A Study On The Oceanic Convection Structure And TRMM Retrieved Data Analyses Over The SCSMEX

Using the data of the TRMM-PR, TRMM-TMI in May—June,1998 during theSouth China Sea (SCS) Monsoon Experiment(SCSMEX),the mesoscale structure andthe strong convective transport and transformation of energy and water vapor on thenorth of the South China Sea (SCS) was studied.Firstly, by using data of Precipitation Radar (PR) and Microwave Imager (TMI)sensors on the Tropical Rainfall Measuring Missions (TRMM), the characteristics ofstructure and precipitation of mesoscale convective clouds over northern SouthChina Sea (15°～25°N,108°～122°E) during monsoon onset of south sea in SCSMEXfrom May to June of 1998 has been studied. The results show that the frontal cloudband started to weaken and dissipate as it entered South China Sea from south Chinacoastal region during premonsoon, and intensified and developed deeper convectiveclouds with heavy precipitation during onset of monsoon. The TRMM PR shows thatthe maximum radar echo and echo top was low during premonsoon, and the echoincreased rapidly and echo top reached about 20 km during onset of monsoon.During monsoon period, the precipitation retrieved from PR was strong, the cloudstructure retrieved from TMI shows that the strong and deep convective warm towerdeveloped and cloud ice content enhanced obviously and distributed more than 8 kmlevel and the total surface precipitation increased prominently and was primarily inconvective precipitation. The latent heating rate also increased more than two timesand penetrated the whole troposphere, which might induce the variation of localatmospheric circulation. The profiles of cloud hydrometeors also changed obviouslyduring monsoon period.Secondly, by using the sounding data of four times a day in May—June,1998collected on two observational ships of "Kexue 1 "and "Shiyan 3" during the SouthChina Sea (SCS) Monsoon Experiment(SCSMEX), the mesoscale structure ofdynamics, temperature and moisture, and the characteristics of oceanic convection Transport of energy and moisture were analyzed. The results show that themesoscale atmospheric dynamics, temperature and humidity experienced a rapid andobvious change after monsoon onset over the SCS. In the period of pre-monsoon, theupper air was convergent and the lower air was divergent showing strong downwardair current in the northern SCS. After monsoon onset, the upper air is divergent at200hPa, the lower air was convergent between 900 and 950hPa, showing a strongupward air current. This noticeable change in dynamic field causes the changes oftemperature and humidity field, and directly leads to the rapid development ofconvection over northern SCS, and the convective activity was accompanied byvertically strong transport and transformation of energy and water vapor.