ISSN 1000-0526
CN 11-2282/P
CN 11-2282/P
Archive > Volume 41 Issue 3 > 2015,41(3):286-295. DOI:10.7519/j.issn.1000-0526.2015.03.003 Prev Next
Study on Rainfall Characteristics in Rainy Season in Western Jiangnan Region and Its Possible Links with SSTA in Tropical Oceans
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Abstract:
By comparing the Western Jiangnan rainy season and the Meiyu season in Eastern China, preliminary analysis on what and how the tropical Pacific and Indian sea surface temperature anomaly (SSTA) affects the regional precipitation was performed, and then the potential mechanism was studied. The results showed that: (1) Western Jiangnan rainy season, which starts early and lasts for a longer period, is an important part of China Meiyu season. It has obvious interannual and interdecadal variations, of which, since the beginning of twenty first century, it has been into a relative dry period. (2) The SSTA in the previous winter in tropical ocean is a strong signal for more or less rainfall in Western Jiangnan rainy season. That is, when SSTA in eastern equatorial Pacific is positive (negative), SSTA in West Pacific and the subtropical area of East Pacific is negative (positive), and SSTA in tropical India Ocean is positive (negative) in north and negative (positive) in south, there will be more (less) precipitation in Western Jiangnan Region in the following rainy season, which corresponds to more (less) rainfall in South and less (more) in North in China in Meiyu season. (3) In the positive (negative) tropical SSTA years, strong easterly (westerly) wind anomalies prevail in India Ocean, and they are difficult (easy) to turn north to become southerly anomalies, that is to say, the Indian monsoon is in a weak (strong) phase. At the same time, there are strong easterly (westerly) anomalies in West Pacific equatorial regions, and an (a) anticyclone (cyclone) anomaly circulation dominates the northern part of Pacific, which means the West Pacific subtropical high extends to westward (eastward), in a stronger (weaker) state. So, it is (not) beneficial to precipitation in Western Jiangnan. (4) In the positive tropical SSTA years, the water vapor source to Western Jiangnan comes mainly from the Western Pacific Ocean and forms net water vapor convergence in this area, conducive to more precipitation; but in the negative tropical SST abnormal years, the water vapor comes from both Pacific and Indian Oceans, and Western Jiangnan is only a vapor transition zone, not easy to form the water vapor convergence there, resulting in less precipitation.
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