Multiple Frontal Structures in the Baiu Frontal Zone Observed by Aircraft on 27 June 2004

Abstract

The structure of the Baiu frontal zone over the East China Sea on 27 June 2004 was investigated using data from aircraft observations. During the period of 09-12 JST (Japanese Standard Time: UTC + 9 hours), three cloud zones appeared over the East China Sea. The Baiu frontal zone is conveniently divided into three zones on the basis of the three cloud zones. The zones on the southern side, in the middle, and on the northern side are called FZ1, FZ2, and FZ3, respectively. The position of FZ2 corresponded with that of a stationary front on the surface weather map. Remarkable variations of winds, potential temperature, and moisture corresponding to the three zones were detected using in situ measurements at 500 m MSL (Mean Sea Level). In FZ1, a decreased southerly wind area associated with a remarkable moisture gradient was seen, although the potential temperature gradient was unclear. FZ2 had remarkable gradients of potential temperature and moisture associated with a drastic change from southwesterly to northwesterly winds. FZ3 also had remarkable gradients of potential temperature and moisture. This study shows observational evidence of the fact that multiple frontal structures exist inside the Baiu frontal zone.