Effects of Sahel Dust Layers upon Nocturnal Cooling of the Atmosphere (ECLATS Experiment)

Daniel Guedalia Laboratoire d'Aérologie, 31062 Toulouse cedex, France

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Claude Estournel Laboratoire d'Aérologie, 31062 Toulouse cedex, France

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Raoul Vehil Laboratoire d'Aérologie, 31062 Toulouse cedex, France

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Abstract

A study of the effect of a desert aerosol layer on the nocturnal cooling of the atmosphere is presented. The experimental data were obtained during the ECLATS experiment which was run in the Sahel region of the Niger in November 1980. This study uses measurements of thermodynamic and radiative parameters, aerosol size distribution, and a radiative model. The results show that the presence of a dust layer at night increases the downward infrared flux at the surface (and then modifies the energy budget) and increases the radiative cooling rate of the atmosphere, slightly in the layers near the ground (∼0.15 K h−1) and in a more important way at the top of the haze layer.

Abstract

A study of the effect of a desert aerosol layer on the nocturnal cooling of the atmosphere is presented. The experimental data were obtained during the ECLATS experiment which was run in the Sahel region of the Niger in November 1980. This study uses measurements of thermodynamic and radiative parameters, aerosol size distribution, and a radiative model. The results show that the presence of a dust layer at night increases the downward infrared flux at the surface (and then modifies the energy budget) and increases the radiative cooling rate of the atmosphere, slightly in the layers near the ground (∼0.15 K h−1) and in a more important way at the top of the haze layer.

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