云微物理参数化方案对地面气温模拟性能的评估与改进

午后地面气温对对流的发生发展具有重要作用,对其准确预报一直是中尺度数值模式的基本要求。针对一次冷云过程,本文基于WRFv3.9.1模式评估了5种云微物理参数化方案对华东地区地面气温的模拟效果。结果表明,各方案模拟的午后及午夜地面气温都存在较大偏差。其中,WDM6方案对地面气温模拟的效果最佳,Thompson方案模拟的云冰含量过低,模拟效果最差。因此对WDM6方案进行进一步评估和改进,通过修改冰核浓度、初始云凝结核数、优化WDM6方案以及替换方案中云水向雨水自动转化过程的公式的方式设计了敏感性试验,以改进WDM6方案对地面气温的模拟。结果表明,使用Grabowski公式替换WDM6方案中的Berry公式,能提高云水含量,有效改善地面气温的模拟。并通过一次梅雨过程对改进方案进行了有效性验证。最后在此基础上将改进后的WDM6方案应用于江苏省精细化天气分析和预报系统PWAFS模式中,显著提高了PWAFS模式对午后地面气温的模拟效果,为模式的业务应用提供了技术支撑。

Evaluation and improvement of the cloud microphysics parameterization schemes for near-surface air temperature simulation performance

The late afternoon near-surface air temperature plays a pivotal role in the initiation and evolution of convective processes, rendering its accurate prediction a fundamental requisite for mesoscale numerical modeling endeavors. This study assessed the simulation outcomes of five representative cloud microphysics parameterization schemes concerning the near-surface air temperature over East China during a cold cloud event employing WRFv3.9.1. Evaluation outcomes reveal substantial deviations in simulated near-surface air temperature during late afternoon and mid-night across all schemes, with the WDM6 scheme demonstrating superior performance in replicating near-surface air temperature, while the Thompson scheme exhibits the least satisfactory results attributed to its deficient cloud ice content. Consequently, further evaluation and improvement of the WDM6 scheme were conducted. Sensitivity experiments were devised, involving adjustments to parameters such as ice nucleus concentration, initial cloud condensation nuclei count, scheme optimization, and replacement of autoconversion process formulas governing cloud water to rainwater transition within the scheme, aimed at enhancing the fidelity of near-surface air temperature simulation by the WDM6 scheme. Sensitivity test outcomes indicate that substituting the Grabowski formula for the Berry formula, delineating the autoconversion process within the WDM6 scheme, enhances cloud water content and effectively improves near-surface air temperature simulation. Furthermore, validation of the improved WDM6 scheme was conducted against a meiyu event.Ultimately, integration of the improved WDM6 scheme into the Precision Weather Analysis and Forecasting System (PWAFS) model in Jiangsu Province significantly enhances the model''s capability in simulating late afternoon near-surface air temperature, thereby furnishing crucial technical support for its operational implementation.