Abstract Present work elucidates the impact of 3DVAR data assimilation technique for the simulation of one of the heavy rainfall events reported over Kotdwara region in the North-West Himalayan (NWH) region on 4th August 2017. We have examined the impact of conventional and satellite-based radiance datasets on the simulated results with and without assimilating the observations into the Weather Research and Forecasting (WRF) model. Three experiments have been designed with 3 nested domains of variable resolutions, one without assimilation (referred as control experiment) and other two experiments after assimilating conventional and satellite radiances observations (refer as DA-OBS and DA-SAT respectively). In the present study, assimilation of surface, upper air and the satellite-based radiance observations has been carried out for the outermost domain with horizontal resolution of 9 km. Statistical analysis suggests that the correlation coefficient is high (0.55) and root mean square error (RMSE) is low (17.12) for DA-SAT experiment as compared to other two experiments. Substantial improvement in the location, pattern and intensity of extreme rainfall event is noted after assimilation of both conventional and satellite observations with respect to the observed rainfall data. However, it is noted that the assimilation of satellite radiances has greater impact in simulating better intensity of the heavy rainfall event as compared to the assimilation of conventional observations. Plausible reason behind this could be the non-availability of the conventional observations close to the extreme rainfall event affected region.

中文翻译：

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使用 WRFDA 在喜马拉雅西北部地区模拟暴雨事件中常规和卫星观测的同化评估

摘要 目前的工作阐明了 3DVAR 数据同化技术对模拟 2017 年 8 月 4 日在西北喜马拉雅 (NWH) 地区科特瓦拉地区报告的强降雨事件之一的影响。基于模拟结果的辐射数据集，无论是否将观测同化到天气研究和预测 (WRF) 模型中。三个实验设计了三个可变分辨率的嵌套域，一个没有同化（称为对照实验），另外两个在同化常规和卫星辐射观测后的实验（分别称为 DA-OBS 和 DA-SAT）。在本研究中，表面同化，对最外域进行了高空和星基辐射观测，水平分辨率为9公里。统计分析表明，与其他两个实验相比，DA-SAT 实验的相关系数高 (0.55) 且均方根误差 (RMSE) 低 (17.12)。在将常规和卫星观测与观测降雨数据同化后，极端降雨事件的位置、模式和强度有了显着改善。然而，值得注意的是，与常规观测的同化相比，卫星辐射的同化在模拟更强的暴雨事件强度方面具有更大的影响。