Abstract

Atmospheric water vapor is exceedingly variable over both space and time, with the vast majority residing in the planetary boundary layer. Remote sensing of the atmosphere with the Global Positioning System (GPS) offers the ability to resolve fine scale structure of these low-level moisture field... Show moreAtmospheric water vapor is exceedingly variable over both space and time, with the vast majority residing in the planetary boundary layer. Remote sensing of the atmosphere with the Global Positioning System (GPS) offers the ability to resolve fine scale structure of these low-level moisture fields. High frequency sampling provides nearly continuous monitoring. Spatial resolution is controlled by the density of the receiving network, especially when using slant path retrieval techniques. Results from dense networks of GPS stations in the Great Plains of the United States and around Beijing, China indicate that large fluctuations in water vapor amounts can occur over time scales of less than 12 hours. These networks also reveal high spatial variability in water vapor over horizontal distances of less than a few 10's of kilometers. Spatial variability is often times found to be as large as 10-20% of the total integrated amount of water vapor. Convergence fields associated with convective initiation, localized rain, and sharp boundaries in the moisture field are observed. These results indicate that GPS can improve the description of the planetary boundary moisture, and that observations of this type have a direct application in numerical weather prediction over time scales of less than 12 hours. Show less