不同云微物理方案对青藏高原一次强降水的模拟影响分析

利用WRF模式中三种云微物理参数化方案(Lin、Eta和WSM6)对青藏高原一次强降水过程进行模拟试验，将模拟降水结果与实测资料进行对比，以评估不同云微物理参数化方案对该区域降水过程的模拟性能。结果表明:三种方案均能够模拟出此次降水天气过程的发生，但在主要降水区域和降水强度两方面仍与实测资料存在偏差；在水凝物方面，三种方案对冰粒子的模拟较接近，Lin和WSM6方案模拟的雪粒子差异较大，但霰粒子无明显差异。进一步对比分析了Lin和WSM6方案模拟的云微物理转化过程，结果表明:这两种方案都表现出了霰向雨水转化的特点。在Lin方案中，通过水汽向霰粒子凝华、霰碰并水汽凝华生成的雪粒子以及霰碰并云水这三种过程生成的霰粒子最终融化为雨水。而在WSM6方案中，一方面水汽凝结成云水，云水被雪和霰粒子碰并收集转化为霰，之后霰融化为雨水；另一方面水汽凝华为冰粒子，一部分冰转化为雪，雪直接融化为雨水或转化为霰融化为雨水，另一部分冰转化为霰，霰融化为雨水。 

THE IMPACT OF DIFFERENT CLOUD MICROPHYSICS PARAMETERIZATION SCHEMES ON THE SIMULATION OF A HEAVY RAINFALL EVENT OVER THE TIBETAN PLATEAU

In the present study, a heavy rainfall event over the Tibetan Plateau was simulated using the WRF model with three different cloud microphysics parameterization schemes, i.e., the Lin scheme, the Eta scheme and the WSM6 scheme. To evaluate the performance of different cloud microphysics parameterization schemes in this simulation, the simulated data and the observed were compared. The results showed that all three simulations could reproduce the event, but there were significant deviations between the simulated and observed main precipitation area and precipitation intensity. All three simulations showed similar results in terms of ice particles. Lin and WSM6 schemes showed great difference in the simulation of snow particles but had no significant difference when simulating graupel particles. Comparison between the cloud microphysical transformation processes simulated by using Lin and WSM6 schemes showed that both of the two schemes managed to show the characteristics of graupel-to-rain conversion. In the Lin scheme, graupel particles were generated by deposition of water vapor, collision and coalescence of snow particles generated by deposition of water vapor, and collision and coalescence of cloud water. These graupel particles eventually melted into rain. In the WSM6 scheme, on the one hand, water vapor condensed into cloud water, which was accreted by snow and graupel particles and formed graupel. Eventually, graupel melted to be rain. On the other hand, water vapor condensed into ice particles; some transformed into snow, which melted directly to be rain or transformed into graupel and then melted to be rain, and the rest transformed directly into graupel which melted to be rain afterwards.