The local climate on the East Antarctic Plateau in relation to large scale flow patterns

Abstract

Although the density of observation sites is low on the East Antarctic Plateau, there are several locations at which meteorological observations are conducted. These observations provide insights into the local climate, and are invaluable for evaluating climate models and satellite observations. Additionally, the ERA5 reanalysis dataset from the European Centre for Medium-range Weather Forecasts (ECMWF) may enable these records to be extended with longer time series and far more complete spatial coverage, providing further insights into local climate conditions. The main purpose of this study is to obtain a better understanding of the variability and trends in local climate on the East Antarctic Plateau, and therefore better understand how conditions on the East Antarctic Plateau react to changes in climate. The first step toward this goal is to assess the agreement between observational records and ERA5 data for the parameters of interest – air temperature, surface pressure, and wind speed – in order to determine whether the ERA5 data are suitable for extending these records. The next step is to analyze the available data by examining climatological averages, comparing conditions at different sites, and investigating variability and trends. In the final step, local variables are examined in relation to indices representing two large-scale atmospheric flow patterns that are known to impact the Antarctic climate: the Southern Annular Mode (SAM) index and the Southern Oscillation Index (SOI). Despite the fact that comparisons between observations and ERA5 data are imperfect, there is often fairly good agreement between them, particularly for air temperature and surface pressure. While no statistically significant temporal trends are found in monthly mean (potential) temperature at any site for either observations or ERA5, some significant temporal trends are found for wind speed in both datasets at some sites, which could be connected to an upward trend in the SAM in recent decades. Both linear regression correlations and empirical orthogonal function (EOF) analysis show the effects of the SAM to be far more prominent than those of the SO in this region. Both (potential) temperature and wind speeds are found to decrease with high SAM index values – when the meridional pressure gradient is stronger between Antarctica and lower latitudes – while any impact from the SO seems absent or negligible. Whether either the SAM or SO has an effect on snow accumulation in this region is unclear.