云微物理参数化对华北降雪影响的数值模拟

对发生在华北地区的一次降雪过程进行了中尺度数值模拟。结果表明,高纬强冷空气南下和低纬倒槽的水汽输送是造成这次长时间降雪过程的主要原因。采用混合方案的中尺度数值模拟表明,这次降雪天气不是对流云造成的,而是稳定性的非对流云降雪。敏感性试验也表明,采用其他积云参数化方案对模拟的降雪量基本没有影响。控制试验模拟的24h降雪量与实际观测比较吻合。模拟结果表明,当采用Dudhia简单冰相方案时,会有过多的云冰、过冷却水及雪;当采用Reisner 1混合相方案时,会有过多的云冰和雪;修改的各个Reisner 2方案对此次降雪的预报改进不大,但各个Reisner 2方案的敏感性试验中云冰混合比、过冷却水混合比和雪混合比稍微有差异。

Numerical Simulation of Impact of the Microphysical Parameterization on Snowfall over North China

The cause of the snowfall formation is analyzed that occurred over North China in December 2002.The results show that the southward strong and cold air on the high-latitude and the vapor transportation on the low-latitude result in this snowfall event. The simulation in a mesoscale model in the hybrid approach shows that the snowfall had no convective snowfall but only nonconvective snowfall.The other cumulus parameterization schemes had no effect on the simulated snowfall by means of sensitive experiments.The simulated 24 h snowfall in control experiment coincides with the observation.The simulated results show that there were too much cloud ice,cloud water and snow when the Dudhia simple ice microphysical scheme was used.There were too much cloud ice and snow when the Reisner 1 mixed phase microphysical scheme was used.The modified Reisner 2 schemes do not modify the forecast of snowfall.However,the cloud ice mixing ratio,cloud water mixing ratio and snow mixing ratio may have some differences when the different modified Reisner 2 schemes were used.