Scherllin-Pirscher Barbara, Steiner Andrea K, Kirchengast Gottfried, Schwärz Marc, Leroy Stephen S
Wegener Center for Climate and Global Change (WEGC) and Institute for Geophysics, Astrophysics, and Meteorology/Institute of Physics University of Graz Graz Austria.
Zentralanstalt für Meteorologie und Geodynamik (ZAMG) Vienna Austria.
J Geophys Res Atmos. 2017 Feb 16;122(3):1595-1616. doi: 10.1002/2016JD025902. Epub 2017 Feb 8.
High-resolution measurements from Global Navigation Satellite System (GNSS) radio occultation (RO) provide atmospheric profiles with independent information on altitude and pressure. This unique property is of crucial advantage when analyzing atmospheric characteristics that require joint knowledge of altitude and pressure or other thermodynamic atmospheric variables. Here we introduce and demonstrate the utility of this independent information from RO and discuss the computation, uncertainty, and use of RO atmospheric profiles on isohypsic coordinates-mean sea level altitude and geopotential height-as well as on thermodynamic coordinates (pressure and potential temperature). Using geopotential height as vertical grid, we give information on errors of RO-derived temperature, pressure, and potential temperature profiles and provide an empirical error model which accounts for seasonal and latitudinal variations. The observational uncertainty of individual temperature/pressure/potential temperature profiles is about 0.7 K/0.15%/1.4 K in the tropopause region. It gradually increases into the stratosphere and decreases toward the lower troposphere. This decrease is due to the increasing influence of background information. The total climatological error of mean atmospheric fields is, in general, dominated by the systematic error component. We use sampling error-corrected climatological fields to demonstrate the power of having different and accurate vertical coordinates available. As examples we analyze characteristics of the location of the tropopause for geopotential height, pressure, and potential temperature coordinates as well as seasonal variations of the midlatitude jet stream core. This highlights the broad applicability of RO and the utility of its versatile vertical geolocation for investigating the vertical structure of the troposphere and stratosphere.
全球导航卫星系统（GNSS）无线电掩星（RO）的高分辨率测量可提供具有高度和压力独立信息的大气廓线。在分析需要高度和压力或其他大气热力变量联合知识的大气特征时，这一独特属性具有至关重要的优势。在此，我们介绍并演示了来自RO的这一独立信息的效用，并讨论了RO大气廓线在等压面坐标（平均海平面高度和位势高度）以及热力坐标（压力和位温）上的计算、不确定性及应用。使用位势高度作为垂直网格，我们给出了RO反演的温度、压力和位温廓线的误差信息，并提供了一个考虑季节和纬度变化的经验误差模型。在对流层顶区域，单个温度/压力/位温廓线的观测不确定性约为0.7 K/0.15%/1.4 K。它在平流层中逐渐增大，在对流层低层则减小。这种减小是由于背景信息的影响增加所致。一般而言，平均大气场的总气候误差主要由系统误差分量主导。我们使用经采样误差校正的气候场来展示拥有不同且准确的垂直坐标的作用。作为示例，我们分析了位势高度、压力和位温坐标下对流层顶位置的特征以及中纬度急流核心的季节变化。这突出了RO的广泛适用性及其通用垂直地理定位在研究对流层和平流层垂直结构方面的效用。
