台风“云娜”在近海强度变化及结构特征的数值研究Ⅰ:云微物理参数化对云结构及降水特征的影响

Numerical research on intensity change and structure feature of Typhoon Rananim near shore.Ⅰ:Impact of cloud microphysical parameterization on cloud structure and precipitation features

首先对AREM模式模拟的台风基本结构和云结构进行验证,检验了模拟结果的可靠性。在此基础上,设计了5组试验来研究云微物理参数化方案对台风"云娜"云结构及降水特征的影响。试验设计主要突出冰相云微物理过程、云微物理特征引发的冷却效应以及霰下落速度的重要性。结果表明:云微物理参数化过程对云的发展和降水特征的影响更为显著。各试验的水凝物分布和强度不同,降水类型和强度存在较大差异,由此引起的云中热力结构也有较大区别;在所有试验方案中,24 h降水率最大差异为52.5 mm/h。云微物理过程对云和降水特征的具体影响表现在:(1)如果不考虑雨水蒸发冷却效应,此时台风内核上升运动强度最强(达到-19 Pa/s),雨水和霰粒子增长最明显,相对于对照试验增量分别为1.8和2.5 g/kg。(2)霰和雪的融化对于螺旋雨带中雨滴的增长十分重要,但他们可能不是云墙中雨水形成的主导因子。(3)不同方案的降水模拟特征也存在较大差别,采用暖云参数化后,降水区域最小,但其中对流降水比例最大(63.19%);霰落速减半后,降水区域最大,其中非对流降水比例也最大(51.15%)。

By using the AREM, the basic typhoon structure and cloud features are simulated, and the simulated reliability is validat- ed. After the model verification, five sets of experiments are designed to investigate effects of cloud microphysieal parameterization scheme on the modeling cloud structure and precipitation features of Typhoon Rananim. The aim of those five experiments is to reveal the importance of the ice-phase microphysical process, the cooling effect due to microphysical characteristics change, and the terminal velocity of graupel. The results indicate that the cloud microphysical processes have great impact on the cloud development and precip- itation features of typhoon compared with that on intensity and track： Big difference of the pattern and content of hydrometeors, and types and amount of rainfall occur between those five experiments, which can lead to different heating and cooling effects. Among ex- periments conducted, the biggest difference of 24 hours rain rate reaches 52.5 mm/h. The impacts of microphysies on cloud and rain- fall features are summarized as below： （1） Updrafts in the inner core are strongest among those five experiments with the maximum vertical velocity of - 19 Pa/s when the cooling effect due to the evaporation of rain water is excluded. Also, rain water and graupel grow most dominantly under this condition with the content increase of 1.8 and 2.5 g/kg respectively in comparison with the control experiment. （2） The melting of snow and graupel mainly affects the growth of rain water in the spiral rainbands, however, it may be an unimportant factor in the formation of rain water in the eyewall area. （3） The warm cloud microphysical parameterization produces the smallest rainfall area and the largest percentage of convective precipitation （63.19 % ）, but we can get the largest rainfall area and the smallest percentage of convective precipitation （48.85 % ） when the terminal velocity of graupel is weakened by half.