Estimates of precipitable water vapour from GPS data over the Indian subcontinent

Water vapour plays a dominant role in the high-energy thermodynamics of the atmosphere, notably, the genesis of storm systems. However, its distribution is difficult to resolve by conventional means, since water vapour exhibits very high spatial and temporal variability. The growing networks of continuously operating GPS systems, however, offer the possibility of estimating the integrated water vapour (IWV) or, equivalently precipitable water vapour (PW). These estimates constitute critical inputs in operational weather forecasting and fundamental research to model atmospheric storm systems, atmospheric chemistry, and the hydrological cycle. This paper presents the results of IWV estimates from GPS data from continuously operating GPS stations established by C-MMACS at Bangalore, Kodaikanal, Hanle and Shillong over the 3-year period (2001-2003). These are the first results of such an endeavor, towards the study of PW at four different geographical locations in the Indian subcontinent.