Hualan Rui¹, Bill Teng¹, Long Chiu ², George Serafino³, Patricia Hrubiak¹, John Bonk¹

GSFC Earth Science Enterprise (GES), Data and Information Service Center (DISC) Distributed Active Archive Center (DAAC) NASA/Goddard Space Flight Center, Greenbelt Maryland, USA 20771

(¹Science Systems and Applications, Inc.; ²George Mason University; ³NASA)

The Tropical Rainfall Measuring Mission (TRMM) is a joint mission of the National Aeronautics and Space Administration (NASA) and the National Space Development Agency (NASDA) of Japan to monitor and study tropical and subtropical rainfall systems. TRMM has been acquiring data from shortly after its launch on November 28, 1997 to the present. All TRMM standard products are processed by the TRMM Science Data and Information System (TSDIS) and archived and distributed by the Goddard Distributed Active Archive Center (GDAAC). In addition to the standard products (accessible via http://lake.nascom.nasa.gov/data/dataset/TRMM/index.html), the GDAAC generates and/or maintains a set of derived TRMM products (e.g., satellite coincidence subsets, parameter subsets, resampled gridded subsets, GIS-compatible files) to facilitate use of TRMM data by the general public. TRMM data are reprocessed with improved science algorithms approximately once per year, currently at version 5.

The GDAAC stores archive and distribution information on TRMM standard and derived products in a database. In order to better understand the data usage patterns and requirements of TRMM users, statistics are routinely derived from the database for the entire TRMM data set or for specific groups of data products. For example, the total cumulative archive and distribution data volumes for TRMM satellite standard products (compressed and as of May 2001) are 11.1 TB and 59.8 TB, respectively. The Utilization Rate (UR), defined as the ratio of the distribution to archive volumes, of these satellite products is 5.4 (not including anonymous ftp distribution). Overall, the UR has increased steadily as TRMM progressed, and the trend is continuing. As measured by the UR, the most frequently requested satellite orbital data products are TMI brightness temperature, and PR and TMI rain profiles, with UR in the range of 10 and above. Most of the satellite gridded data products have a UR above 10, with a few above 20. Because some of the gridded products can also be accessed via anonymous ftp, the statistics of which are not included here, their UR is actually even higher. The complete, detailed statistics and their analysis will be presented. These statistics not only help the GDAAC to better serve its TRMM users, but also are useful inputs to the design of future satellite data support systems, such as those of the TRMM follow-on mission, the Global Precipitation Mission (GPM).