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- Title
Evaluation of Precipitation Forecast by the Operational China Meteorological Administration Mesoscale Model During the 2020 Meiyu Period.
- Authors
Shi, Wenru; Zhu, Kefeng; Li, Xin; Zhang, Bing
- Abstract
This study evaluated the precipitation forecast produced by the operational China Meteorological Administration Mesoscale model (CMA‐MESO) during the "super violent" Meiyu season of 2020. Generally, CMA‐MESO, which runs with ∼3‐km‐grid resolution, is able to reproduce the distribution and diurnal variation of precipitation. However, the precipitation amount is greatly overestimated, especially in eastern coastal areas of China. Precipitation in that region usually occurs with two peaks: one in the morning that mostly reflects organized precipitation systems, and the other in the afternoon generated mostly by local convection. Analyses showed that overestimation of low‐level wind speed is the main reason for the overestimation of precipitation. CMA‐MESO produces low‐level winds that are overly strong, which greatly enhance the predicted convergence at night, leading to overestimation of precipitation. Additionally, the stronger wind speed increases the estimated transport of water vapor to the eastern coastal area, producing fake convection near the coastal mountains as the perturbed wind direction turns toward the mountain area in the afternoon. In comparison with ERA5, CMA‐MESO tends to overestimate (underestimate) the temperature in the northwest (southeast), and the larger temperature gradient increases the pressure gradient, resulting in the stronger low‐level wind speed. Plain Language Summary: The resolution of the operational China Meteorological Administration Mesoscale model (CMA‐MESO) was upgraded to 3 km in 2020. However, the overall performance of the precipitation forecast has not been evaluated comprehensively, and the main factors causing precipitation forecast biases are not well understood. This study analyzed the CMA‐MESO precipitation forecasts during the 2020 super Meiyu season. Generally, CMA‐MESO well reproduced the distribution and propagation of precipitation, but the intensity was overestimated, especially in eastern coastal areas of China. CMA‐MESO tended to produce an overly strong southwesterly low‐level wind that transported too much warm moist air to eastern coastal areas, resulting in excessive rainfall. Further comparative evaluation suggested that the overestimation of low‐level winds might be related to the larger NW–SE temperature gradient of CMA‐MESO. The findings of the current study could provide guidance for improving physical parameterization in the future. Key Points: Performance of the operational CMA‐MESO in China at convection‐permitting resolution was evaluatedCMA‐MESO can well reproduce the distribution and propagation of precipitation, but overestimates precipitation in eastern coastal areasOverestimation of low‐level wind speed is the main reason for the overestimation of precipitation in eastern coastal areas
- Subjects
CHINA; PRECIPITATION forecasting; WIND speed; WATER vapor transport
- Publication
Journal of Geophysical Research. Atmospheres, 2024, Vol 129, Issue 11, p1
- ISSN
2169-897X
- Publication type
Article
- DOI
10.1029/2023JD039156