Kinematic Characteristics of a Mei-yu Front Detected by the QuikSCAT Oceanic Winds

Abstract

Based on conventional surface observations and NASA Quick Scatterometer (QuikSCAT) data, a heavy rainfall event that occurred in the Taiwan mei-yu season was chosen to further study the kinematic characteristics of the accompanying surface front. With the help of the QuikSCAT oceanic surface winds, it was found that the location and propagation of a mei-yu front over the ocean to the east of Taiwan during 10?12 June 2000 are better represented by the frontal wind shift line, which was located approximately on the leading edge of the baroclinic zone. The mesoscale system with cyclonic circulation embedded within the frontal zone was clearly shown in the wind field and kinematic parameters (horizontal divergence and vorticity) as well as satellite clouds and rainfall estimations. The conditional instability of the second kind (CISK) process was suggested to be responsible for the intensification of the mei-yu front and the frontal disturbance over the ocean. Under the influence of island topography over Taiwan and the mountains over southern China, the frontal wind shift line distorted and receded within the Taiwan Strait after the mei-yu front reached northern Taiwan. In the later period, the front moved southward faster to the area immediately east of Taiwan as compared to that over southwestern Taiwan and the Taiwan Strait due to earlier arrival of strong postfrontal northerly winds. The localized southwesterly jetlike feature was observed to the southeast of Taiwan and persisted until the arrival of the strong northerly winds. These localized phenomena were detected by the QuikSCAT oceanic winds.