Comparison of the Integral Water Vapor Content of the Atmosphere by Data of the Global Forecast System (GFS) and GNSS Observations (Primorski Krai, Russia)

The article analyzes the integral atmospheric water content by data of continuous GPS/GLONASS observations over 2017–2019 at 13 observation points of the GNSS network in the territory of the Primorski Krai. The procedure of IWV evaluation is based on the decomposition of the total zenith tropospheric delay of satellite signal into the hydrostatic and humidity components. The GNSS-estimates of IWV were verified using radiosonde data from two weather stations of the Primorski Department of Hydrometeorological Service. The correlation between the results of GNSS and radiosonde observations was 0.93–0.99. The obtained IWV estimates were compared with Global Forecast System data. The comparison involved 16 nodes of the model grid nearest to each sensor. It was shown that the correlation of GNSS estimates of IWV with GFS data at the moment of forecast is, on the average, >0.90; starting from the forecast advance time of 48 h, the coefficient of correlation decreases to 0.60. The coefficient of correlation with GFS is 0.85–0.97 in the warm season and ≤0.60 in the cold season. The analysis of the spatial distribution of the correlation coefficient showed that the measured IWV values are linearly related with the PWEA model values, which refer to the grid nodes that show lesser elevation difference with the GNSS point. The results of the study suggest the conclusion that the expenses for the acquisition and processing of GNSS data are minimal and the operation of grid points does not depend on weather conditions. This makes the results of GNSS sounding promising for use in regional atmospheric models.