Introduction
Tropospheric delay in GNSS microwave signals is estimated through GNSS data processing, as introduced in Atmospheric Sensing with GPS (GNSS) .
Research that utilizes GNSS-derived tropospheric parameters—such as precipitable water vapor (PWV), zenith total delay (ZTD), and slant-path delay—for meteorological applications is known as ground-based GNSS meteorology (or GPS meteorology).
In contrast, studies that investigate GPS radio occultation by the atmosphere using GPS antennas and receivers onboard low Earth orbit (LEO) satellites are referred to as space-based GNSS meteorology.
Real-time Estimates of GNSS PWV
The map above shows real-time GPS PWV of GEONET (GPS Earth Observation NETwork) of GSI, Japan. processed with RTNet software. The processing is done in a few seconds just after getting real-time streaming data for all about 1,200 GEONET stations, and conversion from ZTD to PWV is done with latency of 1 to 2 minutes. Such latency is almost similar with general meteorological sensors which also be needed to transfer observation data.
The real-time PWV data is mainly used as input for NWP (called as data assimilation). Also, researches to use real-time PWV (or ZTD) for nowcasting of moisture/precipitation have been performed. The primary contribution of GNSS tropospheric delay is weather forecast.
Related Product (Amazon)
The Book of Clouds by John A. Day (Author)