Comparison of ground-based microwave measurements of precipitable water vapor with radiosounding data

Resumo

Microwave (MW) radiometers are widely used for monitoring the precipitable water vapor (PWV), which is a key greenhouse gas in the Earth’s atmosphere. Different measurement campaigns are carried out to estimate the accuracy of MW measurements of PWV. In this work, we compare the results of PWV measurements performed with a ground-based MW radiometer RPG-HATPRO at the Peterhof station of Saint Petersburg State University with radiosounding data from the Voyeykovo station. More than 850 measurements (at the day and nighttime) in the period from March 13, 2013, to May 31, 2014, are included in the comparison. It is shown that the discrepancy of PWV values measured with both methods is caused by the errors of the methods and by the spatial inhomogeneity of the PWV field. The discrepancy can attain tens of percent, which is to be taken into account in the intercomparison and validation of different methods for PWV retrieval. Exclusion of the cases with strong spatial inhomogeneity allowed reducing the mean deviations between MW and radiosounding measurements to 3–4% and the standard deviations between two sets of measurements to 12–14%.