A statistical study on the relationship between rain top heights and lightning activity over the global tropics utilizing TRMM PR2A25 and LIS data

Utilizing 5 years of TRMM PR2a25 version5 and LIS data, relationships between the rain top height and lightning activity are studied in the global tropics. In the deep tropics from 20N to 20S, rain-weighted-mean rain top heights are 7.4km over ocean and 9.2km over land for convective rain, 6.5km and 7.3km for stratiform rain, and, 6.9km and 8.0km for total rain, respectively. The ratio of deep convective rain (RDCR) to the total convective rain, determined with the rain top height (RTH) larger than the -20degC level, is typically less than 50% over ocean, while it is typically 60-70% over land. However, during the monsoon mature season, RDCR over land reduces to the typical oceanic values. Oceanic rain is also characteristic of larger contribution of warm rain. The ratio of rain with RTH less than 4.5km is 19% over ocean, while it is 4% over land. Rain-thunderstorm ratio, proposed in Zipser (1994), is one order larger over ocean than over land, as expected from previous studies. And it is shown to correlate well with RDCR. While ocean-land contrast of lightning activity and large reduction of lightning activity in the mature monsoon season are documented in previous studies (e.g. Zipser and Lutz 1994; Williams et al 1992), availability of TRMM data enabled the quantification and studies of their relationship to the rain-depth in the global tropics.