【作者】 张楠；

【导师】 沈新勇；

【作者基本信息】 南京信息工程大学 ， 气象学， 2011， 硕士

【摘要】 暴雨的发生不仅仅与宏观尺度的天气现象有关系,微观过程更为深入研究暴雨的机理和发生发展过程提供了一个好的研究角度。本文利用二维云分辨模式对2008年6月10日-15日的华南暴雨过程做了模拟,并设计了云辐射敏感性实验,与控制实验对比分析。控制实验中降水过程区域平均对流降水率大于层云降水率。初始阶段,区域平均降水率较小；成熟阶段区域平均降水强度最大；衰退阶段,区域平均降水率减小的原因主要在于水汽辐合率的减小和局地水汽增加抑制了降水的发展。在降水性层状云区,降水主要来自于水汽辐合,水汽的主要消耗项是局地水汽增加。对流云区,降水主要来自于水汽辐合与局地大气变干,水汽主要消耗项是水凝物生成。热量变化特征是,区域平均大气温度变化率主要受区域平均的热辐散率与区域平均的潜热释放影响,在成熟阶段区域平均大气冷却达到最强,初始阶段和衰退阶段的局地大气温度变化率相对较小,并且区域平均大气冷却主要来自于层状云区。对流云区的潜热释放率始终大于降水性层状云区,对增强区域平均潜热释放率起到了重要作用。区域平均热辐散主要来自于降水性层状云区和对流云区。云辐射敏感实验的降水特征是,无云辐射效应使得区域平均水汽辐合减小,但却通过使局地大气变干和局地水凝物减少率增强的方式来增加降水的水汽来源,使得区域平均降水强度大于控制实验。其中局地大气变干率和局地水凝物减少率均在降水的成熟阶段达到最大,在降水性层状云区和对流降水区,引起对流云区降水强度普遍增强,主要来自于局地水汽凝结大气变干过程；降水性层状云区的降水强度普遍减弱,主要原因在于水汽辐合率的减弱抑制了降水的发展。对流降水强度增加量大于层云降水强度的减弱量,因此无云辐射效应导致了区域平均降水强度的增加。云辐射敏感性实验的热量收支特征是,在初始阶段,平均局地大气冷却加强。成熟阶段,平均局地大气冷却率相对初始阶段增强,本阶段局地温度主要受辐射冷却和潜热释放减小的影响。衰退阶段,平均辐射冷却率仍然增强,平均潜热释放率减小程度相对于成熟阶段减小一个量级,平均热辐散率减弱程度小于成熟阶段。更多还原

【Abstract】 Microphysical processes provide us a unique angle to have a better study of the mechanism and development process of heavy rains, which is more than just having a relationship with large-scale phenomenon. In this paper, heavy rainfall event occurred in 10-15 June 2008 in southern China is simulated with a two-dimensional cloud-resolving model. Besides, sensitivity experiment of cloud radiation is designed to be compared with control-experiment to show the results.Convective domain mean rain rate is larger than that of stratiform in control experiment. In onset phase, domain mean rain rate is small;in mature phase, domain mean rain rate reaches maximum; in decay phase domain mean rain rate is decreased mainly because the rainfall development process is depressed by the decreasing of vapor convergence rate and increasing of local vapor content. In raining stratiform regions, rainfall is mainly from vapor convergence and vapor sink is mainly from local vapor increasing. In convective regions, vapor convergence and local atmospheric drying are the major source for rainfall. Local hydrometeor gain is the major vapor sink. Feature of heat budget is that heat divergence and domain mean latent heat release are the main contributors to domain mean temperature change. Domain mean local atmospheric cooling reaches maximum in mature phase, and local atmosphere temperature change rate is relatively small in onset phase and decay phase. Local mean atmospheric cooling is mainly from stratiform regions (raining stratiform regions and non-raining stratiform regions). Latent heat release in convective regions is consistently large than that of raining stratiform regions, which plays an important role in enhancing local mean latent heat release. Domain mean heat divergence is mainly from raining stratiform regions and convective regions.Rainfall characteristics of the cloud radiation sensitivity experiment is that domain mean vapor convergence rate is decreased, but vapor source is increased by local atmospheric drying and local hydrometeor loss, as a result, the domain mean rain rate is larger than that in control experiment. Local atmospheric drying and local hydrometeor loss reach maximum in mature phase. In raining stratiform regions and convective regions, rain rate is generally increased in convective regions, which rainfall source is mainly from local hydrometeor loss, namely local atmospheric drying. Rain rate is generally decreased in raining stratiform regions, and the major reason is vapor convergence rate is depressed. Increasing of convective rain rate is more than decreasing of raining stratiform rain rate, therefore domain rain rate is enhanced in the sensitivity experiment of cloud radiation. Feature of heat budgets of cloud radiation sensitivity experiment is that local mean atmosphere cooling is increasing in onset phase. Domain mean local atmospheric cooling rate in mature phase is larger than that in onset phase, and local temperature is mainly affected by radiative cooling and decreasing of latent heat release. In decay phase, mean radiative cooling rate is still increasing, and the magnitude of mean latent heat release rate is one degree smaller than that in mature phase, mean heat divergence rate is smaller than that in mature phase.更多还原