Abstract

Global Navigation Satellite System (GNSS) estimates of precipitable water vapor (PW) provide a continuous and all-weather way to monitor water vapor through the entire atmosphere. These estimates can be assimilated into numerical weather prediction (NWP) models to improve their predictive capabil... Show moreGlobal Navigation Satellite System (GNSS) estimates of precipitable water vapor (PW) provide a continuous and all-weather way to monitor water vapor through the entire atmosphere. These estimates can be assimilated into numerical weather prediction (NWP) models to improve their predictive capability, and can also be used to observe spatial and temporal variations of atmospheric moisture associated with local climate conditions. The majority of GNSS stations that are used for atmospheric applications publish data in half-hourly or hourly batches. This latency and time resolution are entirely suitable for assimilation into NWP models that are designed to make forecasts that extend out for hours, but is not especially useful in monitoring the real-time state of the atmosphere and how it is evolving. Forecasts ranging between zero and three hours are commonly called “nowcasts”. They are usually a synthesis of NWP models and dense observational systems including weather radars, with more weight frequently given to observations than model dynamics. GNSS estimates also have the potential to improve nowcasts where continuous monitoring of the atmospheric state is essential to identify severe weather systems and improve the forecasting of thunderstorms, tornadoes, and Show less