Essential factors for formation and organization of afternoon rainfall: 
A case study on 30 Jun 2018

Dr. Satoki Tsujino (Dept. of Atmos. Sci., National Taiwan University) 
[辻野智紀 博士 (台灣大學 大氣科學系)]

Afternoon rainfalls in the Taipei basin often cause severe
meteorological disasters in the metropolitan area. Full understanding
of essential factors for formation and organization of the afternoon
rainfalls is important for accurate weather prediction using numerical
models. In this study, two realistic numerical simulations of a
heavy-rainfall case and no-rainfall case are performed to clarify the
essential factors using a non-hydrostatic atmosphere model with full
physics. The simulation of the rainfall case succeed to capture the
realistic rainfall clouds in the Taipei basin. The two simulations are
verified by in-situ observations in a field campaign. Moreover, two
idealized numerical simulations of the same cases are performed with
vertical profiles of temperature and humidity based on atmospheric
soundings. The four simulations clarify that (1) depth of see-breeze
circulation in the Taipei basin and (2) moisture and large-scale flow
in the middle troposphere are essential factors for the formation and
organization of the afternoon rainfalls.