S. M. Sakerin

Information system for network solar photometers

The paper presents an information system designed for processing and systematized storage of network solar photometer data. The system is developed in the Builder C++ environment and integrates individual program modules that perform the following operations: calculation of instrument functions of the photometer spectral channels and band functions of atmospheric gases transmission, calculation of aerosol optical depth parameters and total moisture content of the atmosphere, filtration of the data distorted by cloudiness, and determination, by spectral data of the atmosphere aerosol transparency, of the aerosol microstructure parameters.

Sun photometers for measuring spectral air transparency in stationary and mobile conditions

SP-9 and SPM multiwavelength sun photometers are described and briefly characterized. The SP-9 sun photometer is designed for year-round monitoring of the spectral air transparency in the 0.3–2.2 μm wavelength range in the regional network. To implement the automated measurement mode (unattended by operators), the instrument includes a solar sensor, an automatic sun pointing/tracking system, a built-in GPS detector, a flash drive, and sensors for meteorological parameters. The SPM portable photometer is a simplified version of SP-9 and is designed for the air transparency measurements in mobile conditions.

Characteristics of the annual behavior of the spectral aerosol optical depth of the atmosphere under conditions of Siberia

Based on multiyear observations in Tomsk (since 1995, in the wavelength range 0.37–4 μm) and other regions of the Asian part of Russia (2003–2008), we determined the specific features of the annual behavior of the characteristics of the spectral aerosol optical depth (AOD) of the atmosphere. It is shown that AOD peaks are observed in April (0.19 in the region of 0.5 μm) and July, a local minimum in June (less than 0.16), and minimum values in the fall (0.12). The seasonal variations of the Angström selectivity exponent are characterized by elevated values in the warm period (maximum in July) and low values in winter. The closeness of the seasonal variations of aerosol turbidity in three Siberian regions is noted, and the Siberia mean annual behavior of atmospheric AOD characteristics is suggested. The average values of the aerosol optical and microphysical characteristics of the atmospheric depth for characteristic periods of intraannual AOD variations are presented.

Aerosol optical depth of the atmosphere over the ocean in the wavelength range 0.37-4 µm

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.

Aerosol optical and microphysical properties over the Atlantic Ocean during the 19th cruise of the Research Vessel Akademik Sergey Vavilov

[1] This paper presents aerosol optical depths in the total atmospheric column, aerosol size distributions, number concentrations and black carbon mass concentrations at the deck level measured in October–December 2004 on board the R/V Akademik Sergey Vavilov. Aerosol optical depths measured within the spectral range 0.34–4.0 mm were close to background oceanic conditions (0.04–0.08) in the high-latitude southern Atlantic. Angstrom parameters derived within 440–870 nm and 870–2150 nm spectral ranges did not exceed 0.6, yielding averages of 0.34 and 0.12, respectively. The mass concentration of black carbon varied within the range 0.02–0.08 mg/m 3 in the 34–55S latitudinal belt. The average of 0.04 mg/m 3 (s.d. 0.015) is close to the reported results for the remote areas of the South Indian Ocean. Aerosol volume size distributions measured within the size range of 0.4–10 mm can be characterized by a geometric volume mean radius 3 mm. This is consistent with the columnar retrievals reported by the Aerosol Robotic Network (AERONET).

Simulation of aerosol direct radiative forcing under typical summer conditions of Siberia. Part 1. Method of calculation and choice of input parameters

We present a method for calculating the broadband solar radiation fluxes under clear sky conditions based on the combination of a statistic simulation algorithm and a version of the k-distribution method. An approach to the choice of the input parameters needed for calculating the fluxes and the direct component of the radiative aerosol forcing at the top and the bottom of the atmosphere is described. The approach is based on the combination of the results of multiyear sun photometer measurements of the aerosol optical thickness on the range from 0.37 to 4.0 μm and the atmospheric moisture content in the region of Tomsk with the available models of aerosols, gas components of the atmosphere, and underlying surfaces for determining the deficient parameters, such as the single scattering albedo, the scattering indicatrix of aerosol particles, and the surface albedo.

Results of spectral measurements of atmospheric aerosol optical depth with sun photometers in the 58th Russian Antarctic Expedition

We discuss the specific features of the spatiotemporal variations in the atmospheric aerosol optical depth (AOD) measured during the 58th Russian Antarctic Expedition on board RVs “Akademik Fedorov” and “Akademik Tryoshnikov” and at the Mirny station. It is shown that the main feature of the spatiotemporal AOD distribution over ocean in the Southern Hemisphere is the linear latitudinal decrease of AOD from 0.15 at the equator to 0.025 near Antarctica. We indicate that the low AOD level in Antarctica (0.022 ± 0.005) has persisted for the last 17 years.

On results of studies of atmospheric aerosol optical depth in arctic regions

We discuss the characteristics of the spectral aerosol optical depth (AOD) of the atmosphere measured using sun photometers in high-latitude regions (Spitsbergen, Tiksi, Yakutsk). The seasonal variations are characterized by a decrease in AOD from spring to fall by approximately a factor of 2 in Yakutia and by a factor of 1.5 in the region of Spitsbergen. It is shown that the high selectivity of the spectral AOD dependence in warm period (with Angström parameters varying from 1.3 to 1.8) was caused by low content of coarsely dispersed aerosol. Multiyear data of MODIS satellite observations are used to estimate the spatial distribution of turbidity; it is shown that satellite observations systematically overestimate AOD over Arctic seas.

Fine and coarse components of atmospheric aerosol optical depth in maritime and polar regions

We discuss the results of comparative analysis of the fine and coarse components of atmospheric aerosol optical depth (AOD), obtained from data of SP sun photometer measurements in 14 regions of the Atlantic, Southern, and Arctic Oceans, and Far East seas. Average (over regions) values of the coarse AOD component vary from 0.007 to 0.24, and average values of the fine AOD component vary from 0.015 to 0.25. Despite the fact that the two AOD components are independent in their origin and occur in a variety of combinations, the distributions of their average values exhibit joint growth from lowermost values in the Southern Ocean to maximal values in the zone of severe continental outflows (the Sea of Darkness and the Japan Sea). Taking into account the natural specific features, we grouped the data with respect to a few types of maritime regions; and for each, we determined the most probable values of the coarsely dispersed component and two parameters (analogous to Ångström parameters), which characterize the finely dispersed AOD component.

The influence of synoptic factors on variations of atmospheric aerosol optical depth under Siberian conditions

Based on multiyear measurements of the atmospheric aerosol optical depth (AOD) in a typical region of Siberia (Tomsk), we analyzed the relationship between the AOD and different synoptic factors. The averaged spectral AOD dependencies for two air mass types (continental polar and Arctic air) and different pressure systems are compared. The effect of cloud cover and precipitation on the AOD is estimated. We discuss the results of wavelet analysis of the time series of the AOD and columnar water vapor for a number of observation sites (AERONET stations in Tomsk, Yekaterinburg, Irkutsk, Yakutsk, and Ussuriisk). The specific features of synoptic-scale quasi-periodic variations at different measurement sites are identified and compared.