Effects of vertical wind shear and cloud radiative processes on responses of rainfall to the large‐scale forcing during pre‐summer heavy rainfall over southern China
Effects of vertical wind shear and cloud radiative processes on responses of rainfall to the large‐scale forcing during pre‐summer heavy rainfall over southern China
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DOI：
10.1002/qj.735
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发表时间：
2011-01
影响因子：
8.9
通讯作者：
Xinyong Shen;Yi Wang;Xiaofan Li
中科院分区：
文献类型：
--
作者：
Xinyong Shen;Yi Wang;Xiaofan Li
使用二维云解析模型模拟了2008年6月3日至8日华南地区的夏前强降雨。该模型与来自国家环境预测中心 (NCEP)/全球数据同化系统 (GDAS) 数据的强加的纬向均匀垂直速度、纬向风、水平温度和蒸汽平流相结合。通过两次敏感性实验与对照实验的对比，分析了风垂直切变和云辐射过程对降雨对大尺度强迫响应的影响。一项敏感性实验排除了大范围垂直风切变，另一项排除了云辐射效应。在对流衰减阶段，由于排除垂直风切变而导致的模型域平均表面降雨率的增加与扰动动能减少的减慢相关，这是由于排除了从平均动能到扰动动能的正压转换。排除云辐射效应而导致的域平均降雨率的增加与由于辐射冷却加强而导致的凝结和相关潜热的增强有关。域平均地表降雨率的增加主要与对流降雨的增加有关，而对流降雨的增加又与局地大气由湿润转干燥的变化有关。在对流发生和成熟阶段，域平均地表降雨率一般对垂直风切变和云辐射效应不敏感，而对流和层状降雨率对垂直风切变和云辐射效应敏感。对流降雨率的降低和层状降雨率的增加主要与水汽浓度从对流区向层状降雨区的输送增强有关。版权所有 © 2011 英国皇家气象学会
The pre‐summer heavy rainfall over southern China during 3–8 June 2008 is simulated using a two‐dimensional cloud‐resolving model. The model is integrated with imposed zonally uniform vertical velocity, zonal wind, horizontal temperature and vapour advection from National Centers for Environmental Prediction (NCEP)/Global Data Assimilation System (GDAS) data. The effects of vertical wind shear and cloud radiative processes on the response of rainfall to large‐scale forcing are analysed through the comparison of two sensitivity experiments with the control experiment. One sensitivity experiment excludes the large‐scale vertical wind shear and the other excludes the cloud radiative effects. During the decay phase of convection, the increase in model domain‐mean surface rain‐rate resulting from the exclusion of vertical wind shear is associated with the slowdown in the decrease of perturbation kinetic energy due to the exclusion of barotropic conversion from mean kinetic energy to perturbation kinetic energy. The increase in domain‐mean rain‐rate from the exclusion of cloud radiative effects is related to the enhancement of condensation and associated latent heat as a result of strengthened radiative cooling. The increase in the domain‐mean surface rain‐rate is mainly associated with the increase of convective rainfall, which is in turn related to the local atmospheric change from moistening to drying. During the onset and mature phases of convection, the domain‐mean surface rain‐rates are generally insensitive to vertical wind shear and cloud radiative effects whereas convective and stratiform rain‐rates are sensitive to vertical wind shear and cloud radiative effects. The decrease in convective rain‐rate and the increase in stratiform rain‐rate are primarily associated with the enhanced transport of hydrometeor concentration from convective regions to raining stratiform regions. Copyright © 2011 Royal Meteorological Society