Types Of Atmospheric Aerosols Research Articles

Analysis of characteristics and changes in three-dimensional spatial and temporal distribution of aerosol types in Central Asia

Atmospheric aerosol types and characteristics have regional and seasonal characteristics mainly due spatial and temporal differences in emission sources and diffuse transport conditions. We explored regional three-dimensional spatial and temporal distribution characteristics of aerosol types in Central Asia from daytime to nighttime by using long-term (2007–2021) CALIPSO lidar measurements. The three results are as follows: (1) Average aerosol optical depth (AOD) values during the 14 years were 0.44 and 0.47 during daytime and nighttime, respectively, with an overall decreasing trend, among which the AOD in spring in the southern border region and in winter in the northern border region showed high values, 0.66 and 0.31 during daytime and 0.69 and 0.33 during nighttime, respectively, and nighttime AOD values were higher than those of daytime, possibly due to the lower signal-to-noise ratio of the CALIPSO during the daytime than during the nighttime. (2) The primary representative aerosol type in the Taklamakan Desert region being pure sand and dust, and more apparent winter-polluted sand and dust exist along the northern slope of the Tianshan Mountains in Xinjiang in winter than in other areas. High-altitude soot mainly existed below 4 km and was primarily concentrated in northern Central Asia, with the highest values (0.016 and 0.003) in summer and winter, respectively, which may be due to different diffusion and transport conditions. (3) Dust aerosols in spring were mainly concentrated in the region of 2–6 km in the Taklamakan Desert area; pure dust particles in summer and fall lifted height diffusion and gradually moved to the northern border region; polluted dust was mainly in northern Xinjiang in fall and winter and spread to northern Central Asia; and the average top height of aerosols in the transmission process reached the top of the troposphere, and transmission height was higher than source area.

Wavelet Analysis of the Interconnection between Atmospheric Aerosol Types and Direct Irradiation over Cameroon

The comparative analysis of the intra- and interannual dynamics between the Direct Normal Irradiation (DNI) under clear sky conditions and five aerosol types (Dust, Sea Salt, Black Carbon, Organic Carbon, and Sulfate) is the purpose of this study. To achieve this aim, we used fifteen-year DNI and aerosols data downloaded at 3-hour time intervals in nine defined zones throughout Cameroon. The wavelet transform is a powerful tool for studying local variability of amplitudes in a temporal dataset and constitutes our principal tool. The results show unequal distribution of aerosol types according to zones, but the Desert Dusts (DU) and Organic Carbon (OM) aerosols have been found as dominant particles in the studied region. The wavelet coherence analysis between DNI and each aerosol type reveals three bands of periodicity: ∼ 4-month band, 8–16-month band, and sometimes after-32-month band, with the most important frequency at 8–16-month band period. However, the intensity of coherence across bands varies with respect to aerosol type as well as each of the nine climate zones. A significant anticorrelation relationship was obtained between DNI and each type of aerosol, emphasizing that the presence of such atmospheric particles could dampen the renewable energy utilized by power systems. Also, the analysis shows that scattering aerosols such as Sulfate and Sea Salt (SU and SS, respectively) lead DNI in phase while absorbing aerosols such as Organic Carbon, Black Carbon, and Dust (OM, BC, and DU, respectively) give phase lag with DNI.

Development and validation of a new cloud simulation experiment for lab-based aerosol-cloud studies.

The Aerosol Interaction and Dynamics in the Atmosphere (AIDA) cloud expansion chamber with a volume of 84m3 was extended for the small cloud expansion chamber AIDA mini (AIDAm) with a volume of 20 L. AIDAm is located in the cold room of AIDA and can perform automated ice-nucleation measurements over longer time periods of hours to days. AIDAm samples from the AIDA chamber, which acts as a reservoir of atmospheric aerosol types, which can slowly be modified by physical or chemical processes similar to those occurring in the atmosphere. AIDAm was validated for accurate ice-nucleation temperature control by measuring homogeneous freezing of pure water droplets at temperatures around -34 °C and for immersion freezing induced by dust aerosol particles in the temperature range between -20 and -30 °C. Further validation experiments at cirrus cloud temperatures of -45 °C revealed that AIDAm can distinguish between heterogeneous ice formation on mineral dust aerosols and homogeneous freezing of sulfuric acid solution particles. The contribution of homogeneous and heterogeneous ice formation processes to the ice-nucleation activity of coated dust particles was investigated in a 7 h long experiment, where solid dust particles were slowly coated with sulfuric acid. The continuous AIDAm measurements with a time resolution of 6minshowed a substantial suppression of the heterogeneous freezing phenomenon and an increasing role of homogeneous freezing while the coating amount was slowly increased. This experiment proved the capability of AIDAm to sensitively detect small changes in the ice-nucleation ability of aerosols, which undergo slow processing like chemical surface coating.

Characteristics of aerosol optical depth dynamics and their causes over typical cities along the 21st Century Maritime Silk Road.

Atmospheric aerosols, i.e., suspension of liquid and/or solid particles in air, have serious impacts on human health. Exploring the variation and patterns of regional atmospheric aerosols is of great significance to monitor and evaluate atmosphere quality, especially in urban areas with large population. Here, with nine typical pivotal cities along the 21st Century Maritime Silk Road through Southeast Asia, South Asia to West Asia as case studies, based on MCD19A2 550 nm AOD products, combined meteorological factors, land use data, and nighttime light data, we analyzed the spatio-temporal distribution, variation features, influencing and/or driving factors of aerosols in developed urban areas over Asia. The results showed that the descending sequence of the annual aerosol optical depth (AOD) of the nine cities was Karachi, Doha, Chittagong, Bangkok, Colombo, Ho Chi Minh, Singapore, Gwadar, and Yangon during 2013-2018. Due to the influence of regional climate system and atmospheric aerosol types, the time series of annual, seasonal, and monthly AODs were significantly different. The high values of AODs in most cities were mainly located in the urban center or rapid socio-economic (e.g., industrial and agricultural) development regions. The effects of different meteorological factors on the AODs varied in different cities. The rainfall, relative humidity, and wind speed had great impacts on AODs in Ho Chi Minh, Bangkok, Singapore, and Yangon. Temperature, relative humidity, and wind speed had close correlations with AODs in Chittagong, Colombo, Karachi, and Gwadar of South Asia and Doha in West Asia. The urban area's AOD was influenced by the combined and synergistic effects of socio-economy, urbanization, and meteorological factors, with that in Karachi being the most significant.

Multi-spectral nephelometer characterization of urban aerosols

Latest developments in science and technology enabled the research community to device numerous methods for real-time monitoring and analysis of aerosol properties. Different types of atmospheric aerosols, originating from both natural and anthropogenic sources, interfere with both incoming and out-going solar radiation and cause changes in weather and climate. The presence of these aerosols over any location is due to a combination of local sources and long-range transport which can result in a variety of mixing (both internal and external) states, mainly because of aging and interaction among diverse types of aerosols. These aerosols directly or indirectly interact with solar radiation and influence the lifetime and albedo of clouds and hence precipitation (Intergovernmental Panel on Climate Change (IPCC), 2007). Added, through their scattering and absorption properties, aerosol particles also affect visibility, air quality (Horvath, 1995), and human health (Brunekreef and Holgate, 2002, Balakrishnan et al., 2012, Nadadur et al., 2015).

Nuclear Magnetic Resonance Characterization of Water Soluble Organic Carbon of Atmospheric Aerosol Types

The water soluble organic carbon of the prevalent atmospheric aerosol sources (traffic exhausts, paved road dust, agricultural soil, native soil, wood combustion, epicuticular waxes from pine and broad-leaved trees, and pollen) has been characterized using 1H (1-dimensional), 1H-1H-correlation spectroscopy and 1H-13C-heteronuclear single quantum correlation 2-dimensional (2D) nuclear magnetic resonance (NMR) spectroscopy. Traffic exhaust particles were mainly constituted of primary alcohols, carbohydrates, functionalized olefins, C3 and C4 oxy- and hydroxyl-carboxylic acids, and short-chain alkanes. Road dust was a mixture of soil particles and traffic components. Agricultural, natural, road dust, and traffic particles contained broad signals that were attributed to poly-carboxylic compounds typically found in humic compounds and humic-like substances. Traces of traffic particles (ie, peaks in the 7.3-7.5 ppm [phthalic acid derivatives] and signals found in the 0.5-3 ppm originating from functionalized carboxylic acids) were also found in natural soil dust. Long-chain (>C3) fatty acids and amino acids were found in road dust, natural soil, pine trees waxes, pollen, and woodburning. The aromatic region mainly constituted of lignin derivatives and cellulose/hemicellulose pyrolysis products (signals in 2D-NMR) in woodburning. Primary biogenic and woodburning particles were uniquely clustered as compared to traffic exhausts, road, agricultural, and natural dust based on the relative ratio of hydro-oxygenated functional groups (H-C-O and H-C-C=O) to the sum of aliphatics. Overall, source-specific NMR spectrometric fingerprints, functional composition profiles, and several organic compounds were identified allowing for the reconciliation of ambient organic aerosol sources including the degree of atmospheric aging.

Optimization of the Photon Path Length Probability Density Function-Simultaneous (PPDF-S) Method and Evaluation of CO₂ Retrieval Performance Under Dense Aerosol Conditions.

The photon path length probability density function-simultaneous (PPDF-S) algorithm is effective for retrieving column-averaged concentrations of carbon dioxide (XCO2) and methane (XCH4) from Greenhouse gases Observing Satellite (GOSAT) spectra in Short Wavelength InfraRed (SWIR). Using this method, light-path modification attributable to light reflection/scattering by atmospheric clouds/aerosols is represented by the modification of atmospheric transmittance according to PPDF parameters. We optimized PPDF parameters for a more accurate XCO2 retrieval under aerosol dense conditions based on simulation studies for various aerosol types and surface albedos. We found a more appropriate value of PPDF parameters referring to the vertical profile of CO2 concentration as a measure of a stable solution. The results show that the constraint condition of a PPDF parameter that represents the light reflectance effect by aerosols is sufficiently weak to affect XCO2 adversely. By optimizing the constraint, it was possible to obtain a stable solution of XCO2. The new optimization was applied to retrieval analysis of the GOSAT data measured in Western Siberia. First, we assumed clear sky conditions and retrieved XCO2 from GOSAT data obtained near Yekaterinburg in the target area. The retrieved XCO2 was validated through a comparison with ground-based Fourier Transform Spectrometer (FTS) measurements made at the Yekaterinburg observation site. The validation results showed that the retrieval accuracy was reasonable. Next, we applied the optimized method to dense aerosol conditions when biomass burning was active. The results demonstrated that optimization enabled retrieval, even under smoky conditions, and that the total number of retrieved data increased by about 70%. Furthermore, the results of the simulation studies and the GOSAT data analysis suggest that atmospheric aerosol types that affected CO2 analysis are identifiable by the PPDF parameter value. We expect that we will be able to suggest a further improved algorithm after the atmospheric aerosol types are identified.

Identification of absorbing aerosol types at a site in the northern edge of Indo-Gangetic Plain and a polluted valley in the foothills of the central Himalayas

Identification of atmospheric aerosol types and characterization of absorbing aerosols, based on AErosol RObotic NETwork (AERONET) data collected during 2013–2014 over two sites in Nepal: Lumbini in the northernmost part of central Indo-Gangetic Plain (IGP) and Kathmandu Valley in foothills of the central Himalayas, have been conducted in the present study. The relationship between four aerosol parameters; Extinction Angstrom Exponent (EAE), Absorption Angstrom Exponent (AAE), Single Scattering Albedo (SSA) and Real Refractive Index (RRI) was analyzed to study the aerosol types. This resulted in the identification of two types of aerosols concerning their origin: biomass burning and urban/industrial mix. Furthermore, to understand the absorbing aerosol types, the relationship between aerosol size parameters; Fine Mode Fraction (FMF) and Angstrom Exponent (AE), and aerosol absorption characteristics; SSA and AAE were investigated. In regards to the absorbing aerosol types, ‘Mostly BC’ was the dominant absorbing aerosol, over both sites, with comparatively negligible contribution from other absorbing aerosol types such as dust. The aerosol subtypes obtained from satellite-borne CALIPSO instrument supported the results derived from the AERONET data. The CALIPSO images also indicated that the aerosols over the foothills of the Himalayas could extend to the height of >5 km above the ground, which could be transported towards the Himalayan and Tibetan Plateau (HTP) region with sensitive ecosystems. The multi-sites based study of long-term records is required to elucidate the nature and trends of aerosols in the HTP region and any perturbation to the atmospheric environment and other environments in this region.

Comparison of operator- and computer-controlled scanning electron microscopy of particles from different atmospheric aerosol types.

Individual aerosol particles from an urban background site in Mainz (Germany), a traffic hotspot site in Essen (Germany), the free troposphere in the Swiss Alps (high altitude research station Jungfraujoch), a rural background/marine site on Cyprus (Cyprus Atmospheric Observatory) and a rural background site in the forested area of Odenwald (Germany) were characterised with two different scanning electron microscopy techniques, operator controlled (opSEM) and computer controlled (ccSEM). For all samples, about 500 particles were investigated by opSEM, and between 1103 and 6940 particles by ccSEM. Large systematic differences (in some cases a factor up to ~ 20) in the abundance of the various particle groups are observed in the results of the two techniques. These differences are dependent on particle type and size. With ccSEM, information on the mixing state of particles (e.g., presence of heterogeneous inclusions, surface coatings or gradients in chemical composition) cannot be obtained, and particle groups which are recognised by their complex morphology (e.g., soot and fly ash particles) are classified into other particle groups. In addition, highly volatile particles (i.e., particles which evaporate under electron bombardment within seconds) will be overlooked by ccSEM. If these limitations of ccSEM are not considered, normalising the particle group abundances to 100% (a popular practise in many publications) may lead to drastic misinterpretation of the real aerosol composition. OpSEM is indispensable when detailed information of particle composition is required, although it suffers from a much higher expenditure of time. In conclusion, both techniques might be used for single particle characterisation as long as drawbacks of each are considered.

ON VERTICAL DISTRIBUTION OF MAJOR AEROSOL TYPES OVER DIFFERENT PARTS OF ASIA

Abstract. Asia, being the largest continent, both in its size and population is affected by different types of atmospheric aerosols. Also, owing to different local emissions/sources along with the long range transport mechanisms, there is a large variability in the distribution of different types of aerosols across the continent. Not only the effects are pertinent to the regional and global climate system, but the loadings also affect human health. Though there have been studies in the past focussing on columnar distribution of aerosol types over Asian region at continental and regional scales, studies focussed on regional vertical distribution of major aerosol types over different regions of Asia need attention. This paper presents the decadal (2007–16) vertical distribution of major aerosol components, i.e., dust, polluted dust and smoke over different parts of Asia as seen from the space-borne lidar, i.e., Cloud Aerosol Lidar with Orthogonal Polarisation (CALIOP) onboard Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO). Such a study can be useful in capacity building focussed on aerosol variability through remote sensing techniques.

Optical scattering communication under various aerosol types based on a new non-line-of-sight propagation model

This paper proposes a model for non-line-of-sight (NLOS) single-scatter propagation in an inhomogeneous atmosphere. This propagation model is used to simulate optical scattering communication under various atmospheric aerosol types. In the traditional NLOS propagation model, the atmosphere is assumed to be homogeneous. The scattering, absorption, and extinction coefficients are fixed values, and the received energy decreases monotonically as the elevation angle of the beam is raised. In the proposed NLOS propagation model, the atmosphere is inhomogeneous. The scattering, absorption, and extinction coefficients decrease as the height increases, and their rates of change are different under various aerosol types. Moreover, the received energy in the simulation does not monotonically decrease, and there is an optimal elevation angle at which the received energy is the highest. We can choose an optimal elevation angle in light communication. The received energy is also distinctive among various aerosol types.

Nitrogen speciation in various types of aerosols in spring over the northwestern Pacific Ocean

Abstract. The cumulative atmospheric nitrogen deposition has been found to profoundly impact the nutrient stoichiometry of the eastern China seas (ECSs: the Yellow Sea and East China Sea) and the northwestern Pacific Ocean (NWPO). In spite of the potential significance of dry deposition in those regions, shipboard observations of atmospheric aerosols remain insufficient, particularly regarding the compositions of water-soluble nitrogen species (nitrate, ammonium and water-soluble organic nitrogen – WSON). We conducted a cruise covering the ECSs and the NWPO during the spring of 2014 and observed three types of atmospheric aerosols. Aluminum content, air mass backward trajectories, weather conditions, and ion stoichiometry allowed us to discern dust aerosol patches and sea-fog-modified aerosols (widespread over the ECSs) from background aerosols (open ocean). Among the three types, sea-fog-modified aerosols contained the highest concentrations of nitrate (536 ± 300 nmol N m−3), ammonium (442 ± 194 nmol N m−3) and WSON (147 ± 171 nmol N m−3); furthermore, ammonium and nitrate together occupied ∼ 65 % of the molar fraction of total ions. The dust aerosols also contained significant amounts of nitrate (100 ± 23 nmol N m−3) and ammonium (138 ± 24 nmol N m−3) which were obviously larger than those in the background aerosols (26 ± 32 for nitrate and 54 ± 45 nmol N m−3 for ammonium), yet this was not the case for WSON. It appeared that dust aerosols had less of a chance to come in contact with WSON during their transport. In the open ocean, we found that sea salt (e.g., Na+, Cl−, Mg2+), as well as WSON, correlated positively with wind speed. Apparently, marine dissolved organic nitrogen (DON) was emitted from breaking waves. Regardless of the variable wind speeds from 0.8 to as high as 18 m s−1, nitrate and ammonium, by contrast, remained in narrow ranges, implying that some supply and consumption processes of nitrate and ammonium were required to maintain such a quasi-static condition. Mean dry deposition of total dissolved nitrogen (TDN) for sea-fog-modified aerosols (1090 ± 671 µmol N m−2 d−1) was 5 times higher than that for dust aerosols (190 ± 41.6 µmol N m−2 d−1) and around 20 times higher than that for background aerosols (56.8 ± 59.1 µmol N m−2 d−1). Apparently, spring sea fog on the ECSs played an important role in removing atmospheric reactive nitrogen from the Chinese mainland and depositing it into the ECSs, thus effectively preventing its seaward export to the NWPO.

Classification of Aerosol over Central Europe by Cluster Analysis of Aerosol Columnar Optical Properties and Backward Trajectory Statistics

AbstractA cluster analysis is applied to the Aerosol Robotic Network (AERONET) data obtained at Belsk, Poland, as well as three nearby Central European stations (Leipzig, Minsk and Moldova) for estimation of atmospheric aerosol types. Absorption Ångstrom exponent (AAE), aerosol optical thickness (AOT) and extinction Ångstrom exponent (EAE) parameters are used. Clustering in both 2D (AOT, EAE) and 3D (AOT, EAE, AAE) is investigated. A method of air mass backward trajectory analysis is then proposed, with the receptor site at Belsk, to determine possible source regions for each cluster. Four dominant aerosol source regions are identified. The biomass burning aerosol source is localized in the vicinity of Belarusian-Ukrainian border. Slovakia and northern Hungary are found to be the source of urban/industrial pollutants. Western Poland and eastern Germany are the main sources of polluted continental aerosols. The most differentiated source region of Scandinavia, Baltic Sea and Northern Atlantic, associated with lowest values of AOT, corresponds to clean continental and possibly maritime type aerosols.

Organics Substantially Reduce HO2 Uptake onto Aerosols Containing Transition Metal ions.

A HO2 mass accommodation coefficient of α = 0.23 ± 0.07 was measured onto submicron copper(II)-doped ammonium sulfate aerosols at a relative humidity of 60 ± 3%, at 293 ± 2 K and at an initial HO2 concentration of ∼ 1 × 10(9) molecules cm(-3) by using an aerosol flow tube coupled to a sensitive fluorescence assay by gas expansion (FAGE) HO2 detection system. The effect upon the HO2 uptake coefficient γ of adding different organic species (malonic acid, citric acid, 1,2-diaminoethane, tartronic acid, ethylenediaminetetraacetic acid (EDTA), and oxalic acid) into the copper(II)-doped aerosols was investigated. The HO2 uptake coefficient decreased steadily from the mass accommodation value to γ = 0.008 ± 0.009 when EDTA was added in a one-to-one molar ratio with the copper(II) ions, and to γ = 0.003 ± 0.004 when oxalic acid was added into the aerosol in a ten-to-one molar ratio with the copper(II). EDTA binds strongly to copper(II) ions, potentially making them unavailable for catalytic destruction of HO2, and could also be acting as a surfactant or changing the viscosity of the aerosol. The addition of oxalic acid to the aerosol potentially forms low-volatility copper-oxalate complexes that reduce the uptake of HO2 either by changing the viscosity of the aerosol or by causing precipitation out of the aerosol forming a coating. It is likely that there is a high enough oxalate to copper(II) ion ratio in many types of atmospheric aerosols to decrease the HO2 uptake coefficient. No observable change in the HO2 uptake coefficient was measured when the other organic species (malonic acid, citric acid, 1,2-diaminoethane, and tartronic acid) were added in a ten-to-one molar ratio with the copper(II) ions.

Time-dependent freezing rate parcel model

Abstract. The time-dependent freezing rate (TDFR) model here described represents the formation of ice particles by immersion freezing within an air parcel. The air parcel trajectory follows an adiabatic ascent and includes a period in time when the parcel remains stationary at the top of its ascent. The description of the ice nucleating particles (INPs) in the air parcel is taken from laboratory experiments with cloud and precipitation samples and is assumed to represent the INP content of the cloud droplets in the parcel. Time dependence is included to account for variations in updraft velocity and for the continued formation of ice particles under isothermal conditions. The magnitudes of these factors are assessed on the basis of laboratory measurements. Results show that both factors give rise to three-fold variations in ice concentration for a realistic range of the input parameters. Refinements of the parameters specifying time dependence and INP concentrations are needed to make the results more specific to different atmospheric aerosol types. The simple model framework described in this paper can be adapted to more elaborate cloud models. The results here presented can help guide decisions on whether to include a time-dependent ice nucleation scheme or a simpler singular description in models.

Retrieving aerosol microphysical properties by Lidar‐Radiometer Inversion Code (LIRIC) for different aerosol types

AbstractLIRIC (Lidar‐Radiometer Inversion Code) is applied to combined lidar and Sun photometer data from Granada station corresponding to different case studies. The main aim of this analysis is to evaluate the stability of LIRIC output volume concentration profiles for different aerosol types, loadings, and vertical distributions of the atmospheric aerosols. For this purpose, in a first part, three case studies corresponding to different atmospheric situations are analyzed to study the influence of the user‐defined input parameters in LIRIC when varied in a reasonable range. Results evidence the capabilities of LIRIC to retrieve vertical profiles of microphysical properties during daytime by the combination of the lidar and the Sun photometer systems in an automatic and self‐consistent way. However, spurious values may be obtained in the lidar incomplete overlap region depending on the structure of the aerosol layers. In a second part, the use of a second Sun photometer located in Cerro Poyos, in the same atmospheric column as Granada but at higher altitude, allowed us to obtain LIRIC retrievals from two different altitudes with independent Sun photometer measurements in order to check the self‐consistency and robustness of the method. Retrievals at both levels are compared, providing a very good agreement (differences below 5 µm3/cm3) in those cases with the same aerosol type in the whole atmospheric column. However, some assumptions such as the height independency of parameters (sphericity, size distribution, or refractive index, among others) need to be carefully reviewed for those cases with the presence of aerosol layers corresponding to different types of atmospheric aerosols.

Shortwave radiative forcing and efficiency of key aerosol types using AERONET data

Abstract. The shortwave radiative forcing (ΔF) and the radiative forcing efficiency (ΔFeff) of natural and anthropogenic aerosols have been analyzed using estimates of radiation both at the Top (TOA) and at the Bottom Of Atmosphere (BOA) modeled based on AERONET aerosol retrievals. Six main types of atmospheric aerosols have been compared (desert mineral dust, biomass burning, urban-industrial, continental background, oceanic and free troposphere) in similar observational conditions (i.e., for solar zenith angles between 55° and 65°) in order to compare the nearly same solar geometry. The instantaneous ΔF averages obtained vary from −122 ± 37 Wm−2 (aerosol optical depth, AOD, at 0.55 μm, 0.85 ± 0.45) at the BOA for the mixture of desert mineral dust and biomass burning aerosols in West Africa and −42 ± 22 Wm−2 (AOD = 0.9 ± 0.5) at the TOA for the pure mineral dust also in this region up to −6 ± 3 Wm−2 and −4 ± 2 Wm−2 (AOD = 0.03 ± 0.02) at the BOA and the TOA, respectively, for free troposphere conditions. This last result may be taken as reference on a global scale. Furthermore, we observe that the more absorbing aerosols are overall more efficient at the BOA in contrast to at the TOA, where they backscatter less solar energy into the space. The analysis of the radiative balance at the TOA shows that, together with the amount of aerosols and their absorptive capacity, it is essential to consider the surface albedo of the region on which they are. Thus, we document that in regions with high surface reflectivity (deserts and snow conditions) atmospheric aerosols lead to a warming of the Earth-atmosphere system.

Urban background aerosols: Negative correlations of particle modes and fragmentation mechanism

We demonstrate new powerful methods of statistical analysis of atmospheric aerosols on the example of urban background aerosol in the Brisbane area, Australia. It is shown that even in the absence of notable features on the size distribution, it is still possible to identify distinct particles modes and analyze their mutual interactions and transformations. The obtained unique anti-symmetric correlation patterns between particle modes may serve as fingerprints of particular evolutionary processes in the background aerosols. The obtained results suggest that thermal fragmentation of nano-particles may be one of the major physical mechanisms shaping urban background aerosols. In particular, based on the fragmentation theorem, we demonstrate possible existence of substantially different time scales for fragmentation of atmospheric aerosols. The proposed approaches and obtained results may also be important for the analysis of different types of atmospheric aerosols on local, regional and global scales.

Relationship between errors in AVHRR‐derived sea surface temperature and the TOMS aerosol index

We investigate the effects of various types of atmospheric aerosols on satellite‐derived sea surface temperature (SST) retrievals. The association between aerosol presence identified by the Earth Probe Total Ozone Mapping Spectrometer (TOMS) aerosol index (AI) and systematic errors in Advanced Very High Resolution Radiometer (AVHRR) Pathfinder SST retrievals is explored. We find a significant increase in systematic PFSST errors in the presence of dust aerosols. Average errors range from 0.34°C for AI values between 0.5 and 1.0 to 1.74°C for AI ≥ 1.5. The bias is introduced by the AVHRR channel brightness temperature difference (T4–T5) which is intended to correct for atmospheric absorption normally due primarily to water vapor. Our study shows that (T4– T5) is sensitive to the dust aerosols (i.e., TOMS AI values). In contrast, smoke aerosols do not seem to have a significant effect on PFSST errors.

Multiple field of view lidar returns from atmospheric aerosols

As a laser pulse propagates into the atmosphere, it becomes broader in the lateral direction as a result of scattering by aerosols. The laser pulse may be described as the superposition of a central, unscattered component of reduced intensity and a surrounding scattered component. A multiple field of view lidar has been developed that makes simultaneous measurements of the backscattered power from the central pulse and multiply scattered power arising from the scattered component. Measurements from various types of atmospheric aerosols and precipitation are presented and compared with simulated returns. The results show how the multiply scattered signals are influenced by the distribution of the aerosols along the lidar path, the characteristic size of the aerosols, and the optical depth. It is shown that the multiple field of view lidar can provide meaningful, additional information about the aerosols that is not available from a conventional single field of view lidar.