The microwave detectors onboard NOAA and DMSP satellites provide a unique capability to probe both into and through clouds, yielding information about surfaces, precipitation, and cloud composition otherwise hidden from detection when using conventional infrared observations.

Total precipitable water (TPW) is easily retrieved over water surfaces from two microwave channels, each of which is sensitive to water vapor and cloud droplets. Using one channel to correct the other for cloud water absorption, the precipitable water is calculated. The frequencies used for the AMSU instrument, 23.8 and 31.4 GHz, result in a product with a 48-km resolution. Note that the technique doesn't work over land or in the presence of rain or high winds. For these situations, a more sophisticated algorithm is required.

The product shown here is an 8-hour composite from NOAA-15 ascending and descending orbits. The AMSU instrument's field of view allows one NOAA satellite to provide data for updated global composites every 8 to 9 hours. Use the Product Listbox to view a similar product generated from DMSP SSM/I microwave measurements. This product can be combined with datasets from the AMSU to significantly reduce the size of gaps in the coverage at low- and mid-latitudes.