ECMWF analyses and reanalyses depiction of ENSO signal in antarctic precipitation

The Fl Nino-Southern Oscillation (ENSO) signal in Antarctic precipitation i s evaluated using European Centre for Medium-Range Weather Forecasts (ECMWF ) operational analyses and ECMWF 15-yr(1979-93) reanalyses. Operational and reanalysis datasets indicate that the ENSO teleconnection with Antarctic p recipitation is manifested through a close positive correlation between the Southern Oscillation index and West Antaretic sector (75 degrees-90 degree s S. 120 degrees W-180 degrees) precipitation from the early 1980s to 1990, and a close negative correlation after 1990. However, a comparison between the operational analyses and reanalyses shows significant differences in n et precipitation (P - E) due to contrasts in the mean component of moisture flux convergence into the West Antarctic sector. These contrasts are prima rily due to the mean winds, which differ significantly between the operatio nal analyses and the reanalyses for the most reliable period of overlap ( 1 985-93). Some of the differences in Row pattern are attributed to an error in the reanalysis assimilation of Vostok station data that suppresses the g eopotential heights over Fast Antarctica. Reanalysis geopotential heights a re also suppressed over the Southern Ocean, where there is a known cold bia s below 300 hPa. Deficiencies in ECMWF reanalyses result in a weaker ENSO s ignal in Antarctic precipitation and cause them to miss the significant upw ard trend in precipitation found in recent operational analyses. Ice-core a nalyses reflect both an upward trend in ice accumulation and the ENSO telec onnection correlation pattern seen in the operational analyses. This study confirms the results of a previous study using ECMWF operational analyses t hat was the first to find a strong correlation pattern between the moisture budget over the West Antarctic sector and the Southern Oscillation index.