Abstract:Zenith troposphere delay (ZTD) of GNSS ground observation stations is extracted by processing GNSS observation data during the period of severe tropical storm ‘Talas’ and tropical storm ‘Roke’. Precipitable water vapor (PWV) is inverted with ZTD. Based on the rainfall data provided by 49 meteorological stations of Hong Kong observatory, the correlation between PWV and actual rainfall is comparatively analyzed, the effects of the two typhoons on space-time distribution of water vapor in Hong Kong are also studied. The results show that PWV rises in the early stage of typhoon period and falls back after heavy rainfall; especially, PWV in the interval of successive typhoons is still higher than the level before typhoon; water vapor accumulation is the precondition of heavy rainfall, and there is a positive correlation between the cumulative time of the water vapor accumulation and the cumulative rainfall when water vapor accumulations are similar. The area with a PWV value greater than 65 mm is correlated to the typhoon grade, and typhoon path has certain influence on local water vapor distribution.