Comparison Of Precipitation Between Rain Gauge Observations And TRMM PR Measurements

Rainrate measured by TRMM PR and 430 rain gauges in the mainland of Southern China from January 1998 to December 2005 are compared on multiple–time-scale, in order to stress differences between these two precipitation data sets. Consistent precipitation distribution was found between the two data sets at 2.5o scale in terms of multiyear average and seasonal mean, expect for those significant differences in extreme value and coverage area. Generally, mean rain rates obtained by rain gauges are relatively higher than those from PR. The region with difference less than 1mm/d occupies over 50% in Southern China against about 30% with difference about 1~2mm/d. However, the difference reaches more than 2mm/d during summer in the most part of Southern China. Analysis indicates that the difference is mainly determined by the spatial density of the rain gauge distribution. The correlation coefficient is higher than 0.7 when the number of rain gauges in each grid is over 6. However, both data sets show less correlation in summer than that in other seasons regardless of the number of rain gauges in each grid. The difference between the two data sets is also larger in the region where the frequency of convective precipitation is higher than that of stratiform precipitation. By using TRMM PR measurements, the distribution of monthly mean rain rate averaged in 8 summers over the Tibetan Plateau is investigated. Results display that there are 2mm/d precipitation areas over the eastern plateau in June, while in July and August 1mm/d rain rate covers the most part of plateau except for the western portion. Besides, rainrate higher 3mm/d appears in the center of the plateau.Research about convective and stratiform precipitation over the mainland of Southern China suggests that the frequency of convective precipitation is two times higher than that of stratiform precipitation. Since the conditional rain rate of convective precipitation is much higher than that of stratiform precipitation,contributions to total precipitation of the two kinds precipitation are almost the same. The distributions of both kinds of precipitation suggest remarkable regionality. The frequency of convective precipitation reaches the peak at afternoon over most part of south China, but different regions with different amplitudes. In contrast, the diurnal cycle of stratiform precipitation is much mild. The diurnal cycle of convective and stratiform precipitation profiles mainly display in the variable of storm top, the variation of precipitation cloud depth as well. The storm top of convective precipitation lies between 9km and 16km, while the storm top of stratiform precipitation is about 9km. The diurnal cycle of the storm top of convective precipitation is sharper than that of stratiform precipitation. Moreover, the profiles of both kinds precipitation over different regions are obviously distinct. The cross sections of both kinds precipitation not only show that the variability of the storm top of convective precipitation is much sharper than that of stratiform precipitation, but also show diurnal cycle of the conditional rain rate of stratiform precipitation is sharper than that of convective precipitation. The conditional rain rate of stratiform precipitation changes more significantly among different regions.