running an ionospheric model for both hemispheres and applying the same patch‐to‐background technique. Further, we present a simple physical mechanism involving a sunlit dayside plasma source concurrent with a dark polar cap, which yields a patch‐to‐background pattern very much like that seen in the TEC mappings for both hemispheres. Plain Language Summary: The tongue of ionization (TOI) is a stream of high‐density plasma flowing antisunward across the polar cap; it may be present as one continuous structure, or it may be fragmented into discrete density patches. There is a well‐studied climatology of when the TOI (and patches) may appear in the Northern Hemisphere polar cap; it has been harder to study this issue for the Southern Hemisphere because observational data there has been comparatively scarce but has improved considerably in recent years. We carry out a systematic search for TOIs and patches in both hemispheres throughout the years 2015–2018 and find that the pattern of patch occurrence in the Southern Hemisphere is very much like that in the Northern Hemisphere, but is seasonally shifted by 6 months and diurnally shifted by 12 hr. This finding, which is based on the use of two‐dimensional grids of observations of total electron content, is very different from results reported in studies that have been based on the use of one‐dimensional satellite tracks. Key Points: Ionospheric data coverage in the Southern Hemisphere is now comprehensive enough to allow a multiyear survey of polar cap density patchesThe seasonal and diurnal distributions of patches in the SH are like those of the NH, but are shifted by 6 months and 12 hrOur results differ in very significant ways from what has been reported in several recent studies using other methodologies [ABSTRACT FROM AUTHOR]

Interannual variability of Ocean Heat Content (OHC) is intimately linked to ocean water mass changes. Water mass characteristics are imprinted at the ocean surface and are modulated by climate variability on interannual to decadal time scales. In this study, we investigate the water mass change and their variability using an isopycnal decomposition of the OHC. For that purpose, we address the thickness and temperature changes of these water masses using both individual temperature‐salinity profiles and optimal interpolated products from Argo data. Isopycnal decomposition allows us to characterize the water mass interannual variability and decadal trends of volume and OHC. During the last decade (2006–2015), much of interannual and decadal warming is associated with Southern Hemisphere Subtropical Mode Water and Subantarctic Mode Water, particularly in the South Pacific Eastern Subtropical Mode Water, the Southeastern Indian Subantarctic Mode Water, and the Southern Pacific Subantarctic Mode Water. In contrast, Antarctic Intermediate Water in the Southern Hemisphere and North Atlantic Subtropical Mode Water in the Northern Hemisphere have cooled. This OHC interannual variability is mainly explained by volume (or mass) changes of water masses related to the isopycnal heaving. The forcing mechanisms and interior dynamics of water masses are discussed in the context of the wind stress change and ocean adjustment occurring at interannual time scale. Key Points: Upper global ocean mode water are the hot spots of 2006–2015 ocean heat trendSouthern Hemisphere mode water gained volume and buoyancy over 2006–2015Wind forcing and oceanic adjustment may partly explain the interannual mode water volume change [ABSTRACT FROM AUTHOR]

We present statistical investigation of the high‐latitude ionospheric current systems in the Northern Hemisphere (NH) and Southern Hemisphere (SH) during low (Kp < 2) and high (Kp ≥ 2) geomagnetic activity levels. Nearly 4 years of vector magnetic field measurements are analyzed from the two parallel flying Swarm A and C satellites using the spherical elementary current system method. The ionospheric horizontal and field‐aligned currents (FACs) for each auroral oval crossing are calculated. The distributions of the mean values of FACs as well as the horizontal curl‐free and divergence‐free currents in magnetic latitude and magnetic local time for each hemisphere and activity level are presented. To estimate the NH/SH current ratios for the two activity levels, we remove seasonal bias in the number of samples and in the Kp distribution by bootstrap resampling. This is done in such a manner that there are equal number of samples from each season in each Kp bin. We find that for the low activity level, the currents in the NH are stronger than in the SH by 12±4% for FAC, 9±2% for the horizontal curl‐free current, and 8±2% for the horizontal divergence‐free current. During the high activity level, the hemispheric differences are not statistically significant. This suggests that the local ionospheric conditions, such as magnetic field strength or daily variations in insolation, may be important and play a larger role during quiet than disturbed periods. This issue must be studied further. Key Points: FACs and horizontal currents from Swarm data are analyzed statistically for both Northern (NH) and Southern Hemispheres (SH) using SECS methodWhen seasonal bias is removed from the data, interhemispheric asymmetry is found for low but not for high magnetic activity caseIn low magnetic activity case both FACs and horizontal currents are about 10% more intense in the NH than in the SH [ABSTRACT FROM AUTHOR]

Several recent studies have suggested that the stratosphere can be a source of subseasonal‐to‐seasonal predictability of Southern Hemisphere circulation during the austral spring and early summer seasons, through its influence on the zonal‐mean eddy‐driven jet. We exploit the large sample size afforded by the hindcasts from the European Centre for Medium‐Range Weather Forecasts Integrated Forecast System to address a number of unanswered questions. It is shown that the picture of coherent seasonal variability of the coupled stratosphere‐troposphere system apparent from the reanalysis record during the spring/early summer period is robust to sampling uncertainty and that there is evidence of nonlinearity in the case of the most extreme variations. The effect of El Niño–Southern Oscillation on the eddy‐driven jet during this time of year is found to occur via the stratosphere, with no evidence of a direct tropospheric pathway. A simple two‐state statistical model of the stratospheric vortex is introduced to estimate the subseasonal‐to‐seasonal predictability associated with shifts of the seasonal cycle in the Southern Hemisphere extratropical atmosphere. This simple model, along with a more general model, is subsequently used to interpret skill scores associated with hindcasts made using the full seasonal forecast system. Together, the results provide evidence of tropospheric predictability on subseasonal‐to‐seasonal timescales during this time of year from at least as early as 1 August and show no evidence of a "signal‐to‐noise paradox" between the hindcasts and the reanalysis. Key Points: Southern Hemisphere midlatitude jet variations in spring and early summer are predictable several months aheadThis subseasonal‐to‐seasonal predictability of the Southern Hemisphere jet comes via the stratospheric polar vortexThe observed influence of ENSO on the jet during this time is via this stratospheric pathway [ABSTRACT FROM AUTHOR]

Using the bow shock crossing events from four spacecraft: IMP 8, Geotail, Magion‐4, and Cluster 1, a new three‐dimensional asymmetric bow shock model is constructed. The model is parameterized by the solar wind dynamic pressure, the interplanetary magnetic field, magnetosonic Mach number, solar wind β, and the Earth's dipole tilt angle. It is shown that the shape and size of bow shock are both affected by the dipole tilt angle. The dipole tilt angle causes asymmetries in the meridional plane: (1) the bow shock subsolar standoff distance and the north‐south asymmetry increase with the dipole tilt angle; (2) as the dipole tilt angle increases, the shock flaring angle in the equatorial plane is slightly reduced, while in the meridional plane the flaring angle obviously decreases in Southern Hemisphere and keeps almost unchanged in the Northern Hemisphere. The flaring angle in the Northern Hemisphere is larger than in the Southern Hemisphere; (3) the effects of negative dipole tilt angle on shock flaring are just the opposite of those for positive tilt, and the effects of dipole tilt angle on the shape of the bow shock are north‐south symmetric. The model results are also validated by comparing with one previous empirical model and with observational crossings, and it is demonstrated that the new model is able to predict the observed crossings more accurately and can better describe the rotational asymmetry and north‐south asymmetry of the Earth's bow shock. Key Points: We construct an asymmetric three‐dimensional bow shock model with dipole tilt effectsShape and size of bow shock are both affected by the dipole tilt angleThe dipole tilt angle causes asymmetries of bow shock in the meridional plane [ABSTRACT FROM AUTHOR]

The study investigates previously unrecognized wind reversals of the daytime thermosphere in the Southern Hemisphere at latitudes of 50°S–70°S employing observations of O(1D) airglow volume emission rates (VER), temperature, and neutral winds at 170–300‐km height by the Wind Imaging Interferometer. Atomic oxygen densities derived from the Wind Imaging Interferometer O+ (732–733 nm) emission observations were also considered together with contemporaneous observations of total electron content by the TOPEX Poseidon satellite mission. The O(1D) VER for fall equinox (March/April 1994) and summer solstice (January 1995) revealed a peak in the VER over the longitude range of 50°E–150°E, for both seasons and daytime local times. The Doppler temperatures also exhibited a maximum at the same location and times. The co‐located zonal wind field shows a westward trough at 50°E–150°E with wind speeds reaching −450 m/s and an eastward peak at 200°E–300°E. Meridional winds show a "peak and trough" structure over the 50°E–150°E region, with a distinct eastern boundary at ~150°E. During summer solstice the atomic oxygen is depleted at the region of the O(1D) VER enhancement in the presence of westward zonal wind. However, the total electron content observations showed a peak that coincided with the O(1D) VER and temperature enhancements. Plain Language Summary: The study investigates unusual perturbations in upper atmospheric winds that occur at a very specific location in the high‐latitude Southern Hemisphere. These include wind reversals, enhancements in the "red line" atomic oxygen airglow emission at 630.0 nm, temperature, depletion of atomic oxygen, and enhancements of ionospheric electron density. The location is 50°E–150°E longitude, 50°S–70°S latitude. The atmospheric observations were made by the Wind Imaging Interferometer, launched on NASA's Upper Atmosphere Research Satellite in 1991; these continued until 2003. The wind reversals involved westward winds of as strong as 450 m/s. The electron densities were of total electron content integrated along the line of sight from the satellite to the Earth and were obtained from the TOPEX satellite for the same time periods as the Wind Imaging Interferometer observations. Measurements were made at equinox and summer solstice and the atmospheric observations were the same for both. These new observations point the way to future studies of this highly localized phenomenon. Key Points: Previously unrecognized perturbations in thermospheric and ionospheric winds are observed at a specific high latitude location, 50°E–150°E and at 50°S–70°SThe neutral winds show a reversal to westward reaching −450 m/s, with a peak and trough structure of meridional wind, having an eastern boundary at ~150°EEnhancements occur in daytime O(1D) emission, temperature, and TEC; atomic oxygen is depleted [ABSTRACT FROM AUTHOR]

Cross‐track ion drifts measured by the Swarm A satellite are compared with colocated line‐of‐sight Super Dual Auroral Radar Network (SuperDARN) velocities in approximately the same directions. More than 200 Swarm A passes over four polar cap SuperDARN radars in the Northern and Southern Hemispheres are considered. Overall, the Swarm‐based velocities are larger than the SuperDARN velocities; the slope of the best fit line to the data is ~0.67. Somewhat stronger differences are found when Swarm A measurements for the entire year 2016 are compared with SuperDARN vector data from global‐scale convection maps. Swarm ion drift data demonstrate known features of the high‐latitude convection patterns, for example, reverse convection cells at interplanetary magnetic field Βz > 0. The latitudes of the convection reversal boundary inferred from SuperDARN are found to be in reasonable agreement with those determined from Swarm A and Swarm B, with Swarm‐based latitudes occurring roughly 1° more equatorward, typically. Key Points: Swarm cross‐track ion drifts are smaller than SuperDARN radar velocitiesOverall Swarm‐SuperDARN differences are by a factor of 1.5 but smaller in many instancesSwarm shows major features of plasma flow patterns and superior in monitoring flow reversals [ABSTRACT FROM AUTHOR]

With the aid of the Neutral Gas and Ion Mass Spectrometer measurements made onboard the Mars Atmosphere and Volatile Evolution, we examine the morphology of the nightside Martian ionosphere near the terminator at 150–250 km in terms of the extension into darkness for a selected set of ion species: O 2+, NO+, HNO+, N 2+/CO+, CO 2+, and HCO+. Our analysis reveals several interesting characteristics, including the presence of dawn‐dusk and north‐south asymmetries and the variability among different species. A full interpretation of the Neutral Gas and Ion Mass Spectrometer observations relies on the combination of impact ionization by precipitating electrons and day‐to‐night plasma transport, as two important sources of plasma in the nightside Martian ionosphere near the terminator. The former partially contributes to the north‐south asymmetry, whereas the latter favorably explains not only the dawn‐dusk asymmetry but also NO+ and HCO+ as two exceptions which are more extended into darkness as compared to the other species on the dusk side. A comparison between the two plasma sources further indicates that the effect of day‐to‐night transport tends to be suppressed over the southern hemisphere. The above results highlight the impacts of crustal magnetic fields on the structural variability of the nightside Martian ionosphere near the terminator, manifest as the shielding of precipitating electrons and the suppression of day‐to‐night transport, both by the presence of strong magnetic anomalies clustering over the southern hemisphere of the planet. Key Points: Dawn‐dusk and north‐south asymmetries in ion density are found in the nightside Martian ionosphere near the terminatorThe observed variations of the near‐terminator ionosphere are the combined result of electron precipitation and day‐to‐night transportThe effect of day‐to‐night transport tends to be suppressed by strong magnetic fields over the southern hemisphere [ABSTRACT FROM AUTHOR]

The largest contributor to the planetary energy imbalance is well‐mixed greenhouse gases (GHGs), which are partially offset by poorly mixed (and thus northern midlatitude dominated) anthropogenic aerosols (AAs). To isolate the effects of GHGs and AAs, we analyze data from the CMIP5 historical (i.e., all natural and anthropogenic forcing) and single forcing (GHG‐only and AA‐only) experiments. Over the duration of the historical experiment (1861–2005) excess heat uptake at the top of the atmosphere and ocean surface occurs almost exclusively in the Southern Hemisphere, with AAs canceling the influence of GHGs in the Northern Hemisphere. This interhemispheric asymmetry in surface heat uptake is eliminated by a northward oceanic transport of excess heat, as there is little hemispheric difference in historical ocean heat storage after accounting for ocean volume. Data from the 1pctCO2 and RCP 8.5 experiments suggests that the future storage of excess heat will be skewed toward the Northern Hemisphere oceans. Plain Language Summary: Climate change is fundamentally an energy balance problem. Due to the influence of greenhouse gas (GHG) emissions, the amount of solar energy absorbed by Earth is currently greater than the amount of energy radiated to space. This energy imbalance is partially offset by particulate matter released into the atmosphere from burning fossil fuels (anthropogenic aerosols, AAs), which is most concentrated in the northern midlatitudes. In this study, model simulations of the historical and future climate are compared to single forcing simulations that apply only GHG or AA emissions. We find that the historical uptake of excess heat is strongly skewed toward the Southern Hemisphere because AAs cancel the influence of GHGs in the Northern Hemisphere. The oceanic storage of that heat shows little difference between the hemispheres due to a strong northward transport of excess heat. In future, the models suggest excess heat storage will skew toward the Northern Hemisphere. Key Points: Single forcing simulations suggest anthropogenic aerosols have caused most historical excess heat uptake to occur in the Southern HemisphereThis interhemispheric asymmetry in heat uptake is eliminated by a northward oceanic transport of excess heatIn the future, the storage of excess heat will be skewed toward the Northern Hemisphere [ABSTRACT FROM AUTHOR]

Impacts of horizontal winds assimilation on thermal tides are investigated by using the Venus atmospheric general circulation model for the Earth Simulator local ensemble transform Kalman filter data assimilation system. The assimilated data are horizontal winds derived from Venus ultraviolet images taken by the Venus Monitoring Camera onboard the Venus Express orbiter. The results show that three‐dimensional structures of the thermal tides are significantly improved not only in the horizontal winds but also in the temperature field, even though the observations are available only at the cloud top level on the southern dayside hemisphere approximately once an Earth day. The reproduced temperature fields agree well with recent radio occultation measurements of the Venus Climate Orbiter Akatsuki. The zonal mean fields of the zonal wind and temperature are also improved globally. This study would enable reanalysis of past Venus observations. Key Points: Three‐dimensional structures of the thermal tides are significantly improved by the data assimilation of horizontal winds derived from Venus UV imagesReproduced temperature fields agree well with those obtained by radio occultation measurements of AkatsukiZonally averaged atmospheric structures are improved globally even though the observations are very limited in space and time [ABSTRACT FROM AUTHOR]

The oceans are warming, but it is unclear how marine productivity will be affected under future climate change. In this study we examined a wide range of paleoproductivity proxies along a latitudinal transect (36–58°S) in the SW Pacific during the early Holocene climatic optimum, to explore regional patterns of productivity in a slightly warmer‐than‐present world. During the early Holocene there is a small increase in productivity in the subtropical waters, no change at the subtropical frontal zone, and conflicting evidence in records immediately south of the subtropical front, where an increase is inferred from one core site, but not at the other. Evidence for an increase in productivity in Antarctic Surface Waters, south of the polar front, is also equivocal. We infer a small increase in productivity in subtropical waters, and the ocean just south of the subtropical front was associated with changes in the ocean circulation of the SW Pacific, driven by changes in the Southern Hemisphere Westerly Winds split‐jet structure in this region. The relatively modest warming during the early Holocene climatic optimum in the SW Pacific indicates that this time period may provide an analog for future productivity for the midcentury (2055) under Intergovernmental Panel on Climate Change Representative Concentration Pathway 8.5 or for the end of the century (2100) under Representative Concentration Pathway 4.5. However, higher‐resolution, downscaled models, with realistic Southern Hemisphere Westerly Winds, will be necessary to forecast future productivity for this oceanographically complex region. Key Points: There is evidence for a small increase in productivity in subtropical water and an expanded subtropical frontal region during the early HoloceneThe expansion of the Subtropical Front is likely due to changes in the Southern Hemisphere Westerly Wind split‐jet structureThe early Holocene is not a suitable analog for future productivity for the end of the century Representative Concentration Pathway 8.5 [ABSTRACT FROM AUTHOR]

Predicted changes in Southern Hemisphere (SH) precipitation and Antarctic ice mass correspond to variations in the meridional moisture flux (MMF). Thirty‐five years of ERA‐Interim reanalysis data are combined with an extratropical cyclone (ETC) identification and tracking algorithm to investigate factors controlling SH MMF variability in the midlatitudes and near Antarctica. ETC characteristics which exert the strongest control on ETC MMF are determined thus identifying which ETCs contribute most to SH moisture transport. ETC poleward propagation speed exerts the strongest control on the ETC MMF across the Antarctic coastline. In SH winter, ETCs with the largest poleward propagation speeds transport 2.5 times more moisture than an average ETC. In the midlatitudes, ETC genesis latitude and poleward propagation speed have a similar influence on ETC MMF. Surprisingly, ETC maximum vorticity has little control on ETC MMF. Cyclone compositing is used to determine the reasons for these statistical relationships. ETCs generally exhibit a dipole of poleward and equatorward MMF downstream and upstream of the cyclone center, respectively. However, ETCs with the largest poleward propagation speeds resemble open frontal waves with strong poleward moisture transport downstream of the cyclone center only and thus result in the largest MMF. These results suggest that inhomogeneous trends and predicted changes in precipitation over Antarctica may be due to changes in cyclone track orientation, associated with changes to the large‐scale background flow, in addition to changes in cyclone number or intensity. Plain Language Summary: We investigate how large‐scale weather systems transport moisture from low latitudes (which are very moist) to high latitudes (which are much drier) in the Southern Hemisphere. Of special interest is how these weather systems transport moisture to Antarctica. For snow (and rain) to occur, there needs to be moisture present in the atmosphere. If the amount of moisture transported from low latitudes to high latitudes changes, the amount of snow falling over Antarctica will also change. This changes the amount of water stored as ice and snow in the Antarctic ice sheet. Changes to the Antarctic ice sheet could have drastic impacts on global sea levels. We study how the amount of moisture transported depends on the type, or characteristics, of weather systems. Weather systems which move the fastest from low latitude or midlatitude toward Antarctic can move 2.5 times more moisture than an average weather system. Surprisingly, the strongest weather systems do not move much more moisture than the average weather system. These results tell us that we should consider how the track of weather systems will change in the future in addition to how the strength or number of these large‐scale weather systems will change. Key Points: Moisture transport by extratropical cyclones (ETC) in the Southern Hemisphere is investigated using 35 years of ERA‐Interim reanalysis dataThe amount of moisture transported poleward by an ETC depends strongly on the ETC poleward propagation speed and weakly on ETC intensityChanges to storm track latitude and tilt may explain observed trends in SH precipitation better than changes in ETC intensity [ABSTRACT FROM AUTHOR]

The first daily mean sea‐level pressure (MSLP) series for the Southwestern Cape region of South Africa is presented for the 19th century, and is one of the longest and oldest for the Southern Hemisphere. Sub‐daily barometer readings from the South African Astronomical Observatory were digitized, together with temperature readings, and extend over the period 1834–1899. Pressure readings were recorded using mercury barometers and so needed to be corrected and reduced to standard conditions. Overall, austral winter (June, July, August) has the highest mean monthly MSLP values, symptomatic of the ridging anticyclones during this season. The year 1862 stands out with particularly low MSLP values and has 27 days during austral winter that were below the 10th percentile. This most likely indicates that the winter of 1862 experienced the highest number of passing cold fronts throughout the 66‐year study period. The first daily MSLP series for the Southwestern Cape region of South Africa is presented for the 19th century, and is one of the longest and oldest for the Southern Hemisphere. Sub‐daily barometer readings were digitized from the original hard copies. These barometer observations were corrected to modern‐day standard conditions, reduced to MSLP and an equivalent 24‐hr daily mean was calculated. The year 1862 stands out with particularly low MSLP values and has 27 days during austral winter that were below the 10th percentile, likely indicative of a high number of passing cold fronts. [ABSTRACT FROM AUTHOR]

All‐sky imagers located in Asiago, Italy (45.87oN, 11.53oE; 40.7o magnetic latitude) and Sutherland, South Africa (32.37oS, 20.81oE; −40.7o magnetic latitude) are used to study magnetically conjugate medium scale traveling ionospheric disturbances (MSTIDs). We present initial results from the first year of joint Asiago‐Sutherland data sets from July 2016 to June 2017. The 630.0‐nm airglow perturbations showing different kinds of waves were frequently observed. Some of these wave events resemble MSTIDs propagating south‐westward in Asiago, typical direction observed at other longitude sectors in the northern hemisphere. They are mostly observed as single bands propagating through the field of view of the all‐sky imagers. We select and analyze five cases of magnetically conjugate bands associated with MSTIDs. The bands observed at Sutherland move mainly westward, noticeably different from the north‐west direction of propagation of MSTIDs observed in the southern hemisphere. We compare the MSTIDs propagation speeds and find that three cases show larger values at Sutherland. When we compare the zonal speeds all the cases show larger values at Sutherland. On average, the propagation speed at Sutherland is 20% larger and the zonal speed is ~35% larger. The westward motion at Sutherland is explained by taking onto account how its magnetic declination (~24oW) affects the orientation of the bands. The larger speed at Sutherland is due to the weaker Earth's magnetic field in the southern hemisphere and the particular configuration of the magnetic field lines in this longitude sector. Key Points: MSTIDs observed at conjugate locations in the Europe‐Africa longitude sector for the first timeDirection of propagation of Sutherland MSTIDs is mostly westward, consequence of its large magnetic declinationPropagation speeds are larger at Sutherland due to weaker Earth's magnetic field and its configuration at this longitude sector [ABSTRACT FROM AUTHOR]

Abstract: Over the last decade there has been mounting evidence that the strength of the Sun's polar magnetic fields during a solar cycle minimum is the best predictor of the amplitude of the next solar cycle. Surface flux transport models can be used to extend these predictions by evolving the Sun's surface magnetic field to obtain an earlier prediction for the strength of the polar fields, and thus the amplitude of the next cycle. In 2016, our Advective Flux Transport (AFT) model was used to do this, producing an early prediction for Solar Cycle 25. At that time, AFT predicted that Cycle 25 will be similar in strength to the Cycle 24, with an uncertainty of about 15%. AFT also predicted that the polar fields in the southern hemisphere would weaken in late 2016 and into 2017 before recovering. That AFT prediction was based on the magnetic field configuration at the end of January 2016. We now have two more years of observations. We examine the accuracy of the 2016 AFT prediction and find that the new observations track well with AFT's predictions for the last 2 years. We show that the southern relapse did in fact occur, though the timing was off by several months. We propose a possible cause for the southern relapse and discuss the reason for the offset in timing. Finally, we provide an updated AFT prediction for Solar Cycle 25 that includes solar observations through January of 2018. [ABSTRACT FROM AUTHOR]