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- Author or Editor: Guy Cautenet x
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Abstract
Simulations are carded out to verify a mesoscale model in order to perform sensitivity tests of satellite response to atmospheric dust content. The model chosen is the mesoscale model of Colorado State University with a modified radiation parameterization in order to take atmospheric dust content into account. Downward and upward longwave irradiances are estimated using a 25-interval model. The shortwave pan of the spectrum is processed by a very fast, highly parameterized, single-interval code. Tests using experimental data gathered during the Etude de la Couche Limite Atmosphérique Tropicale Sèche (ECLATS) experiment performed during the 1980 dry season near Niamey (Niger, West Africa) prove that dust content is satisfactorily handled. Three 24-h simulations performed under various meteorological and turbidity conditions show that ground surface energy exchanges are satisfactorily described, so that surface temperature is predicted with a standard deviation of about 1°C. Vertical profiles of computed air temperature and shortwave and longwave irradiances are also realistic.
Abstract
Simulations are carded out to verify a mesoscale model in order to perform sensitivity tests of satellite response to atmospheric dust content. The model chosen is the mesoscale model of Colorado State University with a modified radiation parameterization in order to take atmospheric dust content into account. Downward and upward longwave irradiances are estimated using a 25-interval model. The shortwave pan of the spectrum is processed by a very fast, highly parameterized, single-interval code. Tests using experimental data gathered during the Etude de la Couche Limite Atmosphérique Tropicale Sèche (ECLATS) experiment performed during the 1980 dry season near Niamey (Niger, West Africa) prove that dust content is satisfactorily handled. Three 24-h simulations performed under various meteorological and turbidity conditions show that ground surface energy exchanges are satisfactorily described, so that surface temperature is predicted with a standard deviation of about 1°C. Vertical profiles of computed air temperature and shortwave and longwave irradiances are also realistic.
Abstract
A method for computing the ground surface heat flux density is tested at two places in West Africa during the rainy season and during the dry season. This method is based upon the Fourier analysis of the experimental ground surface temperature. The only required parameter is the soil thermal inertia. The results of these calculations agree with the measurements. This method avoids the use of empirical formulas relating the ground heat flux density to other terms of the surface energy budget. It is shown that these relations are not universal.
Abstract
A method for computing the ground surface heat flux density is tested at two places in West Africa during the rainy season and during the dry season. This method is based upon the Fourier analysis of the experimental ground surface temperature. The only required parameter is the soil thermal inertia. The results of these calculations agree with the measurements. This method avoids the use of empirical formulas relating the ground heat flux density to other terms of the surface energy budget. It is shown that these relations are not universal.
Abstract
The use of the mesoscale model described and qualified in Part I is arranged with radiative transfer codes for the simulation of the thermal infrared response of Meteosat from a Sahelian target. The sensitivity of the satellite response to various atmosphere and surface parameters, either relevant or extraneous to dustiness, is analyzed and physically interpreted throughout the daily cycle, considering especially the thermal impact of the dust at the ground surface. The most significant parameters, according to this criterion of sensitivity, are the amount of dust in the atmosphere and its radiative characteristics, and the ground surface emissivity in the satellite channel. If neglected, the atmospheric water vapor content may be a large source of error for the retrieval of dustiness from the satellite data. The theoretical results are discussed and compared with earlier published experimental work.
Abstract
The use of the mesoscale model described and qualified in Part I is arranged with radiative transfer codes for the simulation of the thermal infrared response of Meteosat from a Sahelian target. The sensitivity of the satellite response to various atmosphere and surface parameters, either relevant or extraneous to dustiness, is analyzed and physically interpreted throughout the daily cycle, considering especially the thermal impact of the dust at the ground surface. The most significant parameters, according to this criterion of sensitivity, are the amount of dust in the atmosphere and its radiative characteristics, and the ground surface emissivity in the satellite channel. If neglected, the atmospheric water vapor content may be a large source of error for the retrieval of dustiness from the satellite data. The theoretical results are discussed and compared with earlier published experimental work.
