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Based on the ERA5 reanalysis datasets during 1980–2019, a total of eleven zonal shear lines (ZSLs) that caused heavy precipitation and lasted more than 60 hours over the Tibetan Plateau in summer are selected for composite analysis. By decomposing the kinetic energy (K) near the ZSL into divergent and rotational kinetic energies (KD and KR) and the kinetic energy of interaction between the divergent wind and the rotational wind (KRD), the influence of the rotational and divergent winds on the evolution of the ZSL intensity is investigated from the perspective of KD and KR. The main results are as follows. The ZSL is a comprehensive reflection of rotation and convergence. The intensity evolution of ZSL is essentially synchronized with those of K, KR, and KRD but lags behind KD by about three hours. The enhancement of K is mainly contributed by KR, which is governed by the conversion from KD to KR. Furthermore, the increase in the conversion from KD to KR is controlled by the geostrophic effect term Af, which is determined by the joint enhancement of the zonal rotational and meridional divergent wind components (uR and vD). Therefore, the joint enhancement of uR and vD controls the increase of the ZSL intensity, leading to increased precipitation.

The topographic dynamical effect from Eurasia (EA_Topo) and North America (NA_Topo) on the winter isentropic meridional mass circulation (IMMC) is investigated using the WACCM. The independent effect of EA_Topo and that of NA_Topo, with the former much stronger, are both to strengthen the IMMC that is composed of the lower equatorward cold air branch (CB) and the upper poleward warm air branch in the extratropical tropopshere (WB_TR) and stratosphere (WB_ST). Further investigation of the individual contributions from changes in stationary vs. transient and zonal-mean flow vs. waves reveals that, due to the topography-forced mass redistribution, changes in the low-level meridional pressure gradient force a zonal-mean counter-clockwise/ clockwise meridional cell in the southern/northern side of topography. This weakens/strengthens the IMMC south/north of 30°N from the troposphere to lower stratosphere, acting as a dominant contributor to the IMMC changes south of 50°N. Meanwhile, the EA/NA_Topo-forced amplification of stationary waves constructively interacts with those determined by land-sea contrast, making the dominant/minor contributions to the strengthening of CB and WB_TR north of 50°N. The related increase in the upward wave propagation further dominates the WB_ST strengthening in the subpolar region. Meanwhile, transient eddy activities are depressed by EA/NA_Topo along with the weakened background westerly, which partly-offset/dominate-over the contribution from stationary flow in midlatitudes and subpolar region. The coexistence of the other topography (NA/EA_Topo) yields destructive mutual interferrence, which can weaken/offset the independent-EA/NA_Topo-forced meridional mass transport mainly via changing the zonal-mean as well as the downstream wave pattern of mass and meridional wind.

We present a climatology of nighttime thermospheric neutral winds between February 2018 and January 2019 measured by a Fabry-Perot interferometer (FPI) located in Sutherland, South Africa (32.2°S, 20.48°E; geomagnetic latitude: 40.7°S). This FPI measures the nighttime oxygen airglow emission at 630.0 nm, which has a peak intensity at an altitude of roughly 250 km. The annual meridional and zonal winds at this location vary between −100 and 120 m/s and show typical midlatitude nocturnal and seasonal variations. During local summer months (December-February), the meridional wind is predominantly equatorward from dusk to predawn. However, during the winter months, the meridional wind is poleward from dusk, turns equatorward around midnight, and either remains in this direction for the rest of the night (June) or turns poleward again just before dawn (July and August). The zonal wind velocity is generally eastward during the evening until just before midnight, changing westward post-midnight. The zonal wind peaks at higher velocities during the winter months compared to the summer months. The eastward-to-westward transition occurs later during the winter months compared to the summer months. We compare results from HWM14 with the FPI measurements and find a better agreement between FPI measured winds and HWM14 modeled winds for the meridional component compared to the zonal component. In addition, the HWM14 zonal wind consistently peaked several hours ( ∼ 3 h) prior to the measured wind. Furthermore, the HWM14-modeled eastward-to-westward transitions times were a couple of hours ( ∼ 2 h) earlier during the months of November to January creating what looks like a phase shift compared to the measured wind. This phase shift was apparent in all months and we suggest this can be attributed to a phase shift of the terdiurnal tide between the model and measurements.

Earth’s upper atmosphere over low latitudes is influenced by the equatorial electrodynamics. Its influence can also be modulated by the thermospheric winds. The effect of these two forces on the thermospheric neutral behaviour in the daytime can be investigated by measuring the variations in the OI 630.0 nm dayglow emission rates as these serve as effective tracers of the altitude region of their origin. The capability to measure dayglow emissions over a large field-of-view presents a unique opportunity to investigate the upper atmospheric behaviour over large spatial extents. Diurnal measurements of OI 630.0 nm dayglow emission rates have been carried out from two different locations in India using multi-wavelength imaging echelle spectrographs, MISE, which, together cover a spatial range from 5 ° -18 ° magnetic latitude. These investigations have been carried out during January-February 2020 (winter season) when solar flux variation was nearly negligible (varied only by 4 solar flux unit from 68-72 solar flux unit). Therefore, latitudinal variations in the daily averaged oxygen dayglow emission intensities have been analyzed to assess their response to the variations in the strength of the equatorial electrodynamics and the meridional winds. The results reveal that these forces show varying effects with the poleward meridional wind contributing to an enhancement in the OI 630.0 nm dayglow emission rates closer to the magnetic equator and a decrement as one moves away from the equator. The equatorial electric field effect, however, continues to be equally effective in the low-latitudes region under consideration.

Changes in the meridional position of the sea surface temperature (SST) anomalies (SSTAs) associated with the interannual component (PC1-I) of the principal component 1 (PC1) of the first leading mode of the North Pacific SST (referred to here as PC1-I-related SSTAs) are investigated using reanalysis products and climate model output. It is found that the PC1-I-related SSTAs (or PC1-I anomalies) significantly shift southward at a rate of 1.04° latitude per decade and have moved southward by 4.4° since the 1960s. Our further analysis indicates that the southward shift of the PC1-I-related SSTAs is due to changes in ENSO teleconnections. Compared to the 1950–75 period (PRE era), the meridional width of the ENSO-induced tropical positive geopotential height (GH) anomaly is narrower during the 1991–2016 period (POST era), inducing a southward shift of the subtropical westerly anomaly over the North Pacific through geostrophic wind relations. This southward shift of the westerly anomaly favors the southward shift of the ENSO-induced negative GH anomaly (cyclonic circulation anomaly) over the North Pacific by positive vorticity forcing of the zonal wind shear. The southward-shifting GH anomaly associated with ENSO further forces the PC1-I anomaly to shift southward. Furthermore, the contraction of the ENSO-induced tropical positive GH anomaly is related to the contraction of the meridional width of ENSO. The modeling results support that the decrease in the ENSO meridional width favors the contraction of the ENSO-induced tropical positive GH anomaly and the southward shift of ENSO teleconnections over the North Pacific, contributing to the southward shift of the PC1-I anomaly.

Crack formation in hemispherical domes is a distinguished problem in structural mechanics. The safety of cracked domes has a long track record; the evolution of the cracking pattern received less attention. Here, we report displacement-controlled loading tests of brittle hemispherical dome specimens, including the evolution of the meridional cracking pattern. The 27 investigated specimens, 20 cm in diameter, were prepared in 3D printed molds, and their material is one of the three mixtures of gypsum and cement. We find that neither the (limited) tensile strength nor the exact value of the thickness significantly affects the statistical description of the cracking pattern, i.e., the cracking phenomenon is robust. The maximal number of the meridional cracks never exceeds seven before the fragments’ disintegration (collapse). We find that the size distribution of the fragments exhibits a lognormal distribution. The evolution is reflected in the load-displacement diagrams recorded in the test, too, as significant drops in the force are accompanied by an emergence of one or more new cracks, reflecting the brittle nature of the phenomenon. A simple, stochastic fragmentation model, in which a segment is fragmented at either in the middle or at the fourth point, fairly recovers the observed size distribution.

The dry air intrusion over India during summer monsoon break phases is well known. It has been argued that this dry air originates over the desert regions of West Asia. Here, we show that a reservoir of saturation deficit air exists over the western and northern Arabian Sea during the summer monsoon season. The monsoon low-level jet (LLJ) that transports the moisture to continental India in the active phase of monsoon, transports the dry air to northern and central India during the break phase. The LLJ undergoes a weakening and broadening before the monsoon break phase in response to increased barotropic instability. The broadening of LLJ leads to an intensification of zonal flow in the poleward flanks and a weakening at the core. The development of a positive meridional SST gradient over the northern Arabian Sea favours an increase in the low-level zonal flow in the north, which advects the moist deficit air across northwest India. The dry air intrusion results in enhanced static stability over northern and central India and strong suppression of convection. Further, the enhanced static stability weakens zonal flow from the northern Arabian Sea region and leads to the demise of the dry air intrusion. Thus, internal mechanisms are responsible for the dry air intrusion over India and its termination during the break phase of the summer monsoon. An index for the dry air intrusion is constructed based on the saturation deficit transport. This dry air intrusion index is used to identify the dry air intrusion events during monsoon breaks during the 1981–2014 period. The statistics show that there were 34 (4) monsoon breaks with (without) dry air intrusion during 1981–2014 period. We also note that the dry air intrusion and the monsoon breaks are happening simultaneously, suggesting that it is difficult to establish a cause-effect relationship.

Temporal variations of net Kuroshio transport are examined for 1972–2018 based on a repeated hydrographic section along 137°E, which is maintained by the Japan Meteorological Agency. The net Kuroshio transport obtained by integration of geostrophic current velocity relative to 1000 dbar depth fluctuates on inter-annual and decadal timescales. The predominant timescale of the net Kuroshio transport changes with time; the inter-annual variation is pronounced in 1972–1990 and 2000–2018, and the decadal variation is detected only before 2000. We find that a winter wind stress curl variation in the central North Pacific which reflects meridional movements of the Aleutian Low and intensity fluctuations of the North Pacific subtropical high on an inter-annual timescale and intensity fluctuations of the Aleutian Low on a decadal timescale, causes the net Kuroshio transport variation. In addition to the inter-annual and decadal variations, we further pointed out a bi-decadal-scale variation of the net Kuroshio transport and its possible link to the Aleutian Low intensity fluctuation. Moreover, our results indicate that during large net Kuroshio transport, sea surface temperature around the Kuroshio and Kuroshio Extension region tends to increase, resulting in vigorous upward sensible and latent heat release.

Observations show that sea surface temperatures along the Gulf Stream and the Kuroshio Current tend to synchronize at decadal time scales. This synchronization, which we refer to as the boundary current synchronization (BCS), is reproduced in global climate models with high spatial resolution. Both in observations and model simulations, BCS is associated with meridional migrations of the atmospheric jet stream. Changes in the strength and path of the ocean currents associated with the jet shifts lead to the synchronicity of surface temperatures. Numerical simulations using a conceptual model and an atmospheric general circulation model are consistent with a notion that BCS is an interbasin air-sea coupled mode. Air temperature patterns similar to the one associated with BCS have been repeatedly observed, including in July of 1994 and 2018.

Treatment of PtMe3I in tetrahydrofuran with either in situ prepared [R-PNP]Li ([R-PNP]- = [(R2P-o-C6H4)2N]-; R = Ph, iPr) or H[R-PNP] in the presence of triethylamine at room temperature affords quantitatively fac-[R-PNP]PtMe3. Thermolysis of fac-[R-PNP]PtMe3 in benzene solutions generates mer-[R-PNP]PtMe3 and ultimately [R-PNP]PtMe and ethane. Complexes mer-[R-PNP]PtMe3 represent the first meridional trialkylplatinum(IV) derivatives to date.

This paper examines the impact of the meridional and vertical structures of a preexisting upstream storm track (PUST) organized by preexisting synoptic-scale eddies on eddy-driven blocking in a nonlinear multiscale interaction model. In this model, the blocking is assumed, based on observations, to be comprised of barotropic and first baroclinic modes, whereas the PUST consists of barotropic, first baroclinic, and second baroclinic modes. It is found that the nonlinearity (dispersion) of blocking is intensified (weakened) with increasing amplitude of the first baroclinic mode of the blocking itself. The blocking tends to be long lived in this case. The lifetime and strength of blocking are significantly influenced by the amplitude of the first baroclinic mode of blocking for given basic westerly winds (BWWs), whereas its spatial pattern and evolution are also affected by the meridional and vertical structures of the PUST. It is shown that the blocking mainly results from the transient eddy forcing induced by the barotropic and first baroclinic modes of PUST, whereas its second baroclinic mode contributes little to the transient eddy forcing. When the PUST shifts northward, eddy-driven blocking shows an asymmetric dipole structure with a strong anticyclone–weak cyclone in a uniform BWW, which induces northward-intensified westerly jet and storm-track anomalies mainly on the north side of blocking. However, when the PUST has no meridional shift and is mainly located in the upper troposphere, a north–south antisymmetric dipole blocking and an intensified split jet with maximum amplitude in the upper troposphere form easily for vertically varying BWWs without meridional shear.

There are numerous studies on polar amplification and its influence on mid-latitude weather and climate. However, assessments on whether polar amplification occurs in Antarctica are rarely conducted. Based on the latest atmospheric reanalysis of ERA5 produced by European Centre for Medium-Range Weather Forecasts (ECMWF), we have defined the Antarctic amplification index, and calculated the trend of annual and seasonal Surface Air Temperature (SAT) mean during 1979–2019 for Antarctic Ice Sheet (AIS) and the trend mean of different meridional sectors of Antarctic sub regions including East Antarctic Ice Sheet (EAIS), West Antarctic Ice Sheet (WAIS) and Antarctic Peninsula (AP). Antarctic amplification shows regional differences and seasonal variations. Antarctica shows a slight warming with the largest magnitude in AP. The temperature anomalies indicate the least fluctuations in austral summer, and the more fluctuations in winter and spring. In austral summer, the warming trend domains EAIS and WAIS, while the cooling trend appears over AP. The zonal mean in Southern Hemisphere maintains a warming trend in the low latitudes, and fluctuates greatly in the middle and high latitudes. The strongest Antarctic amplification phenomenon occurs in spring, with the amplification index of 1.20. For AP, the amplification occurs in austral autumn, and the amplification index is 2.16. At South Pole and the surrounding regions, SAT for land only fluctuates largely and shows different trends in different seasons. The mechanism of Antarctic amplification is unclear till now, and its research suffers from the limitation of measured data. This suggests that future research needs progress in comprehensive ground observation network, remote sensing data accumulation, and high-resolution climate modeling with better representation of both atmospheric and cryospheric processes in Antarctica.

Linearized wave solutions on the equatorial beta plane are examined in the presence of a background meridional moisture gradient. Of interest is a slow, eastward-propagating n = 1 mode that is unstable at planetary scales and only exists for a small range of zonal wavenumbers (). The mode dispersion curve appears as an eastward extension of the westward-propagating equatorial Rossby wave solution. This mode is therefore termed the eastward-propagating equatorial Rossby wave (ERW). The zonal wavenumber-2 ERW horizontal structure consists of a low-level equatorial convergence center flanked by quadrupole off-equatorial gyres, and resembles the horizontal structure of the observed MJO. An analytic, leading-order dispersion relationship for the ERW shows that meridional moisture advection imparts eastward propagation, and that the smallness of a gross moist stability–like parameter contributes to the slow phase speed. The ERW is unstable near planetary scales when low-level easterlies moisten the column. This moistening could come from either zonal moisture advection or surface fluxes or a combination thereof. When westerlies instead moisten the column, the ERW is damped and the westward-propagating long Rossby wave is unstable. The ERW does not exist when the meridional moisture gradient is too weak. A moist static energy budget analysis shows that the ERW scale selection is partly due to finite-time-scale convective adjustment and less effective zonal wind–induced moistening at smaller scales. Similarities in the phase speed, preferred scale, and horizontal structure suggest that the ERW is a beta-plane analog of the MJO.

This study is based on a three-dimensional hydrodynamic model of the global climate including a atmospheric general circulation model, a model of the ocean in the geostrophic approximation with a frictional term in the equations of horizontal momentum with the actual configuration of depths and continents, and a model of the evolution of sea ice. Computations of forecasting the climate until 2100 with the use of scenarios of a growth in CO2 are presented. A significant decrease in meridional water flow in the Atlantic in the case of the stringent scenario is established.

This paper examines the impact of Ural blocking (UB) on winter sub-seasonal Siberian cold anomalies under the different background conditions of the winter East Asian trough (EAT). It is found that the meridional displacement and the strength of the winter EAT possibly modulate the persistence or lifetime of UB and associated sub-seasonal cold anomalies over Siberia through changing background circulation conditions. Statistical analysis reveals that UB events tend to occur more frequently in strong or southward EAT winters than in weak or northward EAT winters. A composite analysis of UB events further shows that UB has larger amplitude and longer lifetime in strong or southward EAT winters (especially the latter) than in weak or northward EAT winters, thus more likely leading to stronger sub-seasonal cold anomalies over Siberia. Moreover, the possible physical cause of why a strong or southward EAT favors UB is further investigated. It is found that winter zonal wind and meridional gradient of potential vorticity (PVy) tend to be weakened on the upstream side of Siberia near the Ural Mountains when the EAT is stronger or located more southward, favoring the maintenance of UB due to the strengthening (weakening) of the nonlinearity (energy dispersion) of UB. In contrast, when the EAT is weak or northward-displaced, a strengthening of winter zonal wind and PVy is more likely seen over the Ural Mountains and adjacent regions, which may suppress UB through enhancing its energy dispersion and reducing its nonlinearity.

This study investigates the responses of the meridional ocean heat transport (OHT) to heat fluxes of equal amplitude but opposite sign into the global ocean surface using the Community Earth System Model (CESM). Results show that the poleward OHT in both hemispheres are weakened in response to the positive forcing (i.e., warming) and strengthened in response to the negative forcing (i.e., cooling), with the latter change exceeding the former, manifesting an overall asymmetric response. The OHT responses in the Indo-Pacific to both the warming and the cooling and thus their asymmetry are dominated by its Eulerian-mean component, due primarily to changes in the Indo-Pacific Subtropical Cells. Similarly, the OHT responses in the Atlantic are determined by changes in the Atlantic Meridional Overturning Circulation, yet their asymmetry is small due to the mediation from the nonlinear effect of temperature and velocity changes. For the Southern Ocean, the Eulerian-mean component still controls the total OHT responses, yet the largest contribution is from changes in vertical temperature structure. In addition, the asymmetric response in the Southern Ocean is a joint effort among the overturning circulation cells, horizontal gyres, eddies, as well as temperature changes.

Detailed ocean currents in the southeastern tropical Indian Ocean adjacent to southern Sumatran and Javan coasts have not been fully explained because of limited observations. In this study, zonal current characteristics in the region have been studied using simulation results of a 1/8∘ global hybrid coordinate ocean model from 1950 to 2013. The simulated zonal currents across three meridional sections were then investigated using an empirical orthogonal function (EOF), where the first three modes account for 75 %–98 % of the total variance. The first temporal mode of EOF is then investigated using ensemble empirical mode decomposition (EEMD) to distinguish the signals. This study has revealed distinctive features of currents in the South Java Current (SJC) region, the Indonesian Throughflow (ITF)–South Equatorial Current (SEC) region, and the transition zone between these regions. The vertical structures of zonal currents in southern Java and offshore Sumatra are characterized by a one-layer flow. Conversely, a two-layer flow is observed in the nearshore and transition regions of Sumatra. Current variation in the SJC region has peak energies that are sequentially dominated by semiannual, intraseasonal, and annual timescales. Meanwhile, the transition zone is characterized by semiannual and intraseasonal periods with pronounced interannual variations. In contrast, interannual variability associated with El Niño–Southern Oscillation (ENSO) and the Indian Ocean Dipole (IOD) modulates the prominent intraseasonal variability of current in the ITF–SEC region. ENSO has the strongest influence at the outflow ITF, while the IOD's strongest influence is in southwestern Sumatra, with the ENSO (IOD) leading the current by 4 months (1 month). Moreover, the contributions (largest to smallest) of each EEMD mode at the nearshore of Java and offshore Sumatra are intraseasonal, semiannual, annual, interannual, and long-term fluctuations. The contribution of long-term variation (19.2 %) in the far offshore eastern Indian Ocean is larger than the interannual (16.3 %) and annual (14.7 %) variations. Future studies should be conducted to investigate this long-term variation.

We investigate the spatio-temporal characteristics of the austral spring Ross Ice Shelf Polynya (RISP) and its relationship with atmospheric circulation anomalies based on the sea ice concentration data from the National Snow and Ice Data Center (NSIDC) and the ERA5 reanalysis data. The RISP area series is derived by choosing 25% sea ice concentration as the threshold. Then the principal spatial patterns of the RISP are acquired by using the empirical orthogonal function (EOF) analysis. The leading EOF (EOF1) has a spatial distribution of a strong negative core in the northeastern RISP with a weak positive core near the Cape Adare, explaining 48.1% of the variance. This mode matches the wind pattern of the northwesterly on the western Ross Sea while southwesterly on the eastern Ross Sea, which reflects the zonal variation of the RISP. There is also a strong positive correlation between the RISP area and the PC1. The EOF2 explains 27.4% of the variance, and is mainly characterized by a large region of low values in the northwestern Ross Sea with a small region of high value near Cape Colbeck. Matching the strong southerly over the western Ross Sea, the EOF2 partly depicts the meridional variation of the RISP. We further explored the connections between the RISP and sea level pressure, and found that a deeper and more eastward Amundsen Sea Low (ASL) in November often coincides with a larger and more eastward RISP in December. This lagged response is partly generated through the influence of the ASL on the RISP in November.

Ocean wind fields form a significant input to ocean wave models. This study evaluates the accuracy of two major reanalysis wind fields: NCEP-NCAR reanalysis-II (NNR-II) and ECMWF ERA5 wind datasets in the marine domain of West Africa. The objective is to identify the reanalysis data that best represents the wind regimes of the sub-region for use in climate studies and ocean wave modelling. The reanalysis datasets were validated against in situ measurements from PIRATA meteorological buoys in the region. Both reanalysis datasets indicate good agreement with in situ measurements and capture the variability in the wind fields. However, ERA5 wind fields outperform the NNR-II wind fields and better represents the variability in wind fields in the region. They display higher correlation coefficients and R-squared values as well as lower bias and RMSE values for all wind components at all PIRATA buoy locations. Correlation coefficients of 0.92, 0.87, 0.94, and 0.98; R-squared values of 0.83, 0.76, 0.89, and 0.96; mean bias of −0.34±0.75 ms−1, 0.25±33.75°, 0.07 ± 0.86 ms−1, and −0.21±0.96 ms−1; and RMSE values of 0.82 ms−1, 33.75°, 0.87 ms−1, and 0.98 ms−1 were observed for ERA5 resolved wind speeds, wind directions, and zonal and meridional winds respectively. NNR-II also recorded correlation coefficients of 0.64, 0.7, 0.73, and 0.9; R-squared values of 0.19, 0.39, 0.32, and 0.79; mean bias of 0.12±1.77 ms−1, 8.91±53.43°, 0.55±2.09 ms−1, and −0.31±2.15 ms−1; and RMSE values of 1.77 ms−1, 54.17°, 2.16 ms−1, and 2.17 ms−1 for resolved wind speeds, wind directions, and zonal and meridional winds, respectively. NNR-II winds tend to highly overestimate zonal wind speeds and underestimate meridional wind speeds. Meridional winds are better predicted compared to zonal winds for both NNR-II and ERA5 winds. There was a general overestimation of lower wind speeds and underestimation of higher wind speeds on the part of both reanalysis datasets although this assertion varied with geographical location. To enhance the accuracy of resolved wind velocities and directions in the region, there is the need to improve the estimation of zonal winds in general by both NNR-II and ERA5 winds but with much efforts needed for NNR-II. In effect, ERA5 reanalysis winds better describe the wind regime of West Africa for climate studies and ocean wave modelling.

Internal waves with high vertical wavenumber structures on the northern part of the eastern ridge in Luzon Strait were investigated using shipboard observations and a wave propagation model. Detailed repeat observations across the ridge revealed complex undulations of isopycnals near the ridge that were characterized by vertically alternating concave and convex structures. In addition, strong eastward and westward flow areas with horizontal and vertical scales of 3–5 km and 150–250 m, respectively, occurred alternately on the downstream side of the ridge. These high-wavenumber structures in flow and density fields were associated with internal waves generated by interactions between diurnal tidal flow and the meridional submarine ridge in the strait; an acoustic Doppler current profiler recorded no signals of the Kuroshio Current and semi-diurnal tides in the zonal flow on the western slope of the eastern ridge. Many temperature inversions around the ridge exhibited vertical scales of predominantly ~ 30 m. Simple calculations of internal wave motion reveal that each internal wave mode tends to stagnate near the summits of the ridge depending on the direction and strength of the background tidal flow. This suggests that the observed high-wavenumber structure in the flow profiles near the ridge is ascribed to the superposition of transient internal wave modes, although this is not the main cause of the temperature inversions. As a possible mechanism to explain the temperature inversions, we propose that higher-mode internal waves emanating from the unresolved topographic undulations are trapped by the observed high-wavenumber structures, resulting in turbulent mixing.

The present work investigates leading modes of winter fog days over eastern China and possible association with sea surface temperature (SST) variability. Based on the Empirical Orthogonal Function (EOF) analysis, two dominant interannual modes of winter fog days are identified: a monopole mode and a meridional dipole mode. The monopole mode displays a significantly positive relationship with El Nino-Southern Oscillation (ENSO). The meridional dipole mode is closely linked to North Atlantic tripole (NAT) SST anomalies. A quasi-barotropic Rossby wave train can be excited by the NAT SST anomalies and propagates eastwards to East Asia. During winters with the positive phase of the NAT SST anomalies, there appear cyclonic and anticyclonic circulation anomalies over northern and southern China, favoring less and more winter fog frequency, respectively. These observed impacts from the ENSO and NAT SST anomalies can be further reproduced by atmospheric general circulation model (AGCM) experiments. Consideration of the NAT SST anomalies can apparently improve the explained variance of winter fog days over eastern China on the basis of the common-used ENSO signal. When ENSO and NAT occur as in-phase combinations and out-of-phase combinations, winter fog days anomalies appear over southern and northern China, respectively. These results have important implications on the seasonal-to-interannual predictability of the winter fog frequency over eastern China.

The calcareous screes are very well represented in Meridional Carpathians, especially in Piatra Craiului Mountains. The paper analyzes the vegetation of these natural habitats from phytosociological point of view. There are 11 plant associations characteristic for calcareous screes in this region, as follows: Cerastio lerchenfeldiani-Papaveretum Boşcaiu, Täuber et Coldea 1977, Cardaminopsio neglectae-Papaveretum Coldea et Pânzaru 1986, Acino-Galietum anisophylli Beldie 1967, Doronico columnae-Rumicetum scutati Boşcaiu et al. 1977, Saxifragetum moschatae-aizoidis Boşcaiu 1971, Cerastio transsilvanici-Galietum lucidi M. Boșcaiu et al. 1998, Achnatheretum calamagrostis Br.- Bl. 1918, Gymnocarpietum robertianae (Kaiser 1926) Tx. 1937, Sedo fabariae-Geranietum macrorrhizi Boşcaiu et Täuber 1977, Thymetum comosi Pop et Hodişan 1963, Parietarietum officinalis Csűrös 1958. The plant associations were characterized and the Relative Euclidean distance was calculated on the basis of the Ward method. The hierarchical analysis revealed the distribution of the plant associations in two clusters corresponding to the Papavero-Thymion pulcherrimi I. Pop 1968 and Stipion calamagrostis Jenny-Lips ex Br.-Bl. 1950 alliances.

Relative impacts of the climatological annual mean, the climatological annual variation, the synoptic, the intra-seasonal and the inter-annual flows on meridional moisture transport were investigated based on reanalysis data. Due to an in-phase relationship between the poleward wind and specific humidity, the synoptic and intra-seasonal motions contribute about 50% and 30% of the maximum zonal and annual mean poleward moisture transport in the middle latitudes, respectively. The preferred latitudinal location (40°N or S) of the maximum zonal mean moisture transport by the synoptic motion is attributed to the combined effect of the maximum wind variability poleward of 40°N or S in association with atmospheric baroclinic instability and the maximum moisture variability equatorward of 40°N or S in association with the anomalous advection of the mean moisture. While the MJO and ENSO have a small contribution to the long-term mean transport, they may strongly affect regional moisture transport through interaction with the mean moisture and through the modulation to higher-frequency modes. A statistical relationship between tropical cyclone (TC) moisture and intensity was constructed based on a large number of high-resolution Weather Research and Forecasting (WRF) model simulations, and the so-derived relationship was further applied to estimate TC moisture transport. It is found that TC transport accounts for about 30% (53%) of the climatological seasonal mean total moisture transport over key northern (southern) hemispheric TC track regions in the northern (southern) hemispheric TC season.

Author(s): Kim, S; Chiang, JCH | Abstract: The range of synoptic patterns that North Pacific landfalling atmospheric rivers form under are objectively identified using genesis day 500 hPa geopotential height anomalies in a self-organizing map (SOM). The SOM arranges the synoptic patterns to differentiate between two groups of climate modes—the first group with ENSO (El Nino Southern Oscillation), PDO (Pacific Decadal Oscillation), PNA (Pacific North American) and NP (North Pacific index) and the second group with AO (Arctic Oscillation), EPO (East Pacific Oscillation), and WPO (West Pacific Oscillation). These two groups have their positive and negative modes organized in opposite corners of the SOM. The ARs produced in each of the synoptic patterns have distinct lifecycle characteristics (such as genesis and landfall location, duration, velocity, meridional/zonal movement) and precipitation impacts (magnitude and spatial distribution). The conditions that favour AR trajectories closer to the tropics tend to produce higher amounts of precipitation. The large-scale circulation associated with AR genesis shows a close relationship between the genesis location and the location and intensity of the upper-level jet in the west/central pacific as well as anomalous, low-level southwesterly winds in the east pacific.

Atmospheric water vapor content (WVC) is a critical factor for East Asian winter precipitation. This study investigates the dominant modes of interannual variability in WVC over East Asia during winter and their underlying mechanisms. Based on the empirical orthogonal function (EOF) method, the leading mode (EOF1, R2 = 28.9%) of the interannual variability in the East Asian winter WVC exhibits a meridional dipole pattern characterized by opposite WVC anomalies over northeastern China and eastern China; the second mode (EOF2, R2 = 24.3%) of the interannual variability in the East Asian winter WVC exhibits a monopole pattern characterized by consistent WVC anomalies over eastern China. EOF1 is mainly modulated by two anomalous zonal water vapor transport (WVT) branches over northeastern China and eastern China, which are associated with an anomalous atmospheric wave train over Eurasia affected by sea ice cover in the Kara Sea-Barents Sea (SIC-KSBS) area in the preceding October-November (ON). EOF2 is mainly modulated by an anomalous westerly WVT branch over eastern China, which is associated with a circumglobal atmospheric zonal wave train in the Northern Hemisphere. This circumglobal zonal wave train is modulated by concurrent central and eastern tropical Pacific sea surface temperature anomalies. The SIC-KSBS anomalies in ON and the concurrent SST anomalies over tropical Pacific may partially account for the interannual variability of EOF1 and EOF2 winter WVC, and thus may provide a theoretical basis for improving the prediction of winter climate over East Asia.

In this study, we analyzed 1979–2019 daily ERA-Interim reanalysis data in winter and performed atmospheric circulation experiments to examine the modulation of Arctic sea ice in western Greenland (Baffin Bay, Davis Strait, and the Labrador Sea, BDL) on winter Greenland blockings. It is found that low BDL sea ice and high BDL surface temperature favor frequent, long-lived, westward-moving Greenland blockings in winter, which cause frequent and strengthening cold surges over the mid-eastern United States. In contrast, high BDL sea ice and low BDL surface temperature favor short-lived, less frequent and quasi-stationary Greenland blockings, mainly leading to cold anomalies in North Europe. Low wintertime BDL sea ice reduces the background potential vorticity meridional gradient (PVy) and zonal wind over the mid-high latitudes of the North Atlantic, which enhances the nonlinearity of Greenland blocking, accelerates the phase speed of its westward movement, and weakens its energy dispersion, thus favoring the occurrence and persistence of Greenland blocking. High BDL sea ice strengthens the background PVy and zonal wind in the mid-high latitudes of the North Atlantic, which weakens the nonlinearity and movement of Greenland blocking, enhances its energy dispersion, and thus suppresses the occurrence and persistence of Greenland blocking and its retrogression. A set of atmospheric circulation experiments supports the above results based on the reanalysis dataset.

Statistical relationships are investigated between changes in total Arctic sea ice volume and variations in mean meridional velocities of air crossing the corresponding sections of the southern Arctic boundary during the summer months in 1979-2018. A consistent significant correlation between the ice volume and northerly wind speeds in the lower tropospheric layers is revealed for the Siberian sector. An increase in the analyzed correlation is found in 2012-2020 for all Northern Hemisphere sectors, except for the Atlantic one, which is supposedly due to the decrease in mean solar activity levels taking place against the intensifying global climate warming.

A facile two-step synthesis of bis(1-methylhydrazinyl)pyrimidine from pyridine-2-carbaldehyde and 2-diphenylphosphanylbenzaldehyde gave access to the new asymmetric ligand 1. The phosphane selectively guides PdII into the softer tridentate N,N,P pocket, yielding monometallic complex 2. A second reaction with a 3d transition metal complex precursor (groups 7 to 12) fills the vacant N,N,N pocket and thus provides a variety of heterobimetallic complexes of the type PdII/MII (M = Mn (3), Fe (4), Co (5), Ni (6), Cu (7), Zn (8)). Single-crystal X-ray diffraction studies were performed for all complexes. The assembly of μ2-chlorido-bridged dimers was observed for complexes 5-7 in the solid state, while DOSY NMR experiments have shown that 5-7 are unbridged monomers in solution. As an exception, FeII prefers to form the homoleptic meridional complex [Fe{PdCl(1)}2](OTf)4 (4). The electrochemical behavior and the effective magnetic moment in solution were investigated for all complexes by cyclic voltammetry and Evans method, respectively. Experimental UV/vis results were interpreted by performing TD-DFT calculations on 1, 2, and 3.

A known adverse side effect of stratospheric aerosol modification (SAM) is the alteration of the quasi-biennial oscillation (QBO), which is caused by the stratospheric heating associated with an artificial aerosol layer. Multiple studies found the QBO to slow down or even completely vanish for point-like injections of SO2 at the Equator. The cause for this was found to be a modification of the thermal wind balance and a stronger tropical upwelling. For other injection strategies, different responses of the QBO have been observed. A theory which is able to explain those differences in a comprehensive manner has not yet been presented. This is further complicated by the fact that the simulated QBO response is highly sensitive to the used model even under identical boundary conditions. Therefore, within this study we investigate the response of the QBO to SAM for three different injection strategies (point-like injection at the Equator, point-like injection at 30∘ N and 30∘ S simultaneously, and areal injection into a 60∘ wide belt along the Equator). Our simulations confirm that the QBO response significantly depends on the injection location. Based on the thermal wind balance, we demonstrate that this dependency is explained by differences in the meridional structure of the aerosol-induced stratospheric warming, i.e., the location and meridional extension of the maximum warming. Additionally, we also tested two different injection species (SO2 and H2SO4). The QBO response is qualitatively similar for both investigated injection species. Comparing the results to corresponding results of a second model, we further demonstrate the generality of our theory as well as the importance of an interactive treatment of stratospheric ozone for the simulated QBO response.

Since its launch in 2018, the European Space Agency’s Earth Explorer satellite Aeolus has provided global height resolved measurements of horizontal wind in the troposphere and lower stratosphere for the first time. Novel datasets such as these provide an unprecedented opportunity for the research of atmospheric dynamics and provide new insights into the dynamics of the upper troposphere and lower stratosphere (UTLS) region. Aeolus measures the wind component along its horizontal line-of-sight, but for the analysis and interpretation of atmospheric dynamics, zonal and/or meridional wind components are most useful. In this paper, we introduce and compare three different methods to derive zonal and meridional wind components from the Aeolus wind measurements. We find that the most promising method involves combining Aeolus measurements during ascending and descending orbits. Using this method, we derive global estimates of the zonal wind in the latitude range 79.7° S to 84.5° N with errors of less than 5 ms−1 (at the 2-sigma level). Due to the orbit geometry of Aeolus, the estimation of meridional wind in the tropics and at midlatitudes is more challenging and the quality is less reliable. However, we find that it is possible to derive meridional winds poleward of 70° latitude with absolute errors typically below ±5 ms−1 (at the 2-sigma level). This further demonstrate the value of Aeolus wind measurements for applications in weather and climate research, in addition to their important role in numerical weather prediction.

Objective. To investigate the influence of the optic-reflex method of accommodation training on the indices of the meridional separable visual acuity in the treatment of children with amblyopia and astigmatism. Material and methods. 24 children aged 5 to 12 years with refractive amblyopia and direct hyperopic astigmatism were examined. Accommodation training was performed by defocusing the image with optical glasses of variable optical power. The course of treatment lasted 10 days. Results. In the group with meridional amblyopia, 2 different clusters were identified: in one of them, the indicators of separable visual acuity were higher in the horizontal meridian and in the other - in the vertical. After treatment, the number of eyes with the same meridional visual acuity increased. Simultaneously with the elimination of the meridional asymmetry of visual acuity, the number of eyes in the category of patients with visual acuity of 0.75-0.8 according to the Sivtsev table increased by 8.52%. Conclusion. In the standard of assessment of visual functions in patients with astigmatism and amblyopia, it is necessary to introduce methods for determining the meridional visual acuity. Evaluation of the effectiveness of treatment of meridional amblyopia should be carried out in homogeneous clusters, which take into account the coincidence or discrepancy of the directions of meridional asymmetries of visual acuity with refractive. Preliminary data on the effectiveness of treatment of amblyopia by the method of accommodation training allows us to consider it as a method of treatment of meridional amblyopia.

This study investigates the role of the background meridional moisture gradient (MMG) on the propagation of the Madden–Julian Oscillation (MJO) across the Maritime Continent (MC) region. It is found that the interannual variability of the seasonal mean MMG over the southern MC area is associated with the meridional expansion and contraction of the moist area in the vicinity of the MC. Sea surface temperature anomalies associated with relatively high and low seasonal mean MMG exhibit patterns that resemble those of the El Niño–Southern Oscillation. By contrasting the years with anomalously low and high MMG, we show that MJO propagation through the MC is enhanced (suppressed) in years with higher (lower) seasonal mean MMG, though the effect is less robust when MMG anomalies are weak. Column-integrated moisture budget analysis further shows that sufficiently large MMG anomalies affects MJO activity by modulating the meridional advection of the mean moisture via MJO wind anomalies. Our results suggest that the background moisture distribution has a strong control over the propagation characteristics of the MJO in the MC region.

Extratropical cyclones (ETCs) over East Asia and Northwest Pacific are identified and tracked by applying an objective algorithm to the 850-hPa relative vorticity fields from the ERA-Interim reanalysis. A total of 2866 ETCs originating at the western side of the date line have been identified in the extended November–March winters from 1979 to 2018. The ETC tracks are counted and visualized using a hexagonal tessellation rather than the regular longitude–latitude grids. Two generalized linear models (GLMs), Poisson regression model and Gamma regression model, are firstly applied to investigate the associations of wintertime ETCs with three atmospheric teleconnection patterns. The West Pacific (WP) pattern and the Pacific/North American (PNA) pattern are more responsible for the meridional variability of ETC activities in the North Pacific, while the influence of the Polar/Eurasia pattern on ETC activities is negligible. Results of composite analysis are qualitatively consistent with that of regression analysis. Composite maps of differences of jet stream, thermal gradient and mid-tropospheric baroclinicity in the positive and negative phases of teleconnection patterns also support the close associations of ETC activities with WP and PNA teleconnection patterns.

The western North Pacific (WNP) intraseasonal oscillation (ISO) is the strongest over the globe, its prediction is the cornerstone for subseasonal prediction of the Asian summer monsoon. Yet, our understanding of the diversity of the WNP ISO is limited, which challenges our modeling and prediction efforts. We study the diversity of observed WNP ISO by performing cluster analysis on propagation patterns of ISO events, targeting three clusters: westward, northeastward, and northwestward propagations. The westward cluster exists within the WNP, while the other two are related to the northeastward propagating rain band originated from the central equatorial Indian Ocean and to the northwestward propagating dipole across the western Pacific and Indian Ocean, respectively. Moist static energy (MSE) tendency contributing to these different propagations is mainly due to horizontal advection, while radiative heating mainly maintains the ISO’s development. Background sea surface temperature (SST) and MSE anomalies partly determine this ISO diversity, especially for those ISOs with large similarity. The westward cluster is related to warm SST anomalies in the western Indian Ocean, as a combination of seasonal cycle and internal interannual-to-interdecadal variability. The northeastward cluster is related to the cold Pacific Meridional Mode and La Nina-like pattern, while the northwestward cluster is related to the opposite warm background, both as the internal variability. Our finding of the background-affected ISO diversity over the WNP can be conducive to both model simulation and subseasonal prediction of the Asian summer monsoon.

The relationship between the Warm Water Volume (WWV) ENSO precursor and ENSO SST weakened substantially after ~2000, coinciding with a degradation in dynamical model ENSO prediction skill. It is important to understand the drivers of the equatorial thermocline temperature variations and their linkage to ENSO onsets. In this study, a set of ocean reanalyses is employed to assess factors responsible for the variation of the equatorial Pacific Ocean thermocline during 1982-2019. Off-equatorial thermocline temperature anomalies carried equatorward by the mean meridional currents associated with Pacific Tropical Cells are shown to play an important role in modulating the central equatorial thermocline variations, which is rarely discussed in the literature. Further, ENSO events are delineated into two groups based on precursor mechanisms: the western equatorial type (WEP) ENSO, when the central equatorial thermocline is mainly influenced by the zonal propagation of anomalies from the western Pacific, and the off-equatorial central Pacific (OCP) ENSO, when off-equatorial central thermocline anomalies play the primary role. WWV is found to precede all WEP ENSO by 6-9 months, while the correlation is substantially lower for OCP ENSO events. In contrast, the central tropical Pacific (CTP) precursor, which includes off-equatorial thermocline signals, has a very robust lead correlation with the OCP ENSO. Most OCP ENSO events are found to follow the same ENSO conditions, and the number of OCP ENSO increases substantially since the 21st century. These results highlight the importance of monitoring off-equatorial subsurface preconditions for ENSO prediction and to understand multi-year ENSO.

The onset of the South China Sea summer monsoon (SCSSM) has traditionally been ascribed to the El Niño–Southern Oscillation (ENSO) on an interannual timescale, but the two do not correspond in some years. The present study applies harmonic analysis on the meridional temperature gradient (MTG) in mid–upper troposphere over South China Sea (SCS) and decomposes the onset process to be a slow-varying seasonal cycle and transient subseasonal component. The ENSO-related air temperature anomaly in the southern SCS provides seasonal predictability of SCSSM onset by a stable and robust relationship between ENSO and MTG seasonal cycle. However, in the northern SCS, the MTG is regulated by an intraseasonal oscillation (ISO) of extratropical air temperature with a significant 10–30-day period. This ISO originates over the western TP, then propagates eastward and gets enhanced by anomalous diabatic heating due to spring rainfall anomaly over South China, as a result of subseasonal thermal forcing of TP. When the ISO arrives to the north of the SCS, it directly changes the tropospheric temperature to modulate the MTG. Meanwhile, the upper-level circulation associated with the ISO alters the meridional potential vorticity advection and pumping effect, followed by the anomalous low-level westerly wind and monsoon convection over the SCS. The SCSSM onset is evidently disrupted from its seasonal cycle when this ISO is more active. Since the independence of its intensity from ENSO, this extratropical ISO over TP and South China provides additional subseasonal predictability of the onset dates of the SCSSM.

Summer precipitation totals in the Alpine Region do not exhibit a systematic trend over the last 120 years. However, we find significant low frequency periodicity of interannual variability which occurs in synchronization with a dominant two-phase state of the atmospheric circulation over the Alps. Enhanced meridional flow increases precipitation variability through positive soil moisture precipitation feedbacks on the regional scale, whereas enhanced zonal flow results in less variability through constant moisture flow from the Atlantic and suppressed feedbacks with the land surface. The dominant state of the atmospheric circulation over the Alps in these periods appears to be steered by zonal sea surface temperature gradients in the mid-latitude North Atlantic. The strength and the location of the westerlies in the mid-latitude Atlantic play an important role in the physical mechanisms linking atmosphere and oceanic temperature gradients and the meridional/zonal circulation characteristics.

Arctic amplification refers to the greater surface warming of the Arctic than of other regions during recent decades. A similar phenomenon occurs in the troposphere and is termed “tropospheric Arctic amplification” (TAA). The poleward eddy heat flux and eddy moisture flux are critical to Arctic warming. In this study, we investigate the synoptic transient eddy activity over the North Pacific associated with TAA and its relationship with the subtropical jet stream, and propose the following mechanism. A poleward shift of the subtropical jet axis results in anomalies of the meridional gradient of zonal wind over the North Pacific, which drive a meridional dipole pattern of synoptic transient wave intensity over the North Pacific, referred to as the North Pacific Synoptic Transient wave intensity Dipole (NPSTD). The NPSTD index underwent an interdecadal shift in the late 1990s accompanying that of the subtropical jet stream. During the positive phase of the NPSTD index, synoptic eddy heat flux transports more heat to the Arctic Circle, and the eddy heat flux diverges, increasing Arctic temperature. This mechanism highlights the need to consider synoptic transient eddy activity over the North Pacific as the link between the mean state of the North Pacific subtropical upper jet and TAA.

In contrast to decreased Arctic sea ice extent, Antarctic sea ice extent shows a somewhat increased trend. There is a large interannual variability of Antarctic sea ice, especially in the Pacific sector of the Southern Ocean. The change and variability of Antarctic sea ice in synoptic timescales in the recent decades remain unclear. We identify synoptic modes of variability of Antarctic summer sea ice by applying the Self Organizing Map (SOM) technique to daily sea ice concentration data for the period 1979–2018. Nearly 40% of the variability is characterized by opposite changes between sea ice cover in the Bellingshausen, Amundsen and western Ross Seas and in the rest of the Antarctic seas, and another 30% by meridional asymmetry in the Weddell, Amundsen, and Ross Seas. Most of these spatial patterns may be explained by the dynamics and thermodynamic processes associated with anomalous atmospheric circulations related to the Southern Annular Mode (SAM) with a structure of strong zonal asymmetry. The interannual variability of the sea ice modes appears to have little connection to SAM, and only a weak relation to ENSO. The annual frequencies of SOM node occurrences also show a great decadal variability. Node 9 appears mainly prior to 1990; while node 1 occurs mainly after 1990. The decadal variability of nodes 1 and 9 is associated with the asymmetrical SAM, which results from two wavetrains excited over northern Australia and the southeastern Indian Ocean. These results further highlight the importance of understanding the role of southern mid-to-high latitude atmospheric intrinsic variability in predicting Antarctic summer sea ice variations from synoptic to decadal timescales.

Investigating Pacific Meridional Modes (PMM) without the influence of tropical Pacific variability is technically difficult if based on observations or fully coupled model simulations due to their overlapping spatial structures. To confront this issue, the present study investigates both North (NPMM) and South PMM (SPMM) in terms of their associated atmospheric forcing and response processes based on a mechanically decoupled climate model simulation. In this experiment, the climatological wind stress is prescribed over the tropical Pacific, which effectively removes dynamically coupled tropical Pacific variability (e.g., the El Niño-Southern Oscillation). Interannual NPMM in this experiment is forced not only by the North Pacific Oscillation, but also by a North Pacific tripole (NPT) pattern of atmospheric internal variability, which primarily forces decadal NPMM variability. Interannual and decadal variability of the SPMM is partly forced by the South Pacific Oscillation. In turn, both interannual and decadal NPMM variability can excite atmospheric teleconnections over the Northern Hemisphere extratropics by influencing the meridional displacement of the climatological intertropical convergence zone throughout the whole year. Similarly, both interannual and decadal SPMM variability can also excite atmospheric teleconnections over the Southern Hemisphere extratropics by extending/shrinking the climatological South Pacific convergence zone in all seasons. Our results highlight a new poleward pathway by which both the NPMM and SPMM feed back to the extratropical climate, in addition to the equatorward influence on tropical Pacific variability.

We examine the role of zonal Ekman transport along the coast of Senegal on 30 August 2015 when the tropical disturbance associated with Tropical Cyclone Fred was located to the west of Senegal, causing considerable coastal damage in the southern Senegal–Gambia domain (south of Dakar, Senegal). Ten-meter winds from three Weather Research and Forecast model simulations were used to estimate zonal Ekman transport, when the maximum values were found on 30 August. These simulations are in agreement with limited coastal observations showing increasing southerly wind speeds during 30 August but overestimated relative to the three coastal stations. The strong meridional winds translate into increased zonal Ekman transport to the coast of Senegal on 30 August and are likely responsible for some coastal flooding. Ekman transport along the coast contributes significantly to the water-level variations during swell events. The use of a coupled ocean model will improve the estimates of Ekman transport along the Guinea-Senegalese coast. The observed damage suggests that artificial and natural barriers (mangroves) should be strengthened to protect coastal communities in Senegal.

The interannual variability of summertime eddy-induced heat transport (EHT) in the western South China Sea (WSCS) is investigated based on the downgradient eddy diffusivity method and explored its formation mechanism. Estimations of long-term mean EHT and its monthly evolution reveal that the largest EHT in the SCS occurs in the WSCS region during the summer. In the WSCS, enhanced EHT and eddy kinetic energy (EKE) levels are simultaneously observed in 1994, 1999, 2002, 2006, 2008, 2009, 2012, 2014 whereas the lower EHT and EKE levels are observed in 1995, 2000, 2001, 2003, 2004, 2007, 2010, 2015, 2017 during JAS (July, August and September) months. Analysis of the Simple Ocean Data Assimilation, version 3.3.1 (SODAv3) data along 110.75° E reveals a strong surface intensification of the summertime eastward jet (SEJ) in the EHT-strong years than the EHT-weak years. Linear stability analysis conducted by adopting a 2 ½-layer reduced gravity model shows that the increased EHT in EHT-strong years is due to the enhanced baroclinic instability caused by the strong vertical shear developed through the surface-intensification of SEJ. The cause for the interannually varying vertical shear can be sought in the interannually varying meridional temperature gradient which is influenced by the combined forcing of the meridional Ekman flux convergence, meridional geostrophic flux convergence, and convergence of the latitudinally dependent surface heat flux forcing. It is also found that the interannual variations of EHT in the SCS are partially influenced by the local wind stress curl and remote forcing from the eastern boundary.

Long-lived metallic ions in the Earth's atmosphere (ionosphere) have been investigated for many decades. Although the seasonal variation in ionospheric “sporadic E” layers was first observed in the 1960s, the mechanism driving the variation remains a long-standing mystery. Here, we report a study of ionospheric irregularities using scintillation data from COSMIC satellites and identify a large-scale horizontal transport of long-lived metallic ions, combining the simulations of the Whole Atmosphere Community Climate Model with the chemistry of metals and ground-based observations from two meridional chains of stations from 1975–2016. We find that the lower thermospheric meridional circulation influences the meridional transport and seasonal variations of metallic ions within sporadic E layers. The winter-to-summer meridional velocity of ions is estimated to vary between −1.08 and 7.45 m/s at altitudes of 107–118 km between 10–60∘ N. Our results not only provide strong support for the lower thermospheric meridional circulation predicted by a whole atmosphere chemistry–climate model, but also emphasize the influences of this winter-to-summer circulation on the large-scale interhemispheric transport of composition in the thermosphere–ionosphere.

The objective was to evaluate the application of foliar nitrogen in different doses and times, as a complement to soil fertilization. The work was conducted in a rural area of the municipality of Terra Nova do Norte – MT, located in the southern of brazilian Amazon. The treatments were a combination of foliar applications of nitrogen at doses of 0, 250, 500 and 750 mL.ha-1, and two application times with different intervals: 15 and 40 days after emergence; and 25 and 40 days after the emergency. The experimental design was a randomized block with four replications, in a factorial 4 x 2, totaling eight treatments. It was found that the variables green mass productivity and dried plant and ear and ear length responded positively as the N rates and application times. It was also observed that the foliar application of nitrogen increased the productivity of corn for silage, and better results are obtained from 750 mL.ha-1 of the studied leaf fertilizer. There was no increase in production factors when the foliar application of nitrogen was split.

Atmospheric feedback involved in the occurrence of coastal upwelling in a small semi-enclosed sea basin, i.e., the Baltic Sea, was analysed, and the regional circulation conditions triggering upwelling in different coastal sections were identified. Upwelling in the summer season (June–August, years 1982–2017) was recognized on the basis of sea surface temperature patterns. Circulation conditions were defined using (1) the established daily indices of zonal and meridional airflow and (2) the synoptic situation at sea level distinguished by applying rotated principal component analysis to sea level pressure data. The 12 daily synoptic patterns differed substantially in the intensity and location of their pressure centres. The mean seasonal frequency of upwelling was generally higher along the western Baltic shores than along the meridionally oriented eastern shores and varied from less than 10 to over 30% along the more predestined coastal sections, i.e., the northwestern coast of the Gulf of Bothnia, the northern Gulf of Finland and the southern Swedish coast. Due to the variable orientations of coastlines, upwelling could occur under almost any prevailing wind direction, and thus, each of the classified synoptic patterns could induce upwelling in some coastal sections. As deduced from the pressure fields for each circulation pattern, mostly alongshore winds triggered upwelling, which is in line with the Ekman rule. With time, upwelling could also be induced by the stress of normal to the coastline seaward winds.

Quasi-decadal climate of the Kuroshio Extension (KE) is pivotal to understanding the North Pacific coupled ocean–atmosphere dynamics and their predictability. Recent observational studies suggest that extratropical-tropical coupling between the KE and the central tropical Pacific El Niño Southern Oscillation (CP-ENSO) leads to the observed preferred decadal time-scale of Pacific climate variability. By combining reanalysis data with numerical simulations from a high-resolution climate model and a linear inverse model (LIM), we confirm that KE and CP-ENSO dynamics are linked through extratropical-tropical teleconnections. Specifically, the atmospheric response to the KE excites Meridional Modes that energize the CP-ENSO (extratropicstropics), and in turn, CP-ENSO teleconnections energize the extratropical atmospheric forcing of the KE (tropicsextratropics). However, both observations and the model show that the KE/CP-ENSO coupling is non-stationary and has intensified in recent decades after the mid-1980. Given the short length of the observational and climate model record, it is difficult to attribute this shift to anthropogenic forcing. However, using a large-ensemble of the LIM we show that the intensification in the KE/CP-ENSO coupling after the mid-1980 is significant and linked to changes in the KE atmospheric downstream response, which exhibit a stronger imprint on the subtropical winds that excite the Pacific Meridional modes and CP-ENSO.