南海登陆热带气旋对长江三角洲地区降水的影响

利用热带气旋年鉴资料统计了1949~2000年南海热带气旋影响期间我国长三角地区的最大降水量，计算有南海热带气旋影响时最大降水量大于50 mm的条件概率为60%。并把历年引起长三角地区50 mm以上降水的南海气旋频数序列作小波变换，发现其具有周期性振荡的特点，并且振荡周期在频率的分布上也有一定的规律。把南海热带气旋频数序列与夏季3个月副高面积指数之和的序列做交叉谱分析，发现两者具有准2年和准5年的耦合周期，气旋频数序列在位相上超前约半年。最后用1951~1999年的500 hPa月平均高度资料统计频数异常年的500 hPa高度场的距平和t统计量，发现在西太平洋、大西洋和极地都有显著的异常。

Precipitation in the Yangtze River Delta Fields Caused by Tropical Cyclones Landing in the South China Sea

The maximum precipitation in the Yangtze River Delta which were caused by the tropical cyclones landing in the South China Sea in 1949—2000 were studied. The probability of precipitations above 50 mm was worked out when there was a tropical cyclone in the South China Sea. It is about 60 percents. A wavelet transform about the frequency of the tropical cyclones was performed. The results show that this series has notable oscillations and the periods vary in some regulations. As results of a cross power spectral analysis about the frequency series of the tropical cyclones and the sum series of the subtropical high area indexes of July, August and September, the two series have quasi-two-year and quasi-five-year coupled oscillations. The anomalies in the West Pacific, the Atlantic and the North Pole were found out when the Northern Hemisphere 500 hPa height data of anomalistic years were analyzed.