On the determination of atmospheric water vapor from GPS measurements
On the determination of atmospheric water vapor from GPS measurements
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DOI：
10.1029/2002jd003235
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发表时间：
2003-11
影响因子：
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通讯作者：
S. Hagemann;L. Bengtsson;G. Gendt
中科院分区：
文献类型：
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作者：
S. Hagemann;L. Bengtsson;G. Gendt
基于地面的GPS天顶路径延迟（ZPD）测量可用于推导大气的垂直综合水汽（IWV）。目前，作为国际GPS服务的一部分，ZPD数据是在一个由160个站点组成的全球网络中收集的。在本研究中，利用欧洲中期天气预报中心（ECMWF）业务分析（OA）获得的观测地表压力和平均大气水汽柱温度，将该网络的ZPD数据转换为IWV。在2000/2001年1 / 7月的4个月里，我们将gps计算的IWV值与ECMWF OA的IWV值进行比较，特别关注月平均差值（偏差）和日差值的标准差。结果表明，gps反演的IWV值可以很好地用于IWV的OA验证。对于大多数GPS台站，IWV数据与分析数据相当吻合，表明它们在这些位置上都是正确的。个别日期的较大差异被解释为分析中的错误。美国中部、加拿大和西伯利亚中部冬季偏干，表明系统分析有误。较大的差异主要出现在山区。这些问题与模型高度与站高之间的表示问题和插值困难有关。此外，IWV比较可以用来识别ZPD观测中的错误或问题。这包括数据本身的误差，例如，测量时间序列中的错误异常值，以及影响某一特定台站的所有IWV值的系统误差。这些电台被排除在相互比较之外。最后，讨论了基于gps的水汽监测系统的长期需求。
[1] Surface-based GPS measurements of zenith path delay (ZPD) can be used to derive vertically integrated water vapor (IWV) of the atmosphere. ZPD data are collected in a global network presently consisting of 160 stations as part of the International GPS Service. In the present study, ZPD data from this network are converted into IWV using observed surface pressure and mean atmospheric water vapor column temperature obtained from the European Centre for Medium-Range Weather Forecasts' (ECMWF) operational analyses (OA). For the 4 months of January/July 2000/2001, the GPS-derived IWV values are compared to the IWV from the ECMWF OA, with a special focus on the monthly averaged difference (bias) and the standard deviation of daily differences. This comparison shows that the GPS-derived IWV values are well suited for the validation of OA of IWV. For most GPS stations, the IWV data agree quite well with the analyzed data indicating that they are both correct at these locations. Larger differences for individual days are interpreted as errors in the analyses. A dry bias in the winter is found over central United States, Canada, and central Siberia, suggesting a systematic analysis error. Larger differences were mainly found in mountain areas. These were related to representation problems and interpolation difficulties between model height and station height. In addition, the IWV comparison can be used to identify errors or problems in the observations of ZPD. This includes errors in the data itself, e.g., erroneous outlier in the measured time series, as well as systematic errors that affect all IWV values at a specific station. Such stations were excluded from the intercomparison. Finally, long-term requirements for a GPS-based water vapor monitoring system are discussed.