12 October 2006 Validation of TOMS UV irradiance with Brewer ground-based measurements at southwestern Spain
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Abstract
Long-term ground-based UV radiometers and satellite UV spectrometers have been utilized for detecting trends in UV radiation and for establishing its climatology. The aim of this work is to compare noon erythemal (CIE) UV irradiance data from NASA Total Ozone Mapping Spectrometer (TOMS) with ground-based measurements from a Brewer spectrophotometer. The Brewer instrument is located at the Atmospheric Sounding Station "El Arenosillo" (ESAt) in Huelva, Southwestern Spain. ESAt, with a high number of cloud-free days per year, is particularly suitable for atmospheric-radiation studies and satellite validation. The period of study covers the years 2000 to 2004. The effect of clouds and aerosols on the satellite vs ground-based bias is evaluated under different atmospheric conditions regarding aerosol load and cloudiness. It is found that under all sky conditions TOMS overestimates the noon CIE irradiance about 8%. This bias is even higher (about 12%) for cloud-free days, showing statistically significant correlation with the aerosol optical depth at 440 nm as measured by a co-located CIMEL-AERONET sunphotometer. However, for thick clouds (high TOMS reflectivity) the bias becomes negative. Regarding aerosols, the bias increases as the aerosol load increases, showing the highest values during dust events. All these facts suggest the need to correct the TOMS UV products mainly under dust conditions.
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Manuel Antón, Manuel Antón, Victoria E. Cachorro, Victoria E. Cachorro, José M. Vilaplana, José M. Vilaplana, Nikolay Krotkov, Nikolay Krotkov, Antonio Serrano, Antonio Serrano, Carlos Toledano, Carlos Toledano, Benito de la Morena, Benito de la Morena, Jay R. Herman, Jay R. Herman, María L. Cancillo, María L. Cancillo, } "Validation of TOMS UV irradiance with Brewer ground-based measurements at southwestern Spain", Proc. SPIE 6362, Remote Sensing of Clouds and the Atmosphere XI, 63622D (12 October 2006); doi: 10.1117/12.689921; https://doi.org/10.1117/12.689921
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