Long-term changes in precipitable water vapour over India derived from satellite and reanalyses data for the past four decades (1980–2020)

India has tropical monsoon climate with significant regional variability in rainfall and temperature, where precipitation is closely connected to precipitable water vapour (PWV). Here, the satellite and reanalysis data are applied to study the spatial and temporal changes of PWV over India in 1980–2020. We have also analysed its potential drivers such as precipitation, surface temperature and evapotranspiration during the same period. The distribution of annual PWV depicts the highest values over the east coast (40–50 mm) and lowest in western Himalaya (< 10 mm). The seasonal distribution shows highest PWV during monsoon (June-July-August-September, about 40–65 mm). Similarly, the monthly cycle of PWV shows the lowest amount in January, which gradually increases with time until it peaks in July, and then decreases thereafter. Interannual variations in PWV show a peak in 1997–1998, which is related to the strong El-Nino Southern Oscillation (ENSO) event during that period. Among the sources, sinks and drivers, evapotranspiration (0.6-–0.9), precipitation (0.7–0.9) and surface temperature (0.5–0.6) are highly correlated with PWV throughout India. The PWV trends in India are found significantly positive (0.6–0.9), which can be attributed to recent increase in surface temperature and thus the rise in atmospheric moisture.  This is concern for regional climate change as PWV is directly connected to water vapour and thus, to temperature and climate.