Evaluation of Atmospheric Circulation in the Southern Hemisphere in 20CRv2

Abstract

Evaluation of the mean climate and climate variability in the Southern Hemisphere(SH) in the Twentieth Century Reanalysis data version 2(20CRv2) is conducted and the results are compared with the NCEP/ NCAR version 2 Reanalysis data(NCEPv2) and the Hadley Center sea-level pressure data(HadSLPv2).The results show that SH polar High,SH subtropical High,upper level split jet,cross-equatorial flow,Antarctic Oscillation(AAO),and the pattern of Pacific-South-America(PSA) has been effectively captured by 20CRv2 during 1979–2010,with an apparent zonal asymmetry of AAO in the austral winter(June-July-August,JJA).The notable upward linear trend of AAO in the entire period of 1871– 2010 is represented in both 20CRv2 and HadSlPv2.The most remarkable discrepancy of the SH climate variability between 20CRv2 and HadSLPv2 occurred in 1897–1920 and was partly caused by such factors as the paucity of meteorological and oceanographic data in the SH to be assimilated,the handling of the specified sea-ice concentration in South Pole,and imperfect climate models.The consistency of these reanalysis data is increased with the use of a large amount of satellite observation and radiosonde data,particularly after 1979.