Total precipitable water (TPW) is an important variable for analyzing weather systems, and especially for forecasting heavy rains. For the past several years CIRA has been producing a blended AMSU/SSM/I TPW product every hour over the global oceans. This product is extremely useful to forecasters but lacks coverage over land.

In order to provide coverage over land, other sources of TPW besides AMSU and SSM/I have been added to the global merge product. A network of roughly 400 GPS surface stations covers the CONUS and adjacent waters, along with Alaska, Hawaii and Puerto Rico. TPW is retrieved from the GPS measurements and has been added to the existing ocean TPW product to provide increased land coverage. In addition, TPW retrievals from the GOES East and West sounder in clear skies have also been added to augment the TPW over land.

The methodology for merging the TPW measurements from this diverse group of sensors will be illustrated. Particular challenges of blending TPW measurements over land in rough topography will be explored. A TPW anomaly product has been developed from this product and depicts very well flows of atmospheric moisture. Future science directions with this product will be discussed, including incorporation of passive microwave retrievals of TPW over land surfaces.