Raman Lidar Applications in Mesoscale Studies

虽然在过去十年中，在了解灾害性天气系统的结构特征方面取得了很大进展，但在触发深对流的关键因素方面仍有许多问题没有答案。 最近的研究表明，干线，一个急剧的水平梯度的水分，经常发现在美国中南部的春季和初夏，创造了一个有利的环境，对流的启动。 这种中尺度现象意义重大，因为它往往与恶劣天气的发生有关，而恶劣天气往往沿着沿着和干线以东发展。 这在冷锋接近时尤其如此，它破坏了湿空气抬升的机制。 然而，迄今为止，已经有很少的水分结构和dryline的演变的详细研究。主要研究人员将进行为期三年的研究，以量化详细的垂直和水平的雷暴前的环境和drylines的水分分层，以及湿度的发展和对流风暴的启动使用的能力拉曼激光雷达系统的潜在作用。 他们将使用拉曼激光雷达来验证干线特性的理论和数值预测干线前的相互作用和相关的对流。 该项目依赖于获取和利用拉曼激光雷达观测的水汽混合比和气溶胶剖面数据，这些数据是1994年至2000年期间在美国不同地区进行的几次实地飞行任务中观测到的。以及由能源部（DOE）大气辐射测量（ARM）计划进行的水汽密集运行（WVIOP）也将被利用。 将综合分析来自拉曼激光雷达、雷达探空仪、雷达、微波辐射计、风廓线仪和其他常规数据集的现有数据，并使用一个数值模型来实现这项研究的目标。 将分析辐合区、锋面和干线的动力、热力和湿度结构以及边界层的时间发展。 重点领域包括干线和冷锋期间水分垂直结构的小尺度变化对风暴启动和对流的影响，以及对流层中层结构在风暴动力学和启动和/或抑制中的作用。 对流有效位能和对流抑制的计算，以及选定的案例研究的简单模式模拟，以更好地了解风切变在对流启动中的作用。研究结果应提供更好地了解干线的日特征，通过证明或反驳预测的数量来补充对流开始的理论预测，并最终有助于改进强对流天气的预报技能。天气条件

While much progress has been made over the last decade in understanding the structural characteristics of severe weather systems, many questions remain unanswered on the critical factors that trigger deep convection. Recent work has shown that the dryline, a sharp horizontal gradient in moisture and often found over the south central United States in spring and early summer, creates a favorable environment for initiation of convection. This mesoscale phenomenon is significant because it is often linked to the occurrence of severe weather, which tends to develop along and to the east of the dryline. This is particularly true during a cold frontal approach, which furnishes a mechanism for the lifting of the moist air. To date however, there have been very few detailed studies of the moisture structure and evolution of the dryline.The Principal Investigators will perform a three year study to quantify the detailed vertical and horizontal moisture stratification of the pre-thunderstorm environment and drylines as well as the potential role of humidity in the development and initiation of convective storms using the capability of Raman lidar systems. They will use the Raman lidar to verify theoretical as well as numerical predictions of dryline characteristics dryline-front interactions and associated convection. This project relies on acquiring and utilizing Raman lidar observations of water vapor mixing ratio and aerosol profile data observed between 1994 and 2000 during several field missions at different parts of the U.S.A. Data from the International H20 Project (IHOP), planned for May-June 2002 in the southern Great Plains of the United states, and the Water Vapor Intensive Operations (WVIOP) conducted by the Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) program, also will be utilized. A combination of analyses of existing data from Raman lidars, rawinsonde, radars, microwave radiometers, wind profilers and other conventional data sets and a numerical model will be used to achieve the objectives of this research. Dynamic, thermodynamic and moisture structure of convergence zones, frontal surfaces, and drylines as well as the temporal development of the boundary layer will be analyzed. Areas of focus include the effects of small-scale variations in the vertical structure of moisture during drylines and cold fronts on storm initiation and convection and the role of the structure of the mid-tropospheric layer in storm dynamics and initiation and/or inhibition. The calculation of convective available potential energy and convective inhibition as well as simple model simulations of selected case studies to better understand the role of wind shear in the initiation of convection are included.The results of the research should provide a better understanding of the diurnal characteristics of the dryline, complement the theoretical predictions of convective initiation by proving or disproving the predicted quantities and eventually contribute towards improvements in the forecasting skills of severe weather conditions.