Case study of misoscale convective echo behavior associated with cumulonimbus development observed by Ka-band Doppler radar in the Kanto region, Japan

Abstract

Simultaneous observations of cumulonimbi by a Ka-band Doppler radar (KaDR) and an X-band polarimetric Doppler radar (MP-X) were performed during the summer of 2011 in the Kanto region, Japan to study the process of cumulonimbus initiation and development. A cumulonimbus developed up to 12 km above sea level (ASL) in the mountainous western part of the Kanto region on the morning of 18 August 2011, and its initiation and development were observed by the two radars. A misoscale convective echo which was newly detected in an RHI or PPI scan and developed vertically (RHI scan) or spatially (PPI scan) was labeled as a 'new misoscale convective echo' (NMCE). In the developing stage (DS), NMCEs occurred one after another, and the echo top height and maximum reflectivity of each individual echo gradually increased. In the first half of the DS, the NMCEs appeared between 2 and 5 km ASL. In contrast, in the second half of the DS, the NMCEs' appearance height stepped up to between 5 and 12 km ASL. These results suggest that the ascent of NMCE appearance height is one of the key factors in the prediction of deep convection, which later causes localized heavy rainfall.