Assessment of the Benefits of Extending the Tropical Rainfall Measuring Mission: A Perspective from the Research and Operations Communities: Interim Report (2006)

In our capacity as Chairman and Vice-Chairman of the Joint Scientific Committee for the World Climate Research Programme (WCRP), we would like to relay the deep concern of our scientific community regarding the possibility of the premature loss of the TRMM (Tropical Rainfall Measurement Mission) satellite. Because of both its dramatic scientific contributions (which would increase significantly as the data record increases) and its use in operational fore-

casting of hazardous weather, we urge you to maintain TRMM’s operational capability for as long as feasible. This issue has been raised by many of our colleagues worldwide who certainly feel that the continuation of TRMM is critical to the development and success of several key projects in climate research. TRMM’s unique orbit and instrumentation (including the only rain radar in space) make its information impossible to replace with other forms of data currently available. We understand that the satellite and instrumentation are in excellent condition. It would seem, therefore, that the operational cost of maintaining the satellite would be a small fraction of the original investment, and certainly worthwhile. Furthermore, TRMM is a key research element for the development of the Global Earth Observation System of Systems advocated both by the US and Japanese governments, and its early termination would seem to go against the very objectives of this initiative.

The main aim of WCRP is to develop the fundamental scientific understanding of the physical climate system and climate processes, as needed to determine to what extent climate can be predicted and the extent of human influence on climate. As an international coordinating body for climate research, WCRP represents a large community of scientific users of Earth Observation satellite data and has developed a strong working relationship with space agencies in order to foster the use of their products and contribute to the definition of missions relevant to its objectives. TRMM is a critical satellite in the monitoring and study of our planet’s water cycle and climate, and thus central to WCRP’s interests.

WCRP is an associated member of CEOS and is actively involved in the international GEO (Group on Earth Observations) initiative. WCRP’s position on space mission requirements for climate research has been recently updated by an international working group, which expressed its deep concern that the TRMM operation might be terminated prematurely. Indeed, it recommended that, “TRMM operations be continued for as long as possible in order to collect the longest possible and unique precipitation dataset over the tropical regions for climate study (and also in preparation for later GPM / Megha Tropiques missions). The group also felt that the benefit for society, including saving of life and property by improved forecasts of extreme meteorological events that could result from continued operation of TRMM, should be put in balance with the risk to life and property related to an uncontrolled re-entry.”

TRMM observations have contributed significantly to the WCRP Global Water and Energy Cycle Experiment (GEWEX), including the on-going CEOP (Coordinated Enhanced Observing Period) project, which represents a pilot global experiment to observe the various components of the global water cycle. Wewould also like to stress the important contribution of TRMM to other WCRP core projects, especially the Climate Variability and Predictability (CLIVAR) study where TRMM data are being used in studies of the monsoons, hurricane forecasting, precipitation over Africa and sea-surface-temperatures. WCRP is presently proposing a new strategic framework for its activities under the acro-

nym COPES (Coordinated Observation and Prediction of the Earth System) in which satellite-derived precipitation measurements will represent a key element. The role of TRMM data will be essential in this undertaking.

In view of the above, various messages of support for TRMM continuation have already been sent to your agencies by the Director of WCRP, the Chairman of GEWEX, and many others in the WCRP scientific community. However, in view of the importance of the matter and the urgency of the situation for a large scientific community relying on your programmes, we felt compelled to personally send this letter to you at the highest management level. On behalf of WCRP, we would highly appreciate any option NASA and JAXA may consider to maintain the TRMM operation as long as reasonably feasible.

We thank you in advance for any action you can take on this matter.