Precipitable Water Vapour Retrieval Modelling Using Indian Regional Navigation Satellite System (IRNSS) Observations over Dehradun

In the present work, a maiden attempt has been made to derive precipitable water vapour (PWV) using IRNSS datasets. A least square differential correction approach is used in modelling to process datasets. PWV is estimated for different days of January, April, July, and November of the year 2019 to observe its variation over different seasons. Meteorological datasets used in the estimation of zenith hydrostatic delay (ZHD) and weighted mean temperature estimation are taken from the National Centers for Environmental Prediction (NCEP) at the location. The obtained PWV values are validated with GPS-derived PWV and Modern-Era Retrospective Analysis for Research and Applications (MERRA) reanalysis datasets. The results show that PWV derived using IRNSS datasets are close to the other reference values. The difference of 3 mm to 7 mm was observed if compared with GPS-derived PWV and MERRA PWV values. Since each satellite signal is available at all times, PWV is estimated using the individual satellite data and combined data from all the IRNSS satellites. As the IRNSS constellation includes both geostationary and geosynchronous satellites, it is observed that PWV estimated using geostationary satellite datasets is close to the reference datasets having a difference of 3 to 5 mm. However, estimated PWV using geosynchronous satellite data have more variation with differences within 3 to 7 mm. Combined data from all the satellites was also used to derive the PWV which has a difference of close to 5 mm in all the cases. The obtained PWV values using IRNSS data show a good correlation with GPS PWV and MERRA PWV values and provide a good estimate of PWV.