地形性降雨を考慮したレーダー短時間降雨予測へのエラーアンサンブルの導入(II)

Abstract

本研究は，山岳域における地形性降雨の定量的影響を評価し，2-3時間先の予測精度の向上を目指すものである．2011年9月に近畿地方に記録的豪雨をもたらした台風12号事例において，移流モデルを用いたレーダー短時間降雨予測手法をベースに，物理的雲水量算定手法と，統計的バイアス補正手法の2つの手法を導入することにより，連続予測を行う事で積算雨量分布の再現に成功した．同時に，台風12号事例の積算雨量に占める地形性降雨の割合を，立平モデルを用いて定量的に示すことができた。

To improve accuracy of short term rainfall prediction, especially for orographic rainfall over mountain areas, a physical approach and a stochastic approach were introduced into a radar image extrapolation method with translation model. In the physical approach, total rain field observed by radar is separated into orographic and non-orographic rain fields by solving physically-based equations. In the stochastic approach, a bias-modified prediction field was calculated from a lot of spatial error distributions of the pre-predicted rain fields. As a result, we could duplicate the spatial distribution of accumulated rainfall in Typhoon 1112 case accurately. In the future, more accurate predictions can be expected by innovating its physical mechanism of the orographic rainfall.