Comparison between experimental data and modeling estimates of aerosol optical depth over Athens, Greece

Ground-based spectroradiometric measurements taken in the atmosphere of Athens during May 1995 have been used to investigate various atmospheric parameters. From the direct-beam irradiance measurements the spectral aerosol optical depths as well as the Angstrom parameters are derived using the least-squares method applied to measured spectral irradiance data. In this way the errors associated with the turbidity coefficient, β, are found to be 0.0029 on average and with the wavelength exponent, α, 0.031. In this paper, a comparative study between the aerosol optical depth derived by the spectral direct-beam irradiance measurements and those estimated through the Angstrom's formula is made. The correlation coefficient between the measured and computed optical depth is higher than 0.93 in most cases, while their greatest differences take place at the shorter wavelengths. A further analysis of the above differences at 500 and 1000 nm shows very low values, especially at 500 nm, indicating the accuracy of the fitting. The differences at 1000 nm are much higher due to uncertainties in the water-vapor optical depth determination. The errors in Angstrom parameters as well as in the Angstrom's formula fitting to the derived spectral aerosol optical depth depend strongly on atmospheric turbidity, reaching to higher values under low atmospheric turbidity conditions.

[1]  H. Kambezidis,et al.  Case studies of spectral atmospheric transmittance in the ultraviolet and visible regions in Athens, Greece , 2000 .

[2]  V E Cachorro,et al.  Determination of the Angstrom turbidity parameters. , 1987, Applied optics.

[3]  H. Kambezidis,et al.  Total Atmospheric Transmittance in the UV and VIS Spectra in Athens, Greece , 2005 .

[4]  T. Nakajima,et al.  Aerosol Optical Properties in the Iranian Region Obtained by Ground-Based Solar Radiation Measurements in the Summer Of 1991 , 1996 .

[5]  H. Kambezidis,et al.  Determination of Ångström and Schüepp's Parameters from Ground-based Spectral Measurements of Beam Irradiance in the Ultraviolet and Visible Spectrum in Athens, Greece , 2001 .

[6]  H. Kambezidis,et al.  Checking the validity of the Ångström's formula with spectral data of direct-beam irradiance obtained in Athens, Greece , 2006 .

[7]  H. Kambezidis,et al.  Radiative transfer. I. Atmospheric transmission monitoring with modeling and ground-based multispectral measurements. , 1997, Applied optics.

[8]  M. P. Utrillas,et al.  The parameterisation of the atmospheric aerosol optical depth using the Ångström power law , 1998 .

[9]  Athanasios G. Paliatsos,et al.  Statistical evaluation of selected air pollutants in Athens, Greece , 1995 .

[10]  Z. D. Adeyewa,et al.  Wavelength dependence of aerosol optical depth and the fit of the Ångström law , 2003 .

[11]  Victoria E. Cachorro,et al.  A revised study of the validity of the general junge relationship at solar wavelengths: Application to vertical atmospheric aerosol layer studies , 1995 .

[12]  W. Gates,et al.  World Climate Research Program , 2003 .

[13]  Fitting ångström's formula to spectrally resolved aerosol optical thickness , 1989 .

[14]  Jun Wang,et al.  Estimation of diurnal shortwave dust aerosol radiative forcing during PRIDE , 2003 .

[15]  María P. Utrillas,et al.  Column‐integrated aerosol optical properties from ground‐based spectroradiometer measurements at Barrax (Spain) during the Digital Airborne Imaging Spectrometer Experiment (DAISEX) campaigns , 2003 .

[16]  H. Kambezidis,et al.  Case studies of spectral atmospheric transmittance in the ultraviolet and visible regions in Athens, Greece: II. Aerosol transmittance , 2000 .

[17]  Radiative transfer. II. Impact of meteorological variables and surface albedo on atmospheric optical properties retrieved from ground-based multispectral measurements. , 1997, Applied optics.

[18]  T. Eck,et al.  Wavelength dependence of the optical depth of biomass burning, urban, and desert dust aerosols , 1999 .

[19]  F. Volz,et al.  Photometer mit Selen-Photoelement zur spektralen Messung der Sonnenstrahlung und zur Bestimmung der Wellenlängenabhängigkeit der Dunsttrübung , 1959 .

[20]  J. Coakley,et al.  Climate Forcing by Anthropogenic Aerosols , 1992, Science.

[21]  T. Eck,et al.  Atmospheric Aerosol Optical Properties in the Persian Gulf , 2002 .

[22]  C. Junge,et al.  THE SIZE DISTRIBUTION AND AGING OF NATURAL AEROSOLS AS DETERMINED FROM ELECTRICAL AND OPTICAL DATA ON THE ATMOSPHERE , 1955 .

[23]  Anders Ångström,et al.  On the Atmospheric Transmission of Sun Radiation and on Dust in the Air , 1929 .

[24]  Michael D. King,et al.  A Method for Inferring Total Ozone Content from the Spectral Variation of Total Optical Depth Obtained with a Solar Radiometer , 1976 .

[25]  M. Iqbal.  An introduction to solar radiation , 1983 .

[26]  Harry D. Kambezidis,et al.  Spectral Aerosol Transmittance in the Ultraviolet and Visible Spectra in Athens, Greece , 2005 .

[27]  V. Cachorro,et al.  Measurements of the atmospheric turbidity of the North-centre continental area in Spain: spectral aerosol optical depth and Ångström turbidity parameters , 2000 .

[28]  Ezio Caroli,et al.  Study of the Relationship between Ångström's Wavelength Exponent and Junge Particle Size Distribution Exponent , 1983 .

[29]  C. P. Jacovides,et al.  Spectral aerosol optical depth and Angstrom parameters in the polluted Athens atmosphere , 2005 .

[30]  O. B. Vasilyev,et al.  Spectral optical properties of the polluted atmosphere of Mexico City (spring‐summer 1992) , 1995 .

[31]  A. Ångström.  The parameters of atmospheric turbidity , 1964 .

[32]  A. T. Young,et al.  Revised optical air mass tables and approximation formula. , 1989, Applied optics.