【作者】 刘飞；

【导师】 何金海；

【作者基本信息】 南京信息工程大学 ， 气象学， 2006， 硕士

【摘要】 高空西风急流的变化对东亚夏季风异常有很大影响,研究西风急流的活动对我国夏季旱涝的预报有重要意义。本文利用ECMWF ERA-40再分析资料和1958～2000年全国160站月平均降水资料,分析了东亚夏季高空西风急流的时空分布特征,定义了东亚夏季西风急流指数(SWJI),研究了西风急流年际变化与大气环流异常及我国夏季降水的关系。结果表明: (1) 夏季纬向风最强位于200hPa,且存在两个中心,分别位于90°E和150°E。EOF分析表明夏季东亚西风急流中心位置存在南北差异,定义了东亚夏季高空西风急流位置指数(SWJI),SWJI能较好的表征东亚夏季西风急流的变化特征,高SWJI年西风急流位置偏北,低SWJI年西风急流位置偏南,急流中心位置总体存在向南的变化趋势,年际变化表现为3年和6年为主的准周期变化特征。 (2) SWJI与长江中下游夏季降水呈显著负相关,与河套、华北地区为正相关。即SWJI高(低)年,夏季长江中下游流域降水明显偏少(多),河套、华北和华南地区降水偏多(少)。 (3) 东亚夏季西风急流位置偏南年,东亚夏季风偏弱,副高位置异常偏西偏南,低层来自高纬的偏北气流和低纬的偏南气流在长江中下游流域汇合,梅雨锋在此维持,长江中下游夏季降水明显偏多。 (4) 西太平洋副高的位置和强度变化及赤道中东太平洋和副热带北太平洋的海温异常对东亚夏季西风急流位置的年际变化具有重要作用。 (5) 东亚夏季西风急流位置指数与前期Nino3指数、南亚高压西侧纬向风强度,北极涛动指数(AOI)和东亚海平面气压距平均存在显著的负相关。这些相关因子可作为东亚夏季西风急流异常的前兆信号,进而为我国夏季旱涝的预报提供参考依据。更多还原

【Abstract】 Anomalies of the summer westerly jet over East Asian have important impacts on East Asian summer monsoon climate anomalies. Based on the reanalysis data from ERA - 40 datasets supplied by ECMWF with resolution 2. 5°x2. 5° and monthly precipitation of 160 Chinese stations from 1958 to 2000 supplied by National Meteorological Information Center, the climate and space - time characteristic and the interannual variability of summer westerly jet over East Asian are analyzed, then an index—East Asian summer westerly jet index (SWJI)—is defined to represent the location fluctuation of East Asian summer westerly jet (EASWJ). In addition, we study the general circulation feature of SWJI anomaly, relationship between it and Summer Rainfall in China and preceding signal of SWJI anomaly. The results demonstrated that: I. The strongest center of summer zonal wind over East Asian lies in 200hPa, there are two centers in 90°E and 150°E separately. It is shown that the location fluctuations of East Asian summer westerly jet have important impact on Summer Rainfall in China, high SWJI year relates to EASWJ moving north from the average,;vice versa. Variation of SWJI exhibit notable three years and six years low frequency oscillation.II .Anomalies of EASWJ have important effects on Summer Rainfall in China, we find that high SWJI year relates to less rainfall in the mid and lower reaches of Yangtse river and more in south China, the mid-reaches of the Huanghe river;vice versa. III. When the EASWJ moves south from the average, the west Pacific subtropical high andwesterly belt in 500hPa also move south from the average, the cross-equatorial flow in 105cE andEast Asian summer monsoon is weak, there is a negative EAP pattern in 500hPa. The northernflow from higher latitudes and southern flow from lower latitudes converge in the mid and lowerreaches of Yangtse river, resulting in the strengthening and maintenance of Meiyu Front, rainfallin the mid and lower reaches of Yangtse river are more than average.IV.It is shown that the changes of subtropical high, SST of the middle and east equatorial Pacificand subtropical north Pacific have important impact on variability of EASWJ.V. The preceding Nino3 index, zonal wind in 200hPa, Arctic Oscillation Index (AOI) and SLPover East Asian could be used to predict the variability of EASWJ and offer some predictivesignals for the summer precipitation forecasting in China更多还原