Abstract
Convective precipitation associated with tropical depression (TD) is one primary type of post-flooding season rainfall in South China (SC). Observations of the Tropical Rainfall Measuring Mission (TRMM) satellite have shown specific diurnal features of convective rainfall in South China, which is somewhat different from that in other seasons or regions of China. Convective precipitation is usually organized into a rainfall band along the southeastern coast of South China in the early morning hours. The rainfall band develops and intensifies quickly in the morning, then moves inland in the afternoon and, finally, diminishes at night. The daily convective rainfall along the coast is much more than that in the inland region, and heavy rainfall is often found along the coast. A long-duration heavy rainfall event associated with tropical depression “Fitow” during the period from 28 August to 6 September 2001, is selected in this study to explore the diurnal feature of convective rainfall and its formation mechanism. Modeling results of the 10-day heavy rainfall event are compared with both rain-gauge observation and satellite-retrieved rainfall. Total precipitation and its spatial distribution, as well as diurnal variations are reasonably simulated and agree well with observations. Further analysis reveals that the development and movement of convective precipitation is mainly related to the land and sea breezes. The anomalous height-latitudinal circulation in the morning-to-noon hours is completely reversed in the afternoon-to-late-evening hours, with the convective rainfall swinging back and forth, following its updraft branch. Sensitivity experiments show that the afternoon convective rainfall in the inland region of SC is caused by the diurnal variation of solar radiation forcing. The mountain range along the coast and the complex topography in the inland region of SC plays a critical role in the enhancement of diurnal convective rainfall everywhere. The formation of a heavy rainfall band along the southeastern coast of SC and the diurnal variation of the rainfall pattern are mainly the results of the land-sea thermal contrast.
Highlights
Warm-season rainfall over China has distinct seasonality under the influence of the East Asian summer monsoon [1]
This study reveals that the diurnal pattern of rainfall associated with tropical depression (TD) is somewhat different from that in other seasons or regions of China
The results suggest that the settings we used in this study give the best simulation, especially for the simulation of the TD track and the temporal and spatial distribution of heavy rainfall
Summary
Warm-season rainfall over China has distinct seasonality under the influence of the East Asian summer monsoon [1]. Yu et al [5] showed that diurnal summer rainfall peaked in late afternoon in the inland region of southern China, around midnight, over most of the Tibetan Plateau and its eastern periphery and in early morning in the middle Yangtze River valley. Li et al [6] pointed out that the peak time of diurnal rainfall in southeastern China appeared in the mid-late afternoon, while in southwestern China, daily maximum precipitation often occurred at midnight or in the early morning. He and Zhang [7].
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