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.

Numerical Study of the Influence of Central Mountain Ranges in Taiwan on a Cold Front

“…4b). In a study of the kinematic characteristics of a Mei-yu front, Yeh et al (2002) demonstrated the usefulness of high-resolution (25 km) oceanic surface wind data, derived from the NASA Quick Scatterometer (QuikSCAT) satellite, which was launched in June 1999. Unfortunately, there was no such kind of data available for validating the location of the windshift line during the TAMEX in 1987.…”

“…Satellite pictures usually show a synoptic-scale stratiform cloud band along the front with organized mesoscale convective systems embedded within the band. Past observational and numerical studies of the kinematic structure of the Mei-yu front revealed very complicated flow patterns due to the influence of organized convective systems (Lin et al 1992;Hsu and Sun 1994;Yeh et al 2002;Sun et al 1995, and others). Once in a while, a dry Mei-yu front without any convective system does occur.…”

“…The eastern part of the front apparently moved much faster than the western part. This phenomenon was frequently observed in the past (Jou and Deng 1992;Chen and Hui 1990;Chen et al 1999;Yeh et al 2002), but the reason for it is still not well understood (Yeh et al 2002). During 1139-1407 UTC 15 June 1987, an aircraft flew a six-level north-south pattern flight across the leading edge of the front to the east of Taiwan.…”

Rain‐gauge network evaluation and augmentation using geostatistics

“…Mei-Yu rainfalls are produced by surface frontal systems which advance southeastward from southern China to Taiwan from mid to late spring through early to mid summer each year. The fronts are usually accompanied by a synoptic-scale cloud band with embedded mesoscale convective systems (MCSs), extending several thousand kilometres from southern Japan to southern China with an approximately east-west orientation (Yeh et al, 2002). During the passage of a Mei-Yu frontal system, a few very active mesoscale convective cells may develop repeatedly, causing heavy and localized rainfall for the area.…”

Diagnosis of Frontal Instabilities over the Southern Ocean

“…Only when decreasing the resolution of the Goddard Earth Observing System general circulation model (GCM) to 0.5°ϫ 0.5°do Conaty et al (2001Conaty et al ( , p.1854 produce frontal features that are "reminiscent of those seen in high-resolution scatterometer wind data." Scatterometer data have been used to study the development of storms in the Southern Hemisphere (Levy and Brown 1991;Levy 1989McMurdie and Katsaros 1991;Yuan et al 1999;Milliff et al 1999;Hilburn et al 2003) and fronts or frontogenesis (Zierden et al 2000;Yeh et al 2002) but not to study frontal instabilities. The goal of this study is to apply an attribution technique to scatterometer data to analyze the development of three fronts over the Southern Ocean.…”