Behavior and structure of convective clouds developing around a mountainous area observed by stereo photogrammetry and ka-band and x-band radars: Case study of northern Kanto, Japan

Abstract

Development of convective clouds on August 24, 2009 in northern Kanto, Japan, was investigated using stereo photogrammetric analysis and Ka-band and X-band radars, in order to clarify the behavior and structure of convective clouds developing around a mountainous area. Convective activity was divided into three stages based on the spatial distribution of X-band radar echoes: stage 1 with no echo (1006-1200 JST), stage 2 with echoes limited to the mountainous area (1200-1400 JST), and stage 3 with echoes developing over the plain (1400-1600 JST). During stages 1 and 2, the convective clouds (echoes) initiated over the mountains, and then moved toward the foot of mountains and dissipated, repeatedly. During stage 3, convective echoes formed over the mountains moved to the plain without dissipating at the foot of the mountains. In stage 2, new convective echoes tended to form to the rear (upshear) side of pre-existing echoes, while in stage 3, some new cellular echoes formed to the front (downshear) side of pre-existing echoes. Specific humidity in the mountains increased in stage 1, while GPS-derived precipitable water at the foot of the mountains increased during stages 2 and 3. The relationship between the behavior of convective clouds and the transport of water vapor by local wind circulation is discussed. © 2013, Meteorological Society of Japan.