ISSN 1000-0526
CN 11-2282/P
CN 11-2282/P
Circulation Analyses on Persistence Rainy Days from February to March 2009
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Abstract:
Based on the JRA-25 (1.25°×1.25°) reanalysis datasets, the circulation features and moist conditions of the persistence rainy days from February to March 2009 are investigated. The results show that: (a) at the middlehigh latitudes, the blocking situations are stable over the Eurasia, and at the middlelow latitudes, the West Pacific subtropical high (WPSH) is intensified over the Philippine Sea. Under these stable circulations, the colddry air from the north contacts the warmwet airflows from the south over the middlelower reaches of Yangtze River for a long time, which forms a stationary front. (b) In the upper troposphere, the axis of the subtropical westerly jet stays around 35°N, enhancing the divergence above the stationary front. The divergence matches the cyclonic convergence north of the southwester lies on the low levels, which forms a favorable rainproducting dynamic structure. (c) The anticyclonic circulation anomaly, according to the intensified WPSH, results in a moisture transport anomaly from the West Pacific and the South China Sea to southern China. The meridional transport anomaly contributes the most of the moist convergence in the rainy area, having significant impacts on the development and persistence of the precipitation.
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