Real-Time Water Vapor Maps from a GPS Surface Network: Construction, Validation, and Applications

S. de Haan, I. Holleman, A.A.M. Holtslag

Research output: Contribution to journalArticleAcademicpeer-review

32 Citations (Scopus)


In this paper the construction of real-time integrated water vapor (IWV) maps from a surface network of global positioning system (GPS) receivers is presented. The IWV maps are constructed using a twodimensional variational technique with a persistence background that is 15 min old. The background error covariances are determined using a novel two-step method, which is based on the Hollingsworth¿Lonnberg method. The quality of these maps is assessed by comparison with radiosonde observations and IWV maps from a numerical weather prediction (NWP) model. The analyzed GPS IWV maps have no bias against radiosonde observations and a small bias against NWP analysis and forecasts up to 9 h. The standard deviation with radiosonde observations is around 2 kg m-2, and the standard deviation with NWP increases with increasing forecast length (from 2 kg m-2 for the NWP analysis to 4 kg m-2 for a forecast length of 48 h). To illustrate the additional value of these real-time products for nowcasting, three thunderstorm cases are discussed. The constructed GPS IWV maps are combined with data from the weather radar, a lightning detection network, and surface wind observations. All cases show that the location of developing thunderstorms can be identified 2 h prior to initiation in the convergence of moist air.
Original languageEnglish
Pages (from-to)1302-1316
JournalJournal of Applied Meteorology and Climatology
Issue number7
Publication statusPublished - 2009


  • global positioning system
  • precipitable water
  • model
  • verification
  • netherlands
  • meteorology
  • radiosonde
  • radiometer
  • errors
  • delay

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