On the Structure of Intermediate-Scale Disturbances on the Baiu Front

[摘要] The present study will treat two intermediate-scale disturbances developing on the Baiu front with a wavelength of about 2, 500km and of about 1, 000km. Three-dimensional structure of the longer wave is analyzed with the aid of the vertical-longitudinal cross sections by means of the harmonic analysis of 6-hourly data, and the shorter wave by meansof composite technique.The results show that these disturbances with a shallow vertical extension below the400-mb level are of warm-core type and the vertical structures are different between northof and in the mean Baiu frontal zone. North of the front, it is cold in the trough, which has a slightly forward tilt. In the frontal zone it is warm in the trough, the axis of which tilts backward vertically. On the horizontal map, the trough line runs NW-to-SE in the northern part and SW-to-NE in the southern part. Velocity divergence and vertical component of relative vorticity have a magnitude of the same order.The disturbance developed in a narrow zone of strong gradient of a Richardson number in the one-week mean field. As it develops, a warm core in the upper layer of the low becomes intense through the latent heat release.

[学科分类] 大气科学