HR: 10:20h
AN: SF52A-01    [Abstracts]
TI: Promise of Climate Benchmarking Using Radio Occultation
AU: * Anderson, J G
EM: anderson@huarp.harvard.edu
AF: Harvard University, Anderson Group, 12 Oxford St., Cambridge, MA 02138 United States
AU: Leroy, S S
EM: leroy@huarp.harvard.edu
AF: Harvard University, Anderson Group, 12 Oxford St., Cambridge, MA 02138 United States
AU: Dykema, J A
EM: dykema@huarp.harvard.edu
AF: Harvard University, Anderson Group, 12 Oxford St., Cambridge, MA 02138 United States
AU: Goody, R M
EM: goody@huarp.harvard.edu
AF: Harvard University, Anderson Group, 12 Oxford St., Cambridge, MA 02138 United States
AB: While a growing body of evidence points towards the anthropogenic increases of greenhouse gases as the cause of twentieth century warming, the world's most sophisticated climate models still show substantial uncertainty in predictions of future warming even when given the same forcing constraints. Successive controlled intercomparisons by efforts such as the IPCC assessment reports and the Coupled Model Intercomparison Project bear this out. The U{.}S{.} Climate Change Science Program has called for a sustained effort to reduce the uncertainties of climate forecasts by climate models, as these climate models are necessary tools in making strategic societal decisions. Efforts to improve models by increasing the sophistication of sub-grid scale parameterizations have not substantially reduced forecast uncertainties. Testing climate models by monitoring the climate using benchmark quality measurements is a promising alternative approach, which additionally places significant new requirements on the U{.}S{.} climate observing effort. GPS radio occultation and radio occultation at 22- and 183-GHz are among the strong candidates for benchmark data types. A climate benchmark measurement is one which is absolutely calibrated, sensitive to ill-constrained feedbacks in the climate system, and is easily accessed and understood for all time. The requirement for absolute accuracy dictates that the measurement be tied to S{.}I{.} standards. In the case of radio occultation, that unit is the second, the most precisely defined of the S{.}I{.} units. Biases induced by undersampling the diurnal cycle are easily overcome with GPS occultation because of the ease with which constellations of GPS LEO receivers can be deployed. Among the least constrained feedbacks in the climate system is the water vapor-longwave radiation feedback. We will show the GPS occultation is sensitive to this feedback in the lower troposphere, albeit weakly so. Radio occultation at 22- and radio occultation at 183-GHz are more sensitive to the water vapor-longwave feedback in the lower and upper troposphere, respectively. Finally, GPS occultation observations can stand alone for all time because successive generations of GPS receiver instrumentation are interpretable in the same way as those of GPS/MET, the first GPS occultation mission flown in 1995-7. We will present a case for the science requirements of GPS, 22-GHz, and 183-GHz radio occultation missions and data processing. We also call for climate observing system simulation experiment (climate OSSE) for radio occultation to demonstrate the viability of radio occultation as a benchmark data type.
DE: 1694 Instruments and techniques
DE: 1610 Atmosphere (0315, 0325)
SC: Special Focus: Advances in Data Acquisition, Management, Analysis and Display [SF]
MN: 2004 AGU Fall Meeting