Principal Investigator (PI): William Rossow, Research Foundation, City University of New York
The proposed work is to enhance the use of observations from the available constellation of satellites for studying the role of clouds in causing weather and climate variations and to extend the data record to the end of NASA's Global Energy and Water Exchanges (GEWEX) project in 2012 as called for in the Global Earth Observing System of Systems (GEOSS) plan.
The International Satellite Cloud Climatology Project (ISCCP) datasets currently provide a description of cloud variations covering the largest range of scales from mesoscale to planetary and from diurnal to interannual (more than 1,300 papers have been published based on the ISCCP datasets). Simply extending the ISCCP record, now the longest, truly global cloud dataset, from 24 to 29 years has a straightforward value for climate studies in expanding the time scales that can be studied to inter-decadal scale.
Another crucial reason to extend the ISCCP record is to overlap the observation period of NASA's CloudSat and Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) missions: this was planned for the last funding period but the launch of these missions was delayed by about two years so that this could not be done. In fact, there will be an unprecedented complement of cloud-observing instruments in orbit during the next few years that cover the electromagnetic spectrum in great detail and provide, for the first time, a global view of the atmosphere's vertical structure: the combination of NASA's "A-train" set of satellites, Terra and Tropical Rainfall Measuring Mission (TRMM) creates rich possibilities for advancing understanding of clouds. This combination of measurements may not be duplicated anytime in the near future.
However, the major limitation of all of these satellite missions is that their time sampling is much too sparse for direct observations of the evolution of cloud systems, precluding straightforward cloud process studies. Hence, the ISCCP datasets, which have much more frequent time sampling (3 hr), provide the essential "glue" for analysis of all these observations by providing the capability to re-arrange the sparsely sampled measurements into an "evolutionary" order for different types of cloud systems. The major limitation of the current ISCCP datasets used for this purpose is their relatively sparse spatial sampling (30 km).
However, work done at the National Oceanic and Atmospheric Administration National Climatic Data Center, with help from the PI's group, is well on the way to refurbishing an alternate collection of the radiance data with 10 km spatial sampling (only a factor of two less dense than the original datasets). Moreover, older radiance data have been found that may allow extension of the ISCCP record back to at least 1981, possibly even to 1979. Thus, the rationale for extending the ISCCP project is to take advantage of the availability of a more densely sampled radiance dataset to produce a much more effective merger of ISCCP products with newer cloud observations, particularly the profiling information from TRMM, Atmospheric Infrared Sounder (AIRS), Microwave Limb Sounder (MLS), CloudSat and CALIPSO. The proposed work includes modifying the ISCCP analysis code for application to the 10 km-sampled radiances with some re-tuning of the algorithm tests, which should produce modest improvements.
Then, the whole record will be completely re-processed using the refined calibrations and analysis methods developed under the current funding. Processing the 10km-sampled radiances has additional consequences:
- NASA's Global Precipitation Climatology Project (GPCP) can use the denser infrared radiance data to interpolate microwave precipitation measurements to obtain higher space-time sampling (possibly 3 hr, 25 km),
- NASA's Global Aerosol Climatology Project (GACP) uses the pixel-level (Level 2) ISCCP product, so the denser sampling would allow resolving smaller time intervals than monthly and
- the GEWEX Surface Radiation Budget project would have much reduced sampling noise in its radiative flux products using the denser ISCCP products.
Distributed by the Atmospheric Science Data Center (ASDC)