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 middle high latitudes, the blocking situations are stable over the Eurasia, and at the middle low latitudes, the West Pacific subtropical high (WPSH) is intensified over the Philippine Sea. Under these stable circulations, the cold dry air from the north contacts the warm wet airflows from the south over the middle lower 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 rain producting 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.