Structure of Mesoscale Convective Systems Observed with polarimetric radar and UHF Wind Profiler During the South China Sea Monsoon Experiment(SCSMEX)

The NCU(National Central University) ISS(Integrated Sounding System)and the BMRC dual-polarimetric doppler radar were deployed in Dongsha island during May 5 to June 25, 1998 for the SCSMEX. The primary goal of this deployment was to measure the mesoscale structure of convective weather system associated with the onset,mainteance and variability of the monsoon over he South China Sea area. A wide variety of convective systems were observed during SCSMEX. The ISS observations provides a detail kinematic and thermodynamic structure change of the monsoon flow. The UHF profiler radar that operate at 915 MHz in ISS are useful for precipitation structure measurement because of its sensitivity to hydrometers. The polarimetric data of the C-Pol radaris very helpful for the understanding of the stratiform and the convective chararteristics and the cloud physics and dynamics of the convective systems. Two major convective events occurred on May 18 and June 8 will be discuss. The preliminary analysis indicated that the convective system occurred before May 21st can be regarded as the frontal mid-latitude influence, while for those occurred after monsoom onset can be identified as having tropical influence. For the mid-latitude influence case(May 18th),there were moderate shear at lower level and strong westerly at middle and upper level. It may explain that there were stratiform regions on both the front and rear sides of the convective region.The polarimetric variable is consistent with reflectivity distribution. For the tropical influence precipitating event(June 8th)the lower level shear was more stronger. The radar observation show a clear convective leading edge and stratiform precipitation trailing behind. The surface observations at ISS show strong squall line with pressure jump at meso high passing through and weak low following later. Temperature dropped 5 degree as cold pool arrived. Futher studies of the microphysics and cloud dynamics of these interesting cases will be discussed also.