Sergei M. Sakerin

Maritime Aerosol Network as a component of Aerosol Robotic Network

The paper presents the current status of the Maritime Aerosol Network (MAN), which has been developed as a component of the Aerosol Robotic Network (AERONET). MAN deploys Microtops handheld Sun photometers and utilizes the calibration procedure and data processing (Version 2) traceable to AERONET. A web site dedicated to the MAN activity is described. A brief historical perspective is given to aerosol optical depth (AOD) measurements over the oceans. A short summary of the existing data, collected on board ships of opportunity during the NASA Sensor Intercomparison and Merger for Biological and Interdisciplinary Oceanic Studies (SIMBIOS) Project is presented. Globally averaged oceanic aerosol optical depth (derived from island-based AERONET measurements) at 500 nm is similar to 0.11 and Angstrom parameter (computed within spectral range 440-870 nm) is calculated to be similar to 0.6. First results from the cruises contributing to the Maritime Aerosol Network are shown. MAN ship-based aerosol optical depth compares well to simultaneous island and near-coastal AERONET site AOD.

Investigation of the aerosol optical thickness of the atmosphere in South Atlantic during the 19th cruise of RV Akademik Sergei Vavilov

The results obtained in a new cycle of investigations of the aerosol optical thickness (AOT) are presented.The investigations have been carried out in the 19th cruise of RV Akademik Sergei Vavilov in the Atlantic Ocean since October through December 2004. The atmospheric transmittance was measured with sun photometer in the extended spectral region of 0.3 1 to 4 μm. The most part of the results have been obtained in the southern hemisphere, in particular, in Antarctic Ocean (southward of 34°S). The main attention is paid to the analysis of statistical characteristics of AOT and peculiarities of its spectral dependence in three regions: tropical zone; coastal region (near Cape Town); and Southern Atlantics. It has been found that the atmosphere over ocean in the southern hemisphere has lower AOT values as compared to even more remote regions of the Pacific Ocean. The atmospheric AOTs in the regions southward of 34°S approach the data obtained earlier in Antarctic. Possible causes for the low aerosol content in the atmosphere of the Antarctic Ocean are discussed.

Peculiarities of the diurnal variability of the spectral structure of aerosol extinction of radiation in the wavelength range 0.44 to 1.06 μm on near-ground and slant paths

A combined data array on diurnal variability of the spectral structure of the aerosol extinction coefficient on near-ground path and the aerosol optical thickness in the wavelength range 0.44 to 1.06 μm obtained in warm seasons 1995-2000 nearby Tomsk is considered. Temporal transformation of the spectral dependence of the effective height of the aerosol atmosphere H0(λ) in the period since 6 a.m. till 6 p.m. is analyzed. It is shown that the characteristics maximum centered at λ=0.52-0.56 μm is well pronounced in the spectral structure of the parameter H0(λ) near noon at minimum concentration of fine aerosol. The fact of existence of such a maximum is indirect confirmation of the hypothesis on the determining role of stratospheric intermediately dispersed particles in formation of rarely observed anomalous spectral dependence of the aerosol extinction in shortwave range.

Specific manner of formation of the disperse structure of the aerosol component of the atmosphere in mid-latitudes of Atlantic

The specific manner of formation of the disperse structure of the aerosol component of the atmosphere in the mid-latitudes of Atlantic is analyzed on the basis of the data on the spectral variability of the aerosol optical thickness measured during the 39-th cruise of the research vessel “Akademik Mstislav Keldysh”. The problem is considered of the efficiency of emission of the aerosol component from two continents, Europe and North America. The characteristics peculiarities are studied of the aerosol disperse composition at disturbances of the optical thickness in open ocean. The specific manner is analyzed of the change of the disperse composition of marine aerosol in the atmospheric column at the increase of wind velocity.

Specific manner of formation of the disperse component of the atmosphere in tropical and equatorial zones of Atlantic

The regularities of variations of the aerosol disperse composition in tropical and equatorial zones of Atlantic are analyzed on the basis of the spectral data on the aerosol optical thickness (AOT) of the atmosphere measured during the 35-th cruise of the research vessel “Academician Mstislav Keldysh”. The characteristic peculiarities are studied of the aerosol disperse composition at different distances from the continent, as well as at intrusion of air masses (AM) enriched with aerosols of continental origin to the region of observations. The estimates show that the distribution of coarse aerosol particles (r>1.0 μm) near continent inside an AM enriched with the dust component is essentially inhomogeneous. Quite fast transition from the disturbed values AOT to weakly disturbed (~ 5-8 hours) is evidence of the compact manner of their distribution inside the AM. As moving from the continent, the aerosol particle distribution gains more homogeneous smooth structure. The enhanced level of the content of large particles in the tropical trade wind zone remains in the atmosphere in the episodes when there are no extreme disturbances of AOT. This “background” from emissions from the continent is almost one order of magnitude greater than the background content of large particles in mid-latitudes.

The height of homogeneous aerosol atmosphere in visible and IR wavelength range

The estimates of the “effective” height of the homogeneous aerosol atmosphere in wide wavelength range (0.44 to 3.9 μm) are obtained for the first time on the basis of simultaneous measurements of the spectral transparency of the atmosphere on near-ground long path and in the atmospheric column. This parameter qualitatively characterizes the height of the mixing layer for particles of different size. The spectral aerosol extinction coefficients in the near-ground layer of α(λ) and the optical thickness of the atmosphere τ(λ) were measured. The effective height of the homogeneous atmosphere was defined as H0(λ)=τ(λ)/α(λ).