Aerosol optical depth of the atmosphere over the ocean in the wavelength range 0.37-4 µm
Abstract:At least two problems, the climatic impact of aerosols and improvement in techniques for space-borne sensing, require investigation of the spatiotemporal variability of the aerosol optical depth (AOD) over the ocean. The marine atmosphere covers an area 2.5 times greater than the continental atmosphere and has essential differences in the composition and manner of aerosol variability, but the quantity of available data is significantly less. Hence, the importance of measurements of the aerosol optical characteristics in marine expeditions is clear. This paper generalizes the results of investigations of the AOD of the atmosphere carried out in the past decade onboard Russian scientific vessels in different regions of the Atlantic Ocean. Statistical characteristics of the AOD are presented for typical regions of the Northern Atlantic: near midlatitude continents, open ocean, tropical and equatorial zones. We show that aerosol turbidity in the atmosphere of the southern hemisphere decreases with latitude, and the minimum values are observed near Antarctica. The results of ship-borne measurements of the AOD of the atmosphere are compared with the data from several island stations of the global Aerosol Robotic Network (AERONET). The spectral behaviour of the AOD in the visible and near-infrared wavelength range (0.37-4 µm) is considered. The Ångström exponent is used for analysis of the wavelength dependence in the shortwave range, and the mean value of the AOD in four 'atmospheric transparency windows' from 1.2 µm to 4 µm is used in the longwave range. Special attention is paid to revealing the dependence of the AOD on relative humidity, wind velocity in the near-water layer and the synoptic factor, the change in air mass.
Document Type: Research Article
Affiliations: 1: Institute of Atmospheric Optics, Siberian Branch, Russian Academy of Sciences, Tomsk, Russia 2: Goddard Earth Sciences and Technology Center, UMBC, Baltimore, MD, USA 3: Goddard Space Flight Center, Greenbelt, MD, USA
Publication date: May 1, 2008