A New Method for Representing Mixed-phase Particle Fall Speeds in Bulk Microphysics Parameterizations
A New Method for Representing Mixed-phase Particle Fall Speeds in Bulk Microphysics Parameterizations
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DOI：
10.2151/jmsj.86a.33
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发表时间：
2008-11
影响因子：
3.1
通讯作者：
J. Dudhia;Song‐You Hong;K. Lim
中科院分区：
文献类型：
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作者：
J. Dudhia;Song‐You Hong;K. Lim
在这里，我们提出了一个简单的方法，改进散装混合相微观物理方案，允许更现实的部分镶边颗粒的代表性。新的程序统一的雪和粒子分配一个单一的下降速度，这是加权的混合比，并适用于沉降和吸积过程的下降速度。这就避免了当<$球形成时，由于沉淀作用而分离出物种的问题，以及<$球由于其相对较高的下落速度而过快地堆积雪的进一步问题。相反，统一的谷粒/雪一起移动，并因成霜而按其相对比例演变，表现为中间或部分成霜颗粒。使用天气研究与预报（WRF）单矩6级（WSM 6）微物理方案进行了新方法的测试在高分辨率理想化模拟和韩国夏季和冬季的中尺度强降水事件中。新的吸积率对云结构和降水的影响被认为是大于单独的改变沉积。对这些试验的验证表明，产生的霰和更多的雪大大减少，影响了云的结构和地面降水场。该方案在改进降水强度和降水类型预报方面显示出希望。
Here we present a simple method of improving bulk mixed-phase microphysical schemes to allow for a more realistic representation of partially rimed particles. The new procedure unifies the snow and graupel particles by assigning a single fallspeed to both that is weighted by the mixing ratios, and applying that fallspeed to both sedimentation and accretion processes. This avoids the problem of the species separating out by sedimentation as graupel forms, and the further problem of graupel then accreting snow too quickly because of its high relative fallspeed. Instead the unified graupel/snow moves together and evolves in its relative ratio due to riming, behaving as intermediate or partially rimed particles.Tests of the new method were carried out using the Weather Research and Forecasting (WRF) Single-Moment 6-class (WSM6) microphysics scheme in a high-resolution idealized simulation, and mesoscale heavy precipitation events in the summer and winter over Korea. The effect of the new accretion rates on cloud structure and precipitation was found to be greater than that of the changed sedimentation alone. Verification of these tests showed a much-reduced production of graupel and more snow, influencing the cloud structure and surface precipitation fields. The scheme shows promise in improving precipitation intensity and precipitation type forecasts.