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The changing climate is threatening everything we hold dear, increasing dangers to food production, to the availability of water, to land and to livelihoods across the globe. In the past century, humanity has become the dominant force shaping the climate system, ramping up greenhouse gas emissions and air pollution. To halt climate change, emissions of greenhouse gases must be reduced to zero as soon as possible. However, the necessary action has not been forthcoming and the overall response has been painfully slow, for a number of reasons. This special issue of the Journal of the Royal Society Te Apārangi addresses many of these issues, with a focus on Aotearoa New Zealand, looking at how we think about climate change and the nature and pace of our response. [ABSTRACT FROM AUTHOR]

In this study, we explore linkages between the monthly mean 500 hPa height field (Z500) and its high-frequency variability over 2–8-day periods, a proxy for Southern Hemisphere storm track activity. We apply maximum covariance analysis to identify leading modes of covariability between the Z500 and high-frequency variance anomalies on monthly and submonthly time scales, using two reanalysis products. We also calculate covariance with indices of large-scale variability [Southern Annular Mode (SAM), El Niño–Southern Oscillation (ENSO), and zonal wave 3 (ZW3)]. We find large-scale circulation patterns emerge as prominent modes of covariability, particularly SAM and ENSO, accounting for 11.1% and 7.8% of covariability on the monthly scale, respectively. The seasonal cycle plays a prominent role in explaining variability in both SAM and ENSO interactions with the storm track. We find that despite a broadly linear response, both SAM and ENSO teleconnections present additional complexities and nonlinearities. Despite strong ZW3 signals in the mean height field, its influence on the high-frequency variance field remains unclear. We conclude the mean height field is most likely strongly linked with high-frequency variance, but interference from other influences may lead to an inconsistent response. We note both fields have an apparent hemispheric response to the SAM, but ENSO has a more regional response and ZW3 a relatively incoherent response. This suggests ENSO and ZW3 patterns depend less on feedbacks between the storm track and the mean height field than the SAM. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM PUBLISHER]

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 center 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 peak intensity. 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. Plain Language Summary: Extra‐tropical cyclones play a major role in the circulation within the atmosphere, acting to transfer heat toward the poles. Here we assess the representation of extreme precipitation within extra‐tropical cyclones. By applying a threshold for precipitation that changes with geographic location, we are able to determine how extreme precipitation varies within a cyclone‐centered coordinate system. When breaking cyclones into lifecycle stages representing deepening, peak intensity and decay, we find that extreme precipitation occurs most often as the cyclone is developing. The area of the cyclone relevant for extremes reduces toward the cyclone center as the threshold for determining extreme precipitation increases. Extreme precipitation weakens at a higher rate as cyclones becomes more intense, highlighting the importance of extremes in the growth phase of the cyclone. Key Points: We detail a new methodology to assess precipitation extremes within cyclone composites using a spatially dependent precipitation thresholdExtreme precipitation occurs preferentially and makes up a larger fraction of total accumulation before cyclones reach peak intensityExtreme precipitation is more constrained around the cyclone center and weakens more rapidly over time compared to moderate precipitation [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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, sea ice, and SAT extremes. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

A polynya is an area of open water or reduced concentration of sea ice surrounded by either concentrated sea ice or land ice. They are often seen as sites of intense ocean–atmosphere heat exchange and as ice production factories. Given their importance, it is crucial to quantify the accuracy of satellite-derived polynya information. Polynyas in their early evolution phase are generally narrow and occur at scales likely too fine to be detected by widely used passive microwave (PMW) radiometric sensors. We derived 40 m scale polynya information over the western Ross Sea from high-resolution Synthetic Aperture Radar (SAR) Sentinel-1 C-band data and examined discrepancies with larger-scale estimates. We utilized two automated algorithms, supervised (a rule-based approach) and unsupervised (a combination of texture analysis with k-means clustering), to accurately identify the polynya areas. We generated data for validation using Sentinel-1 data at instances where polynyas can be visually delineated. Results from PMW sensors (NSIDC and AMSR2) and SAR-based algorithms (rule-based and texture-based) are compared with manually delineated polynya areas obtained through Sentinel-1. Analysis using PMW sensors revealed that NSIDC overestimates larger polynyas and underestimates smaller polynyas compared to AMSR2. We were more accurately able to identify polynya presence and area using Sentinel-1 SAR observations, especially in clear cases and cases when PMW data miscalculates the polynya's presence. Of our SAR-based algorithms, the rule-based approach was more accurate than the texture-based approach at identifying clear polynyas when validated against manually delineated regions. Altogether, we emphasize the need for finer spatio-temporal resolution data for polynya studies. [ABSTRACT FROM AUTHOR]

Extreme temperature events (ETEs) have evolved alongside the warming climate over most parts of the world. This study provides a statistical quantification of how human influences have changed the frequencies of extreme temperatures in New Zealand, depending on the synoptic weather types. We use the ensembles under pre‐industrial conditions (natural scenarios with no human‐induced changes) and present‐day conditions (anthropogenic scenarios) from the weather@home regional climate model. The ensemble simulations under these two scenarios are used to identify how human influences have impacted the frequency and intensity of extreme temperatures based on their connection to different large‐scale circulation patterns derived using self‐organizing maps (SOMs). Over New Zealand, an average two to three fold rise in frequencies of extremes occurs irrespective of seasons due to anthropogenic influence with a mean temperature increase close to 1°C. For some synoptic situations, the frequency of extremes are especially enhanced; in particular, for low‐pressure centres to the northeast of New Zealand where the frequency of occurrence of daily temperature extremes has increased by a factor of 7 between anthropogenic and natural ensembles for the winter season, though these synoptic patterns rarely occur. For low‐pressure centres to the northwest of New Zealand, we observe high temperatures frequently in both anthropogenic and natural ensembles which we expect is probably associated with warm air advection from the Tropics. The frequency of occurrence of high temperatures in these synoptic patterns has also increased by a factor of 2 between the natural and anthropogenic ensembles. For these synoptic states, the extremes are observed in the North Island and along the east coast of the country with the highest temperature along the Canterbury coast and Northland. The change between the natural and anthropogenic ensembles is largest on the west coast along the Southern Alps for all the synoptic circulation types. [ABSTRACT FROM AUTHOR]

Extreme temperature events (ETEs) have evolved alongside the warming climate over most parts of the world. This study provides a statistical quantification of how human influences have changed the frequencies of extreme temperatures in New Zealand, depending on the synoptic weather types. We use the ensembles under pre‐industrial conditions (natural scenarios with no human‐induced changes) and present‐day conditions (anthropogenic scenarios) from the weather@home regional climate model. The ensemble simulations under these two scenarios are used to identify how human influences have impacted the frequency and intensity of extreme temperatures based on their connection to different large‐scale circulation patterns derived using self‐organizing maps (SOMs). Over New Zealand, an average two to three fold rise in frequencies of extremes occurs irrespective of seasons due to anthropogenic influence with a mean temperature increase close to 1°C. For some synoptic situations, the frequency of extremes are especially enhanced; in particular, for low‐pressure centres to the northeast of New Zealand where the frequency of occurrence of daily temperature extremes has increased by a factor of 7 between anthropogenic and natural ensembles for the winter season, though these synoptic patterns rarely occur. For low‐pressure centres to the northwest of New Zealand, we observe high temperatures frequently in both anthropogenic and natural ensembles which we expect is probably associated with warm air advection from the Tropics. The frequency of occurrence of high temperatures in these synoptic patterns has also increased by a factor of 2 between the natural and anthropogenic ensembles. For these synoptic states, the extremes are observed in the North Island and along the east coast of the country with the highest temperature along the Canterbury coast and Northland. The change between the natural and anthropogenic ensembles is largest on the west coast along the Southern Alps for all the synoptic circulation types. [ABSTRACT FROM AUTHOR]

ABSTRACT This study characterizes rainfall and temperature variability for the whole of Vietnam and for climate sub-regions over 40 years from 1971 to 2010. Vietnam's average temperature has increased at a rate of 0.26 ± 0.10 °C per decade since the 1970s, approximately twice the rate of global warming over the same period. The rate of increase is greater in winter than in summer. Except for the Central Highland, annual average temperatures in southern regions are increasing more rapidly than in the North. The increases in temperatures are statistically significant in most sub-regions; however this is not the case for rainfall. The locations of climate boundaries between sub-regions are also discussed and suggestions for repositioning of these are made. Temperature and rainfall variability are shown to be linked to El Niño-Southern Oscillation on both national and sub-regional scale. This relationship is stronger in lower latitudes and in winter. [ABSTRACT FROM AUTHOR]

Intraseasonal relationships between Antarctic sea ice and atmospheric circulation have been investigated using a 29-yr record of pentad-mean Antarctic sea ice concentration and Southern Hemisphere 500-hPa height fields. Analyses were carried Out for four sea ice seasons: minimum extent, growth, maximum extent, and decay. interannual variability was removed from both datasets to focus on intraseasonal variations. Patterns of sea ice variability and linkages to the atmospheric circulation varied markedly with season. The strongest and most coherent relationships were evident during the maximum ice extent period and to a lesser degree during the growth period. At those times of year, the strongest relationships were associated with atmospheric circulation anomalies leading sea ice anomalies by 4 or 5 days, suggesting that variations in the atmospheric circulation force changes in the sea ice field. Ice decreases are generally found in regions of poleward flow and ice increases are found in regions of equatorward flow. Mechanisms appear to be related both to thermal advection and to mechanical forcing, with the relative importance of each varying in space and in time. During the period of maximum ice extent, the leading pattern from a maximum covariance analysis between 500-hPa height and sea ice concentration accounted for 38% of the squared covariance between fields, and the associated time series were correlated at 0.74. The leading patterns of variability exhibit clear zonal wavenumber 3 signatures and appear to be largely a result of internal variability in the extratropical circulation. [ABSTRACT FROM AUTHOR]

Weather types (WTs) are often used to assess the relationships between synoptic‐scale atmospheric dynamics and local scale climate anomalies. We focus here on Aotearoa New Zealand (ANZ) where pre‐existing WTs have recently been characterized using a set of descriptors monitoring the daily location and intensity of their main atmospheric centres of action (ACAs). We show here that the precipitation and temperature anomalies associated with the WTs in ANZ are more complex than previously thought. They do not solely depend on type occurrence, but are also strongly modulated by within‐type changes in the location and intensity of ACAs, and their interaction with surface terrain. Thus, the mere analysis of WT occurrence is not sufficient to explain climate variability over ANZ. The magnitude and sign of daily minimum and maximum temperature anomalies are strongly driven by meridional advection of temperature, which is also driven by within‐type changes in ACAs. The amplitude of precipitation anomalies is likewise strongly variable within WTs. Associated mechanisms involve interactions between the underlying terrain and atmospheric fluxes modulated by ACAs, modifying the strength and location of orographic uplift. Finally, daily extreme precipitation can occur under several cyclonic WTs, more particularly when their low‐pressure ACAs are significantly more intense than normal. This situation is associated with more intense moisture transport towards ANZ, promoting heavy precipitation there. These results provide a detailed assessment of within‐type variability in temperature and precipitation patterns at both synoptic and local scales. They also help to improve understanding of local effects of larger scale synoptic patterns, thereby allowing for more accurate use of analogues in forecasting. [ABSTRACT FROM AUTHOR]

Abstract: New Zealand''s climate during the Last Glacial Maximum (LGM) has been investigated using the United Kingdom Met Office global (HadAM3H) and regional model (HadRM3H). All models were set up according to the glacial conditions as specified by the Paleoclimate Modelling Intercomparison Project (PMIP), although SSTs and sea-ice were supplied from a set of prior coupled model (HadCM3) runs. The simulated climate of New Zealand during the LGM was mainly compared against a control simulation which was set up for pre-industrial conditions. New Zealand''s simulated LGM climate was cooler than today, varying spatially between 2.5 and 4°C. There was an increase in seasonality in temperature with the seasonal cooling being largest during winter. Excluding the Alpine/Fiordland region, the largest cooling geographically took place in the east of the South Island (ESI). Annual mean precipitation was reduced but there were significant regional and seasonal variations. The main band of precipitation along the West Coast shifted westwards, resulting in a reduction in precipitation over those regions in the Southern Alps that receive the largest amount of precipitation in today''s climate. The westerly circulation increased considerably over the North Island and the northern part of the South Island, but did not change much over the rest of the South Island. The stronger westerly wind accentuated the cooling over the western and northern parts of the North Island and it probably reduced the occurrence of incursions of tropical lows over the north of the North Island. The westerly winds were weaker over New Zealand during winter, which appears to be related to enhanced blocking activity during that season. The number and the strength of the southerlies increased, and they were capable of bringing very cold polar air over most of the country. The east of the South Island was affected especially by these cold winds. The simulated cooling during the LGM is not sufficient to limit forest growth. It is proposed here, that together with the general drier and colder conditions, it was the increase in seasonality and extremes of climate that limited the growth of certain vegetation types. [Copyright &y& Elsevier]

The article reports on the use of a high-resolution nested regional climate model (RCM) in the simulation of New Zealand's climate. The relation of RCM with GCM is presented, both are run under pre-industrial condition. Also, the comparison of RCM's seasonal mean output against the country's national climate database and the National Centers for Environmental Prediction (NCEP) data is mentioned. It shows that the seasonal and regional aspects of the modelled surface precipitation and temperature, which main difference are relative to the difficulty of incorporating the country's orography appropriately and to the initial and lateral limit conditions. An overview of the NCEP data on the correlation patterns of precipitation and temperature with mean sea-level pressure is offered.

In terms of the effects of future climate change upon society, some of the most important parameters to estimate are associated with changing risks of extreme rainfall events, both floods and droughts. However, such aspects of the climate system are hard to estimate well using general circulation models (GCMs)—in particular, for a small mountainous landmass such as New Zealand. This paper describes a downscaling technique using broad-scale changes simulated by GCMs to select past analogs of future climate. The analog samples are assumed to represent an unbiased sample of future rainfall and are used to develop detailed descriptions of rainfall statistics using hidden semi-Markov models of rainfall breakpoint information. Such models are used to simulate long synthetic rainfall time series for comparison with the historical record. Results for three New Zealand sites show overall increases in rainfall with climate change, brought about largely by an increased frequency of rainfall events rather than an increase in rainfall intensity. There was little evidence for significant increases in high-intensity short-duration rainfalls at any site. Such results suggest that, although regional increases of rainfall are consistent with expected future climate changes, it may be that circulation changes, rather than temperature (and vapor pressure) changes, will be the more important determinant of future rainfall distributions, at least for the coming few decades. [ABSTRACT FROM AUTHOR]

Long time series of reanalyses, from NCEP–NCAR and from ECMWF, are used to investigate the occurrence of persistent positive anomalies (PPAs) in the 500-hPa geopotential height field over the Southern Hemisphere extratropics during 1958–2001. Defining persistent anomalies as those of at least 100 m in magnitude lasting for at least 5 days, it is found that the region of most frequent occurrence is over the South Pacific. A cluster analysis of monthly PPA counts shows two distinct patterns, one a zonal wavenumber-1 (ZW1) pattern centered over the southeast Pacific near 60°S and the other a zonal wavenumber-3 (ZW3) pattern with centers near New Zealand and over the southern Atlantic and Indian Oceans. Results were insensitive to the choice of dataset, and to the removal of a linear trend from the daily height fields. The southeast Pacific PPA region is strongly modulated by ENSO, while the ZW3 pattern appears only weakly related to ENSO variability. A strong upward trend is apparent in occurrence of the ZW3 cluster, related to a matching trend in the variance of the height fields, particularly those from ECMWF. Such trends are at least in part a consequence of changes in the observing system, particularly the introduction of satellite soundings in the late 1970s. [ABSTRACT FROM AUTHOR]

A statistical scheme for predicting New Zealand seasonal-mean temperatures at the beginning of each season has been developed. It is significantly more skillful (in terms of the percentage explained variance) than earlier schemes, raising overall predictive skill to more than 30%, compared to less than 20% skill for prior schemes. Careful selection of predictors, based largely on physical reasoning, is the key reason behind the relatively high skill levels achieved. In particular, summer rainfall is identified as a useful predictor for autumn temperatures. This appears to be related to deep-level soil moisture and temperature, vegetation cover, and their subsequent effects on air temperature. This study emphasizes the importance of spatial coherence between regions in the selection of predictors. Seasonally dependent predictors are shown to significantly improve predictive skill, while spatially dependent predictors generally decrease skill. Estimates of the potential predictability of seasonal-mean New Zealand temperatures suggest that, in all seasons except summer, the statistical relationships documented here capture around 80% of the potential predictive skill. [ABSTRACT FROM AUTHOR]

Relationships on the seasonal timescale between Southern Hemisphere 500-hPa height, sea surface temperature, and Antarctic sea ice variability have been investigated using NCEP-NCAR reanalyses, NCEP sea surface temperatures, and Met Office sea surface temperature and sea ice data. The dominant region of interannual variability in the Southern Hemisphere circulation, over the southeast Pacific Ocean, is found to be relied to ENSO variability in tropical Pacific sea temperatures, as shown in a number of earlier papers. It is also relied to Antarctic sea ice variability, where an out-of-phase relationship is found between sea ice extent in the central Pacific and in the southwest Atlantic Ocean. Sea ice extent is enhanced in one region when the atmospheric flow anomaly is equatorward, presumably through a combination of anomalous heat flux and direct advection. At the same time, the atmospheric flow anomaly in the other region tends to be poleward, resulting in a poleward retreat in the sea ice edge. Such an interaction accounted for 63% of the total squared covariance between hemispheric 500-hPa height and sea ice edge anomalies. Averaged over the full data series used, no strong lag relationships were found, suggesting that circulation, sea ice, and sea surface temperatures respond to one another on intraseasonal timescales. However, a composite analysis with respect to the times of maxima or minima in Pacific sea ice extent did show apparently nonlinear lag behavior. The negative height anomalies over the southeast Pacific associated with maxima in Pacific sea ice tend to precede the ice maximum, or at least show no tendency to persist after the time of the ice maximum. However, positive height anomalies over the southeast Pacific associated with minima in Pacific sea ice tend to persist for some months after the ice minimum. The latter effect may be relied to anomalous surface heat fluxes associated with the upstream reduction in sea ice. [ABSTRACT FROM AUTHOR]

Presents responses to John Sloboda's article 'Emotion, functionality and the everyday experience of music: Where does music education fit?' published in the September 1, 2002 issue of the journal 'Music Education Research.' Reasons for the lack of retention in instrumental programs; Value of music for school students in Australia.

Improvements in observing systems over the last two decades now permit more detailed examinations of variability in the mid- and high-latitude Southern Hemisphere circulation. In this study the leading modes of variation in the extratropical sea surface temperature are identified from the Reynolds optimal interpolation (OI) dataset between November 1981 and December 1999. Although attempts were made to exclude the strong contribution due to El Niño-Southern Oscillation (ENSO) by confining the analysis between 60° and 15°S, the three leading modes were all ENSO-related. The first EOF with 13.9% of the monthly variance lags the Southern Oscillation index (SOI) by 2 months and depicts sea temperature variations characteristic of mature ENSO events. The second EOF, accounting for 8.8% of the variance, shows a "precursor" pattern that is strongly correlated with the SOI and with EOF1, which it leads by 9-10 months. This pattern is characterized by anomalies west and east of Australia (extending north of New Zealand), a dipole in the Atlantic, and a further center to the southwest of South America. The third EOF expresses variations in the amplitude of the southern arm of the "horseshoe" pattern of the opposite sign surrounding the ENSO anomaly in the central Pacific. In view of these strong links to ENSO and identification of the precursor pattern, further analysis was made of ENSO development patterns over the 1980s and 1990s in combination with datasets expressing lower- and upper-tropospheric flow patterns, outgoing longwave radiation, sea ice extent, and cyclone frequency. These show the expected pattern of behavior in the tropical belt. Farther south, the sea temperature anomaly off the east Australian coast is seen to strengthen and propagate eastward over the Pacific near 30°S. During warm events Rossby waves, initiated by convection in the midPacific, apparently force an anomalous anticyclonic circulation near 60°S in the eastern... [ABSTRACT FROM AUTHOR]

Investigates the patterns of convection in the tropical pacific and their influence on New Zealand weather. Characteristic patterns of convection in the tropical Pacific Ocean; Effects of these convection patterns on the New Zealand climate; Equatorial convection near the Philippines; Impact of changes in wind regimes over the New Zealand region; Skewing of the meridional flow over New Zealand; Spatial anomaly patterns in the climatic elements.

This study investigates common trends and individual differences in children's practice according to six dimensions of self-regulation. Seven children, aged between 7 and 9 years at the beginning of the study, regularly videotaped their practice over a 3-year period. Behavioural coding addressed the content of practice, the nature of errors and off-task behaviours, and the interaction of family members. Low levels of self-regulatory behaviour, as evidenced in the children's ability to monitor and control their own learning, were found during practice. Learning strategies were confined almost exclusively to playing through pieces once or twice. Most errors were either ignored or corrected by repeating one or two notes. Results show that self-regulatory processes vary widely between students, even from the very early stages of musical development, and help to explain why some learners develop their performance skills quickly while others struggle. Implications for music education and future research are discussed. [ABSTRACT FROM AUTHOR]

Presents information on a study which assessed the skills of global numerical prediction models in weather forecasting in Southern Hemisphere extratropics. Methodology; Results of the study; Identification of predictable and unpredictable weather patterns.

Provides information on a study which explored blocking over the southeast Pacific Ocean and its association with wave propagation from the tropics. Description of the datasets and statistical methods; Description of a series of simple barotropic modeling experiments; Conclusions.

Interannual variability in the frequency of atmospheric blocking events over the southern Pacific Ocean is analyzed in terms of variations in the El Niño--Southern Oscillation (ENSO) cycle, using a 16-yr record of Southern Hemisphere 500-hPa height fields. The number of days of blocking tends to increase on average during the warm phase of the ENSO cycle, particularly over the southeast Pacific during the southern spring and summer. Over the southeast Pacific between September and February, more than twice as many days of blocking are observed on average during El Niño events than during neutral or La Niña conditions. Changes in the frequency of days of blocking are found to be related to changes in the mean circulation and more strongly to changes in the variance of circulation over the South Pacific. [ABSTRACT FROM AUTHOR]

This study examines the month-to-month variations in the tracks of Southern Hemisphere weather systems and their relation to low-frequency circulation variability. Cyclones and anticyclones are identified and tracked from ECMWF analyses during 1980--94 via an automated method and the principal patterns of variation identified by EOF analysis of monthly track density anomaly fields. Only the first three EOFs of cyclone track density involving about one-third of the total track variance were distinguishable from noise. Spatial patterns derived from both unrotated and rotated EOF analysis were not reproducible on subsets of the data, pointing to secular changes in the variance structure of the cyclone dataset. An increase in cyclone numbers over the Southern Ocean during the 1980s suggested that detection of small-scale cyclones is sensitive to changes in data coverage and analysis procedure, as associated changes in the mean circulation were small during this period. EOFs of anticyclone track data were found to be more robust, indicating a variety of seesaw patterns across the hemisphere. The leading modes of sea level pressure variability are found to be associated with regional variations in cyclone and anticyclone activity. The first pressure EOF, the so-called high-latitude mode, modulates cyclone activity between middle and high latitudes, with increased (decreased) westerlies near 558--568S accompanied by more (fewer) cyclones in the circumpolar regions and fewer (more) in middle latitudes. The second and third EOFs have centers of action near 608S, 1208W and 558S, 1658W, respectively, and are linked with blocking activity in these two regions. Blocks in the New Zealand sector occur in conjunction with a zonal wavenumber 3 pattern, while southeast Pacific blocks have no significant correlations outside the Pacific. A coherent cyclone response to ENSO was also found. During El Niño winters, increased cyclone activity occurs in a band... [ABSTRACT FROM AUTHOR]

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 Niño-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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Anthropogenic climate change is affecting rivers worldwide, threatening water availability and altering the risk of natural hazards. Understanding the pattern of regional streamflow trends can help to inform region-specific policies to mitigate and adapt to any negative impacts on society and the environment. We present a benchmark dataset of long, near-natural streamflow records across Aotearoa New Zealand (NZ) and the first nationwide analysis of observed spatiotemporal streamflow trends. Individual records rarely have significant trends, but when aggregated within homogenous hydrologic regions (determined through cluster analyses), significant regional trends emerge. A multitemporal approach that uses all available data for each region and considers trend significance over time reveals the influence of decadal variability in some seasons and regions, and consistent trends in others. Over the last 50+ years, winter streamflow has significantly increased in the west South Island and has significantly decreased in the north North Island; summer streamflow has significantly decreased for most of the North Island; autumn streamflow has generally dried nationwide; and spring streamflow has increased along the west coast and decreased along the east coast. Correlations between streamflow and dynamic and thermodynamic climate indices reveal the dominant drivers of hydrologic behavior across NZ. Consistencies between the observed near-natural streamflow trends and observed changes in circulation and thermodynamic processes suggest possible climate change impacts on NZ hydrology. [ABSTRACT FROM AUTHOR]

ABSTRACT 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 Niño-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. [ABSTRACT FROM AUTHOR]

ABSTRACT 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. [ABSTRACT FROM AUTHOR]

During austral warm seasons (November - March, NDJFM) of 1934/35, 2017/18, 2018/19 and 2021/22 the New Zealand (NZ) region experienced the most intense coupled ocean/atmosphere (MHW/AHW) heatwaves on record. Average temperature anomalies over land and sea were +1.2 to 1.4°C above average. Common to all four events were maximum sea surface temperature (SST) anomalies to the west of the South Island of NZ. Atmospheric circulation anomalies showed a pattern of blocking high pressure over the Tasman Sea and Pacific Ocean to the south, and southeast of NZ, and reduced trough activity over and to the east of NZ, accompanied by strongly positive Southern Annular Mode conditions. Hindcasts for 2017/18, 2018/19 and 2021/22 NDJFM indicate that positive temperature anomalies around 1°C occurred in the Tasman Sea, and near 1.5°C for the Chatham Rise. The temperature anomalies in the upper 50m of the ocean are consistent with the 500hPa atmospheric height anomalies. The temperature anomalies in the upper 50m of the ocean are consistent with the 500hPa atmospheric height anomalies and associated winds. The eastern Tasman Sea during August 2021 to July 2022 experienced the highest annual number of MHW days during the satellite-era (1981-present) from OISSTv2.1 data. Under 1.5°C of global warming the four events would have ERIs of 2-3 years, and with 2°C of warming all would be considered cool years relative to the +2°C climate. For the 1957-2022 period, the two most intense heatwaves have ERIs of between 30 to 150 years. Major loss of glacial ice occurred from Southern Alps glaciers with rapid melt of seasonal snow in all cases. Slow advances in grape phenology since 1948 may be associated with increases in temperature over the same period. Cherries and apricot harvest dates advanced by one to two weeks. Marine impacts may be linked to starvation of kororā/Little Penguin (Eudyptula minor) chicks in the Bay of Plenty. Chicks weighed less and had a lower body condition score in 2020 and 2021 compared to 2019 and rescue calls in 2021 reached the highest volumes since 2015. The first record of warm-water prey species in the diet of yelloweyed penguins at Moeraki occurred, as well as widespread sea-sponge bleaching around northern and southern NZ. [ABSTRACT FROM AUTHOR]

Presents a reply to comments about the atmospheric blocking over the South Pacific and Rossby wave propagation. Austral springtime maximum in Rossby wave activity.

ABSTRACT 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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

ABSTRACT 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. [ABSTRACT FROM AUTHOR]

Palaeoclimate-proxy data provide an invaluable source of evidence for past climatic conditions, which can be compared with data from climate model simulations. This study illustrates how high-resolution regional climate model simulations can be used to estimate the difference in the climate of New Zealand between 6000 years before present (yr BP) and the pre-industrial era (c. ad 1750). Four pairs (pre-industrial and 6000 yr BP) of atmosphere-only global and regional climate model simulations were run with prescribed sea surface temperatures (SST). The SSTs are derived from four different fully coupled ocean–atmosphere general circulation model simulations, resulting in a different lower-boundary forcing in each of the atmosphere-only simulations. We find evidence for generally cooler conditions and for wetter (drier) conditions over eastern (western) New Zealand 6000 yr BP. The work compares well with model and proxy estimates of temperature and precipitation in the New Zealand region between 7000 and 6000 yr BP. The results also highlight the added value of regional model studies in regions with such complex terrain as New Zealand. This study also shows the limitations of applying uniformitarian principles when downscaling global model fields (and ‘up-scaling’ palaeo-proxy data) to infer past climatic conditions. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Synoptic classifications over the Southern Ocean in the Ross Sea region of Antarctica (50°S-Antarctic coast, 150°E-90°W) have been derived from NCEP reanalysis data (1979-2011), producing a set of six synoptic types for the region. These types describe realistic synoptic conditions for the region and represent the moisture-bearing low pressure systems that circulate around Antarctica. The types are described as follows: low Bellingshausen/Amundsen (L-BA), low (L), zonal (Z), low Ross (L-R), ridge (R), and low Amundsen (L-A). Seasonal frequencies of the synoptic types reflect the seasonal zonal shift of the Amundsen Sea low (ASL) and also correlate well with the Southern Oscillation index (SOI) and the southern annular mode (SAM). Variability in the occurrences of the synoptic types L-R and L-BA indicate a shifting of the position of the ASL farther east (west) toward (away from) the Antarctic Peninsula during La Niña (El Niño) and positive (negative) SAM conditions. A joint linear regression of the SOI and SAM indices show the strongest correlations with the types L-BA and L-R in the spring and quantifies the joint forcing effect of these climate cycles on synoptic variability in the region. As a demonstration of how synoptic classification provides links between large-scale atmospheric circulation and local climate parameters, the synoptic types are related to precipitation and temperature at Roosevelt Island, an ice core site on the Ross Ice Shelf (80°S, 160°W). The synoptic types provide quantification of distinct precipitation and temperature regimes at this site, which allows for more fundamental understanding of the precipitation source regions and transport pathways that drive the variability in snow and ice proxies. [ABSTRACT FROM AUTHOR]

The new South Pacific Enhanced Archive for Tropical Cyclones (SPEArTC) dataset provides an opportunity to develop a more complete climatology of tropical cyclones (TCs) in the southwest Pacific. Here, spatial patterns and characteristics of TCs for the 41-yr period beginning with the 1969/70 season are related to phases of the El Niño-Southern Oscillation (ENSO), taking into account the degree of ocean-atmosphere coupling. Twentieth-century reanalysis data and the coupled ENSO index (CEI) were used to investigate TC genesis areas and climate diagnostics in the extratropical transition (ETT) region at and south of 25°S during different CEI ENSO phases. This is the first study looking at CEI-based ENSO phases and the more detailed relationship of TCs to the coupling of the ocean and atmosphere during different ENSO phases. Consistent with previous findings, positive relationships exist among TCs, sea surface temperature, and atmospheric circulation. A statistically significant greater frequency of major TCs was found during the latter half of the study period (1991-2010) compared to the 1970-90 period, again consistent with the findings of other studies. Also found were significant and consistent linkages highlighting the interplay of TCs and sea surface temperature (SSTs) in the southwest Pacific basin west of 170°E and a closer connection to atmospheric circulation east of 170°E. Moreover, this study demonstrates subtle differences between a fully coupled El Niño or La Niña and atmospheric- or ocean-dominated phases, or neutral conditions. [ABSTRACT FROM AUTHOR]