Columnar characteristics of aerosols by spectroradiometer measurements in the maritime area of the Cadiz Gulf (Spain)

• Published in: International journal of climatology Vol. 25; no. 13; pp. 1781 - 1804
• Main Authors: Vergaz, Ricardo, Cachorro, Victoria E., De Frutos, Ángel M., Vilaplana, José M., De La Morena, Benito A.
• Format: Journal Article
• Language: English
• Published: Chichester, UK John Wiley & Sons, Ltd 15.11.2005; Wiley
• Subjects: aerosol types; AOD; Earth, ocean, space; Exact sciences and technology; External geophysics; Geophysics. Techniques, methods, instrumentation and models; Marine; marine aerosol characteristics; Meteorology; Particles and aerosols; spectral data; α Ångström coefficient; Iberian Peninsula; Southern Europe; North Atlantic; Gulf of Cadiz; Atlantic Ocean; Spain; ANE, Atlantic, Cadiz Gulf; Turbidity coefficient; Spectroradiometry; Marine atmosphere; aerosols; Europe; marine aerosol characteristics; aerosol types; classification; troposphere; trajectory; Coastal zone; Interannual variation; spectral data; Air mass; AOD; irradiance; a Ångström coefficient; Optical thickness; Direct solar radiation; seasonal variations; Measurement error
• ISSN: 0899-8418; 1097-0088
• DOI: 10.1002/joc.1208

Atmospheric aerosol characteristics represented by the spectral aerosol optical depth AOD) and the α Ångström turbidity parameter were determined in the coastal area of the Gulf of Cádiz, (southwest of Spain). The columnar aerosol properties presented here correspond to the 1996–1999 period, and were obtained by solar direct irradiance measurements carried out by a Licor1800 spectroradiometer. The performance of this type of medium‐spectral resolution radiometric system is analysed over the measured period. The detailed spectral information of these irradiance measurements enabled the use of selected non‐absorption gases spectral windows to determine the columnar spectral AOD that was modelled by Ångström formula to obtain the α coefficient. Temporal evolutions of instantaneous values together with a general statistical analysis represented by seasonal values, frequency distributions and some representative correlations for the AOD and the derived α Ångström coefficient gave us the first insight of aerosol characteristics in this coastal area. Special attention was paid to the analysis of these aerosol properties at the nominal wavelengths of 440 nm, 670 nm, 870 nm and 1020 nm for the near‐future comparisons with the Cimel sun‐photometer data. However, taking the most representative aerosol wavelength of 500 nm, the variability of the AOD ranges from 0.005 to 0.53, with a mean of 0.12 (s.d = 0.07) and that of the α parameter is given by a mean value of 0.93 (s.d. = 0.58) falling inside the range of marine aerosols. A quantitative discrimination of aerosol types was conducted on the basis of the spectral aerosol properties and air mass back trajectory analysis, which resulted in a mixed type because of the specificity of this area, given by very frequent desert dust episodes, continental and polluted local influences. This study represents the first extended data characterization about columnar properties of aerosols in Spain which has been continued by Cimel‐AERONET data. Copyright © 2005 Royal Meteorological Society.