The uncertainty of the atmospheric integrated water vapour estimated from GNSS observations

[摘要] Within the Global Climate Observing System (GCOS) Reference Upper-AirNetwork (GRUAN) there is a need for an assessment of theuncertainty in the integrated water vapour (IWV) in the atmosphereestimated from ground-based global navigationsatellite system (GNSS) observations. All relevant errorsources in GNSS-derived IWV are therefore essential to beinvestigated. We present two approaches, a statistical and atheoretical analysis, for the assessment of the uncertainty of theIWV. The method is valuable for all applications of GNSS IWV data inatmospheric research and weather forecast. It will be implemented tothe GNSS IWV data stream for GRUAN in order to assign a specificuncertainty to each data point. In addition, specificrecommendations are made to GRUAN on hardware, software, and dataprocessing practices to minimise the IWV uncertainty. By combiningthe uncertainties associated with the input variables in theestimations of the IWV, we calculated the IWV uncertainties forseveral GRUAN sites with different weather conditions. The resultsshow a similar relative importance of all uncertainty contributionswhere the uncertainties in the zenith total delay (ZTD) dominate theerror budget of the IWV, contributing over 75 % of the totalIWV uncertainty. The impact of the uncertainty associated with theconversion factor between the IWV and the zenith wet delay (ZWD) isproportional to the amount of water vapour and increases slightlyfor moist weather conditions. The GRUAN GNSS IWV uncertainty datawill provide a quantified confidence to be used for the validationof other measurement techniques.

[学科分类] 几何与拓扑