Impact of Wind Profiler Data on Regional Model Prediction in South China

Weather analysis demonstrates that upper-level jet, low-level jet, and wind shear are closely related with rainstorms and severe convections in South China. Wind profiler radar can continuously observe wind, making it the most direct resource of upper wind observation comparing with conventional observations. A network of observation stations with 18 wind profiler radars is built in Guangdong, data of which are assimilated every 3 hours in GRAPES_Meso model in real time, and the influence of wind profiler data is evaluated. A precipitation process in the pre-flood season of South China from 28 March to 9 April in 2014 is simulated through three designed experiments by GRAPES_Meso model. Results of assimilation trials show that wind profile data contribute a lot to analysis increment of zonal wind at levels from 1000 hPa to 850 hPa, especially at 850 hPa, and this effect rapidly diminishes above 700 hPa level. The root mean square error (RMSE) of forecasted variables at radiosonde stations are calculated in terms of sounding observations and the outcome of three experiments. Results show that profiler data mostly improve RMSE at 850 hPa, which announces a 0.7 m·s^-1 reduce of forecasted wind speed error, for 700 hPa level there's no evident improvement, and for 925 hPa level it becomes even worse. The same RMSE analysis is done at 12 wind profiler stations. The result is in accordance with radiosonde stations, which shows that the RMSE decreases at 850 hPa as well and the improvement is not evident at 925 hPa. The analysis indicates that the quality of wind profiler data is relatively better at 850 hPa. Results of two sensitive experiments for 1200 UTC 30 March 2014 is examined, revealing that the RMSE of the forecasted wind speed is even greater when wind profiler data are used in assimilation at locations of heavy rain grade or above. Besides, it seems that the RMSE of the forecasted wind speed also increases in the downstream direction of this heavy rain location. Causes of these two phenomena still need to be analyzed.