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Aerosol Optical Depth and Single Scattering Albedo climatology inferred from OMI and MODIS compared with ground data of AERONET-RIMA - El Arenosillo station

Yasmine Bennouna(1), Victoria E. Cachorro(1), Carlos Toledano(1), Alberto Berjón(2), Benjamín Torres(1), Natalia Prats(1), Rubén Rodrigo(1) and Angel M. de Frutos(1)

(1) Grupo de Óptica Atmosférica - UVA, Dpto. Física Teórica, Atómica y Óptica, 47011 - Valladolid, Spain
(2) Laboratoire LOA, Université des Sciences et Technologies, F-59655 Villeneuve d'Ascq Cédex, France


Natural and anthropogenic aerosols are known to play a significant role in the Earth’s radiation budget, and still the magnitude of their impact remains one of the largest uncertainties in our understanding of the climate system. Since the Iberian Peninsula undergoes the influence of different air masses, it is a key location for the study of particle properties and for addressing various aerosol related issues. In particular, intrusions of Saharan dust are often observed in the southern part of Spain, as demonstrated by the measurements obtained at the site of El Arenosillo [Cachorro et al., 2006; Toledano et al., 2007] and in the Canary Islands [Bergametti et al., 1989; Smirnov et al., 1998, Alastuey at al., 2005]. Although satellite undoubtedly constitute the most appropriated tool to characterize the properties of atmospheric particles over large scales, aerosol products derived from satellite data suffer from a number of recognized uncertainties. As a consequence, the ability of satellite observations to reproduce seasonal trends of aerosol properties on global and regional scales is a challenging task [Mischenko et al., 2007]. There is thus, a crucial need for more comparison analysis of satellite-derived versus ground-based aerosol properties, a fortiori for long term datasets. The Iberian Network for Aerosol Measurements (RIMA), which also acts as part of the AERONET network, ensures the provision of long-term and quality-controlled data at several locations across Spain, Portugal and the Canary Islands. These data have the great advantage to be further supported by means of “on site” calibration procedures [Cachorro et al., 2004]. The present study focuses on the seasonal variability of the Aerosol Optical Depth (AOD) and Single Scattering Albedo (SSA) properties observed at the site of El Arenosillo (Huelva, Spain, 37.1N, 6.7W), for a period lasting over more than four years between July 2004 to December 2008. The collocated AOD and SSA products from the A-Train MODIS/Terra/Aqua (MODerate resolution Imaging Spectroradiometer) [Remer et al., 2005; Levy et al., 2007] and OMI/Aura (Ozone Monitoring Instrument) [Torres et al., 2007] sensors, were used to build a satellite-based climatology of aerosol optical properties for the area in the Gulf of Cadiz, representative of South-West Atlantic of the Iberian Peninsula. This work also analyses the satellite climatology and the observed seasonal variability with that given by the ground-station of “El Arenosillo” belonging to the AERONET-RIMA. Preliminary considerations and possible explanations for the general agreement and differences are also presented.