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Ann. Geophys., 24, 1493-1510, 2006
www.ann-geophys.net/24/1493/2006/
© European Geosciences Union 2006
Study of desert dust events over the southwestern Iberian Peninsula in year 2000: two case studies
V. E. Cachorro1, R. Vergaz1,*, A. M. de Frutos1, J. M. Vilaplana2, D. Henriques3, N. Laulainen4, and C. Toledano1
1Grupo de Optica-Atmosférica, GOA-UVA, Universidad de Valladolid, Spain
2ESAT-El Arenosillo-INTA, Huelva, Spain
3Instituto de Meteorologia de Portugal, Lisboa, Portugal
4PNNL, Pacific Northwest National Laboratory, Richland, WA, USA
*now at: Dpto. Tecnología Electrónica, Universidad Carlos III, Madrid, Spain
Abstract. Strong desert dust events occurring in 2000 over the southwestern Atlantic
coast of the Iberian Peninsula are detected and evaluated by means of the
TOMS Aerosol Index (A.I.) at three different sites, Funchal (Madeira Island,
Portugal), Lisboa (Portugal) and El Arenosillo (Huelva, Spain). At the El
Arenosillo station, measurements from an AERONET Cimel sunphotometer allow a
more precise retrieval of the spectral AOD and the derived alpha
Ångström coefficient. After using different threshold values of
these parameters, we conclude that it is difficult to establish reliable and
robust criteria for an automatic estimation of the number of dust episodes
and the total number of dusty days per year. As a result, additional
information, such as airmass trajectories, were used to improve the
estimation, from which reasonable results were obtained (although some
manual editting was still needed). A detailed characterization of two
selected desert dust episodes, a strong event in winter and another of less
intensity in summer, was carried out using AOD derived from Brewer
spectrometer measurements. Size distribution parameters and radiative
properties, such as arefractive index and the aerosol single scattering
albedo derived from Cimel data, were analyzed in detail for one of these two
case studies. Although specific to this dust episode, the retrieved range of
values of these parameters clearly reflect the characteristics of desert
aerosols. Back-trajectory analysis, synoptic weather maps and satellite
images were also considered together, as supporting data to assess the
aerosol desert characterization in this region of study.
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