Impacts of Radar Data Assimilation on Simulations of Typhoon Namadol(2011)

The observation of radar network in Taiwan was used to investigate the impacts of radar data assimilation on typhoon simulation. The case of Typhoon Nanmadol(2011)was chosen for this study, it struck Taiwan from 28 Aug 2011 to 29 Aug 2011. The purpose of this study was to adjust the initial field of the numerical model to improve the short-term typhoon predictions near Taiwan by using Doppler radar radial wind data assimilation. The typhoon track,structure, and precipitation were also inspected to clarify the effect of radar data assimilation on simulation of typhoon approaching Taiwan. In this study, Weather Research and Forecasting(WRF V3.2.1) model and 3D-VAR method of WRF Data Assimilation system(WRFDA V3.2.1)were used to assimilate Doppler radar data. Based on a series of experiments, we obtained some conclusions :(1)Compared with the one-time radar data assimilation, cycling of the multiple-time radar data assimilation has more positive impact on typhoon simulation, (2)Larger influence factor of horizontal scale (R2 = 0.12)also has more positive impact than smaller influence factor of horizontal scale(R1 = 0.06)for typhoon simulation in Taiwan. More assimilation cycle collocate with a larger influence factor of horizontal scale(R2 = 0.12), had improved the accuracy of the numerical simulation. Compared with the non-assimilate experiment, the precipitation pattern and typhoon track in the assimilation experiment were closer to the observations.