Properties Of Atmospheric Aerosols Research Articles

Formation of cloud microstructure during hygroscopic seeding

The evolution of cloud microstructure initiated by hygroscopic seeding is studied on the basis of numerical simulation of cloud formation in the initial stage of condensation. The influence of both physicochemical properties of atmospheric aerosol and atmospheric conditions controlling the cloud type on the microstructure of a developing cloud (without hygroscopic seeding) is analyzed. It is shown that cloud seeding with additional particles whose sizes exceed the characteristic size of atmospheric condensation nuclei leads to a decrease in the concentration of cloud droplets and an increase in their sizes. This result of cloud seeding represents a positive effect for stimulation of precipitation from convective clouds. It is shown that this positive effect is achieved if there are some relationships between the parameters characterizing the hygroscopic particles and the atmospheric conditions. In particular, the maximum effect of action can be achieved at some optimal concentration of seeded particles. The decrease in the concentration of cloud droplets because of hygroscopic seeding is compared to the results of numerical simulations performed by other authors with allowance for coagulation processes in clouds. It is shown that this decrease can serve as an estimate for the effectiveness of hygroscopic seeding as a means for artificial intensification of precipitation from convective clouds.

Cloud formation of particles containing humic‐like substances

Humic like substances (HULIS) are a class of compounds that are suspected to have an effect on cloud droplet activation properties of atmospheric aerosols because they decrease the surface tension of aqueous solutions quite efficiently. Surface active organic compounds have a tendency of concentrating on the surfaces of liquid droplets. If the total amount of surface active compound is small enough, partitioning of the substance on the surface depletes it from the droplet interior, decreasing the Raoult effect and increasing the Kelvin effect. Thus, the surface partitioning causes an increase of the critical supersaturation (Köhler curve maximum), and the effect gets stronger with decreasing size of the cloud condensation nucleus. In this study, the effects of HULIS on the activation of cloud droplets was studied by cloud parcel model calculations. Model results indicate that if the surface partitioning is not taken into account, the number of activated droplets can be highly overestimated. The simulations were made using particles containing 10–80% mass fraction of HULIS, while the remaining fraction of the particle was ammonium sulfate. The calculations indicated that the surface tension effects of humic‐like compounds on the cloud activation become significant only when the weight fraction of the organics is very high. In contrast, if the surface partitioning is not taken into account, already a small weight fraction of organics will lead to significant increase in number of cloud droplets.

Measurements of optical properties of atmospheric aerosols in Northern Finland

Abstract. Three years of continuous measurements of aerosol optical properties and simultaneous aerosol number size distribution measurements at Pallas GAW station, a remote subarctic site in the northern border of the boreal forest zone, have been analysed. The scattering coefficient at 550 nm varied from 0.2 to 94.4 Mm−1 with an average of 7.1±8.6 Mm−1. Both the scattering and backscattering coefficients had a clear seasonal cycle with an autumn minimum and a 4–5 times higher summer maximum. The scattering was dominated by submicron aerosols and especially so during late summer and autumn. The Ångström exponent had a clear seasonal pattern with maximum values in late summer and minimum values during wintertime. The highest hemispheric backscattering fraction values were observed in autumn. To analyse the influence of air mass origin on the aerosol optical properties a trajectory climatology was applied to the Pallas aerosol data. The most polluted trajectory patterns represented air masses from the Kola Peninsula, Scandinavia and Russia as well as long-range transport from Britain and Eastern Europe. These air masses had the largest average scattering and backscattering coefficients for all seasons. Higher than average values of the Ångström exponent were also observed in connection with transport from these areas.

Preliminary results of a non-spherical aerosol method for the retrieval of the atmospheric aerosol optical properties

There is experimental evidence that the non-sphericity of certain atmospheric particles can cause scattering properties different from those predicted by standard Mie theory. Numerous studies indicate the need to consider the presence of non-spherical particles in modeling the optical properties of atmospheric aerosols. On the other hand, natural aerosols show a great variety of shapes, making difficult a realistic choice of a particle shape (or shape mixture) model. In this paper, we test a parameterization of the particle shape in the retrieval of size distribution, phase function, single scattering albedo and asymmetry parameter from direct and sky-radiance measurements. For this purpose we have substituted the Kernel based on the Mie theory included in the model SKYRAD.PACK by one derived for non-spherical particles. The method is applied under different atmospheric conditions, including Saharan dust outbreak, polluted and local mineral episodes. We compare the results with those obtained by the well known spheroids algorithm used in the AERONET network.

Information content of multiwavelength lidar data with respect to microphysical particle properties derived from eigenvalue analysis

The multiwavelength Raman lidar technique in combination with sophisticated inversion algorithms has been recognized as a new tool for deriving information about the microphysical properties of atmospheric aerosols. The input optical parameter sets, provided by respective aerosol Raman lidars, are at the theoretical lower limit at which these inversion algorithms work properly. For that reason there is ongoing intense discussion of the accuracy of these inversion methods and the possibility of simultaneous retrieval of the particle size distribution and the complex refractive index. We present results of the eigenvalue analysis, used to study the information content of multiwavelength lidar data with respect to microphysical particle properties. Such an analysis provides, on a rather mathematical basis, more insight into the limitations of these inversion algorithms regarding the accuracy of the retrieved parameters. We show that the effective radius may be retrieved to 50% accuracy and the real and imaginary part of the complex refractive index to +/- 0.05 and +/- 0.005i, if the imaginary part is < 0.02i. These results are in accordance with the classic approach of simulation studies with synthetic particle size distributions. Major difficulties are found with a particle effective radius of < 0.15 microm. In that case the complex refractive index may not be derived with sufficient accuracy. The eigenvalue analysis also shows that the accuracy of the derived parameters degrades if the imaginary part is > 0.02i. Furthermore it shows the importance of the simultaneous use of backscatter and extinction coefficients for the retrieval of microphysical parameters.

Aerosol mass closure and reconstruction of the light scattering coefficient over the Eastern Mediterranean Sea during the MINOS campaign

Abstract. As part of the Mediterranean Intensive Oxidant Study (MINOS) performed during August 2001 in the Eastern Mediterranean Region, intensive measurements of chemical and radiative properties of atmospheric aerosols were performed at two remote sites on Crete Island, located in the marine boundary layer (MBL), and in the lower free troposphere (FT), respectively. Gravimetric particulate mass, as well as chemically-derived masses of water soluble ions, organic and elemental carbon, and tracer elements for dust aerosols were measured for fine (&lt;1.2 µm) and coarse (&gt;1.2 µm) particles at the two sampling sites. Although strongly bound water, mainly associated with inorganic species, could have slightly altered our results (10% of the reconstructed mass), chemical mass closure was achieved most of the time for the fine and coarse size fractions and at both sites. Our conversion factor of 2.1 for organic carbon (OC) to particulate organic matter (POM) is at the upper end of those reported in the literature, but fits with the aged smoke particles collected during the campaign. The results indicate that this conversion factor changed during the campaign along with the BC/TC ratio. The particulate mass (PM) concentration for fine aerosols at the MBL and FT sites averaged 17.4±4.7 µg/m3 and 11.2±3.2 µg/m3, respectively, and is among the highest reported in the literature for remote sites; more than 90% of this PM was composed equally of ammonium sulfate and carbonaceous aerosols. Comparison between the MBL and FT sites showed a slight vertical gradient for PM that was not observed for dust aerosols, which averaged 10.5±4.8 and 11.7±5.0 µg/m3 for the MBL and FT sites, respectively. The results were used to reconstruct the ambient light scattering coefficient (σsp) that was measured at ambient Relative Humidity (RH) for fine particles at the MBL site. Reconstruction of σsp was achieved using ratios of wet to dry scattering, f(RH), that depend on RH for ammonium sulfate, but are kept equal to 1 for POM. This results in a low water adsorption for our organic-rich carbonaceous aerosols, although these aged biomass smoke aerosols are supposed to be highly oxidized. Mass scattering efficiencies of the main aerosol components were obtained by multivariate regression analysis, and were 2.66 and 4.19 m2/g (at the 95% confidence level) for dry ammonium sulfate and POM, respectively. The calculations indicate that one third of the reconstructed σsp was due to water uptake by ammonium sulfate aerosols, demonstrating their major role in the radiative aerosol properties in the eastern Mediterranean.

Impact of palmitic acid coating on the water uptake and loss of ammonium sulfate particles

Abstract. While water insoluble organics are prevalent in the atmosphere, it is not clear how the presence of such species alters the chemical and physical properties of atmospheric aerosols. Here we use a combination of FTIR spectroscopy, Transmission Electron Microscopy (TEM) and Aerosol Mass Spectrometry (AMS) to characterize ammonium sulfate particles coated with palmitic acid. Coated aerosols were generated by atomizing pure ammonium sulfate, mixing the particles with a heated flow of nitrogen with palmitic acid vapor, and then flowing the mixture through an in-line oven to create internally mixed particles. The mixing state of the particles was probed using the AMS data and images from the TEM. Both of these probes suggest that the particles were internally mixed. Water uptake by the mixed particles was then probed at 273 K. It was found that for ammonium sulfate containing ~20 wt% palmitic acid the deliquescence relative humidity (DRH) was the same as for pure ammonium sulfate (80±3% RH). For particles with ~50 wt% palmitic acid however, the mixed particles began to take up water at relative humidities as low at 69% and continued to slowly take up water to 85% RH without fully deliquescing. In addition to studies of water uptake, water loss was also investigated. Here coatings of up to 50 wt% had no impact on the efflorescence relative humidity. These studies suggest that even if insoluble substances coat salt particles in the atmosphere, there may be relatively little effect on the resulting water uptake and loss.

Organic aggregate formation in aerosols and its impact on the physicochemical properties of atmospheric particles

Abstract Fatty acid salts and “humic” materials, found in abundance in atmospheric particles, are both anionic surfactants. Such materials are known to form organic aggregates or colloids in solution at very low aqueous concentrations. In a marine aerosol, micelle aggregates can form at a low fatty acid salt molality of ∼10 −3 m. In other types of atmospheric particles, such as biomass burning, biogenic, soil dust, and urban aerosols, “humic-like” materials exist in sufficient quantities to form micelle-like aggregates in solution. I show micelle formation limits the ability of surface-active organics in aerosols to reduce the surface tension of an atmospheric particle beyond about 10 dyne cm −1 . A general phase diagram is presented for anionic surfactants to explain how surface-active organics can change the water uptake properties of atmospheric aerosols. Briefly such molecules can enhance and reduce water uptake by atmospheric aerosols at dry and humid conditions, respectively. This finding is consistent with a number of unexplained field and laboratory observations. Dry electron microscope images of atmospheric particles often indicate that organics may coat the surface of particles in the atmosphere. The surfactant phase diagram is used to trace the particle path back to ambient conditions in order to determine whether such coatings can exist on wet ambient aerosols. Finally, I qualitatively highlight how organic aggregate formation in aerosols may change the optical properties and chemical reactivity of atmospheric particles.

First aerosol optical thickness measurements at Dome C (East Antarctica), summer season 2003–2004

In the framework of a calibration project concerning satellite sensors over a remote site of inland Antarctica, the temporal variations of atmospheric aerosol properties have been investigated in relation to their strong influence on the transfer of visible radiation. For this, a sunphotometer was installed at Concordia station (75°S, 123°E, 3200 m a.s.l.) on the Antarctic plateau during summer season 2003–2004. Meteorological parameters were recorded for the same period. Very low aerosol optical thickness values were observed with a mean AOT of 0.02 at 440 nm and 0.007 at 870 nm for clear sky conditions, and a small standard deviation. Angstrom coefficients were high with an average of 1.65 at 440 nm. These values reflect the high purity of the atmosphere and the small size of particles, mainly sulfate aerosols. Higher AOT values are observed under diamond dust conditions (0.025 at 440 nm and 0.013 at 870 nm). Temporal variations are also observed at the daily and seasonal levels. Dome C, therefore, appears to be an excellent site for satellite sensor calibration as well as investigations concerning the background atmospheric composition and global atmosphere changes caused by human activities.

Measurement of Wavelength-Resolved Light Absorption by Aerosols Utilizing a UV-VIS Extinction Cell

The principle, technical details, and performance of the long path extinction spectrometer (LOPES), a new folded-path extinction cell with a spectral range from the mid-UV (200 nm) to the near infrared (1015 nm), is presented. Using nonabsorbing glass beads the measured extinction spectrum of LOPES was validated by Mie calculations and was compared with scattering coefficients in the visible measured by a three-color integrating nephelometer (TSI, mod. 3563). For absorbing aerosols (here soot and biomass burning aerosol with single-scattering albedos of about 0.2 and 0.74 at 550 nm), LOPES was combined with a TSI 3563 nephelometer to determine the wavelength-dependent absorption coefficients from the difference of the extinction and scattering coefficients. These absorption coefficients were found to agree with the measurements by two state-of-the-art absorption techniques, the multiangle absorption photometry (MAAP) and photoacoustic spectrometry (PAS), which measure the absorption coefficient at the single wavelength of 532 nm and 670 nm, respectively. Finally, based on a comprehensive analysis of the TSI 3563 nephelometer errors and their propagation into the determination of the absorption coefficients from the LOPES and nephelometer data, we discuss implications for improving in situ measurements of the optical properties of atmospheric aerosols.

Investigation of Efflorescence of Inorganic Aerosols Using Fluorescence Spectroscopy

The phase transition is one of the most fundamental phenomena affecting the physical and chemical properties of atmospheric aerosols. Efflorescence, in particular, is not well understood, partly because the molecular interactions between the solute and water molecules of saturated or supersaturated solution droplets have not been well characterized. Recently, we developed a technique that combines the use of an electrodynamic balance and a fluorescence dye, 8-hydroxyl-1,3,6-pyrenetrisulfonate (pyranine), to study the distributions of solvated and free water in aqueous droplets (Choi, M. Y.; Chan, C. K.; Zhang, Y. H. J. Phys. Chem. A 2004, 108, 1133). We found that the equality of the amounts of solvated and free water is a necessary but not sufficient condition for efflorescence. For efflorescing compounds such as Na2SO4, (NH4)2SO4, and a mixture of NaCl and Na2SO4, the amount of free water decreases, while that of solvated water is roughly constant in bulk measurements and decreases less dramatically than that of free water in single-particle measurements as the relative humidity (RH) decreases. Efflorescence of the supersaturated droplets of these solutions occurs when the amounts of free and solvated water are equal, which is consistent with our previous observation for NaCl. For nonefflorescing compounds in single-particle levitation experiments such as MgSO4 and Mg(NO3)2, the amounts of free and solvated water are equal at a water-to-solute molar ratio of about 6, at which spectral changes due to the formation of contact ion pairs between magnesium and the anions occur as shown by Raman spectroscopy. Fluorescence imaging shows that the droplets of diluted Mg(NO3)2 (at 80% RH) and MgSO4 are homogeneous but those of NaCl, Na2SO4, (NH4)2SO4, and supersaturated Mg(NO3)2 (at 10% RH) are heterogeneous in terms of the solvated-to-free water distribution. The solvated-to-free water ratios in NaCl, Na2SO4, and (NH4)2SO4 droplets are higher in the outer regions by about half a radius deep than at the center of the droplets.

Scattering properties of atmospheric aerosols over Lanzhou City and applications using an integrating nephelometer

The data, measured by a three-wavelength Integrating Nephelometer over Lanzhou City during the winters of 2001/2002 and 2002/2003 respectively, have been analyzed for investigating the scattering properties of atmospheric aerosols and exploring their relationship and the status of air pollution. The aerosol particle volume distribution is inverted with the measured spectral scattering coefficients. The results show that the daily variation of the aerosol scattering coefficients is in a tri-peak shape. The average ratio of backscattering coefficient to total scattering coefficient at 550 nm is 0.158; there exists an excellent correlation between the scattering coefficients and the concentration of PM10. The average ratio of the concentration of PM10 to the scattering coefficients is 0.37 g m−2, which is contingent on the optical parameters of aerosol particles such as the size distribution, etc.; an algorithm is developed for inverting the volume distribution of aerosol particles by using the histogram and Monte-Carlo techniques, and the test results show that the inversion is reasonable.

MAX‐DOAS O4 measurements: A new technique to derive information on atmospheric aerosols—Principles and information content

Multi AXis Differential Optical Absorption Spectroscopy (MAX‐DOAS) observations of the oxygen dimer O4 which can serve as a new method for the determination of atmospheric aerosol properties are presented. Like established methods, e.g., Sun radiometer and LIDAR measurements, MAX‐DOAS O4 observations determine optical properties of aerosol under atmospheric conditions (not dried). However, the novel technique has two major advantages: It utilizes differential O4 absorption structures and thus does not require absolute radiometric calibration. In addition, O4 observations using this method provide a new kind of information: since the atmospheric O4 profile depends strongly on altitude, they can yield information on the atmospheric light path distribution and in particular on the atmospheric aerosol profile. From O4 observations during clear days and from atmospheric radiative transfer modeling, we conclude that our new method is especially sensitive to the aerosol extinction close to the ground. In addition, O4 observations using this method yield information on the penetration depth of the incident direct solar radiation. O4 observations at different azimuth angles can also provide information on the aerosol scattering phase function. We found that MAX‐DOAS O4 observations are a very sensitive method: even aerosol extinction below 0.001 could be detected. In addition to the O4 absorptions we also investigated the magnitude of the Ring effect and the (relative) intensity. Both quantities yield valuable further information on atmospheric aerosols. From the simultaneous analysis of the observed O4 absorption and the measured intensity, in particular, information on the absorbing properties of the aerosols might be derived. The aerosol information derived from MAX‐DOAS observations can be used for the quantitative analysis of various trace gases also analyzed from the measured spectra.

Hygroscopic properties of levoglucosan and related organic compounds characteristic to biomass burning aerosol particles

Biomass burning, which is characterized by pyrolysis as well as vaporization and condensation of biomass constituents, is a significant source of atmospheric organic aerosols. In this study, hygroscopic properties of five organic compounds (levoglucosan, D‐glucose, and vanillic, syringic, and 4‐hydroxybenozoic acids), which are major pyrolysis products of wood, were measured using a tandem differential mobility analyzer. Levoglucosan, which is typically the most abundant species in wood burning aerosols, showed a significant hygroscopic growth for particles with a diameter of 100 nm. No efflorescence was observed under the measured relative humidity, and a supersaturated condition of levoglucosan‐water particles was observed. The growth factors of levoglucosan are 1.08, 1.18, 1.23, and 1.38 at relative humidity (RH) of 60, 80, 85, and 90%, respectively. The measured hygroscopic curves are in general consistent with those estimated from ideal solution theory and Uniquac Functional‐Group Activity Coefficient (UNIFAC) and Conductor‐Like Screening Model for Real Solvent (COSMO‐RS) methods. Significant hygroscopic growth was also observed for D‐glucose, whose growth factor is quite similar to that of levoglucosan. However, three model pyrolysis products of lignin (i.e., vanillic‐, syringic‐, and 4‐hydroxybenzoic acids) did not show any hygroscopic growth under the RH conditions up to 95%. On the basis of the organic composition of wood burning aerosols, the water absorption attributed to levoglucosan in wood burning aerosols is calculated to be up to 30% of the organic mass at 90% RH. This study demonstrates that oxygenated organics emitted from biomass burning could significantly enhance the hygroscopic properties of atmospheric aerosols.

Influence of asian dusts on the physicochemical properties of atmospheric aerosols in taiwan district — using the penghu islands as an example

Using the Penghu Islands as an example, this study investigates the influence of Asian dusts on the physicochemical properties of atmospheric aerosols in Taiwan District in the year of 2002. An aerosol-sampling site was established at Xiaumen, the Penghu Islands, to collect sea level atmospheric aerosols for further analysis of their physicochemical properties. This study revealed that, during the sampling campaign, three Asian dust storms were transported from North China and Mongolia to the Penghu Islands. The mass concentrations of atmospheric aerosols, particularly PM 2.5∼10, were generally 2∼3 times higher than the regular level. An increase of coarse particle mode in the size distribution of atmospheric aerosols further validated the invasion of Asian dusts. Moreover, the comparison of water-soluble ionic species, carbonaceous content, and metallic content of atmospheric aerosols indicated that Asian dusts could significantly influence the chemical properties of atmospheric aerosols in Taiwan District. A significant increase of Cl −, Br −, Na +, K +, SO 4 2−, Mg 2+ and Ca 2+ concentration on coarse particle mode was observed. It suggested that not just natural soil dusts and oceanic spray, but also anthropogenic pollutants could accompany Asian dusts. Source apportionment of atmospheric aerosols indicated that the concentration (percentage) of aerosol particles contributed from soil dusts increased significantly from 20.98 μg·m −3 (29.2%) to 60.37 μg·m −3 (47.7%), and then decreased to the regular level of 22.44 μg·m −3 (28.2%).

Aerosol optical and radiative properties observed at Anmyeon and Jeju, Korea in the spring of 2000 and 2001.

The radiative properties of atmospheric aerosols are determined by their masses, chemical characteristics, and optical properties, such as aerosol optical depth (AOD), Angström parameter (alpha) and single scattering albedo (SSA). In particular, the aerosol optical properties determine the surface temperature perturbation that may give some information in understanding regional atmospheric radiative forcing. To understand the radiative forcing and regional source of an aerosol, the present study focused on the analysis of the aerosol optical properties based on two different observations in the spring season, during the special Asian dust storm period. The Korean Global Atmosphere Watch Observatory (KGAWO), at Anmyeon Island, and the ACE-Asia super-site, at Gosan, Jeju Island, have measured radiations and aerosols since 2000. The sites are located in the mid-west and south of the Korean peninsula, which are strongly affected by the Asian dust coming from China every spring. The aerosol optical properties, measured by ground-based sun and sky radiometers, over both sites were analyzed to gain an understanding of the radiation and climate properties. The probability distributions of the aerosol optical depths were rather narrow, with a modal value of approximately 0.38 at both sites during 2001 and 2002. The Angström parameter frequency distributions showed two peaks at Anmyeon GAW, but only one peak at the Jeju ACE-Asia super site. One peak, around 0.63, characterizes the situation of a day having Asian dust, the second peak, around 1.13, corresponded to the relatively dust-free cases. The correlation between the aerosol optical depth and the Angström exponents resulted in a wide range of the Angström parameter, alpha, over a wide range of optical depths at Anmyeon, whereas a narrow range of alpha, with moderate to low values for the AOD at Jeju. Under dust free conditions the single scattering albedo (SSA) decreased with wavelength, while in the presence of Asian dust, the SSA either stayed neutral, or increased slightly with wavelength at Anmyeon, and showed higher value than Jeju. The change in the surface temperature was highly correlated with increases in the aerosol optical depth at Anmyeon to a greater extent than at Jeju.

Application of Fluorescence Spectroscopy To Study the State of Water in Aerosols

The knowledge of the state of water molecules, particularly the amounts of solvated water and free water in aqueous droplets, is valuable in understanding the hydration properties of atmospheric aerosols. A novel technique combining the use of an electrodynamic balance and a fluorescence dye, 8-hydroxyl-1,3,6-pyrenetrisulfonate (pyranine), was used to study the state of the water molecules in single levitated aqueous droplets from subsaturation to supersaturation concentrations. The steady-state fluorescence spectra of sucrose, glucose, and NaCl solutions doped with 100 ppm pyranine were measured. The fluorescence emission of pyranine is sensitive to the proton-transfer capacity of its microenvironment. When excited by radiation at around 345 nm, pyranine fluoresces and the spectrum consists of two peaks, one at about 440 nm and the other at about 510 nm, which correspond to the presence of solvated and free water, respectively. The fluorescence peak intensity ratios of the 440-nm peak to the 510-nm peak ...

Atmospheric Aerosols over the Western Pacific Ocean during the R/V Mirai Cruises in 2002

The optical and chemical properties of atmospheric aerosols were measured over the Pacific Ocean during two R/V Mirai cruises. One was the MR02-K02 cruise (winter cruise), crossing the western Pacific from Japan to 5°S between February 21 and March 31, 2002. The second was the MR02-K04 cruise (summer cruise), that covered the western Pacific Ocean, the Indian Ocean, and the seas around Indonesia from Japan to 10°S between June 25 and August 22, 2002. The surveys mainly encountered three kinds of air masses, maritime air masses (marine aerosol), air masses influenced by fossil fuel combustion (FF aerosol), and those influenced by biomass burning (BB aerosol). From 10°N to 20°N, marine aerosols were observed both in the summer and winter cruises with the value of the single scattering albedo (ω) above 0.98 in the summer and, 0.92 in the winter. The concentrations of anthropogenic components such as elemental carbon, vanadium, and arsenic were somewhat low. Sea salt particles play a dominant role in the variation of the scattering coefficients, and the optical thickness in this region. Between 30°N and 40°N, FF aerosols were observed on both cruises. With the absorptive aerosols, the mean ω in the winter cruise was 0.74, while with the transparent aerosols in the summer cruise, the mean ω was 0.92. This seasonal difference comes mainly from differences in the concentrations of elemental carbon. There were BB aerosols around Indonesia in the summer, with a mean ω of 0.72. This air mass contained the most absorptive aerosol measured on these cruises. The chemical compositions of BB particles were different from the other aerosols, with carbonous components and non-sea salt potassium in high concentrations and metal components, such as vanadium and arsenic, in low concentrations.

Manifestation of Specific Features of the Optical Properties of Atmospheric Aerosol over the Black Sea in the Interpretation of SeaWiFS Data

We consider the problem of quantitative evaluation of the optical characteristics of seawater according to the data of satellite measurements. The principal physical mechanisms responsible for the errors in the atmospheric correction made with the help of the standard NASA algorithm are established. It is shown that the models of atmospheric aerosol realized with the help of this algorithm are inconsistent with its actual properties over the Black Sea.

Interrelation of aerosols, water vapor and clouds on a global scale

Each retrieval algorithm for atmospheric aerosols, clouds and water vapor from ADEOS/POLDER data is described. A POLDER sensor, mounted on the Earth observation satellite ADEOS in 1996, is a unique sensor which can gather multi-directional (up to 14) polarization measurements of one target. Atmospheric aerosol properties as optical thickness and Ångström exponent are derived from the POLDER polarization data at wavelengths of 0.670 and 0.865 μm. The polarization data at 0.865 μm. is also available for cloud retrieval. Two channels in the near infrared wavelengths are used to estimate the total column water vapor content. The first channel is in the water vapor absorption band of 0.910 μm. and the second is in the gas absorption-free band of 0.865 pin. In practice, a ratio of each reflectance for these two channels is used in this study. Then the obtained global maps of aerosol properties, cloud microphysics and water vapor content are compared with one another. It is shown that column number density of aerosols has a negative correlation with the effective radius of cloud particles and proportionally correlates with the optical thickness and the column number density of cloud particles. These results confirm the indirect effect of aerosols, namely aerosols play sufficient role as cloud condensation nuclei (CCN).