Precipitable water vapour estimation using the permanent single GPS station in Zanjan, Iran

Abstract

Meteorological investigations using the global positioning system (GPS) are based on expensive permanent networks and they are not developed globally on the Earth. In this study it is confirmed that single station GPS meteorology is feasible where there is no possibility for development of a sophisticated dense GPS network. Since 1 January 2011 a GPS station has been installed in the Institute for Advanced Studies in Basic Sciences in the province of Zanjan, Iran, where upper air meteorological data are not available. The GPS data were processed in order to estimate the zenith total delay (ZTD) of GPS signals due to the troposphere. The estimated ZTD was then transformed to precipitable water vapour (PWV) using the ERA-Interim globally available humidity and temperature vertical profiles. Three kinds of validation were applied to the estimated PWV and all of them reasonably proved the validity of the GPS results: (1) the measured surface water vapour pressure and dew point temperature show 87.8 and 86.6% correlation respectively with the estimated PWV; (2) the PWV measured using radiosondes in three neighbouring cities of Zanjan (Tabriz, Tehran and Kermanshah) with nearly the same climatic regime show 81.1, 71.7 and 66.4% correlation respectively with the GPS PWV time series, and (3) the global reanalysis datasets for Zanjan show 89.2% correlation with the GPS results. These validations indicate that, in the absence of permanent GPS networks, if proper data processing strategies are adopted the low cost single station GPS meteorology can be considered as a possibility for meteorological monitoring.