Validation of line-of-sight water vapor measurements with GPS

The resulting measurements are validated using a WVR which pointed in the direction of the observed satellites. The double-difference technique used to make these water vapor observations does not depend on accurate satellite clock estimates. Therefore it is especially well suited for near-real-time application in weather prediction and allows for sensing atmospheric structure that is below the noise level of current satellite and receiver clock errors.

This paper describes the analysis technique and provides precision estimates for the GPS-measured nonisotropic water vapor as a function of elevation angle for use with data assimilation systems.