Anomalies of Ocean and Atmospheric Circulation in 2011 and Their Impacts on Climate in China

Based on the real-time and historical observation data,the climatic anomaly of 2011 in China and its causes were analyzed by climate statistics and climate diagnostic methods.The result showed that global ocean sea surface temperature forcing and the atmospheric circulation abnormality features attributed to the internal atmospheric dynamic processes,may lead to the climatic anomalies and major climate events in China,with such significant anomalies of climatic features as less precipitation,higher air temperature and warm-dry type in 2011.Results manifested that the eastern and central equatorial Pacific entered the La Nina conditions again in September 2011,with the La Nina event of 2010/2011 starting at July 2010 and ending in April 2011;The subtropical high over the West Pacific(SHWP) was abnormally weaker than normal and further east to its normal position before May 2011,which resulted in severe meteorological drought in the Middle and Lower Reaches of the Yangtze River during spring,while SHWP stronger than normal from then on,especially abnormally stronger in June,which led to more Meiyu precipitation amounts and rapid transition between drought and flood in the Middle and Lower Reaches of the Yangtze River;The SHWP was further north to its normal position in autumn,together with the phased cold air activities,those resulted in more precipitation during the season in the area of Huaxi and Huanghuai.The tropical Indian Ocean SSTA firstly experienced negative Indian Ocean Dipole(IOD) mode in 2011,then turned into the basin-wide warming mode in summer.The East Asian winter monsoon(EAWM) intensity was stronger than normal in 2010/2011 winter,while intensity of the East Asian subtropical summer monsoon (June-August) was near normal.The intensity of the South China Sea(SCS) summer monsoon was weaker than normal on the whole,with the earlier onset and later ending.In accord with the decadal background, tropical cyclone generated number was less than the normal in the SCS and West Pacific in 2011.