CLARREO Climate Product Evaluation using AIRS and IASI Data Sets

Measured, spectrally-resolved radiances will be used to investigate the characteristics of monthly and annual mean, regional spectral products. Although existing observations lack the full spectral coverage of CLARREO and do not provide unbiased temporal or complete spatial coverage, they do provide key spectral properties that we should study as part of our CLARREO development. The goal is to characterize the (1) fundamental information content that can be extracted from such products, and (2) short term climate and weather "noise" properties. These products will be created with a number of different assumptions on field of view size, grid dimensions, and temporal averaging and with a range of ancillary information to aid interpretation (e.g. cloud masks and estimated atmospheric state). The Atmospheric InfraRed Sounder (AIRS) is a high spectral resolution grating spectrometer operating from the NASA EOS Aqua platform. The AIRS record provides a 5+ year record for characterizing multi-year properties of a 13:30 afternoon orbit. The Infrared Atmospheric Sounding Interferometer (IASI) provides sampling of a different time of day (10:30) from the METOP-A satellite platform with nearly 2 years of observations at high spectral resolution and broad spectral coverage. IASI can be used to rigorously emulate AIRS spectral observations in order to evaluate the sampling of the diurnal cycle. Observations from METOP-A will allow us to start accumulating CLARREO- like data records with complete spectral coverage from 3.3 to 15 microns from IASI along with coincident GPS vertical profile observations of pressure, temperature, and humidity from the Global Navigation Satellite System Receiver for Atmospheric Sounding (GRAS). Histograms of selected sounder channel radiances will be presented to illustrate the distributions observed in the true atmosphere in order to support the CLARREO mission requirements definition of field of view size and orbital sampling.