我国春季降水的分布特征及其与环流异常的关系

The distribution feature of spring rainfall and its relation to circulation anomaly in China

利用EOF、小波分析和相关分析讨论了我国春季降水的分布特征及降水异常的环流背景,结果表明:春季降水(3～5月)主要集中在北纬30°以南的中东部地区,而北方则降水稀少,西部降水有增加的趋势,中东部降水有减少的趋势,但不是很明显.EOF1表明长江以南和长江以北的降水呈反向分布,长江以南大范围降水变化的特征时间尺度分别为2,7a和15a,且15a时间尺度变化有明显向较大时间尺度演变的趋势,EOF2表明长江中下游与华南降水呈反向分布,长江中下游大范围降水变化的特征时间尺度分别为2,9a和更大时间尺度,且9a时间尺度变化具有明显的向较小时间尺度演变的趋势.当退居在中太平洋的副高偏强,西伸,副高北侧气压梯度力加大时,有利于长江以南地区降水,当副高偏北,西伸到长江中下游上空,乌拉尔山阻高偏强时,则有利于长江中下游地区降水.

Using EOF, wavelet analysis and correlation method, distribution feature of spring rainfall and its relation to circulation anomaly are investigated. The results show that spring rainfall mainly concentrates in the center and eastern areas of the south to the North Latitude 30, but less in north. The spring rainfall increases in the west and decreases in the center and eastern areas, but not apparent. EOF1 shows that relation between rain- fall to the south of Chang Jiang River and to north of Chang Jiang River is contrary. There are 2year,7year and 15year characteristic timescale for variability of a wide range rainfall to the south of Chang Jiang River, and 5year characteristic timescale has a tendency to move towards larger timescale. EOF2 shows that the distributions of rainfall in the South of China and the middle and lower Chang Jiang River are contrary. There are 2year,9year and lager characteristic timescale for variability of a wide range rainfall in middle and lower Chang Jiang River, and 9year characteristic timescale has a tendency to move towards smaller timescale. It is helpful for a wide range rainfall to the south of Chang Jiang River when subtropical high in the middle of Pacific ocean is increasing and extending to west while pressure - gradient force is increasing in north of subtropical high. It is helpful for a wide range rainfall in middle and lower Chang Jiang River when the subtropical high is moving to the north, extending to middle and lower Chang Jiang River and Ural Mountains blocking high is increasing.