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

地球上的降水主要是由深厚的积云产生的。 积云对流的许多方面都受到卷吸的影响，卷吸是湍流云从云外引入干燥空气的过程。 卷吸导致云的稀释，从而降低上升气流速度和云高，并可能阻止降水的形成。 该奖项将为系统调查发生在环境风切变地区的风暴中的夹带提供资金，这些条件可以维持超级单体雷暴。 研究人员计划开发风切变、积云夹带和对流降水之间的一般关系，这些关系可用于改善雷暴开始以及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。 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卷吸（与非剪切情况相比）在其热态阶段进入云上升气流，但定向垂直风切变降低了这种增强，2）在具有足够强的垂直风切变以产生旋转上升气流的环境中，类热初始上升气流转变为类喷流上升气流，减少了旋转上升气流的卷吸和稀释，3）在其热阶段云上升气流的卷吸和稀释增加，急流阶段的夹带和稀释的减少导致风暴内降水量的不可忽略的（分别为10%）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.