Toward a Better Modeling of Surface Emissivity to Improve AMSU Data Assimilation Over Antarctica

• Published in: IEEE transactions on geoscience and remote sensing Vol. 48; no. 4; pp. 1976 - 1985
• Main Authors: Guedj, S., Karbou, F., Rabier, F., Bouchard, A.
• Format: Journal Article
• Language: English
• Published: New York, NY IEEE 01-04-2010; Institute of Electrical and Electronics Engineers; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Advanced Microwave Sounding Unit (AMSU); Antarctica; Applied geophysics; Atmosphere; Atmospheric measurements; Atmospheric modeling; Clouds; Computer simulation; Concordiasi; Data assimilation; Earth sciences; Earth, ocean, space; Emissivity; Exact sciences and technology; Ice; Internal geophysics; Lambertian; Meteorological satellites; microwave surface emissivity; Microwaves; Ocean temperature; Satellite broadcasting; Sea measurements; Sea surface; Seasons; specular; surface assumption; Winter; polar regions; Antarctica; microwaves; Advanced Microwave Sounding Unit (AMSU); models; projects; simulation; radiative transfer; specular; sounding; Lambertian; assimilation; frequency; brightness temperature; Concordiasi; Antarctica; data assimilation; data bases; microwave surface emissivity; surface assumption
• ISSN: 0196-2892; 1558-0644
• DOI: 10.1109/TGRS.2009.2036254

This work is in direct line with the Concordiasi international project. It aims to better constrain atmospheric analyses by improving the assimilation of low-level Advanced Microwave Sounding Unit (AMSU)-A and AMSU-B microwave observations over Antarctica. So far, a very small amount of available AMSU observations is effectively assimilated over Antarctica. To assimilate more observations, different issues have to be dealt with. In this work, the surface emissivity issue over Antarctica is examined. In a first step, a thorough review of the use of a specular assumption to calculate emissivity from AMSU-A measurements has been undertaken. The effect of five different assumptions about the surface on retrieved AMSU emissivities has then been evaluated using a one-year database: specular, Lambertian, and three intermediate assumptions. Simulations of brightness temperatures at AMSU sounding frequencies have been produced using a radiative transfer model. The emissivities obtained using the five assumptions have been found very useful in improving these simulations. The most successful schemes are found to be the Lambertian scheme during the winter season and a specular or an intermediate scheme (50% specular, 50% Lambertian) during Antarctica's short summer.