葵花八号红外辐射率资料同化在一次东北暴雨中的应用研究

Application of Assimilating Infrared Radiance Data from Himawari-8 Satellite in a Heavy Rainfall in Northeast China

摘要:

基于WRF模式配套的WRFDA同化系统中葵花八号AHI辐射率资料的同化模块，考察葵花八号AHI 3个水汽通道辐射率资料的直接同化对一次东北暴雨预报的影响。结果表明：质量控制和偏差订正能够显著去除异常资料，使背景场观测残差的均值趋于0，分析场较背景场观测残差的标准差与均方根误差进一步减小。与控制试验相比，同化AHI辐射率资料后，风和温度在中低层的均方根误差分别下降约0.2 m/s和0.1 K，比湿在低层的均方根误差下降约0.03 g/kg。卫星资料同化对吉林省中部有正向的相对湿度增量贡献，改进了吉林省内3 h降水的预报效果。同化卫星资料的试验对所有阈值的ETS和偏差评分改进幅度均超过0.1。其中对于50 mm的阈值，ETS和偏差评分提升率分别达64%和58%。同化AHI辐射率资料对于观测降水中心单站点的逐小时降水预报趋势与观测更加吻合。

Abstract:

Based on the assimilation module for Himawari-8 AHI radiance data in the weather research and forecasting model data assimilation (WRFDA) system with WRF model, this paper investigated the impact of direct assimilation of the radiance data of the three water vapor channels from Himawari-8 AHI on the forecast of a heavy rainfall in Northeast China. The results show that the quality control and bias correction are effective in eliminating anomalous data, making the mean of observation minus background (OMB) closer to 0, while the standard deviation and root mean square error of observation minus analysis (OMA) are further reduced. Compared with the control experiment, after assimilating AHI radiance data, the root mean square errors are reduced by about 0.2 m/s and 0.1 K in the middle and lower layers for the wind and temperature respectively, and the root mean square error of specific humidity decreases by about 0.03 g/kg in the lower layers. Besides, the assimilation of satellite data contributes positively to the increment of relative humidity in the central part of Jilin Province. The final forecast of 3 h precipitation is improved. The experiments involving satellite data assimilation show an improvement in the ETS and bias scores exceeding 0.1 of all thresholds. For the 50 mm threshold, the improvement rates for ETS and bias scores reach 64% and 58%, respectively. In addition, the assimilation of AHI radiation data enhances the alignment of the hourly precipitation forecast trends at a single observation station with the actual observations.