Quantifying Entrainment and its Effects in Isolated, Sheared Cumuli and Thunderstorms

地球的降水主要是由深积云产生的。积云对流的许多方面都受到夹带的影响，夹带是湍流云从云外引入干空气的过程。夹带导致云的稀释，从而降低上升气流速度和云的高度，并可能阻止降水的形成。该奖项将为发生在环境风切变地区的风暴夹带的系统研究提供资金，这些条件可以维持超级单体雷暴。研究人员计划发展风切变、积云夹带和对流降水之间的一般关系，这些关系可用于改进对雷暴开始以及在这些风暴中形成的雨、冰雹和闪电的预测。此外，该项目将有助于培养两名早期职业研究人员，他们将接受大气科学和高性能计算方面的培训。以往关于积云夹带的研究在很大程度上没有考虑到风切变。该项目将使用CM1云模型来解决三个主要假设：1)单向垂直风切变增强了云上升气流在类热阶段的夹带作用（与非剪切情况相比），但方向性垂直风切变减弱了这种增强作用。2)在垂直风切变足够强的环境中，产生旋转上升气流，类热的初始上升气流转变为射流状上升气流，减少了旋转上升气流的夹带作用和稀释作用。(3)热阶段云上升气流夹带和稀释的增加，以及急流阶段夹带和稀释的减少导致风暴内降水产生不可忽略（分别为10%）的减少和增加。

Earth's precipitation is primarily produced by deep cumulus clouds. Many aspects of cumulus convection are affected by entrainment, the process by which turbulent clouds introduce dry air from outside the cloud. Entrainment results in the dilution of the cloud which decreases the updraft speed and cloud height, and potentially prevents precipitation formation. This award will provide funding for the systematic investigation of entrainment in storms that occur in regions with environmental wind shear, the conditions that can sustain supercell thunderstorms. The researcher plans to develop general relationships between wind shear, cumulus entrainment, and convective precipitation which can be used to improve prediction of thunderstorm initiation, and rain, hail and lightning that form within these storms. In addition, the project will contribute to the development of two early-career researchers who will be trained in atmospheric science and high performance computing.Prior research on cumulus entrainment has largely not taken wind shear into consideration. This project will use the CM1 cloud model to address three main hypotheses: 1) Unidirectional vertical wind shear enhances entrainment (compared to the non-sheared case) into a cloud updraft in its thermal-like stage, but directional vertical wind shear decreases this enhancement, 2) In environments with sufficiently strong vertical wind shear to generate a rotating updraft, the thermal-like initial updraft transforms into a jet-like updraft, decreasing the entrainment into, and dilution of, the rotating updraft, 3) The increased entrainment and dilution into a cloud updraft in its thermal stage, and the decreased entrainment and dilution of the jet stage results in non-negligible (10%) decreases and increases (respectively) in precipitation production within the storm.