Atmospheric Measurement Techniques Discussions www.atmos-meas-tech-discuss.net 1867-8610 3 3 2010 10.5194/amtd-3-2367-2010 http://www.atmos-meas-tech-discuss.net/3/2367/2010/ http://www.atmos-meas-tech-discuss.net/3/2367/2010/amtd-3-2367-2010.html http://www.atmos-meas-tech-discuss.net/3/2367/2010/amtd-3-2367-2010.pdf 2367 2387 2010-05-28 Columnar aerosol size distribution function obtained by inversion of spectral optical depth measurements for the Zanjan, Iran A. Masoumi masoumi@iasbs.ac.ir A. Bayat H. R. Khalesifard Institute for Advanced Studies in Basic Sciences (IASBS), P.O. Box 45195-1159, Zanjan, 45195, Iran We are reporting the calculated values of columnar aerosol size distribution function for atmosphere of Zanjan, a city in Northwest Iran (36.70° N, 48.51° E). Ground-based measurements of the total optical depth of the Zanjan atmosphere at 440 nm, 670 nm, 870 nm, and 1020 nm are recorded using a Cimel CE318-2 sunphotometer in the period of October 2006 to September 2008. The spectral aerosol optical depth has been obtained by subtraction of molecular optical depth from the total optical depth for each wavelength channel. Also the Ångström exponent is determined by a logarithmic fit to the aerosol optical depth when it is plotted versus the logarithm of the wavelength. Daily averages of the measured aerosol optical depth and Ångström exponent values have been implemented in an inversion algorithm for calculation of the columnar aerosol size distribution function. In this algorithm, the aerosols are considered as spheres of different size and refractive index of 1.45. We found that for 82% of the days, aerosols are in the coarse mode. For these days, more than 50% of the aerosol volume concentration has a radius &gt;1 &mu;m. We believe this is related to the geographical location of Zanjan in a mostly dry area and subject to frequent dust winds. Angstrom, A.: On the atmospheric transmission of sun radiation and on dust in the air, Geogr. Ann., 11, 156–166, 1929. Bodhaine, B. A., Wood, N. B., Dutton, E. G., and Slusser, J. R.: On Rayleigh optical depth calculations, J. Atmos. Ocean. Tech., 16, 1854–1861, 1999. Draxler, R. R. and Rolph, G. D.: HYSPLIT (HYbrid Single-Particle Lagrangian Integrated Trajectory) Model access via NOAA~ARL READY Website: http://ready.arl.noaa.gov/HYSPLIT.php, last access: 27~May~2010, NOAA Air Resources Laboratory, Silver Spring, MD, 2010. Dubovik, O., Holben, B. N., Eck, T. F., Smirnov, A., Kaufman, Y. J., King, M. D., Tanre, D., and Slutsker, I.: Variability of absorption and optical properties of key aerosol types observed in worldwide locations, J. Atmos. Sci., 59, 590–608, 2002. Haywood, J. M. and Boucher, O.: Estimates of the direct and indirect radiative forcing due to tropospheric aerosols: a review, Rev. Geophys., 38, 513–543, 2000. Holben, B. N., Eck, T. F., Slutsker, I., Tanre, D., Buis, J. P., Setzer, A., Vermote, E., Reagan, J. A., Kaufman, Y. J., Nakajima, T., Lavenu, F., Jankowiak, I., and Smirnov, A.: AERONET-A federated instrument network and data archive for aerosol characterization, Remote Sens. Environ., 66, 1–16, doi:10.1016/S0034-4257(98)00031-5, 1998. Kaskaoutis, D. G., Kambezidis, H. D., Adamopoulos, A. D., and Kassomenos, P. A.: Comparison between experimental data and modelling estimates of aerosol optical depth over Athens, Greece, J. Atmos. Sol.-Terr. Phy., 68, 1167–1178, doi:10.1016/j.jastp.2006.02.011, 2006. Kaskaoutis, D. G., Kambezidis, H. D., Hatzianastassiou, N., Kosmopoulos, P. G., and Badarinath, K. V. S.: Aerosol climatology: dependence of the Angstrom exponent on wavelength over four AERONET sites, Atmos. Chem. Phys. Discuss., 7, 7347–7397, doi:10.5194/acpd-7-7347-2007, 2007. King, M. D., Byrne, D. M., Herman, B. M., and Reagan, J. A.: Aerosol size distributions obtained by inversion of spectral optical depth measurements, J. Atmos. Sci., 35, 2153–2167, doi:10.1175/1520-0469(1978)035$<$2153:ASDOBI$>$2.0.CO;2, 1978. Liou, K. N.: An Introduction to Atmospheric Radiation, in: International Geophysics Series, Second Edition, Vol 84, edited by: Dmowska, R., Holton, J. R., and Rossby, H. T., Academic Press, USA, 2002. Lohmann, U. and Feichter, J.: Global indirect aerosol effects: a review, Atmos. Chem. Phys., 5, 715–737, doi:10.5194/acp-5-715-2005, 2005. Mortazavy, F.: Characterizing the resources and type of aerosols in the Zanjan atmosphere using the data recorded by a sunphotometer, Hysplit4 and Giovanni models, M Sc Thesis, IASBS, Zanjan, Iran, 2009. Prospero, J. M., Ginoux, P., Torres, O., Nicholson, S. E., and Gill, T. E.: Environmental characterization of global sources of atmospheric soil dust identified with the Nimbus~7 total ozone mapping spectrometer (TOMS) absorbing aerosol product, Rev. Geophys., 40(1), 1002, doi:10.1029/2000RG000095, 2002. Rolph, G. D.: Real-time Environmental Applications and Display sYstem (READY) Website: http://ready.arl.noaa.gov, last access: 27~May~2010, NOAA Air Resources Laboratory, Silver Spring, MD, 2010. Romanov, P., O'Neill, N. T., Royer, A., and McArthur, B. L. J.: Simultaneous retrieval of aerosol refractive index and particle size distribution from ground-based measurements of direct and scattered solar radiation, Appl. Optics, 38, 7305–7320, 1999. Wang, Y., Fan, S., Feng, X., Yan, G., and Guan, Y.: Regularized inversion method for retrieval of aerosol particle size distribution function in W~space, Appl. Optics, 45, 7456–7467, 2006. Yamamoto, G. and Tanaka, M.: Determination of aerosol size distribution from spectral attenuation measurements, Appl. Optics, 8, 447–453, 1969.