The goal of SCSMEX was to better understand the onset, maintenance and variability of the monsoon in southeast Asia and the western Pacific. As part of this program an Intensive Flux Array (IFA) was established in the northern South China Sea to measure hydrologic processes and investigate the mesoscale evolution of precipitation systems. IFA measurement platforms included the BMRC dual-Polarimetric Doppler radar located on Dongsha Is ( 20oN 43'E 116o 43'E), the Tropical Ocean Global Atmosphere radar on the People's Republic of China (PRC) Shiyan #3 located 45 km southeast of Dongsha Is. The radar configuration provided a unique dual-Doppler area in a true oceanic environment. Two Intensive Observational Periods were conducted from May 5-May 25 (onset phase) and June 5- June 25 (post onset), 1998. The purpose of this paper will be to present a brief overview of the structure and evolution of mesoscale weather systems observed within the SCSMEX IFA.
All observed convection had the "typical" characteristics of oceanic convection observed elsewhere. Reflectivity maxima (~55 dBZ) were primarily constrained below the melting level with relatively weak reflectivities above that level. These conditions imply weak vertical motion unable to support growth of a significant mixed phase regime. However, the storms were still deep extending to 13-15 km height especially in disturbed conditions. Disturbed periods also exhibited significant mesoscale organisation which was varied and often complex.
Both parallel and perpendicular to shear convective bands were often evident within the one domain and at times interacting with one another. The result was extensive and persistent stratiform decks with embedded convective lines. For the shear perpendicular systems trailing and leading anvils formed at various times depending on environmental conditions.
During suppressed conditions (associated with dry mid-level air)
cells were less frequent and much weaker and shallower. The maximum height of cells under these conditions was typically <10 km but more often constrained below 5 km height. The typical lifetime of onvection under these conditions was less than one hour in the form of shallow "pop-corn" type cells. Merger between cells did not typically occur and stratiform decks were hardly ever formed. The most consistent form of meoscale organisation observed under these conditions were shear parallel bands which could extend 100 km consisting of single cells aligned in narrow bands or in somewhat wider bands of cell "clumps".
On the microscale at least four waterspouts were observed within the IFA during SCSMEX. Persistent and slow moving "fine lines" were also observed often with wave-like appearance especially when associated with decaying cold pools.
Examples of the observed systems will be presented along with a brief discussion of on-going research