The western disturbances (WD) form over the Mediterranean region as extra-tropical low-pressure systems and lose the frontal structure while moving eastward to reach India. These systems bring cold waves, snowfalls, hailstorms and rain over north and north-west India during post monsoon and winter months. The first part (Part A) of the present paper investigates the performance of Advanced Research WRF (ARW) model with 8 combinations of cloud microphysics and cumulus convection schemes in simulating 20 WD cases. These 20 cases were simulated using a single-domain WRF model of horizontal resolution 27 km. The combination of Lin et al. cloud microphysics scheme and Betts–Miller–Janjic cumulus convection scheme (mp2cu2) performs better than other combinations in simulating temperature at 2 m height and precipitation. The performance of the combination of Ferrier (new Eta) microphysics scheme and Betts-Miller-Janjic cumulus convection scheme (mp3cu2) is very close to that of mp2cu2 combination. Analysis of box-whisker plot also shows that the combinations mp2cu2 and mp3cu2 perform better than others. In the second part (Part B) 10 cases are simulated using a double-nested WRF model with inner and outer domain resolutions 9 km and 27 km, respectively. Four cases of part B are simulated with (mp2cu2 and mp3cu2) and without (mp2cu0 and mp3cu0) cumulus convection schemes to understand the response of cloud microphysics to explicit convection and also to select the best combination of cloud microphysics and cumulus convection scheme. The combination mp2cu2 has lower RMSE of precipitation than other combinations. Remaining six cases were then simulated with the combination of mp2cu2 using the double-nested model. Spatial distribution of model simulated and TRMM estimated precipitation agree well in most of the cases. The domain-averaged RMSE of model-simulated precipitation with respect to TRMM 3B42 V7 estimated precipitation varies from 2.89 to 4.12 cm for the six WD cases. The box-whisker diagram shows that the model overestimates the maximum rainfall amount in most of the cases but it is consistent in simulating precipitation over the model domain for all the six cases.

中文翻译：

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积云对流和云微物理参数化对西部扰动预测的影响

西部扰动（WD）在地中海地区形成为温带低压系统，在向东移动到达印度时失去锋面结构。这些系统在季风过后和冬季给印度北部和西北部带来寒潮、降雪、冰雹和降雨。本论文的第一部分（A 部分）研究了具有 8 种云微物理和积云对流方案组合的 Advanced Research WRF (ARW) 模型在模拟 20 WD 案例中的性能。使用水平分辨率为 27 公里的单域 WRF 模型模拟了这 20 个案例。林等人的组合。云微物理方案和 Betts-Miller-Janjic 积云对流方案 (mp2cu2) 在模拟 2 m 高度的温度和降水方面比其他组合表现更好。Ferrier（新 Eta）微物理方案和 Betts-Miller-Janjic 积云对流方案（mp3cu2）组合的性能与 mp2cu2 组合的性能非常接近。盒须图的分析还表明，mp2cu2 和 mp3cu2 组合的性能优于其他组合。在第二部分（B 部分）中，使用内域和外域分辨率分别为 9 公里和 27 公里的双嵌套 WRF 模型模拟了 10 个案例。使用（mp2cu2 和 mp3cu2）和不使用（mp2cu0 和 mp3cu0）积云对流方案模拟 B 部分的四种情况，以了解云微物理对显式对流的响应，并选择云微物理和积云对流方案的最佳组合。mp2cu2 组合的降水均方根误差低于其他组合。然后使用双嵌套模型与 mp2cu2 的组合模拟剩余的六个案例。在大多数情况下，模型模拟的空间分布和 TRMM 估计的降水量吻合得很好。对于六个 WD 案例，模型模拟降水的域平均 RMSE 相对于 TRMM 3B42 V7 估计降水从 2.89 到 4.12 厘米不等。箱须图表明，该模型在大多数情况下高估了最大降雨量，但在模拟所有六种情况下模型域上的降水时是一致的。12 cm 用于六个 WD 机箱。箱须图表明，该模型在大多数情况下高估了最大降雨量，但在模拟所有六种情况下模型域上的降水时是一致的。12 厘米，用于六个 WD 机箱。箱须图表明，该模型在大多数情况下高估了最大降雨量，但在模拟所有六种情况下模型域上的降水时是一致的。