Integrated water vapor from IGS ground-based GPS observations: initial results from a global 5-min data set

摘要

Ground based GPS zenith path delay (ZPD) measurements are well established as apowerful tool for integrated water vapor (IWV) observation. TheInternational GNSS Service (IGS) provides ZPD data of currentlymore than 300 globally distributed GPS stations. To derive IWVfrom these data, meteorological information (ground pressure andmean temperature above the station) are needed. Only a limitednumber of IGS stations is equipped with meteorological groundsensors up to now. Thus, meteorological data for IWV conversionare usually derived from nearby ground meteorological observations(ground pressure) and meteorological analyses (mean temperature).In this paper we demonstrate for the first time the applicabilityof ground pressure data from ECMWF meteorological analysis fieldsin this context. Beside simplified data handling (no single station data and qualitycontrol) this approach allows for IWV derivation if nearbymeteorological stations are not available.Using ECMWF ground pressure and mean temperaturedata the new IGS 5-min ZPD data set has been converted to IWVfor the first time. We present initial results from selectedstations with ground meteorological sensors including pressure andtemperature comparisons between ECMWF and local measurements. TheGPS IWV is generally validated by comparison with ECMWF IWV. TheECMWF derived station meteorological data are compared with localmeasurements at all accordingly equipped stations. Based on thiscomparison, the mean error (in terms of standard deviation)introduced by time interpolation of the6-hourly ECMWF data is estimated below 0.2 mm IWV.