A new series of quasi-global, near-real-time, TRMM-based precipitation estimates is now available to the research community via anonymous ftp. The estimates are provided on a global 0.25 ° x0.25 ° grid over the latitude band 50 ° N-S within about seven hours of observation time. Three products are being provided: A TRMM-calibrated merger of all available TMI, AMSR-E, SSM/I, and AMSU-B precipitation estimates (three-hourly accumulations); a geosynchronous infrared estimate which is calibrated by the merged-microwave data (hourly estimates); and a combination of the first two fields (three-hourly accumulations).

These products are being developed in the Laboratory for Atmospheres of the NASA Goddard Space Flight Center by the precipitation research team of Dr. Robert Adler, Dr. George Huffman, David Bolvin, and Eric Nelkin. The real-time infrastructure and computational facility are being provided by the TRMM Science Data and Information System, spearheaded by Erich Stocker. Funding is being provided through the TRMM Project (Dr. Ramesh Kakar, TRMM Program Manager).

These products are the latest in a decade of development work by Dr. Adler's group to combine precipitation estimates from different sources to obtain progressively more-accurate estimates of global precipitation. Previous research yielded monthly and daily data sets, versions of which are distributed as operational products in both the Global Precipitation Climatology Project and TRMM. However, this is the first time that the group has attempted to post their work in nearly real time, opening the data sets to a whole new class of users. In particular, surface hydrology and process researchers, crop forecasters, and atmospheric data assimilation researchers are likely to be early users. This is one of a handful of such data sets in the world.

A post-real-time research version that includes scaling by rain guage information is now available for the period 1998 to the present as TRMM produce 3B42, available from http://lake.nascom.nasa.gov/data/dataset/TRMM/ . This version is recommended over the real-time whenever it is available.

Future development will focus on developing validation statistics, improving the products based on input from early users, testing the throughput of the system, and seeking more-accurate infrared schemes. The team anticipates that the concepts being developed will be helpful in planning for the Global Precipitation Measurement project.

The data are available under ftp://trmmopen.gsfc.nasa.gov/pub/merged . Users are urged to download the README first for additional details.

The technical point of contact is Dr. George Huffman.