Monsoon Characteristics Observed during the South China Sea Monsoon Experiment

One of the main goals of the South China Sea Monsoon Experiment was to observe the onset, maintenance, and variability of the monsoon in the South China Sea. These observations would help in understanding of key atmospheric necessary to initiate and maintain the monsoon in this region. An enhanced network of instruments monitored the ocean and atmospheric conditions during the period of 5 May 1998 and 25 June 1998. Numerous upper air sites were added to the existing network. Also, two C-Band Doppler radars were deployed in the center of the monitoring array along with rain gauges, disdrometers, and ocean profiling instrumentation (CTDs). The two radars provided detailed observations of the 3-Dimensional structure of precipitation and wind fields of the convective systems that propagated through the area. The Tropical Rainfall Measuring Mission (TRMM) satellite overpasses the region on many occasions, which provided an independent measurement of the spatial distribution of the precipitation structures.

Radar and sounding observations show that the onset and the first active phase of the monsoon occurred during the period of 15-20 May 1998. Radar observations showed increased organization of the convection compared to pre-monsoon conditions. Wind observations obtained from soundings show the lower atmospheric wind field changing from light and variable in the pre-monsoon to sustained southwesterly during onset and active phase of the monsoon.

This study examines the characteristics of the onset, maintenance, and variability of the monsoon for the period of 15-20 May using radar, sounding, and surface measurements collected during this period. These in situ measurements will be compared and related to large-scale circulation patterns.