Vorticity and Thermodynamic Budgets in Easterly Waves -- PREDICT Participation

该奖项由2009年《美国复苏与再投资法案》(公法111-5)资助。新墨西哥州矿业与技术研究所的研究人员将参与该项目的规划、实地和数据分析阶段(热带地区云系的萧条前调查)。这个实地项目将利用美国国家科学基金会/国家大气研究中心高空研究飞机，在大西洋中部和西部以及加勒比地区部署下降探测仪，并对东风波和其他气旋前扰动进行各种其他测量，以更好地了解热带气旋在这些扰动中的发展。热带气旋的形成涉及大气低层环流的分裂。这种自旋(主要)是由于发展区的绝对涡度流入和表面摩擦之间的不平衡造成的，绝对涡度的流入往往会使系统自转，表面摩擦则会使系统自转。在这个项目中，我们特别关注支持或不支持绝对涡度输入的因素。低层质量辐合是控制涡度流入的主要因素。这反过来又与水汽汇聚和净降雨量(降雨量减去地表蒸发量)有关。最近的工作有助于阐明控制热带海洋降雨量的因素。一个极其重要的因素是热带对流层的饱和分数，其定义为可降水量除以饱和可降水量。目标区域的湿熵收支控制着饱和分数，这将从滴状探空仪的观测中得到。热带气旋形成的第三个因素是虚拟温度廓线的形状，对流层低层温度较低，高层温度较高，有利于更强的降水。即使在低纬度地区，这种结构也是由准平衡动力学控制的，也将由Dropsonde观测得到。智力优势：这个项目将解释深层大气对流如何与热带海洋地区普遍存在的东风波相互作用，以及这些波在什么情况下放大成热带气旋。更广泛的影响：该项目将帮助隔离那些需要在大型大气数值模式的深对流处理中准确表示的过程。在这些模型中准确表示对流的目标将取得重大进展，这将是诸如预测之类的观测计划的结果。

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).Researchers from the New Mexico Institute of Mining and Technology will participate in the planning, field, and data analysis phases of the PREDICT (PRE-Depression Investigation of Cloud-systems in the Tropics) project. This field project will use the NSF/National Center for Atmospheric Research high altitude research aircraft to deploy dropsondes and make various other measurements in easterly waves and other pre-cyclone disturbances in the central and western Atlantic as well as the Caribbean, in order to understand better the development of tropical cyclones out of these disturbances.The formation of a tropical cyclone involves the spinup of a circulation at low levels in the atmosphere. This spinup results (mainly) from the imbalance between the inflow of absolute vorticity in the development region, which tends to spin up the system, and surface friction, which tends to spin it down. In this project we focus particularly on the factors which favor or disfavor the import of absolute vorticity. Mass convergence at low levels is a primary factor governing the vorticity inflow. This in turn is related to the moisture convergence and the net rainfall (rain minus surface evaporation). Recent work has helped elucidate the factors controlling the rainfall over tropical oceans. An extremely important factor is the saturation fraction of the tropical troposphere, defined as the precipitable water divided by the saturated precipitable water. The moist entropy budget of the target region controls the saturation fraction, and this will be derived from the dropsonde observations. A third factor in tropical cyclone formation is the shape of the virtual temperature profile, with cooler temperatures in the lower troposphere and warmer temperatures at higher levels favoring stronger precipitation. This structure is controlled by quasi-balanced dynamics even at low latitudes, and also will be derived from the dropsonde observations.Intellectual merit: This project will explain how deep atmospheric convection interacts with the ubiquitous easterly waves of tropical, oceanic regions, and in what circumstances these waves amplify into tropical cyclones. Broader impacts: This project will help isolate those processes which need to be accurately represented in treatments of deep convection in large-scale numerical atmospheric models. Significant progress toward the goal of accurately representing convection in these models will be made as a result of observational programs such as PREDICT.