Microwave Remote Sensing Of Tropical Deep Convective Cloud, Their Distribution And Variation Feature

The deep convective clouds play an important role in the Earth's climate by transporting heat, moisture and momentum from lower troposphere to upper troposphere. The convective overshooting is the deep convective clouds which penetrating the tropopause layer. They affect the air exchange between the troposphere and the stratosphere. Since the tropic is the high occurrence region of deep convective cloud, the quantification of frequency, location and variation of tropical deep convective clouds is the prerequisite to understanding the physical and chemical processes in tropical troposphere and stratosphere.The passive microwave remote sensing on satellite promotes a new way on detecting the deep convective clouds. Using its advantage in penetrating clouds, it can avoid the influence from cirrus which causes the problem in infrared measurements. This study promotes a new arithmetic to derive the deep convective clouds according to the brightness temperature differences between the three water vapor channels on Advanced Microwave Sounding Unite-B (AMSU-B). This new arithmetic is the improvement of the method which is first promotes by Hong (2005). According to the statistic analysis on NOAA16 data from 2001 to 2007, the new thresholds of the brightness temperature are set as the criteria to identify the deep convective clouds and convective overshooting.Base on the new arithmetic, the seven years (2001-2007) mean geographical distribution of deep convective clouds and convective overshooting, their seasonal cycle and trend are calculated. According to the calculated results, the major concentration of deep convective clouds and convective overshooting are found in Intertropical Convergence Zone (ITCZ), the South Pacific Convergence Zone (SPCZ), tropical Africa, South America, Indian Ocean and Indonesia. The observed convective overshooting is higher on land. In the NH subtropical (15°N– 30°N) and SH subtropical (15°S– 30°S), the observation of deep convective clouds and convective overshooting show the pronounced seasonal cycle both on land and ocean. The seasonal cycle is stronger on land. From the trend analysis of deep convective clouds and convective overshooting during 2001 to 2007, the deep convective clouds show increase trend over the tropic, the increase trend is more obviously on land. The highest increase trend of deep convective clouds is on the land at 15°N to 15°S, about 0.663% /decade. The variation of convective overshooting do not as strong as deep convective clouds. It shows weak decrease trend on the tropical ocean.