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基于飞机观测资料的丹江口流域春季过冷云水预报检验个例研究

A Verification Study of Supercooled Cloud Water Forecasting over the Danjiangkou Basin in Spring Based on Aircraft Observations

  • 摘要: 本文借助2024年5月10日丹江口流域春季飞机观测个例,结合风云卫星(FY-4B)数据,对CMA-CPEFS v2.0模式模拟过冷云水开展检验研究。在模式模拟的云类型与观测较吻合的前提下,对比飞机观测与模式预报的过冷云水粒子谱分布、有效粒子直径及液水含量等云微物理特征。结果表明,虽然模式较准确重现了过冷水出现的时间、地点与高度,以及液水含量和等效粒子直径随高度的变化趋势,但预报的过冷云水含量总体偏低,过冷云滴有效粒子直径小于观测值,在5.9 km和6.3 km高度层低估过冷云滴数浓度,尤其14 µm粒径左右的过冷云水含量。同时,6.9 km高度层的云滴谱模拟与实际观测较为接近。通过分析云内水凝物垂直分布及过冷云水的源汇项发现,冷云内以冰相粒子为主,霰粒子居多,5-8 km云内存在一定过冷云水、少量雪粒子和云冰,凝结为过冷云滴主要源项,凇附为主要汇项。研究指出了模式在过冷云水微物理参数化中的关键偏差,为后续改进微物理参数化方案过程及支撑人工增雨作业提供了参考。

     

    Abstract: The performance of the CMA-CPEFS(Cloud and Precipitation Explicit Forecasting System) v2.0 model in forecasting supercooled cloud water was evaluated by comparing its outputs with aircraft observations collected over the Danjiangkou basin on 10 May 2024, supplemented with Fengyun-4B satellite data. Assuming that the simulated cloud type is generally consistent with observations, microphysical characteristics—such as droplet spectra, effective particle diameter, and liquid water content—are compared between aircraft observations and model forecasts. Results show that the model accurately reproduces the occurrence time, location, and altitude of supercooled water, as well as the vertical variation trends of liquid water content and effective particle diameter. However, it systematically underestimates the overall content of supercooled cloud water and the effective diameter of supercooled cloud droplets and significantly underestimates the droplet number concentrations—especially for droplets with diameters around 14 μm—at altitudes of 5.9 and 6.3 km (MSL). In contrast, the modeled droplet spectrum at 6.9 km agrees more closely with observations. An analysis of the vertical distribution and source–sink terms of cloud hydrometeors reveals that ice-phase particles, particularly graupel, dominate the cold cloud. The 5–8 km layer contains some supercooled water, together with small quantities of snow particles and cloud ice, with condensation serving as the main source and riming as the main sink for supercooled droplets. Overall, the study identifies key deficiencies in the model’s microphysical parameterizations of supercooled cloud water and provides a scientific reference for future improvements to microphysical schemes and operational cloud seeding activities..

     

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