Atmospheric water vapour content determined from zenith delay assuming a local model of troposphere

The local model of troposphere is constructed on the basis of 7300 individual aerological soundings performed and processed over a period of 10 years in Poznań, Poland. The values of the zenith wet delay (ZWD) calculated using this model are shown to coincide very well with the real values obtained directly from individual aerological soundings, the systematic differences between them are not greater than the error of ZWD determination. Much larger differences were obtained assuming the standard model commonly used and the values estimated from the GPS measurements. The differences are particularly large in summer. The local model of troposphere is concluded to be the optimum for determination of water vapour content from ZWD.