92nd American Meteorological Society Annual Meeting (January 22-26, 2012)

Thursday, 26 January 2012
Introduction to CREST Land Emissivity Product
Hall E (New Orleans Convention Center )
Hamidreza Norouzi, New York City College of Technology-CUNY, NOAA/CREST, Brooklyn, NY; and M. Temimi, W. B. Rossow, M. Azarderakhsh, and R. Khanbilvardi

Initializing weather and climate models greatly depends on the quality of land emissivity. For a better retrieval of several atmospheric parameters such as the Total Precipitable Water TPW, an accurate surface emissivity is necessary. More than six years of instantaneous land surface emissivity estimates from the Advanced Microwave Scanning Radiometer - Earth Observing System (AMSR-E) are provided with consideration of the penetration depth effect. The developed product complements existing land emissivity products from SSM/I and AMSU by adding land emissivity estimates at two lower frequencies, 6.9 and 10.65 GHz (C- and X-band, respectively). Observations at these low frequencies penetrate deeper into the soil layer. Ancillary data used in the analysis, such as surface skin temperature and cloud mask, are obtained from International Satellite Cloud Climatology Project (ISCCP). Atmospheric properties are obtained from the TIROS Operational Vertical Sounder (TOVS) observations to determine the small upwelling and downwelling atmospheric emissions as well as the atmospheric transmission. A sensitivity test is conducted to investigate the effect of the atmosphere parameters, skin temperature, and microwave brightness temperature accuracy on emissivity estimates. The difference in depth of originations causes an inconsistency between diurnal variation of infrared and microwave brightness temperatures, which can cause more than 10% difference between day and night determined land emissivity. This discrepancy is resolved by construction of the diurnal cycle of microwave brightness temperature at different channels using the constellation of satellites. A principal component analysis (PCA) is conducted to evaluate spatial variation of diurnal cycle of brightness temperature at global scale. A lookup table of effective physical temperature representative of the contributing layers of the microwave signal at each channel and month is adopted based on the diurnal cycle of brightness temperature. The implementation of the proposed effective temperature diurnal cycle lookup table showed that it can mitigate the differences between day and night retrieved emissivities significantly from AMSR-E observations. The product is available to public through NOAA-CREST website (http://crest.ccny.cuny.edu/).

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