M. J. Salinger

New Zealand climate: temperature and precipitation variations and their links with atmospheric circulation 1930–1994

New Zealand’s complex orography gives distinct regional responses to variations in atmospheric circulation. By using rotated principal components, three spatially coherent temperature, and eight rainfall regions are defined for describing climate variations and trends for the period 1930‐1994. Two main circulation changes have occurred in the New Zealand area over the record examined, around 1950 and 1975, making it convenient to analyse the data in three periods: 1930‐1950, 1951‐1975 and 1976‐1994. From 1930 to 1950 more south to southwest anomalous flow occurred, relative to later years. All three temperature regions recorded lower temperatures, and wetter years occurred in the northeast of the South Island, with drier years in the north and west of the South Island. Airflow from the east and northeast increased during the period 1951‐1975. This was accompanied by increases in mean temperature in all regions, with wetter conditions in the north of the North Island, and drier conditions in the southeast of the South Island. In the final period analysed (1976‐1994) more

Variations in Surface Air Temperatures. Part 3: The Antarctic, 1957–82

Abstract Antarctic temperature variations for 1957°82 have been objectively analyzed by gridding monthly data, from 16 stations, onto a 5° latitude by 10° longitude grid, from 65 to 90°S. These gridded data were used to calculate monthly values of the spatial mean temperature south of 65°S. The uncertainty in the area average is estimated to be 0.22°C for the annual values prior to 1970. After 1970 there is an additional uncertainty of about 0.10−0.16°C due to the cessation of Byrd station. The annual mean and summer areas averages show significant linear warming trends amounting to 0.74 and 0.77°C respectively. Spatial characteristics of the annual and seasonal temperature variations are described using principal components analysis of the station anomaly data. The first two principal components of the annual and winter data are similar PC1-winter is also similar to the winter pattern for linen trend found by van Loon and Williams for 1956–73. The warming trend associated with this pattern ceased in the ...

EXTRATROPICAL CIRCULATION INDICES IN THE SOUTHERN HEMISPHERE BASED ON STATION DATA

Zonal and meridional pressure gradient indices of the Southern Hemisphere (SH) circulation are analysed in the mid-to-high (35–65°S) latitude zone. The dearth of land regions, and hence long pressure records, means that these are restricted to the southern South American and New Zealand sectors. The Trans Polar Index (TPI) is the only large-scale station pressure based extratropical SH index that has been proposed, and is based on the normalised pressure difference between Hobart, Tasmania and Stanley, Falklands. This index is compared with variants which involve stations in the vicinity of New Zealand and southern South America. The index shows considerable year-to-year and some decadal-scale variability and is a measure of wavenumber 1 of the SH pressure field. Significant correlations (r≈−0.3 to −0.5) occur between the TPI and southern South American temperatures in the austral summer and autumn seasons. Similar size correlations of the opposite sign occur in New Zealand but only in the austral summer season. In New Zealand and southern South America, temperature series are strongly affected by the strength of the local meridional circulation (r values≈−0.4 to −0.7 over New Zealand depending on season and period and values of ≈−0.2 to −0.4 for southern South America). In both regions there is no concomitant increase in northerly flow or decrease in southerly flow to explain the long-term increase in temperatures. The relationships are mostly at the interannual rather than the decadal and longer timescales. The decadal temperature rise, therefore, reflects a general warming of the Southern Ocean, rather than decadal-scale variations in the circulation. Copyright