Nowcasting and Short-range Forecast Systems in Social Experiments on Extreme Weather Resilient Cities in Tokyo metropolitan area

S. Shimizu1), A. Kato1), T. Mesaka1), T. Kobayashi2), R. Misumi1), S. Suzuki1), K. Saito2). a nd M. Maki1).

(1) National Research Institute for Earth Science and Disaster Prevention, Japan (NIED)
(2) Meteorological Research Institute, Japan (MRI)

Large cities are inherently vulnerable to severe weathers such as torrential rainfall, lightning, and tornados. The number of occurrences of urban heavy rainfall has been increasing, which may be due to the global warming. The present research project aims to understand the process and mechanism of extreme weather using dense meteorological observation networks designed in the Tokyo metropolitan area, to develop the monitoring and predicting system of extreme phenomena, and to implement social. The field experiments TOMACS (Tokyo Metropolitan Area Convection Study) started from the summer in 2011. The TOMACS has a dense observation network, including C-band and X-band polarimetric radars, Ku-band radar, six Doppler lidars, GPS receivers for the estimation of precipitable water.
Real-time nowcasting and 3DVAR forecast systems using X-band polarimetric radar network (X-NET) in the TOMACS were developed by NIED. The nowcasting system is a two-dimensional advection model based on the rainfall estimation using specific differential phase (Kdp) to improve the accuracy of rainfall forecast within 1 hour. The 3DVAR data assimilation system uses Doppler radial velocity observed in the X-NET and precipitable water derived from GPS network to improve the accuracy of rainfall forecast within a few hours.