Assimilation of radar‐derived rain rates into the convective‐scale model COSMO‐DE at DWD
Assimilation of radar‐derived rain rates into the convective‐scale model COSMO‐DE at DWD
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DOI：
10.1002/qj.269
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发表时间：
2008-07
影响因子：
8.9
通讯作者：
K. Stephan;S. Klink;C. Schraff
中科院分区：
文献类型：
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作者：
K. Stephan;S. Klink;C. Schraff
为了改进特别是对流情况下的超短期预报，开发了一个明确模拟深对流的COSMO模式（以前称为LM）版本（水平网格长度：2.8 km），目前正在DWD运行。该模型采用预测型降水计划占下降水凝物的水平漂移。为了初始化对流尺度事件，潜热轻推（LHN）方法已被用于同化从雷达反射率数据导出的地面降水率。结果发现，一个传统的LHN方案设计的更大规模的模式与诊断处理的降水表现不佳，并导致强烈高估的降水时，应用到对流尺度模式与降水的预报处理。如图所示，在这样的模式中，地面降水和垂直积分潜热在水平和时间上的相关性远远低于诊断降水，这意味着违反了LHN的基本假设。
To improve very‐short‐range forecasts particularly in convective situations, a version of the COSMO‐Model (formerly known as LM) which simulates deep convection explicitly (horizontal grid length: 2.8 km) has been developed and is now run operationally at DWD. This model uses a prognostic type of precipitation scheme accounting for the horizontal drift of falling hydrometeors. To initialise convective‐scale events, the latent heat nudging (LHN) approach has been adopted for the assimilation of surface precipitation rates derived from radar reflectivity data. It is found that a conventional LHN scheme designed for larger‐scale models with diagnostic treatment of precipitation does not perform well and leads to strong overestimation of precipitation when applied to the convective‐scale model with a prognostic treatment of precipitation. As illustrated here, surface precipitation and vertically integrated latent heating are far less correlated horizontally and temporally in such a model than with diagnostic precipitation, and this implies a violation of the basic assumption of LHN.