On the determination of atmospheric water vapor from GPS measurements

[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.

[1]  S. Hagemann,et al.  Sensitivity of large-scale atmospheric analyses to humidity observations and its impact on the global water cycle and tropical and extratropical weather systems in ERA40 , 2004 .

[2]  S. Hagemann,et al.  On the determination of the global water cycle from re-analysis data , 2004 .

[3]  B. Soden,et al.  WATER VAPOR FEEDBACK AND GLOBAL WARMING 1 , 2003 .

[4]  Alan Dodson,et al.  The use of GPS measurements for water vapor determination , 2003 .

[5]  Heini Wernli,et al.  A Lagrangian analysis of stratospheric ozone variability and long‐term trends above Payerne (Switzerland) during 1970–2001 , 2002 .

[6]  David Carlson,et al.  Corrections of Humidity Measurement Errors from the Vaisala RS80 Radiosonde—Application to TOGA COARE Data , 2002 .

[7]  L. Bengtsson,et al.  Secular trends in daily precipitation characteristics: greenhouse gas simulation with a coupled AOGCM , 2002 .

[8]  Gunnar Elgered,et al.  Climate monitoring using GPS , 2002 .

[9]  James W. Hurrell,et al.  Quality of Reanalyses in the Tropics , 2001 .

[10]  John R. Lanzante,et al.  Sensitivity of Tropospheric and Stratospheric Temperature Trends to Radiosonde Data Quality , 2000 .

[11]  S. Manabe,et al.  The Role of Water Vapor Feedback in Unperturbed Climate Variability and Global Warming , 1999 .

[12]  Benjamin Kirtman,et al.  Tropospheric Water Vapor and Climate Sensitivity , 1999 .

[13]  Steven Businger,et al.  The Promise of GPS in Atmospheric Monitoring , 1996 .

[14]  Christian Rocken,et al.  GPS/STORM—GPS Sensing of Atmospheric Water Vapor for Meteorology , 1995 .

[15]  Steven Businger,et al.  GPS Meteorology: Mapping Zenith Wet Delays onto Precipitable Water , 1994 .

[16]  Steven Businger,et al.  Sensing atmospheric water vapor with the global positioning system , 1993 .

[17]  Lester L. Yuan,et al.  Sensing Climate Change Using the Global Positioning System , 1993 .

[18]  Gunnar Elgered,et al.  Tropospheric Radio-Path Delay from Groundbased Microwave Radiometry , 1993 .

[19]  M. Janssen Atmospheric Remote Sensing by Microwave Radiometry , 1993 .

[20]  T. Herring,et al.  GPS Meteorology: Remote Sensing of Atmospheric Water Vapor Using the Global Positioning System , 1992 .

[21]  A. Hollingsworth,et al.  Monitoring of observation and analysis quality by a data assimilation system , 1986 .

[22]  I. Shapiro,et al.  Geodesy by radio interferometry: Effects of atmospheric modeling errors on estimates of baseline length , 1985 .

[23]  J. Holton An introduction to dynamic meteorology , 2004 .

[24]  J. Giraytys symposium on meteorological observations and instrumentation , 1969 .

[25]  S. Barnes,et al.  A Technique for Maximizing Details in Numerical Weather Map Analysis , 1964 .

[26]  H H Schmid,et al.  The Use of Artificial Satellites for Geodesy. , 1964, Science.