Spectral actinic flux in the lower troposphere: measurement and 1-D simulations for cloudless, broken cloud and overcast situationsReportar como inadecuado




Spectral actinic flux in the lower troposphere: measurement and 1-D simulations for cloudless, broken cloud and overcast situations - Descarga este documento en PDF. Documentación en PDF para descargar gratis. Disponible también para leer online.

1 NILU - Norwegian Institute for Air Research 2 Physics Department 3 ISAC - Istituto di Scienze dell-Atmosfera e del Clima 4 Laboratory of Atmospheric Physics Aristotle University of Thessaloniki 5 Leibniz-Instituts für Troposphärenforschung 6 Institut fur Meteorologie 7 IMK - Institute for Meteorology and Climate Research 8 Institute of Medical Physics 9 Meteorologie Consult GmbH 10 Department of Physics 11 Deutsches Zentrum für Luft- und Raumfahrt

Abstract : In September 2002 an extensive campaign to study the influence of clouds on the spectral actinic flux in the lower troposphere was carried out in East Anglia, England. Measurements of the actinic flux, the irradiance and aerosol and cloud properties were made from four ground stations and by aircraft. For cloudless conditions the measurements of the actinic flux were reproduced by a 1-D radiative transfer model within the measurement and model uncertainties of about ±5%. For overcast days 1-D radiative transfer calculations reproduce the overall behaviour of the actinic flux measured by the aircraft. Furthermore the actinic flux is increased by between 60?100% above the cloud when compared to a cloudless sky with the largest increase for the optically thickest cloud. Similarily the below cloud actinic flux is decreased by about 55?65%. Just below the cloud top the downwelling actinic flux has a maximum which is seen in both the measurements and the model results. For broken clouds the traditional cloud fraction approximation is not able to simultaneously reproduce the measured above cloud enhancement and below cloud reduction in the actinic flux.





Autor: A. Kylling - A. R. Webb - R. Kift - G. P. Gobbi - L. Ammannato - F. Barnaba - A. Bais - S. Kazadzis - M. Wendisch - E. Jäkel - S

Fuente: https://hal.archives-ouvertes.fr/



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