Measurements from various sounding instruments onboard polar-orbiting meteorological satellites quantify contributions to the total radiation at various microwave or infrared frequencies from different levels of the atmosphere. Satellite data assimilation adjusts model profiles of temperature and water vapor by minimizing the differences between observations and model simulations to search for the maximum likelihood estimate of the atmospheric states. The accuracy and precision of satellite data assimilations depend on the model vertical resolution. Sensitivity studies are carried out to compare the data assimilation and forecast results over a domain centered on the Tibetan Plateau (TP) using three different model vertical resolutions: 43, 61, and 92 vertical levels from the surface to ~ 1 hPa. The NCEP Gridpoint Statistical Interpolation (GSI) analysis system and the Advanced Research Weather Research and Forecasting (ARW) model are used with a domain size of 600 × 500 grid boxes at a 15-km horizontal resolution. It is shown that the ARW/GSI system with the coarsest (highest) model vertical resolution outperforms the remaining two for the 24-h short-range (48-h medium-range) quantitative precipitation forecasts (QPFs) downstream of the TP. The satellite data assimilation at the highest model vertical resolution produced more significant positive impacts on the 36-h forecasts of a mid-tropospheric trough located to the northeast of the TP that lead to a localized precipitation event. Improvements in the QPFs with the 92-vertical-level configuration come mainly from the best match of rainfall distributions between observations and forecasts.

中文翻译：

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不同模式垂直水平卫星资料同化对青藏高原下游QPF的影响

极轨气象卫星上各种探测仪器的测量结果量化了来自大气不同层的各种微波或红外频率对总辐射的贡献。卫星数据同化通过最小化观测和模型模拟之间的差异来调整温度和水汽的模型剖面，以搜索大气状态的最大似然估计。卫星资料同化的准确度和精度取决于模型的垂直分辨率。进行了敏感性研究，以比较以青藏高原 (TP) 为中心的区域的数据同化和预报结果，使用三种不同的模式垂直分辨率：从地表到约 1 hPa 的 43、61 和 92 个垂直水平。使用 NCEP 网格点统计插值 (GSI) 分析系统和高级研究天气研究和预测 (ARW) 模型，域大小为 600 × 500 网格框，水平分辨率为 15 公里。结果表明，对于青藏高原下游的 24 小时短程（48 小时中程）定量降水预报（QPF），具有最粗（最高）模式垂直分辨率的 ARW/GSI 系统优于其余两个系统。最高模式垂直分辨率下的卫星数据同化对位于青藏高原东北部的对流层中槽的 36 小时预报产生了更显着的积极影响，从而导致局部降水事件。