华南前汛期开始日期异常与大气环流和海温变化的关系

利用1961—2012年美国国家环境预报中心/大气研究中心(NCEP/NCAR)的再分析资料、NOAA海温资料,CMAP降水资料和华南261个测站降水观测资料,首先分析华南前汛期开始日期(以下简称华南开汛)异常的气候特征,然后采用相关分析、合成分析的方法研究华南开汛异常与3—4月大气环流以及海温变化的关系。结果表明,近52 a来华南开汛具有显著的年际变化特征,但变化趋势不明显。开汛最早出现在1983年3月1日,最晚出现在1963年6月1日,1961—2012年华南平均开汛日期是4月6日。华南开汛主要出现在3—4月,占92.3%。华南开汛与3—4月华南降水相关最显著,开汛偏早(晚),对应华南3—4月降水偏多(少)。华南开汛偏早年,在3—4月,对流层高层副热带西风急流偏强,中层西太平洋副热带高压偏强偏西、低层南支槽偏强,华南上空西南气流偏强;华南开汛偏晚年则相反。华南开汛与3—4月中国南海及周边地区海温显著相关,海温偏低(高)对应华南开汛偏晚(早)。华南开汛偏晚年的海温和大气环流异常比早年显著。

Anomalous onset date of the first rainy season in South China and its relationship with the variation of the atmospheric circulation and SST

Using the NCEP/NCAR reanalysis data, the NOAA Sea Surface Temperature (SST) data, the CMAP precipitation data and the rainfall observations from the 261 stations in South China from 1961 to 2012, the anomalous climatic characteristic of the onset date of the first rainy season (OSFRS) in South China was analyzed. The relationship between OSFRS in South China with the variations of the atmospheric circulation and preceding SST on March-April were analyzed by the correlation and composite analysis methods. The results showed that OSFRS in South China had significant interannual variation in the last 52 years, but its the variation trend wasn't obvious. the earliest OSFRS in South China was on March 1, 1983, the latest was on June 1, 1963. The mean OSFRS during 1961-2012 was on April 6. OSFRS in South China were usually in March and April (account for 92.3%). There was a significant correlation between OSFRS in South China and the precipitation in March-April in South China, with the precipitation in March-April in South China more (less) in years of earlier (later) OSFRS in South China. In March-April of the years of earlier OSFRS in South China, the subtropical westerly jet stream was stronger compared with the mean in the upper troposphere, the western North Pacific subtropical high was stronger and shifts westwards in mid-troposphere, the southwest air current was stronger in South China and the south branch trough was stronger in the lower troposphere, but was opposite in the years of later OSFRS in South China. There was significant correlation between OSFRS in South China and SST in March-April in the South China Sea and its surrounding areas. The SST of the South China Sea and its surrounding areas was lower (higher) while in the years of later (earlier) OSFRS in South China. The atmospheric circulation and SST anomaly in the years of later OSFRS in South China was more notable than that in earlier year.