Analysis of Occurrence Frequency of Precipitation Feature over Tibetan Plateau, East China and Subtropical North America in Boreal Summer Using TRMM Data
Using TRMM data from 1998 to 2011, occurrence frequency of radar precipitation feature (RPF) over Tibetan Plateau (TP), eastern China (EC), west subtropical North America (WNA) and east subtropical North America (ENA) in boreal summer (June-August) are comparatively analyzed. A RPF is defined as a three dimensional object consisting of pixels with precipitation near the ground observed by the TRMM precipitation radar. For each region, RPFs are divided into three groups: all RPF, large RPF (area larger than 1000 km2), and small RPF (area less than or equal to 400 km2). Occurrence frequency of RPF number and occurrence frequency of RPF pixel number in each group over each region are analyzed. The results are as follows: (1) The maximum and minimum occurrence frequencies of RPF number are over TP and ENA, respectively. In contrast, the maximum and minimum occurrence frequencies of RPF pixel number are over EC and TP, respectively. (2) Diurnal variations of occurrence frequency of RPF over the four regions mainly present a single peak in afternoon to late afternoon, with the peak of the large RPF appearing later than that of the small RPF. In contrast, diurnal variation of occurrence frequency of RPF pixel number over EC presents double peaks. (3) Diurnal variations of occurrence frequency of RPF pixel number are consistent with those of rainfall based on rain gauge observations in previous literature.