Title :
Toward a Better Modeling of Surface Emissivity to Improve AMSU Data Assimilation Over Antarctica
Author :
Guedj, Stephanie ; Karbou, Fatima ; Rabier, Florence ; Bouchard, Aurelie
Author_Institution :
Nat. Centre for Meteorol. Res. (CNRM)/GAME, Meteo-France, Toulouse, France
fDate :
4/1/2010 12:00:00 AM
Abstract :
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.
Keywords :
atmospheric techniques; data assimilation; emissivity; radiative transfer; radiometry; AMSU data assimilation; AMSU sounding frequencies; Advanced Microwave Sounding Unit; Antarctica; Concordiasi international project; Lambertian scheme; brightness temperatures; microwave observations; radiative transfer model; surface assumption; surface emissivity; winter season; Advanced Microwave Sounding Unit (AMSU); Antarctica; Concordiasi; Lambertian; data assimilation; microwave surface emissivity; specular; surface assumption;
Journal_Title :
Geoscience and Remote Sensing, IEEE Transactions on
DOI :
10.1109/TGRS.2009.2036254