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The Southern Hemisphere storm track is a key component of the Earth’s global circulation patterns, with a prominent role in the movement of heat and momentum across the mid-latitudes, and a controlling influence over the behaviour of synoptic eddies. Storm track characteristics are expected to change with anthropogenic forcings, leading to changes in regional weather patterns, and impacting communities through its influence on extreme events. We document projected storm track climatologies at the end of the 21st century under high- and low-emissions scenarios using the CMIP6 generation of models. We find previously described projections – the poleward migration of the storm track, and intensification of storm activity – persist in CMIP6. We explore projections of spatio-temporal variability of the Southern Annular Mode, and consequences for the storm track.

ERA5 reanalysis is used to examine extreme precipitation using a spatially dependent precipitation threshold applied within a cyclone compositing framework. This is used to account for regional variation in precipitation generating processes within Southern Hemisphere mid-latitude cyclones across the cyclone lifecycle. The spatial extent of extreme precipitation is limited to a smaller region around the cyclone centre compared to non-extreme precipitation, though extreme precipitation displays a good spatial correlation with non-extreme precipitation. Extreme precipitation occurs more often during the deepening phase of the cyclone before it reaches a maximum depth. Precipitation occurrence at the 90th and 98th percentiles reduces to 46% and 30% of the deepening value across the cyclone lifecycle, averaged over the composite. Precipitation fraction at the 90th and 98th percentile reduces to 80% and 60% of the deepening value. Our methodology provides a quantitative assessment of precipitation extremes both spatially and temporally, within a cyclone compositing framework.

Storm tracks are a key component of global atmospheric circulation. Their influence ranges from macro- to mesoscale dynamics, from large-scale movement of heat and momentum to extreme weather events. The scale of their impact makes understanding storm track dynamics critical to forecasting and climate projections. In this study, we assess CMIP6 historical experiment fidelity to observations of the Southern Hemisphere storm track. Specifically, storm track climatology, variability, and its interactions with low-frequency variability, with the aim of providing confidence for projections of future climate. We find CMIP6 models replicate results from the ERA-5 reanalysis with high fidelity in some regards; namely, capturing climatology of the 500hPa geopotential height field, the role of large-scale variability, and the baroclinic connection with high-frequency variability. However, models fail to capture the magnitude and variability of the storm track, particularly canonical zonal asymmetry. Our results indicate the importance of the storm track is underestimated in CMIP6.

ERA5 reanalysis output is compared to WindSat measurements over cyclones at Southern Hemisphere mid- to high-latitudes. WindSat provides an independent measure of how well ERA5 represents cyclones, as WindSat is not assimilated into ERA5. We implement a tracking scheme to identify cyclone centres and tracks, before using cyclone composites to match concurrent data in ERA5 and WindSat. We find that both ERA5 and WindSat show comparable spatial structures for low level wind speed, total column water vapour, cloud liquid water and precipitation. Compared to WindSat, ERA5 underestimates total column water vapour by up to 5\% and cloud liquid water by up to 40\%. ERA5 underestimates precipitation in the warm sector by up to 15\%, but overestimates in the cold sector by up to 60\%. Similar biases in ERA5 are seen when comparing to AMSR-E data, even though AMSR-E radiances are assimilated into ERA5. Comparing ERA5 and WindSat across the cyclone lifecycle, a strong correlation is seen across the cyclone as it deepens and reaches peak intensity, before slightly declining as the cyclone decays. In the cold sector ERA5 shows underestimation of cloud liquid water, yet overestimates precipitation at all lifecycle stages. However, in the warm sector precipitation is underestimated. This potentially suggests the presence of biases within the ERA5 parameterisations of cloud and precipitation causing a disconnect between the two. Despite this, ERA5 shows strong correlation with WindSat and determines cyclone structure well across the cyclone lifecycle, showing its value for use in cyclone compositing analysis.

Here we examine the water stable-isotope data from the Roosevelt Island Climate Evolution (RICE) ice core. Roosevelt Island is an independent ice rise located at the northeastern margin of the Ross Ice Shelf. In this study, we use empirical orthogonal function (EOF) analysis to investigate the relationship between RICE ice-core oxygen-18 isotopes (δ18O) and Southern Hemisphere atmospheric circulation during the extended austral winter (April–November). The RICE δ18O record is correlated with Southern Annular Mode (SAM) and Pacific–South American pattern 1 (PSA1), which both project onto the Amundsen–Bellingshausen Sea (ABS) geopotential height field. Pacific sector Southern Ocean, eastern Ross Sea, and West Antarctic’s atmospheric circulation, sea ice, and surface air temperature (SAT) anomalies, as well as RICE δ18O, are strongest when El Niño–Southern Oscillation (ENSO) and SAM are “in-phase”. That is when the SAM−/PSA1+ (El Niño) and SAM+/PSA1− (La Niña) phasing prevails. When in-phase, the δ18O correlation with the 500-hPa geopotential height (Z500) is strong in regions (e.g., the Amundsen Sea) where their anomalies associated with SAM and PSA1 show the same sign. SAM−/PSA1+ (El Niño) and SAM+/PSA1− (La Niña) is associated with positive and negative δ18O anomalies, respectively. RICE δ18O can aid in establishing past natural variability of the strength of the SH high-latitude Pacific sector ENSO-SAM connection and associated atmospheric circulation, SIC, and SAT extremes.

This paper introduces a set of descriptors applied to weather regimes, that allow for a detailed monitoring of the location and intensity of their atmospheric centers of action (e.g. troughs and ridges) and the gradients between them, when applicable. Descriptors are designed to document the effect of climate variability and change in modulating the character of daily weather regimes, rather than merely their occurrence statistics.As a case study, the methodology is applied to Aotearoa New Zealand (ANZ), using ERA5 ensemble reanalysis data for the period 1979-2019. Here, we analyze teleconnections between the regimes and their descriptors, and large-scale climate variability. Results show a significant modulation of centers of action by the phase of the Southern Annular Mode, with a strong relationship identified with the latitude of atmospheric ridges. Significant associations with El Niño Southern Oscillation are also identified. Modes of large-scale variability have a stronger influence on the regimes’ intrinsic features than their occurrence. This demonstrates the usefulness of such descriptors, which help understand the relationship between mid-latitude transient perturbations and large-scale modes of climate variability.In future research, this methodological framework will be applied to analyze (i) low-frequency changes in weather regimes under climate change, in line with the southward shift of storm tracks, and (ii) regional-scale effects on the climate of ANZ, resulting from interaction with its topography.

Over the last three decades, the South Pole has experienced a record-high statistically significant warming of 0.61 ± 0.34 °C per decade, more than three times the global average. Here, we use an ensemble of climate model experiments to show this recent warming lies within the upper bounds of the simulated range of natural variability. The warming resulted from a strong cyclonic anomaly in the Weddell Sea caused by increasing sea surface temperatures in the western tropical Pacific. This circulation, coupled with a positive polarity of the Southern Annular Mode, advected warm and moist air from the South Atlantic into the Antarctic interior. These results underscore the intimate linkage of interior Antarctic climate to tropical variability. Further, this study shows that atmospheric internal variability can induce extreme regional climate change over the Antarctic interior, which has masked any anthropogenic warming signal there during the twenty-first century. Surface air temperatures at the South Pole warmed at over three times the global rate in recent decades. Research shows this trend was driven remotely by the tropics and locally by a positive phase of the Southern Annular Mode, increasing the influx of warm moist air atop anthropogenic warming.

During austral summers (DJF) 1934/35, 2017/18 and 2018/19, the New Zealand (NZ) region (approximately 4 million km2) experienced the most intense coupled ocean-atmosphere heatwaves on record. Average air temperature anomalies over land were + 1.7 to 2.1 °C while sea surface temperatures (SST) were 1.2 to 1.9 °C above average. All three heatwaves exhibited maximum SST anomalies west of the South Island of NZ. Atmospheric circulation anomalies showed a pattern of blocking centred over the Tasman Sea extending south-east of NZ, accompanied by strongly positive Southern Annular Mode conditions, and reduced trough activity over NZ. Rapid melt of seasonal snow occurred in all three cases. For the two most recent events, combined ice loss in the Southern Alps was estimated at 8.9 km3 (22% of the 2017 volume). Sauvignon blanc and Pinot noir wine grapes had above average berry number and bunch mass in 2018 but were below average in 2019. Summerfruit harvest (cherries and apricots) was 14 and 2 days ahead of normal in 2017/18 and 2018/19 respectively. Spring wheat simulations suggested earlier flowering and lower grain yields compared to average, and below-average yield and tuber quality in potatoes crops occurred. Major species disruption occurred in marine ecosystems. Hindcasts indicate that the heatwaves were either atmospherically driven or arose from combinations of atmospheric surface warming and oceanic heat advection.

Two reports of Antarctic region potential new record high temperature observations (18.3°C, 6 February 2020 at Esperanza station and 20.8°C, 9 February 2020 at a Brazilian automated permafrost monitoring station on Seymour Island) were evaluated by a World Meteorological Organization (WMO) panel of atmospheric scientists. The latter figure was reported as 20.75°C in the media. The panel considered the synoptic situation and instrumental setups. It determined that a large high pressure system over the area created föhn conditions and resulted in local warming for both situations. Examination of the data and metadata of the Esperanza station observation revealed no major concerns. However, analysis of data and metadata of the Seymour Island permafrost monitoring station indicated that an improvised radiation shield led to a demonstrable thermal bias error for the temperature sensor. Consequently, the WMO has accepted the 18.3°C value for 1200 LST 6 February 2020 (1500 UTC 6 February 2020) at the Argentine Esperanza station as the new “Antarctic region (continental, including mainland and surrounding islands) highest temperature recorded observation” but rejected the 20.8°C observation at the Brazilian automated Seymour Island permafrost monitoring station as biased. The committee strongly emphasizes the permafrost monitoring station was not badly designed for its purpose, but the project investigators were forced to improvise a nonoptimal radiation shield after losing the original covering. Second, with regard to media dissemination of this type of information, the committee urges increased caution in early announcements as many media outlets often tend to sensationalize and mischaracterize potential records.

This study contributes to an improved understanding of Central Southwest Asia (CSWA) wintertime (November–April) precipitation by analyzing the dominant spatial–temporal modes of the regional winter precipitation and examining their relationship with global sea surface temperature (SST) and large-scale atmospheric circulation fields, for 1950/51–2014/15. Empirical orthogonal function (EOF) analysis results show that the first mode (EOF-1) of winter precipitation is characterized by a mono-sign pattern, with significant links to El Nino-Southern Oscillation (ENSO). EOF-2 displays a north–south dipole related to the latitudinal shift in the jet stream position, while the west–east dipole in EOF-3 appears to be influenced by the thermal contrast between the equatorial regions and higher latitudes. Further, we focus on the interdecadal change of connection between wintertime ENSO and EOF-1 observed around the early 1980s. The relationship is weak during 1950/51–1983/84 (P1), but strong and statistically significant in 1984/85–2014/15 (P2). In P1, without the ENSO signal, EOF-1 related atmospheric circulation anomalies are confined mainly over the mid- to high-latitudes of the Northern Hemisphere, associated with the extratropical East Atlantic–Western Russia (EA–WR) teleconnection. In P2, however, a close connection to the tropical Pacific is observed that includes a pronounced SST expression similar to that of ENSO. As a result of the increased relationship between ENSO and EOF-1 in P2, the regional impact of EA–WR observed over CSWA in P1 is linearly superimposed by the anomalous hemispheric–wide atmospheric response forced by the ENSO conditions in the Pacific.

The South Pacific convergence zone (SPCZ) is the largest rainfall feature in the Southern Hemisphere, and is a critical component of the climate for South Pacific island nations and territories. The small size and isolated nature of these islands leaves them vulnerable to short- and long-term changes in the position of the SPCZ. Its position and strength is strongly modulated by El Niño–Southern Oscillation (ENSO), leading to large interannual variability in rainfall across the southwest Pacific including seasonal droughts and pluvials. Currently much of the analysis about SPCZ activity has been restricted to the satellite observation period starting in 1979. Here, the representation of the SPCZ in the Twentieth Century Reanalysis (20CR), which is a three-dimensional atmospheric reconstruction based only on surface observations, is discussed for the period since 1908. The performance of two versions of the 20CR (version 2 and version 2c) in the satellite era is compared with other reanalyses and climate observation products. The 20CR performs well in the satellite era. Extra surface observations spanning the SPCZ region from the longitude of the Cook Islands has improved the representation of the SPCZ during 1908–57 between 20CRv2 and 20CRv2c. The well-established relationship with ENSO is observed in both the representation of mean SPCZ position and intensity, and this relationship remains consistent through the entire 1908–2011 period. This suggests that the ENSO–SPCZ relationship has remained similar over the course of the past century, and gives further evidence that 20CRv2c performs well back to 1908 over the southwest Pacific region.

An assessment has been made of the ability of the UK Met Office Unified Model (UM) to simulate the Antarctic stratospheric circumpolar vortex and, in particular, the extent to which the vortex acts as a barrier to meridional transport. It is important that models simulate this barrier well as it determines spatial gradients in radiatively active gases, such as ozone, which then determine the spatial morphology of the radiative forcing field. The assessment was made by comparing metrics of meridional impermeability calculated from dynamical fields extracted from UM simulations and from analogous fields obtained from NCEP-CFSR reanalysis. Two different UM configurations were assessed: global atmosphere 3.0 (GA3.0) using the New Dynamics dynamical core, and GA7.0 using the newer ENDGame dynamical core, with both versions run at N96 resolution (1.25 $$^{\circ }$$ latitude by 1.875 $$^{\circ }$$ longitude). The GA7.0 configuration appears to better simulate the dynamical isolation of the Antarctic stratospheric vortex in the lower stratosphere up to about 600 K, while GA3.0 provides a better simulation in the upper stratosphere. However, neither UM configuration simulates the same degree of dynamical isolation suggested by the reanalysis. In particular the UM configurations produce a wider and more poleward meridional band of high wind-speed and steep PV gradients when compared with the NCEP-CFSR reanalysis, leading to a stronger barrier in GA7.0 and a weaker barrier in GA3.0. Possible causes of discrepancies between model simulations and reanalysis and between the two model configurations are discussed. It is pointed out that further work is needed to identify ways of resolving these discrepancies in model simulations.

Antarctica’s sea ice cover is an important component of the global climate system, yet the drivers of sea ice variability are not well understood. Here we investigated the effects of climate variability on sea ice concentration (SIC) around East Antarctica by correlating the 40-years (1979–2018) satellite sea ice record and ERA5 reanalysis data. We found that summer and autumn SIC around Dronning Maud Land (DML) between 10 and 70°E exhibited a statistically significant negative correlation with the Nino 3.4 index. Sea ice in DML was also correlated with sea surface temperature (SST) anomalies in the tropical Pacific, and to an atmospheric wave train pattern extending from the South Pacific to DML. We suggest that a southward-propagating atmospheric wave train triggered by SST anomalies in the tropical Pacific extends into DML and alters sea ice concentration by encouraging meridional airflow. Our results showed that shifts in meridional flow in DML affected sea ice thermodynamically, by altering local heat transport and in turn altering sea ice formation and melt.Isaacs, Renwick, Mackintosh & Dadic, 2021, ENSO Modulates Summer and Autumn Sea Ice Variability Around Dronning Maud Land, Antarctica, 'Journal of Geophysical Research: Atmospheres', 126, Citation number, 10.1029/2020jd033140. To view the published open abstract,go to http://dx.doi.org (http://dx.doi.org) and enter the DOI.

This work provides an updated set of 12 dominant geopotential height fields - or 'regimes' - over Aotearoa New Zealand. These regimes were initially produced by Kidson (2000) and have provided the ...

We re-evaluated speleothem isotope series from Aotearoa New Zealand that were recently contributed to the Speleothem Isotopes Synthesis and AnaLysis (SISAL) database. COnstructing Proxy Records from Age Models (COPRA) software was used to produce Bayesian age models for those speleothems. The new age modelling helped us examine Late Quaternary temporal coverage for the national speleothem network, and also supported our exploration of three different isotope master record generation techniques using Holocene &delta, 18O data from Waitomo. We then applied the output from one of the isotope master record techniques to test an application case of how climate transfer functions can be developed using climate model simulated temperatures. Our results suggest Holocene &delta, 18O trends at Waitomo capture air temperature variations weighted toward the primary season of soil moisture (and epikarst) recharge during winter. This interpretation is consistent with the latest monitoring data from the Waitomo region. Holocene &delta, 18O millennial-scale trends and centennial-scale variability at Waitomo likely reflect atmospheric circulation patterns that concomitantly vary with surface water temperature and the isotopic composition of the Tasman Sea. A climate model simulation context for the Holocene millennial-scale trends in the Waitomo &delta, 18O isotope master record suggest that site is sensitive to changes in the subtropical front (STF) and the Tasman Front. Our comparison of isotope master record techniques using Waitomo &delta, 18O data indicate that caution is needed prior to merging &delta, 18O data series from different caves in order to avoid time series artefacts. Future work should incorporate more high-resolution cave monitoring and climate calibration studies, and develop new speleothem data from northern and eastern regions of the country.

International audience; The South Pacific Convergence Zone (SPCZ) is a diagonal band of intense rainfall and deep atmospheric convection extending from the equator to the subtropical South Pacific. Displacement of the SPCZ causes variability in rainfall, tropical-cyclone activity and sea level that affects South Pacific island populations and surrounding ecosystems. In this Review, we synthesize recent advances in understanding the physical mechanisms responsible for the SPCZ location and orientation, its interactions with the principal drivers of tropical climate variability, regional and global effects of the SPCZ and its response to anthropogenic climate change. Emerging insight is beginning to provide a coherent description of the character and variability of the SPCZ over synoptic, intraseasonal, interannual and longer timescales. For example, the diagonal orientation of the SPCZ and its natural variability are both the result of a subtle chain of interactions between the tropical and extratropical atmosphere, forced and modulated by the underlying sea surface temperature gradients. However, persistent biases in, and deficiencies of, existing models limit confidence in future projections. Improved climate models and new methods for regional modelling might better constrain future SPCZ projections, aiding climate change adaptation and planning among vulnerable South Pacific communities.

As greenhouse gases continue to accumulate in Earth’s atmosphere, the nature of extreme weather events (EWEs) has been changing and is expected to change in the future. EWEs have contributions from anthropogenic climate change as well as from natural variability, which complicates attribution statements. EWERAM is a project that has been funded through the New Zealand Ministry of Business, Innovation and Employment Smart Ideas programme to develop the capability to provide, within days of an EWE having occurred over New Zealand, and while public interest is still high, scientifically defensible statements about the role of climate change in both the severity and frequency of that event. This is expected to raise public awareness and understanding of the effects of climate change on EWEs.A team of researchers from five institutions across New Zealand are participating in EWERAM. EWE attribution is a multi-faceted problem and different approaches are required to address different research aims. Although robustly assessing the contribution of changes in the thermodynamic state to an observed event can be more tractable than including changes in the dynamics of weather systems, for New Zealand, changes in dynamics have had a large impact on the frequency and location of EWEs. As such, we have initiated several lines of research to deliver metrics on EWE attribution, tailored to meet the needs of various stakeholders, that encompass the effects of both dynamical and thermodynamical changes in the atmosphere. This presentation will give an overview of EWERAM and present the methodologies and tools used in the project.

The Track Zero Charitable Trust (http://trackzero.nz) was founded in early 2018 with the goal of inspiring action on climate change through engagement with the arts. The main motivation is that art...

de Freitas et al. (2015) (henceforth dFDB) report a trend of 0.28 °C per century over the period 1909–2009 for New Zealand land surface temperatures, from their reanalysis of a composite of seven long-term records. This is much lower than the warming trend of about 0.9 °C per century reported previously by other researchers and much smaller than trends estimated from independent sea surface temperature data from the surrounding region. We show these differences result primarily from the way inhomogeneities in temperature time series at individual stations due to site or instrument changes are identified and adjusted for in the dFDB paper. The adjustments reported in that paper are based on a method designed by one of us (Salinger), but use only a short (1–2-year) overlap period with comparison stations and consider only inhomogeneities in monthly mean (rather than monthly maximum and minimum) temperatures. This leads to underestimates of the statistical significance of individual temperature discontinuities and hence rejection of many valid adjustments. Since there was a systematic tendency for the seven-station sites to be relocated to colder locations as the early half of the twentieth century progressed, this rejection of valid adjustments produces an artificially low rate of warming. We therefore disagree with the trend calculations in the dFDB paper and consider there is no reason to reject the previous estimates of around 0.9 °C warming per century.

Persistent positive 500-hPa geopotential height anomalies from the ECMWF ERA-Interim reanalysis are used to quantify Amundsen–Bellingshausen Sea (ABS) anticyclonic event occurrences associated with precipitation in West Antarctica (WA). We demonstrate that multi-day (minimum 3-day duration) anticyclones play a key role in the ABS by dynamically inducing meridional transport, which is associated with heat and moisture advection into WA. This affects surface climate variability and trends, precipitation rates and thus WA ice sheet surface mass balance. We show that the snow accumulation record from the Roosevelt Island Climate Evolution (RICE) ice core reflects interannual variability of blocking and geopotential height conditions in the ABS/Ross Sea region. Furthermore, our analysis shows that larger precipitation events are related to enhanced anticyclonic circulation and meridional winds, which cause pronounced dipole patterns in air temperature anomalies and sea ice concentrations between the eastern Ross Sea and the Bellingshausen Sea/Weddell Sea, as well as between the eastern and western Ross Sea.

Over the past 60 years, the climate of East Antarctica cooled while portions of West Antarctica were among the most rapidly warming regions on the planet. The East Antarctic cooling is attributed to a positive trend in the Southern Annular Mode (SAM) and a strengthening of the westerlies, while West Antarctic warming is tied to zonally asymmetric circulation changes forced by the tropics. This study finds recent (post-1979) surface cooling of East Antarctica during austral autumn to also be tied to tropical forcing, namely, an increase in La Nina events. The recent increase in La Nina conditions forces a Rossby wave into the Southern Hemisphere that increases anticyclonic circulation over the South Atlantic. The South Atlantic anticyclone is associated with cold air advection, weakened northerlies, and increased sea ice concentrations across the western East Antarctic coast, which has increased the rate of cooling at Novolazarevskaya and Syowa stations after 1979. This enhanced cooling over western East Antarctica is tied more broadly to a zonally asymmetric temperature trend pattern across East Antarctica during autumn that is consistent with a tropically forced Rossby wave rather than a SAM pattern; the positive SAM pattern is associated with ubiquitous cooling across East Antarctica, which is not seen in temperature observations after 1979. We conclude that El Nino–Southern Oscillation-related circulation anomalies, particularly zonal asymmetries that locally enhance meridional wind, are an important component of East Antarctic climate variability during autumn, and future changes in tropical Pacific climate will likely have implications for East Antarctica.

Central southwest Asia (CSWA; 20°–47°N, 40°–85°E) is a water-stressed region prone to significant variations in precipitation during its winter precipitation season of November–April. Wintertime precipitation is crucial for regional water resources, agriculture, and livelihood; however, in recent years droughts have been a notable feature of CSWA interannual variability. Here, the predictability of CSWA wintertime precipitation is explored based on its time-lagged relationship with the preceding months’ (September–October) sea surface temperature (SST), using a canonical correlation analysis (CCA) approach. For both periods, results indicate that for CSWA much of the seasonal predictability arises from SST variations in the Pacific related to El Niño–Southern Oscillation (ENSO) and the Pacific decadal oscillation (PDO). Additional sources of skill that play a weaker predictive role include long-term SST trends, North Atlantic variability, and regional teleconnections. CCA cross-validation skill shows that the regional potential predictability has a strong dependency on the ENSO phenomenon, and the strengthening (weakening) of this relationship yields forecasts with higher (lower) predictive skill. This finding is validated by the mean cross-validated correlation skill of 0.71 and 0.38 obtained for the 1980/81–2014/15 and 1950/51–2014/15 CCA analyses, respectively. The development of cold (warm) ENSO conditions during September–October, in combination with cold (warm) PDO conditions, is associated with a northward (southward) shift of the jet stream and a strong tendency of negative (positive) winter precipitation anomalies; other sources of predictability influence the regional precipitation directly during non-ENSO years or by modulating the impact of ENSO teleconnection based on their relative strengths.

Using empirical orthogonal function (EOF) analysis and atmospheric reanalyses, the principal patterns of seasonal West Antarctic surface air temperature (SAT) and their connection to sea ice and the Amundsen Sea low (ASL) are examined. During austral summer, the leading EOF (EOF1) explains 35% of West Antarctic SAT variability and consists of a widespread SAT anomaly over the continent linked to persistent sea ice concentration anomalies over the Ross and Amundsen Seas from the previous spring. Outside of summer, EOF1 (explaining ~40%–50% of the variability) consists of an east–west dipole over the continent with SAT anomalies over the Antarctic Peninsula opposite those over western West Antarctica. The dipole is tied to variability in the southern annular mode (SAM) and in-phase El Niño–Southern Oscillation (ENSO)/SAM combinations that influence the depth of the ASL over the central Amundsen Sea (near 105°W). The second EOF (EOF2) during autumn, winter, and spring (explaining ~15%–20% of the variability) consists of a dipole shifted approximately 30° west of EOF1 with a widespread SAT anomaly over the continent. During winter and spring, EOF2 is closely tied to variability in ENSO and a tropically forced wave train that influences the ASL in the western Amundsen/eastern Ross Seas (near 135°W) with an opposite-sign circulation anomaly over the Weddell Sea; the ENSO-related circulation brings anomalous thermal advection deep onto the continent. The authors conclude that the ENSO-only circulation pattern is associated with SAT variability across interior West Antarctica, especially during winter and spring, whereas the SAM circulation pattern is associated with an SAT dipole over the continent.

We performed an Empirical Orthogonal Function (EOF) analysis to assess the intraseasonal variability of 5–60 day band-pass filtered Antarctic sea-ice concentration in austral winter using a 20-year daily dataset from 1995 to 2014. Zonal wave number 3 dominated in the Antarctic, especially so across the west Antarctic. Results showed the coexistence of stationary and propagating wave components. A spectral analysis of the first two principal components (PCs) showed a similar structure for periods up to 15 days but generally more power in PC1 at longer periods. Regression analysis upon atmospheric fields using the first two PCs of sea-ice concentration showed a coherent wave number 3 pattern. The spatial phase delay between the sea-ice and mean sea-level pressure patterns suggests that meridional flow and associated temperature advection are important for modulating the sea-ice field. EOF analyses carried out separately for El Niño, La Niña and neutral years, and for Southern Annular Mode positive, negative and neutral periods, suggest that the spatial patterns of wave number 3 shift between subsets. The results also indicate that El Niño-Southern Oscillation and Southern Annular Mode affect stationary wave interactions between sea-ice and atmospheric fields on intraseasonal timescales.

This study is concerned with blocking events (BEs) in the Southern Hemisphere (SH), their past variability, and future projections. ERA-Interim (ERA-I) is used to compare the historical output from four general circulation models (GCMs) from phase 5 of the Coupled Model Intercomparison Project (CMIP5); the output of the representative concentration pathway 4.5 and 8.5 (RCP4.5 and RCP8.5) projections are also examined. ERA-I shows that the higher latitudes of the South Pacific Ocean (SPO) are the main blocking region, with blocking occurring predominantly in winter. The CMIP5 historical simulations also agree well with ERA-I for annual and seasonal BE locations and frequencies. A reduction in BEs is observed in the SPO in the 2071–2100 period in the RCP4.5 projections, and this is more pronounced for the RCP8.5 projections and occurs predominantly during the spring and summer seasons. Preliminary investigations imply that the southern annular mode (SAM) is negatively correlated with blocking activity in the SPO in all seasons in the reanalysis. This negative correlation is also observed in the GCM historical output. However, in the RCP projections this correlation is reduced in three of the four models during summer, suggesting that SAM may be less influential in summertime blocking in the future.

During 1979–2014, eastern tropical Pacific sea surface temperatures significantly cooled, which has generally been attributed to the transition of the Pacific Decadal Oscillation to its negative phase after 1999. We find the eastern tropical Pacific cooling to be associated with: (1) an intensified Walker Circulation during austral summer (December–February, DJF) and autumn (March–May, MAM); (2) a weakened South Pacific Hadley cell and subtropical jet during MAM; and (3) a strengthening of the circumpolar westerlies between 50 and 60°S during DJF and MAM. Observed cooling in the eastern tropical Pacific is linearly congruent with 60–80 % of the observed Southern Hemisphere positive zonal-mean zonal wind trend between 50 and 60°S during DJF (~35 % of the interannual variability), and around half of the observed positive zonal-mean zonal wind trend during MAM (~15 % of the interannual variability). Although previous studies have linked the strengthened DJF and MAM circumpolar westerlies to stratospheric ozone depletion and increasing greenhouse gases, we note that the continuation of the positive SAM trends into the twenty-first century is partially associated with eastern tropical Pacific cooling, especially during MAM when zonal wind anomalies associated with eastern tropical Pacific cooling project strongly onto the observed trends. Outside of DJF and MAM, eastern tropical Pacific cooling is associated with opposing zonal wind anomalies over the Pacific and Indian sectors, which we infer is the reason for the absence of significant positive SAM trends outside of DJF and MAM despite significant eastern tropical Pacific cooling seen during all seasons.

Recent warming of the Antarctic Peninsula during austral autumn, winter, and spring has been linked to sea surface temperature (SST) trends in the tropical Pacific and tropical Atlantic, while warming of the northeast Peninsula during summer has been linked to a strengthening of westerly winds traversing the Peninsula associated with a positive trend in the Southern Annular Mode (SAM). Here we demonstrate that circulation changes associated with the SAM dominate interannual temperature variability across the entire Antarctic Peninsula during both summer and autumn, while relationships with tropical Pacific SST variability associated with the El Nino-Southern Oscillation (ENSO) are strongest and statistically significant primarily during winter and spring only. We find the ENSO-Peninsula temperature relationship during autumn to be weak on interannual timescales, and regional circulation anomalies associated with the SAM more important for interannual temperature variability across the Peninsula during autumn. Consistent with previous studies, western Peninsula temperatures during autumn, winter, and spring are closely tied to changes in the Amundsen Sea Low (ASL) and associated meridional wind anomalies. The interannual variability of ASL depth is most strongly correlated with the SAM index during autumn, while the ENSO relationship is strongest during winter and spring. Investigation of western and northeast Peninsula temperatures separately reveals that interannual variability of northeast Peninsula temperatures is primarily sensitive to zonal wind anomalies crossing the Peninsula and resultant lee-side adiabatic warming rather than to meridional wind anomalies, which is closely tied to variability in the zonal portion of the SAM pattern.

Reanalysis and observation data from 1979 to 2010 are used to study the climatological behavior of regional vortices over the Southeast Asian sea–Maritime Continent region (SEAMC). After eliminating tropical cyclones from the International Best Tracks Archive for Climate Stewardship (IBTrACS), significant numbers of vortices remained over the region. The results also show that the vortices, rather than being relatively stationary near the Borneo coast in the winter, were consistently present over the SEAMC throughout the year, migrating from the area of the coast of Vietnam, the Philippines, and the Southeast Asian sea in summer to the island of Borneo region in winter. These vortices can produce significant amounts of rainfall in Vietnam, especially in central coastal regions during the postsummer monsoon (autumn) period.

This article presents a detailed comparison of ten precipitation products over the central southwest Asia (CSWA) region. The spatial characteristics and temporal variations of wintertime precipitation over CSWA region are assessed using four gauge-only [Asian Precipitation – Highly Resolved Observational Data Integration Towards Evaluation of Water Resources (APHRODITE), Climate Prediction Center Unified Rain gauge (CPC-uni), Global Precipitation Climatology Center Full Data Reanalysis (GPCC) and Climate Research Unit (CRU)]; three satellite-derived (3B42-V6, 3B42-V7 and GPCP-1DD) and three reanalysis [Climate Forecast System Reanalysis (CFSR), ERA-Interim and Modern-Era Retrospective Analysis for Research and Applications (MERRA)] precipitation products. The analysis is performed for two different periods: (1979–2007) for the gauge-only/reanalyses and (1998–2007) for the satellite-derived products. Using an ensemble average of four gauge-only observational data sets as our reference, we carry out comprehensive qualitative assessment of the uncertainties/biases associated with each data set. Additionally, we examine the relationship pattern between CSWA wintertime precipitation and El Nino-Southern Oscillation (ENSO) phases. In the gauge-only category, APHRODITE and GPCC perform better than CPC-uni and CRU data sets in terms of the spatial and temporal variations of skill matrices. Overall, GPCC shows the best performance (including the precipitation sensitivity to ENSO events) and is the preferable observational data set for long-term climatological analysis over the CSWA region. Among the satellite-derived precipitation products, 3B42-V7 displays the most realistic wintertime precipitation distribution pattern when compared to 3B42-V6 and GPCP-1DD; however, efforts are needed to further improve the accuracy of satellite-derived products over the dry arid and semi-arid areas of CSWA. In the reanalysis category, MERRA's performance is relatively better than CFSR and ERA-Interim, although significant biases exist in all of the reanalyses due to overestimation of precipitation over the mountainous regions of CSWA.

New insight is provided regarding 21st century projections of synoptic scale atmospheric circulation over the New Zealand region. Daily mean sea level pressure patterns from a number of general circulation models (GCMs) participating in the 5th Coupled Model Intercomparison Project (CMIP5) were analysed through a self-organizing map (SOM) technique. In terms of simulating the synoptic climatology found in reanalyses, an initial model evaluation revealed quite substantial differences in model skill. Generally, those models with relatively high horizontal atmospheric resolution skilfully simulated the historical frequency and mean lifetime of large scale synoptic patterns over this region. Analysing future projections under this smaller subset of better-performing models indicated robust and quite substantial increases in the annual frequency of widespread anticyclonic conditions over New Zealand, accompanied by a general decrease in widespread low pressure. These projected changes in frequency of synoptic occurrences become the most pronounced towards the end of the 21st century and for winter, whereas changes in the average synoptic pattern lifetime remain small. While not robust for all models in this subset, significant 21st century trends in the intensification of geostrophic westerly flow conditions within certain synoptic patterns were also found. Linking synoptic patterns to surface climate variables has also provided evidence that these circulation changes may collectively manifest as a significant non-uniform climatic change across New Zealand. These findings should encourage further focused studies on circulation-relevant applications and impacts in a climate change context.

We present a 16 000-year vegetation and climate reconstruction from pollen and plant macrofossil records obtained at a small alpine lake in South Island, New Zealand (41°S). The expansion of lowland forest taxa suggests a lifting of the altitudinal forest limits because of a warming pulse between 13 and 10k cal a BP and between 7 and 6k cal a BP, while their decline relative to upland forest taxa indicates cooling phases between 10 and 7k cal a BP and over the last 3000 years. The modern treeline was first established locally by 9.7k cal a BP. Forest persisted at the site until 3k cal a BP then disappeared from the record. Close correspondence between the temperature trends inferred from the pollen and macrofossil records and proxies from Antarctica and the Southern Ocean suggests a strong teleconnection between New Zealand and the Southern Hemisphere high-latitudes between 15 and 6k cal a BP. We note that the breakdown of this coupling, a cooling trend in Adelaide Tarn and the local disappearance of beech forest after 3k cal a BP occur during a period of increased frequency of El Nino events, suggesting an enhanced teleconnection with the low-latitudes during the late Holocene.

As the linked impacts of climate change and degradation of ecosystems continue to be felt, particularly in developing countries, it is vital that methods for development that concurrently address adaptation to climate change, rapid urbanisation, and ecosystem degradation be explored. Further development of approaches which are participatory and embedded in an understanding of the importance of symbiotic relationships between socio-cultural and ecological systems is particularly important. Ecosystem-based adaptation (EbA) is one such method that is gaining recognition and momentum in areas where developing nations face converging pressures and drivers of change. EbA methodologies to date, are often ill-defined in an urban context and lack consideration of future social and ecological scenarios however. In response, this paper describes a methodology for developing urban EbA projects in a small island developing nation context. The methodology was developed and applied by a multi-disciplinary team working under the auspices of the Secretariat of the Pacific Regional Environment Programme (SPREP). The application of this methodology in Port Vila, Vanuatu indicated: i) the needs of local people must be at the forefront of project planning, requiring a participatory design process; ii) EbA solutions development must be multidisciplinary and iterative; iii) appropriate quantitative and qualitative data is vital as a basis for EbA project development, requiring adequate time for data gathering; iv) urban and coastal EbA projects must be developed holistically, recognising socio-ecological systems that extend beyond the urban area itself; v) the complex overlapping landscape of governmental and international aid financed projects must inform the development of new EbA projects; vi) potential monetary and non-monetary benefits, costs and risks across multiple factors must be carefully assessed in EbA project development; and vii) project implementation requires ongoing engagement and a readiness to adapt to on-the-ground realities.

Brown haze has been observed over a number of urban centres in different geographical locations around the world. It is a clear indication of degradation in air quality above a city; however, little is known about its underlying causes. This study examines the incidence of brown haze over the subtropical city of Auckland, New Zealand between 2001 and 2011. Using photographs to document the incidence and severity of the haze and a combination of near-surface meteorological observations, reanalysis data and three-dimensional modelling approaches, a detailed climatology of the incidence of haze is developed. The results show that haze is observed during weekday mornings in the cool months, most commonly associated with cold, calm conditions. These conditions are most commonly prevalent with the slow eastward movement of anticyclones (classified as Kidson weather types H and HSE). However, the conditional probability of haze events occurring within these classes is less than 25%, and there is little consistency in the thresholds of surface meteorological conditions between classes. Re-analysis of the mean sea-level pressure at regional to synoptic scales reveals that the strength and stability of the anticyclone is important in determining the occurrence and severity of brown haze events. Brown haze development is associated with a strong NE-SW temperature gradient immediately prior to the event, and anticyclonic development is enhanced by a well-developed wave train across the Southern Ocean. Back trajectory modelling shows these conditions are associated with slow moving air masses and suggest that the source of pollution is most likely to be local in origin. The results demonstrate the importance of a detailed understanding of synoptic and regional scale meteorology in predicting urban scale pollution events, even when the source of the pollution is local.

Significant austral spring trends have previously been observed in West Antarctica and Antarctic Peninsula temperatures and in atmospheric circulation across the southern Pacific and Atlantic. Here, physical mechanisms for the observed trends are investigated through analysis of monthly circulation and temperatures from the ERA-Interim dataset and outgoing longwave radiation (OLR) data. The negative pressure trend over the South Pacific during spring is strongest in September, while the positive pressure trend over the South Atlantic is strongest in October. Pressure trends in November are generally nonsignificant. The authors demonstrate that a significant September trend toward increased convection (reduced OLR) in the poleward portion of the South Pacific convergence zone (SPCZ) is statistically related to Rossby wave–like circulation changes across the southern oceans. The wave response is strongest over the South Pacific in September and propagates eastward to the South Atlantic in October. OLR-related changes are linearly congruent with around half of the observed total changes in circulation during September and October and are consistent with observed trends in South Pacific sea ice concentration and surface temperature over western West Antarctica and the western Antarctic Peninsula. These results suggest SPCZ variability in early spring, especially on the poleward side of the SPCZ, is an important contributor to circulation and surface temperature trends across the South Pacific/Atlantic and West Antarctica.

Black Saturday (BS), 7 February 2009, is recognized as Australia's most severe bushfire event on record. The meteorology that day, although extreme, was typical of southeast Australian bushfire events, characterized by gusty northerly winds before a cool change brought strong southerly winds and a dramatic temperature drop. This study investigates a range of extra-tropical atmospheric (pressure, temperatures) and oceanic temperature anomalies that occurred on or leading up to BS. Results show several parameters were within the top 5% or were record breaking for the satellite era. Of particular note are the anomalies that occurred over the Antarctic region, having the strongest signal and appearing in unison with the pre-BS heatwave. We suggest that a combination of a warm polar ocean and an enhanced mid-latitude thermal contrast in the Indian Ocean aided in triggering sub-polar blocking and an intense cyclone, which brought the catastrophic cold front on BS.

This paper evaluates the seasonal (winter, premonsoon, monsoon, and postmonsoon) performance of seven precipitation products from three different sources: gridded station data, satellite-derived data, and reanalyses products over the Indian subcontinent for a period of 10 years (1997/98–2006/07). The evaluated precipitation products are the Asian Precipitation–Highly-Resolved Observational Data Integration Towards Evaluation of the Water Resources (APHRODITE), the Climate Prediction Center unified (CPC-uni), the Global Precipitation Climatology Project (GPCP), the Tropical Rainfall Measuring Mission (TRMM) post-real-time research products (3B42-V6 and 3B42-V7), the Climate Forecast System Reanalysis (CFSR), and the European Centre for Medium-Range Weather Forecasts (ECMWF) interim reanalysis (ERA-Interim). Several verification measures are employed to assess the accuracy of the data. All datasets capture the large-scale characteristics of the seasonal mean precipitation distribution, albeit with pronounced seasonal and/or regional differences. Compared to APHRODITE, the gauge-only (CPC-uni) and the satellite-derived precipitation products (GPCP, 3B42-V6, and 3B42-V7) capture the summer monsoon rainfall variability better than CFSR and ERA-Interim. Similar conclusions are drawn for the postmonsoon season, with the exception of 3B42-V7, which underestimates postmonsoon precipitation. Over mountainous regions, 3B42-V7 shows an appreciable improvement over 3B42-V6 and other gauge-based precipitation products. Significantly large biases/errors occur during the winter months, which are likely related to the uncertainty in observations that artificially inflate the existing error in reanalyses and satellite retrievals.

The simulation of Antarctic sea ice in global climate models often does not agree with observations. In this study, we examine the compactness of sea ice, as well as the regional distribution of sea ice concentration, in climate models from the latest Coupled Model Intercomparison Project (CMIP5) and in satellite observations. We find substantial differences in concentration values between different sets of satellite observations, particularly at high concentrations, requiring careful treatment when comparing to models. As a fraction of total sea ice extent, models simulate too much loose, low-concentration sea ice cover throughout the year, and too little compact, high-concentration cover in the summer. In spite of the differences in physics between models, these tendencies are broadly consistent across the population of 40 CMIP5 simulations, a result not previously highlighted. Separating models with and without an explicit lateral melt term, we find that inclusion of lateral melt may account for overestimation of low-concentration cover. Targeted model experiments with a coupled ocean–sea ice model show that choice of constant floe diameter in the lateral melt scheme can also impact representation of loose ice. This suggests that current sea ice thermodynamics contribute to the inadequate simulation of the low-concentration regime in many models.

The focus of this study is the climatological relationship between southwest Pacific Tropical Cyclone (TC) activity and the Madden-Julian Oscillation (MJO) on the interannual time-scale. It investigates TC seasonal characteristics (e.g. cyclogenesis, track morphology, ex-tropical transition, and intensity) as modulated by the phase and intensity of the MJO. The approach is novel as in addition to the focus on the intraseasonal variability of TCs there is also a focus on the interannual variability of TCs even though the MJO is an intraseasonal phenomenon. Links between the MJO, the Southern Annular Mode (SAM) and TC variability are also investigated. Using the MJO phases defined by Wheeler and Hendon (2004), southwest Pacific TC frequency exhibited a statistically significant decrease during MJO phases 2 and 3, and an increase during phases 6 and 7; and during the positive phase of the SAM, an increased frequency of TCs undergoing extratropical transition was observed. In summary, the results show a clear intraseasonal climatological relationship between specific phases of the MJO with respect to a decreased (increased) frequency of TCs during the paired MJO phases 2-3 (6-7); as well as the existence of a statistically significant relationship between the MJO and SAM with respect to the extratropical transition (ETT) of TCs. During positive phases of the SAM, coincident with weak interannual MJO phases 4-5 and 6-7, there are statistically significant greater frequency percentages of TCs undergoing ETT.

In this study, we focus on possible climatological relationships between southwest Pacific tropical cyclone (TC) activity and the Southern Annular Mode (SAM) and ENSO, at both interannual and synoptic time-scales. The investigation focuses on TC seasonal characteristics (e.g. cyclogenesis, track characteristics, extratropical transition, and intensity) as modulated according to the polarity of the SAM and ENSO. At synoptic time-scales, we also look at possible triggers of TC cyclogenesis in the SAM signal up to 20 days in advance. The physical basis for this relationship is assessed using a number of different gridded data fields. During seasons characterized by positive phases of SAM and both positive and negative Southern Oscillation Index (SOI) values, there is an increased frequency of TCs undergoing extratropical transition near New Zealand. At synoptic time-scales, we found an interesting yet inconclusive relationship between the SAM and tropical cyclogenesis during SOI positive seasons. While statistically significant, there is no clear physical mechanism linking the mid-latitude SAM phenomenon to the genesis of TCs. In summary, the results show a clear interannual climatological relationship between an increased frequency of TCs undergoing extratropical transition near New Zealand and the positive phase of SAM.

A cluster analysis-based synoptic classification scheme, known as the Kidson types, was applied to reanalyses and Coupled Model Inter-comparison Project phase 3 (CMIP3) general circulation model (GCM) output over New Zealand to identify the potential for future changes in regional circulation. Results indicate that a number of GCM 20th century control runs reproduce the type frequencies observed in reanalysis data. Application to future scenario runs for the periods 2046–2065 and 2081–2100 displays little variation in the annual frequency of the synoptic types relative to the 20th century, especially when uncertainty associated with the model ensemble is considered. This is surprising in the context of previous work on possible future movements in jet position and subsequent impacts on weather patterns. A sensitivity analysis that mimics the movement of the jet position was performed, revealing that the annual type frequencies are relatively insensitive to change. To determine whether this is a problem with the synoptic typing scheme, a correlation-based classification technique was also used, but showed similar results. This work highlights issues with applying synoptic classification schemes to GCM output and indicates that if such schemes are to be used they should be designed and tested with this application in mind.

A new objective approach is proposed to identify the seasonal cycle of rainfall for major monsoon regions of the globe. Mean sea level pressure and low-level zonal wind are combined to establish a standardized monsoon index. The index is able to determine the timing of the summer monsoon rainy season across all major monsoon regions in Asia-Australia, Africa, and the Americas. A detailed application of the index in detecting the monsoon onset-withdrawal phases is demonstrated for the Vietnam-South China Sea region. A significant advantage of the index is that it can be used both for studies of monsoon rainfall variability and for monsoon predictability at seasonal time scales.

During austral summer (DJF) 2017/18, the New Zealand region experienced an unprecedented coupled ocean-atmosphere heatwave, covering an area of 4 million km2. Regional average air temperature anomalies over land were +2.2oC, and sea surface temperature anomalies reached +3.7oC in the eastern Tasman Sea. This paper discusses the event, including atmospheric and oceanic drivers, the role of anthropogenic warming, and terrestrial and marine impacts. The heatwave was associated with very low wind speeds, reducing upper ocean mixing and allowing heat fluxes from the atmosphere to the ocean to cause substantial warming of the stratified surface layers of the Tasman Sea. The event persisted for the entire austral summer resulting in a 3.8±0.6 km3 loss of glacier ice in the Southern Alps (the largest annual loss in records back to 1962), very early Sauvignon Blanc wine-grape maturation in Marlborough, and major species disruption in marine ecosystems. The dominant driver was positive Southern Annular Mode (SAM) conditions, with a smaller contribution from La Nina. The long-term trend towards positive SAM conditions, a result of stratospheric ozone depletion and greenhouse gas increase, is thought to have contributed through association with more frequent anticyclonic "blocking" conditions in the New Zealand region and a more poleward average latitude for the Southern Ocean storm track. The unprecedented heatwave provides a good analogue for possible mean conditions in the late 21st century. The best match suggests this extreme summer may be typical of average New Zealand summer climate for 2081-2100, under the RCP4.5 or RCP6.0 scenario.

Auckland, New Zealand, is influenced by ex-tropical cyclones (ETCs); however, there is no established climatology for these weather systems at present. In this study, we present a climatology of ETCs for Auckland and investigate whether their spatio-temporal traits are influenced by large-scale climate modes such as the El Ni˜ no-Southern Oscillation (ENSO) and the Southern Annular Mode (SAM). We utilize the South Pacific Enhanced Archive for Tropical Cyclone research (SPEArTC) to establish a climatology that covers the high-quality TC data period from 1970 to 2010. ETCs have entered a region within 550km of Auckland city regardless of ENSO or SAM phase, and on average one event per year occurs. Peak ETC season for Auckland is during March, preceded by an increase in activity during February, with a wide-range of meteorological impacts. Regional circulation patterns, including reduced blocking in the southwest Pacific and synoptic type presence, allow ETCs into the Auckland sector of the southwest Pacific while guiding them either to the east or west of the city.

Little Ice Age (LIA) austral summer temperature anomalies were derived from palaeoequilibrium line altitudes at 22 cirque glacier sites across the Southern Alps of New Zealand. Modern analog seasons with temperature anomalies akin to the LIA reconstructions were selected, and then applied in a sampling of high-resolution gridded New Zealand climate data and global reanalysis data to generate LIA climate composites at local, regional and hemispheric scales. The composite anomaly patterns assist in improving our understanding of atmospheric circulation contributions to the LIA climate state, allow an interrogation of synoptic type frequency changes for the LIA relative to present, and provide a hemispheric context of the past conditions in New Zealand. An LIA summer temperature anomaly of −0.56 °C (±0.29 °C) for the Southern Alps based on palaeo-equilibrium lines compares well with local tree-ring reconstructions of austral summer temperature. Reconstructed geopotential height at 1,000 hPa (z1000) suggests enhanced southwesterly flow across New Zealand occurred during the LIA to generate the terrestrial temperature anomalies. The mean atmospheric circulation pattern for summer resulted from a crucial reduction of the ‘HSE’-blocking synoptic type (highs over and to the west of NZ; largely settled conditions) and increases in both the ‘T’- and ‘SW’-trough synoptic types (lows passing over NZ; enhanced southerly and southwesterly flow) relative to normal. Associated land-based temperature and precipitation anomalies suggest both colder- and wetter-than-normal conditions were a pervasive component of the base climate state across New Zealand during the LIA, as were colder-than-normal Tasman Sea surface temperatures. Proxy temperature and circulation evidence were used to corroborate the spatially heterogeneous Southern Hemisphere composite z1000 and sea surface temperature patterns generated in this study. A comparison of the composites to climate mode archetypes suggests LIA summer climate and atmospheric circulation over New Zealand was driven by increased frequency of weak El Nino-Modoki in the tropical Pacific and negative Southern Annular Mode activity.