Airborne Measurement of Cloud Perturbation Pressures Using Differential Global Positioning System (GPS)

气压梯度力是描述大气运动强迫的运动方程中的主要项。为了了解大气流动的动力学，有必要知道水平压力梯度力（PGF）。在过去的二十年里，机载平台已被用于试图辨别各种尺度上的水平气压场的变化，以了解中尺度到天气尺度运动场的动力学。在不规则地形上使用基于高度测量的方法进行飞行时遇到了严重的问题，这些问题阻碍了PGF的广泛应用。最近，它已被证明，精确检测水平压力梯度力的机载平台在中尺度到微尺度的距离是可能的，通过使用差分GPS。在这种技术中，使用来自固定和精确测量的基站的GPS测量值来校正由飞机上的双频接收机进行的GPS位置测量值。通过使用自动驾驶仪在等压面上飞行，可以确定等压面的斜率，该斜率是PGF的量度。这项技术首次使一种手段来描绘强迫的微尺度到中尺度大气环流复杂地形的机载平台。智力优势：这项研究的主要目标是研究潜在的差分GPS定位测量从怀俄明州国王航空大学（UWKA）平台，以确定与对流云在美国西部高原平原的压力扰动水平压力扰动是云动力学研究的基础和对流的理解至关重要。气压扰动是由于浮力气团上升时伴随对流运动的大气质量调整造成的。了解云压扰动将有助于了解对流运动对当地环境强迫的空间范围和大小，以及验证高分辨率数值模拟实验的方法。将于2008年8月在怀俄明州拉勒米外进行一次实地试验，以评估对流云造成的水平压力扰动，对流云的大小范围可达积云阶段。怀俄明州大学的云雷达将部署在UWKA上，以提供有关对流云内运动场的额外信息。水平压力扰动测量将从云底开始，在平均风的沿着和垂直方向进行。更广泛的影响：如果这种测量被证明是成功的，全球定位系统对云引起的水平压力扰动的探测将成为机载平台上的常规测量，并成为UWKA的标准，并用于大气科学界的其他研究人员。这代表了云物理学和动力学的未来研究的显着增强，因为水平运动的基本强迫项可以直接测量。这种全球定位系统技术的成功应用还将带来一系列新的测量机会，包括研究云的夹带、云运动场的改进以及与云尺度环流有关的动力学演变。

The pressure gradient force is the dominant term in the equation of motion that describes the forcing of atmospheric motions. To understand the dynamics of atmospheric flows, it is necessary to know the horizontal pressure gradient force (PGF). For the past two decades, airborne platforms have been used in attempt to discern variations in the horizontal pressure field over a variety of scales to understand the dynamics of mesoscale to synoptic-scale motion fields. Serious problems have been encountered when conducting flight legs over irregular terrain using altimetry-based methods that have prevented the PGF application from widespread use. Recently it has been shown that accurate detection of the horizontal pressure gradient force from airborne platforms over mesoscale to microscale distances is possible by using differential GPS. In this technique, GPS position measurements by a dual-frequency receiver onboard an aircraft are corrected using GPS measurements from a fixed and precisely surveyed base station. By flying on an isobaric surface using the autopilot, the slope of the isobaric surface, which is a measure of the PGF, can be determined. This technique enables for the first time a means to depict forcing of microscale to mesoscale atmospheric circulations over complex terrain by airborne platforms. Intellectual Merit: The primary goal of this research is to examine the potential of differential GPS position measurements from the University of Wyoming King Air (UWKA) platform to determine pressure perturbations associated with convective clouds over the high western plains of the U.S. Horizontal pressure perturbations are fundamental to studies of cloud dynamics and critical to an understanding of convection. Pressure perturbations result from the atmospheric mass adjustment that accompanies convective motions as buoyant air parcels rise. Knowledge of the cloud pressure perturbations will permit an understanding of the spatial extent and magnitude of the forcing of the local environment by convective motions as well as a means to validate high resolution numerical modeling experiments. A field experiment will be conducted during August 2008 based out of Laramie WY to evaluate the horizontal pressure perturbations that result from convective clouds that range in size up to the cumulus congestus stage. The University of Wyoming Cloud Radar will be deployed on the UWKA to provide additional information regarding the motion field within convective clouds. Horizontal pressure perturbation measurements will be made in directions along and normal to the mean wind beginning at cloud base. Subsequent passes will be made at higher levels within the cloud to provide information on the vertical structure of the horizontal pressure perturbations Broader Impacts: If such measurements are shown to be successful, GPS detection of the cloud-induced horizontal pressure perturbations will become a routine measurement on airborne platforms and become standard for the UWKA and of use to other investigators within the atmospheric science community. This represents a significant enhancement for future studies of cloud physics and dynamics since the fundamental forcing term for horizontal motions can be directly measured. Successful application of this GPS technology will also enable a host of new measurement opportunities, including studies of entrainment in clouds, refinements in cloud motion field and the evolution in dynamics associated with cloud-scale circulations.