Abstract
Because they scatter and absorb solar and terrestrial radiation, aerosol plumes can easily be detected on satellite images. Thus, the time-dependent spatial extension of the aerosol clouds can be derived from space-borne observations. However, using remote observations for estimating particle concentrations, let alone for apportioning aerosol loads between all the potential sources of particulate matter, is less straightforward. Indeed, this apportionment would require perfect knowledge of the scattering and absorbing potential of particles of different origins as well as the spectral dependence of these potentials. Contrary to what can be done with most atmospheric gases, it is usually impossible to reproduce in the laboratory the complexity of natural atmospheric aerosols. As a consequence, measuring their wavelength-dependent optical properties can only be done during specially designed experiments performed in natural conditions. This is the case of the Cairo Aerosol CHaracterization Experiment (CACHE) that was performed in the Egyptian capital from the end of October 2004 to mid April 2005. During this period a wide variety of aerosol conditions have been sampled, but this work is focused on the spring intensive observation period during which several occurrences of mineral dust transport to Cairo were observed. We detail the modifications of optical properties resulting from these inputs of mineral particles into the background ‘urban aerosol’ and show that scattering and absorption, as well as their spectral dependence are extremely sensitive to the proportions of the “urban pollution/mineral dust” mixtures that form over Cairo during the dust events. Unfortunately, this precludes the use of predefined aerosol models supposed to represent particularly simple aerosol types (e.g., urban pollution, mineral dust,...) for inverting satellite observations over areas where aerosol mixing is known to be the rule rather than the exception (e.g., over the eastern Mediterranean in spring, over or downwind of continental China during the dust season, over west Africa during the biomass burning period, ...). In these cases, sophisticated parameterizations of the optical properties must be used for assessing the impact of aerosol mixtures on radiative transfer.
Access this chapter
Tax calculation will be finalised at checkout
Purchases are for personal use only
Preview
Unable to display preview. Download preview PDF.
References
Alfaro, S.C., L. Gomes, J.L. Rajot, S. Lafon, A. Gaudichet, B. Chatenet, M. Maille, G. Cautenet, F. Lasserre, and X.Y. Zhang, 2003, Chemical and optical characterization of aerosols measured in Spring 2002 at Chinese Ace-Asia Supersite (Zhenbeitai) China, J. Geophys. Res, Vol. 108, No. D23, 8641, doi10.1029/2002JD003214.
Alfaro, S.C., S. Lafon, J.L. Rajot, P. Formenti, A. Gaudichet, and M. Maille, 2004, Influence of Iron oxides on light absorption by pure desert dust: An experimental study, J. Geophys. Res., Vol. 109, D08208, doi10.1029/2003JD004374.
Alfaro1 S.C, E. Terrenoire1, O. Favez2, K.F. Mahmoud3, M. Abdel Wahab4, A. Gaudichet1, J. Sciare2, B. Chatenet1, and M. Maillé1, Optical properties of mineral dust and urban pollution mixtures in Cairo, Egypt, submitted to J. Geophys. Res
Bergstrom, R. W., P. Pilewskie, J. Pommier, M. Rabbette, P. B. Russell, B. Schmid, J. Redemann, A. Higurashi, T. Nakajima, and P. K. Quinn, 2004, Spectral absorption of solar radiation by aerosols during ACE-Asia, J. Geophys. Res., 109, D19S15, doi:10.1029/2003JD004467.
Bond, T.C., T.L. Anderson, and D. Campbell, 1999, Calibration and intercomparison of filter-based measurements of visible light absorption by aerosols, Aerosol Sci. Technol., 38, 1823–1832.
Colarco, P.R., O. Toon, O. Torres, and P. Rasch, 2002, Determining the UV imaginary index of refraction of Saharan dust particles from Total Ozone Mapping Spectrometer data using a three-dimensional model of dust transport, J. Geophys. Res, Vol. 107, No. D16, doi:10.1029/2001JD00903.
Dubovik, O., B. Holben, T. F. Eck, A. Smirnov, Y. J. Kaufman, M. D. King, D. Tanre, and I. Slutsker, 2002, Variability of absorption and optical properties of key aerosol types observed in worldwide locations, J. Atmos. Sci., 59, 590–608.
Lafon, S., 2004, Les oxydes de fer dans l’aérosol désertique en relation avec ses propriétés optiques: caractérisation physico-chimique de poussières minerals générées en soufflerie, Ph.D Thesis, Université de Paris 12 Val de Marne, Créteil, France.
Petzold, A., C. Kopp, and R. Niessner, 1997, The dependence of the specific attenuation cross-section on black carbon mass fraction and particle size, Atmos. Environ., 31,5, 661–672.
Sokolik, I.N., and O.B. Toon, 1999, Incorporation of mineralogical composition into models of the radiative properties of mineral aerosol from UV to IR wavelengths, J. Geophys. Res, Vol. 104, No. D8, 9423–9444.
Tanré D., Y.J. Kaufman, B.N. Holben, B. Chatenet, A. Karnieli, F. Lavenu, L. Blarel, O. Dubovik, L.A. Remer, and A. Smirnov, 2001, Climatology of dust aerosol size distribution and optical properties derived from remotely sensed data in the solar spectrum, J. Geophys. Res, Vol. 106, No. D16, 18,205–18,217.
Author information
Authors and Affiliations
Corresponding author
Editor information
Editors and Affiliations
Rights and permissions
Copyright information
© 2006 Springer
About this paper
Cite this paper
Alfaro, S.C., Wahab, M.A. (2006). Extreme Variability of Aerosol Optical Properties: The Cairo Aerosol Characterization Experiment Case Study. In: Perrin, A., Ben Sari-Zizi, N., Demaison, J. (eds) Remote Sensing of the Atmosphere for Environmental Security. NATO Security through Science Series. Springer, Dordrecht. https://doi.org/10.1007/978-1-4020-5090-9_18
Download citation
DOI: https://doi.org/10.1007/978-1-4020-5090-9_18
Publisher Name: Springer, Dordrecht
Print ISBN: 978-1-4020-5089-3
Online ISBN: 978-1-4020-5090-9
eBook Packages: Earth and Environmental ScienceEarth and Environmental Science (R0)