100km

1. Nerima Narita Haneda m 0 100km Assimilation Experiment of the Heavy Convective Rainfall Eventwith a Cloud Resolving Nonhydrostatic 4 Dimensional Variational Data Assimilation System Takuya Kawabata1 (tkawabat@mri-jma.go.jp),Hiromu Seko1, Tohru Kuroda1, Kyuichiro Tamiya2, Kazuo Saito1, Tadashi Tsuyuki2 1: Meterological Research Institute 2: Japan Meteorological Agency Abstract Design of the assimilation The Meteorological Research Institute of the Japan Meteorological Agency has developed a cloud-resolving nonhydrostatic 4-dimensional variational assimilation system (NHM-4DVAR)based on the Japan Meteorological Agency Nonhydrostatic Model (JMA-NHM), in order to investigate the mechanism of heavy rainfall events induced by mesoscale convective systems (MCSs). The horizontal resolution of the NHM-4DVAR is set to 2 km to resolve MCSs and the length of the assimilation window is 1-hour. The control variables of the NHM-4DVAR are horizontal wind, vertical wind, nonhydrostatic pressure, potential temperature, surface pressure and pseudo relative humidity. Perturbations to the dynamical processes and the advection of water vapor are considered, but these to the other physical processes. The NHM-4DVAR is applied to the heavy rainfall event observed at Nerima, central part of Tokyo metropolitan area, on 21 July 1999. Doppler radar’s radial wind data (RW), GPS precipitable water vapor data (GPS-PWV)and surface temperature and wind data were assimilated as high temporal and spatial resolution data. The Nerima heavy rainfall is well reproduced in the assimilation and subsequent forecast with respect to time sequence of 10-minute rainfall amount. Observations and the time interval of the assimilation. Radial Wind1 minute interval GPS-PWV1 minute interval Surface wind & temperature1 minute interval 14JST 17JST 15JST 16JST Assimilation window 3-hour forecast Time evolution of Nerima heavy rainfall Formation Develop Mature Design of the assimilation experiment: Assimilation window, forecast time. Time evolution of Nerima cells are indicated. Assimilation result Observation and Forecast result Assimilation area and Observation stations: Nerima AMeDAS station (■), the Haneda and the Narita airport Dopplar radars (●) and the GPS-PWV observation stations (Δ). Assimilation system Model specifications 10-minute rainfall amount at Nerima Cost function Observation Forecast result Distribution of PWV the observation (circles) and the analysis (contours) at 1440 JST. Surface wind field the observation (red arrows) and the analysis (black arrows) at 1440 JST. Color contours show the model orography. Nerima heavy rainfall Hourly accumulated rainfall amount Radar reflectivity (dBZ) First guess 1448JST 1507JST 1525JST 1545JST Observations B B B A A A Control variables A C C No heavy rainfall Forecast results 1450JST 1510JST 1530JST 1550JST B A A A A KAWABATA et al., An Assimilation and Forecasting Experiment of the Nerima Heavy Rainfall with a Cloud-Resolving Nonhydrostatic 4-Dimensional Variational Data Assimilation System, Journal of the Meteorological Society of Japan (submitted) Symbols of A, B and C denote MCSs. C C C