The cumulonimbus incus in summer Asia as detected by the TRMM PR.

The precipitation type of “others” defined in the algorithm of the Tropical Rainfall Measuring Mission (TRMM) Precipitation Radar has not been attached importance to for long time. So it’s unknown what their physical significances are. Based on cases analysis and statistics analysis, the “others” precipitation in summer Asia of the last ten years was investigated. The case analyses indicate that the profiles of the “others” show the shape of cumulonimbus incus with the profile peak (about 0.6-1.0 mm/h) appearing at the altitude of 8-10 km, together with the mean reflectivity over 0.8 and mean infrared brightness temperature below 215 K. According to these features of cumulonimbus incus profiles, statistics on cumulonimbus incus is performed with the accumulative total rain rate greater than 1 mm/h above 5 km altitude defined as the incus profile in this paper. The results reveal that the cumulonimbus incus samples are near 70% of the total samples of “others” type with their occurring frequency ranging from 0.1% to 0.4% in summer Asia, which is at least in excess of a tenth of the convective precipitation frequency therein. The results also show that the frequency of cumulonimbus incus over land is greater than that over ocean. Generally, the averaged thickness of cumulonimbus incus is about 3-4 km with its bottom located at 6 km altitude and its top altitude of about 10-12 km. The statistical calculations indicate that the mean reflectivity for such cumulonimbus incus is from 0.8 to 0.9 with the mean infrared brightness temperature below 220 K.