雨滴粒径分布の鉛直プロファイルを利用したレーダー雨量推定手法の構築

Abstract

Purposes of this research are to observe and analyze the vertical profile of the rain drop size distribution (DSD), and to utilize the results into formulating a new method of estimating rainfall intensity and/or amount by making use of information detected by operational radar observations. Firstly, observations of DSD were carried out both by the Disdrometer in conjunction with an optical instrument on ground surface, and also by a vertical pointing VHF Doppler radar in Japan named the MU (Middle and Upper) Radar, which can detect vertical profiles of the Doppler spectrum that are composed of both the rain drop itself and air movements. Secondly, formulations to correlate the ground surface-based rainfall intensity to the radar reflectivity by taking into account both ⅰ) the difference in rainfall intensities between radar beam and rain gage height as well as ⅱ) the width of the Doppler spectrum were completed. Finally, the foymulation was applied into two case studies.One was to a operational volume scanning radar, in which we can directly use information from the vertical profiles of DSD observed by the MU Rader, thereby checking the feasibility of the formulation, (although we can not currently use the information on the spectrum width in the operational sense). The other was to the Blue River Basin in Oklahoma, U. S. A. covered by a NEXRAD radar observation domain, which can also operationally provide information on the Doppler spectrum width although the radar is not a vertical pointing radar.