Special Sensor Microwave/Imager (SSM/I)

Total Precipitable Water

Overview

The SSM/I contains a vertical polarization channel at 22.235 GHz. This channel frequency is at the peak of a weak water vapor absorption line. Over ocean, this allows for the retrieval of integrated water vapor, commonly referred to as total precipitable water (TPW). Retrievals over land are impossible due to the high and varying emissivity of land surfaces. The TPW mainly corresponds to low level water vapor (i.e., 700 mb and below).

The monthly mean TPW is generated over ocean and have been screened for precipitation using the 85 GHz scattering algorithm.

References

Alishouse, J.C., S. Snyder, J. Vongsathorn, and R.R. Ferraro, 1990: Determination of oceanic total precipitable water from the SSM/I. IEEE Trans. Geo. Rem. Sens., 28, 811-816.