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From past many decades, the integrating nephelometers are generally used to measure the aerosol scattering coefficient for ground level at different wavelengths. In recent years, the research focus has been shifted toward the airborne observations using either tethered balloons or drones. For this particular purpose, one needs light-weight instruments which are capable of measuring the aerosol scattering coefficient suitable for airborne activities. Thus, we report the design and development of a light-weight scattering coefficient counter (weight ~ 500 g, 7″ × 3″) with high sensitivity. This instrument has been specifically designed and developed for the measurement of aerosol scattering coefficient at 633 nm wavelength. The aerosol scattering coefficient calculation becomes extremely important for modeling aerosol optical/radiative properties. Delhi is one of the regions with high aerosol loadings, so one needs such Light-weight instruments for the aerosol scattering coefficient measurements. At present, this instrument has only been evaluated at ground level. But, before using the developed instrument for airborne observations, there is a strong need for comparison of the instrument against routinely used nephelometers for performance evaluation. Comparisons were performed between the light-weight scattering coefficient counter and high-end AURORA 3000 Nephelometer for two different seasons. For both the seasons, i.e., the monsoon season (July 25–August 24, 2017) and the winter season (February 1–28, 2018), we found a strong correlation (i.e., R2 = 0.99). However, the highest value of scattering coefficient was found to be 98 ± 32 Mm−1 with a mean value of 55 Mm−1 for the monsoon season, while the same for the winter season was observed to be 270 ± 108 Mm−1 with a mean value of 165 Mm−1. This light-weight instrument could be a potential instrument for aerosol scattering observations, especially for airborne platforms with payload mass limitations.

COVID-19 is evolving into one of the worst pandemics in recent history, claiming a death toll of over 1.5 million as of December 2020. In an attempt to limit the expansion of the pandemic in its initial phase, nearly all countries imposed restriction measures, which resulted in an unprecedented reduction of air pollution. This study aims to assess the impact of the lockdown effects due to COVID-19 on in situ measured aerosol properties, namely spectral-scattering (bsca) and absorption (babs) coefficients, black carbon (BC) concentrations, single-scattering albedo (SSA), scattering and absorption Ångström exponents (SAE, AAE) in Athens, Greece. Moreover, a comparison is performed with the regional background site of Finokalia, Crete, for a better assessment of the urban impact on observed differences. The study examines pre-lockdown (1–22 March 2020), lockdown (23 March–3 May 2020) and post-lockdown (4–31 May 2020) periods, while the aerosol properties are also compared with a 3–4 year preceding period (2016/2017–2019). Comparison of meteorological parameters in Athens, between the lockdown period and respective days in previous years, showed only marginal variation, which is not deemed sufficient in order to justify the notable changes in aerosol concentrations and optical properties. The largest reduction during the lockdown period was observed for babs compared to the pre-lockdown (−39%) and to the same period in previous years (−36%). This was intensified during the morning traffic hours (−60%), reflecting the large decrease in vehicular emissions. Furthermore, AAE increased during the lockdown period due to reduced emissions from fossil-fuel combustion, while a smaller (−21%) decrease was observed for bsca along with slight increases (6%) in SAE and SSA values, indicating that scattering aerosol properties were less affected by the decrease in vehicular emissions, as they are more dependent on regional sources and atmospheric processing. Nighttime BC emissions related to residential wood-burning were slightly increased during the lockdown period, with respect to previous-year means. On the contrary, aerosol and pollution changes during the lockdown period at Finokalia were low and highly sensitive to natural sources and processes.

Smoke from fires significantly influences climate, weather, and human health. Fire smoke is traditionally detected using an aerosol index calculated from spectral contrast changes. However, such methods usually miss thin smoke plumes. It also remains challenging to accurately separate smoke plumes from dust, clouds, and bright surfaces. To improve smoke plume detections, this paper presents a new scattering-based smoke detection algorithm (SSDA) depending mainly on visible and infrared imaging radiometer suite (VIIRS) blue and green bands. The SSDA is established based on the theory of Mie scattering that occurs when the diameter of an atmospheric particulate is similar to the wavelength of the scattered light. Thus, smoke commonly causes Mie scattering in VIIRS blue and green bands because of the close correspondence between smoke particulate diameters and the blue/green band wavelengths. For developing the SSDA, training samples were selected from global fire-prone regions in North America, South America, Africa, Indonesia, Siberia, and Australia. The SSDA performance was evaluated against the VIIRS aerosol detection product and smoke detections from the ultraviolet aerosol index using manually labeled fire smoke plumes as a benchmark. Results show that the SSDA smoke detections are superior to existing products due chiefly to the improved ability of the algorithm to detect thin smoke and separate fire smoke from other surface types. Moreover, the SSDA smoke distribution pattern exhibits a high spatial correlation with the global fire density map, suggesting that SSDA is capable of detecting smoke plumes of fires in near real-time across the globe.

Objectives: Due to the crisis in protective equipment caused by a pandemic, it generates needs for equipment rationing among professionals working in the health area, with the need for many health professionals to use homemade masks. Therefore, this is a comparative study regarding the relative efficiencies of commercial respiratory masks (medical masks) and homemade fabric masks.Methods: A liquid aerosol line was created that passes through a chamber with 6 optical windows that allows the fixation of tissue or masks in the aerosol flow. The measures used two spectroscopic techniques that made it possible to relate the amount of aerosols with the scattering of light..Results: Fabrics with a higher percentage of cotton, and a greater number of layers and more closed wefts proved to be more efficient in blocking aerosols, however, fabrics without treatments obtained results far below the real needs of professionals working in the health area, with efficiency below 75% for liquid aerosols among the tissues tested.Conclusion: Homemade masks prove to be effective in reducing the spread of the virus among ordinary citizens in past infections, the efficiency of homemade masks is very low for health professionals who are directly exposed to the biological agent, so, it is necessary for public administrations to seek new alternatives with greater efficiency for this type of professional during the absence of surgical masks and n95.

The aerosol scattering (σsp) and absorption (σap) coefficients and single scattering albedo (SSA) were continuously measured and analyzed at an urban site in Wuhan of central China from November 2014 to July 2017. The average σsp (532 nm), σap (532 nm), and SSA in Wuhan during the study period were 244 ± 212 Mm–1, 27 ± 17 Mm–1, and 0.86 ± 0.09, respectively. The aerosol optical properties had pronounced and distinctive diurnal cycles in the Wuhan area. The σsp and σap exhibited the highest values between 06:00 and 08:00 local time (LT) and the lowest values between 14:00 and 16:00 LT, which was mainly due to being coupled with increasing traffic emissions. PM2.5 was a major contributor to the large optical parameters. During pollution periods, the mean σsp (624 Mm–1) was roughly 3 times that during clean periods (214 Mm–1), and the σap (58 Mm–1) was about 2.5 times that during clean periods (24 Mm–1). The wind speed and direction also strongly affected the aerosol optical properties during the different periods. The high σsp and σap values for the pollution periods were accompanied by calm winds (0–2 m s–1), from 0° to 45°, whereas the low σsp and σap values of the clean periods were observed with high wind speeds (above 4 m s–1), from 0° to 90°. Moreover, the σap showed a clear positive correlation (R2 = 0.412) with the PM2.5 concentrations for the clean periods, whereas the σsp had a good positive correlation (R2 = 0.406) with the PM2.5 concentrations during the pollution periods.

Lidar polarization measurements of stratospheric aerosol were performed over Obninsk in 2012–2015. In all, over 300 altitude profiles of the aerosol backscattering coefficient at a wavelength of 532 nm in the altitude interval from 10 to 40 km were obtained. Overall, the measured aerosol backscattering characteristics are close to the known background values. During spring 2013, an elevated content of spherical-type aerosol was noted in the tropopause region, seemingly associated with sedimentation of aerosol structures formed during the fall of the Chelyabinsk meteorite. In July 2014 and 2015, layers of increased aerosol scattering were observed in the altitude interval from 10 to 15 km, associated with transcontinental transport of aerosol from Canadian forest fires. Integrated backscattering and extinction characteristics are estimated for the lower (from tropopause level to 15 km) and middle (from 15 to 30 km) stratospheric layers. It is found that the contribution of the lower layer to these optical characteristics is 1.8 and 1.6 times larger than the contribution of the middle layer.

In this study, we propose a novel approach to describe the scattering effects of atmospheric aerosols in a complex urban environment using water vapor (H2O) slant column measurements in the near infrared. This approach is demonstrated using measurements from the California Laboratory for Atmospheric Remote Sensing Fourier Transform Spectrometer on the top of Mt. Wilson, California, and a two-stream-exact single scattering (2S-ESS) radiative transfer (RT) model. From the spectral measurements, we retrieve H2O slant column density (SCD) using 15 different absorption bands between 4000 and 8000 cm−1. Due to the wavelength dependence of aerosol scattering, large variations in H2O SCD retrievals are observed as a function of wavelength. Moreover, the variations are found to be correlated with aerosol optical depths (AODs) measured at the AERONET-Caltech station. Simulation results from the RT model reproduce this correlation and show that the aerosol scattering effect is the primary contributor to the variations in the wavelength dependence of the H2O SCD retrievals. A significant linear correlation is also found between variations in H2O SCD retrievals from different bands and corresponding AOD data; this correlation is associated with the asymmetry parameter, which is a first-order measure of the aerosol scattering phase function. The evidence from both measurements and simulations suggests that wavelength-dependent aerosol scattering effects can be derived using H2O retrievals from multiple bands. This understanding of aerosol scattering effects on H2O retrievals suggests a promising way to quantify the effect of aerosol scattering on greenhouse gas retrievals and could potentially contribute towards reducing biases in greenhouse gas retrievals from space.

Combination of numerical modeling (MERRA) and ground based (AERONET) monitoring of atmospheric aerosol parameters were used to discover a possible connection to seismic activities within the territory of Tien-Shan. The obtained results demonstrated consistent behavior between increase of aerosol optical thickness (AOT) and powerful earthquakes, epicenters of which were located within 200 km from the “Issyk-Kul” station (AERONET). Thereat, the dominant role was played by fine-dispersed particles, which virtually determined the nature of AOT evolution. We also observed well-defined changes of the ratio between mass fraction PM1.0 (particles less than 1.0 μm aerodynamic diameter) and optical thickness of aerosol scattering several days before an earthquake of M > 5.0 magnitude.

We investigated the variability of the aerosol scattering (σsp; 1974–2015) and absorption (σap; 2000–2015) coefficients at the Mauna Loa Observatory using surface in situ measurements. Although σsp decreased during the morning (1.85 ± 3.43 Mm–1 at 550 nm, 8–11 local standard time [LST]), it increased during the afternoon (3.72 ± 7.63 Mm–1 at 550 nm, 14–17 LST) due to the development of thermally induced boundary layer winds. No distinct diurnal variation was observed in σap. The obvious increase in σsp and σap during the spring under free troposphere conditions (8–11 LST) is attributed to long-range-transported aerosols from Asia, especially dust and pollution aerosols from Northeast Asia and biomass burning aerosols from Southeast Asia. Accordingly, σsp increased from 1974 till 2015 (at 1.89% year–1), whereas no significant trend was noted for either σsp or σap from 2000 till 2015. An increasing trend for σsp prevailed in air masses originating in Northeast Asia (+0.51 Mm–1 decade–1).

The profile of aerosol extinction coefficient can help understand the air pollution transportation and development of the atmospheric boundary layer. The charge-coupled device (CCD)-laser aerosol detection system (CLADS) was widely used to measure the profile of aerosol extinction coefficient, which has excellent resolution near the ground. Traditionally, a constant aerosol scattering phase function and single scattering albedo (SSA) is assumed when retrieving the profile of aerosol extinction coefficient using the measured signals from CLADS. Sensitivity studies in this research show that aerosol scattering phase function leads to an uncertainty up to 462% of the retrieved profile of aerosol extinction coefficient, while SSA leads to an uncertainty up to 25%. A new method is proposed to derive the profile of aerosol extinction coefficient by using two CCD cameras. The aerosol scattering phase function can be determined by minimizing the difference between profiles of aerosol extinction coefficient from the two CCD cameras without any assumption. The profile of aerosol extinction coefficient can be retrieved with high accuracy by using our optimized aerosol scattering phase function. This method is validated by simulation studies where the relative difference between the pre-parameterized aerosol extinction profile and retrieved aerosol extinction profile is below 6%. This dual CCD detection system is employed in a field measurement and proved to be reliable. Our proposed method can obtain more accurate profile of aerosol extinction coefficient for further works about air pollution and atmospheric boundary layer development.

Both higher temperatures and increased CO2 concentrations are (separately) expected to increase the emissions of biogenic volatile organic compounds (BVOCs). This has been proposed to initiate negative climate feedback mechanisms through increased formation of secondary organic aerosol (SOA). More SOA can make the clouds more reflective, which can provide a cooling. Furthermore, the increase in SOA formation has also been proposed to lead to increased aerosol scattering, resulting in an increase in diffuse radiation. This could boost gross primary production (GPP) and further increase BVOC emissions. In this study, we have used the Norwegian Earth System Model (NorESM) to investigate both these feedback mechanisms. Three sets of experiments were set up to quantify the feedback with respect to (1) doubling the CO2, (2) increasing temperatures corresponding to a doubling of CO2 and (3) the combined effect of both doubling CO2 and a warmer climate. For each of these experiments, we ran two simulations, with identical setups, except for the BVOC emissions. One simulation was run with interactive BVOC emissions, allowing the BVOC emissions to respond to changes in CO2 and/or climate. In the other simulation, the BVOC emissions were fixed at present-day conditions, essentially turning the feedback off. The comparison of these two simulations enables us to investigate each step along the feedback as well as estimate their overall relevance for the future climate. We find that the BVOC feedback can have a significant impact on the climate. The annual global BVOC emissions are up to 63 % higher when the feedback is turned on compared to when the feedback is turned off, with the largest response when both CO2 and climate are changed. The higher BVOC levels lead to the formation of more SOA mass (max 53 %) and result in more particles through increased new particle formation as well as larger particles through increased condensation. The corresponding changes in the cloud properties lead to a −0.43 W m−2 stronger net cloud forcing. This effect becomes about 50 % stronger when the model is run with reduced anthropogenic aerosol emissions, indicating that the feedback will become even more important as we decrease aerosol and precursor emissions. We do not find a boost in GPP due to increased aerosol scattering on a global scale. Instead, the fate of the GPP seems to be controlled by the BVOC effects on the clouds. However, the higher aerosol scattering associated with the higher BVOC emissions is found to also contribute with a potentially important enhanced negative direct forcing (−0.06 W m−2). The global total aerosol forcing associated with the feedback is −0.49 W m−2, indicating that it has the potential to offset about 13 % of the forcing associated with a doubling of CO2.

The evolution of aerosol absorption and the contribution of absorbing species under different severities of particulate pollution are poorly understood, though absorption is key in aerosol radiative forcing. To resolve the problems, aerosol absorbing properties from low to high particulate pollution were investigated by using intensive observations of aerosol optical properties in the winter of 2019–2020 in Lanzhou, Northwest China. The aerosol scattering coefficient increased linearly with increasing particulate matter

An analysis of extensive (scattering, β s c a and absorption, β a b s coefficients) and intensive (single scattering albedo -SSA, Angstrom exponent - α, backscatter fraction - b, and asymmetry parameter - g) properties of aerosols are simultaneously examined for the first time over a source region; urban environment - Ahmedabad, and background site; a high altitude remote location - Gurushikhar over western India revealed significant diurnal, monthly and seasonal variations. β s c a and β a b s over Ahmedabad are always higher by a factor of 3–5 than Gurushikhar. β s c a corrected for variation in relative humidity shows maximum change (>50%) during August, thereby, emphasizing the importance of RH correction on aerosol scattering. SSA is lower over Ahmedabad due to the dominance of absorbing aerosols from the anthropogenic emissions. The annual mean β s c a , β a b s , SSA, α, and g are found to be 235 ± 128 M m − 1 , 64 ± 40 M m − 1 , 0.81 ± 0.03, 0.60 ± 0.03 respectively over Ahmedabad, whereas these values are 78 ± 31 M m − 1 , 12 ± 6 M m − 1 , 0.87 ± 0.04, 1.19 ± 0.31, and 0.61 ± 0.02 respectively over Gurushikhar. A comparison reveals that among the urban regimes Ahmedabad SSA is higher than Delhi, and among the high-altitude locations Gurushikhar SSA is higher than Mukteshwar, and lower than Nainital SSA. The interannual variability in aerosol properties is estimated to be less significant (

A humidified nephelometer system was deployed to measure the aerosol scattering coefficients at RH 30% and RH in the range of 40 to 85% simultaneously in megacity Beijing in March 2018. The aerosol optical properties and aerosol hygroscopicity of two sizes (PM

The solution of aerosol scattering characteristics has always been a hot topic in the field of atmospheric science owing to its basic status. The difficulty of solving aerosol scattering characteristics is increased. Therefore, there is not yet a unified scattering theory which can be used to calculate various aerosol particles. In this paper, firstly, the basic principles and research progress of existing methods for solving the scattering characteristics of aerosol light are summarized. Secondly, the advantages and disadvantages of these solution methods are compared. Finally, the problems existing in the current research and the future development prospects are analyzed.

To study the diurnal behavior of hygro- and thermooptical parameters, the cycles of intensive measurements with artificial humidification and heating of the aerosol under study were carried out four to six times a day. The parameter of condensation activity γ characterizes variability of the aerosol scattering coefficient under the change of the relative humidity of air, and the thermooptical parameters are determined by the decrease of the volume concentration of particles in the respective temperature range. Diurnal behavior of the parameter of condensation activity is the most pronounced in spring. Its characteristic peculiarities are maximum in the daytime (~ 3 pm) and minimum in the evening (~10 pm). Diurnal behavior of the parameter determining the aerosol fraction evaporated in the temperature range 100 – 250°C also is well pronounced.

As part of the Observations and Modeling of the Green Ocean Amazon (GoAmazon 2014/5) Experiment, detailed aerosol and trace gas measurements were conducted near Manaus, a metropolis located in the central Amazon Basin. Measurements of aerosol particles and trace gases were done downwind Manaus at the sites T2 (Tiwa Hotel) and T3 (Manacapuru), at a distance of 8 and 70 km from Manaus, respectively. Based on in-plume measurements closer to Manaus (site T2), the chemical signatures of city emissions were used to improve the interpretation of pollutant levels at the T3 site. We derived chemical and physical properties for the city's atmospheric emission ensemble, taking into account only air masses impacted by the Manaus plume at both sites, during the wet and dry season Intensive Operating Periods (IOPs). At T2, average concentrations of aerosol number (CN), CO and SO2 were 5500 cm−3 (between 10 and 490 nm), 145 ppb and 0.60 ppb, respectively, with a typical ratio ΔCN/ΔCO of 60–130 particles cm−3 ppb−1. The aerosol scattering (at RH < 60%) and absorption at 637 nm at T2 ranged from 10 to 50 M m−1 and 5–10 M m−1, respectively, leading to a mean single scattering albedo (SSA) of 0.70. In addition to identifying periods dominated by Manaus emissions at both T2 and T3, the plume transport between the two sampling sites was studied using back trajectory calculations. Results show that the presence of the Manaus plume at site T3 was important mainly during the daytime and at the end of the afternoons. During time periods directly impacted by Manaus emissions, an average aerosol number concentration of 3200 cm−3 was measured at T3. Analysis of plume evolution between T2 and T3 indicates a transport time of 4–5 h. Changes of submicron organic and sulfate aerosols ratios relative to CO (ΔOA/ΔCO and ΔSO4/ΔCO, respectively) indicate significant production of secondary organic aerosol (SOA), corresponding to a 40% mass increase in OA and a 30% in SO4 mass concentration. Similarly, during air mass arrival at T3 the SSA increased to 0.83 from 0.70 at T2, mainly associated with an increase in organic aerosol concentration. Aerosol particle size distributions show a strong decrease in the Aitken nuclei mode (10–100 nm) during the transport from T2 to T3, in particular above 30 nm, as a result of efficient coagulation processes into larger particles. A decrease of 30% in the particle number concentration and an increase of about 50 nm in geometric mean diameter were observed from T2 to T3 sites. The study of the evolution of aerosol properties downwind of the city of Manaus improves our understanding of how coupling of anthropogenic and biogenic sources may be impacting the sensitive Amazonian atmosphere. © 2018 The Authors

An array of spectral aerosol extinction coefficients is calculated from measurements of the spectral transparency of the atmosphere on a 1 km long horizontal path in 10 regions of the wavelength range 0.5 – 4 μm. An array of angular dependences of the aerosol scattering coefficients in the angular range 1.2 – 15° is obtained by means of an aureole photometer with closed scattering volume. Measurements were carried out under conditions of smoky atmosphere. Inverse problem was solved for two empirical data arrays obtained synchronously (200 realizations) and the aerosol particle cross section size distributions were calculated. It is shown that the results of two experiments are in quite good agreement in the particle size range from 0.18 to 1.8 μm. Objective. Determination of the aerosol particle size range, in which the results of aerosol monitoring by two instrumentation complexes are most representative. Method for solving the problem. The inverse problem was solved for two empirical data arrays: a) spectral aerosol extinction coefficients β ext (λ) in the wavelength range 0.5 – 3.9 μm; b) angular dependences of the aerosol scattering coefficients β sct (φ) in the angular range Φ = 1.2 – 15° at the wavelength of 650 nm. The arrays β ext (λ) and β sct (φ) were obtained in synchronous measurements by means of two independent instrumentation complexes [1,2]. In order to obtain the aerosol particle cross-section size distribution dS/dr, the inverse problem was solved using the algorithms [3-5]. The spectral dependence of the optical constants of aerosol particles was determined from the empirical data [6, 7]. Finally, two arrays of distributions dS/dr corresponding to the initial experiments data β ext (λ) and β sct (φ) were calculated.

We introduce the path length probability density function (PPDF) method, which is based on an equivalence theorem and parameterizes the aerosol scattering effect by adding four factors to the atmospheric transmittance model. Using simulated observations in the O2-A band, we examined the utility of the PPDF-based method to account for the aerosol scattering effect. First, observations were simulated using a forward model under different aerosol conditions; PPDF factors were then retrieved using an optimal estimation method; PPDF factors were used to reconstruct the observations; and finally, simulated true observations and reconstructions were compared. Analysis of the difference between the true observations and reconstructions confirmed the utility of the PPDF-based method. Additionally, the O2 band was demonstrated to be an efficient observing band for assisting the remote sensing of atmospheric trace gases in the near-infrared band.

Continuous real-time measurements of aerosol scattering properties were investigated at Anantapur (14° 62′ N, 77° 65′ E, 331 m asl), a semi-arid region in southern India for the period of January 2011–December 2011, using a three-wavelength Integrating Nephelometer. Aerosols scattering properties like the scattering coefficient (σsp), backscattering coefficient (σbsp), scattering Angstrom exponent (A), backscattering ratio (bλ) and asymmetry parameter (gλ) were measured for the period of study. The average values of (±standard deviation) σsp, σbsp at 550 nm ( σ sp 550 , σ bsp 550 ) and A(700/450) were found to be 97 (±9.2) M m−1 and 14 (±0.93) M m−1 and 1.02 (±0.3), respectively. The estimated average values of bλ and gλ at 550 nm from σ sp 550 and σ bsp 550 were 0.13 (±0.09) and 0.59 (±0.1), respectively. The maximum asymmetry parameter at 550 nm was found to be 0.63 ± 0.01 in the month of October and minimum (0.52 ± 0.03) during March, which shows the opposite trend with backscattering ratio. Significant correlation coefficients were noticed between different aerosol optical properties. The highest values of σ sp 550 were observed during weekdays whereas low values during weekends. Scattering Angstrom exponent for the summer and winter seasons has been consistent with the input of fine mode particles from anthropogenic origin.

This paper describes aerosol optical and physical properties and the corresponding meteorological analysis during a winter-time fine aerosol event at a regional background station, Gosan, in Korea. Spatio-temporal distributions of air pollutants over Northeast Asia during winter are governed by continental outflows; however, winter is the highest in magnitude (9.5 ± 8.7 Mm−1) of aerosol absorption coefficient (σa) among other seasons and the second highest in magnitude (105.3 ± 104.8 Mm−1) of aerosol scattering coefficient (σs) after spring at the Gosan site. Values for σs and σa at Gosan during the winter polluted period (WPP; January 3 to 10, 2008) were recorded as 238.97 ± 123.85 and 18.42 ± 8.49 Mm−1, respectively, which were approximately 5 times greater than those during the winter clean period (WCP; January 13 to 16, 2008) of this study. An ensemble analysis of the OMI aerosol index, wind vectors and background trajectories during the WPP reveals that a slow-moving anticyclonic system, preceded by a frontal system, brought heavy aerosol loading from the Asian continent to the Gosan site. Space-based lidar CALIOP observations support the presence of heavy loadings of aerosol and pollutant plumes over the Yellow sea, before arriving at the Gosan.

Daily PM 2.5 samples were collected in Guangzhou — the largest megacity in South China, for a period of one month in each season during 2009–2010. Mass concentrations of water-soluble inorganic ions, organic carbon (OC) and elemental carbon (EC) in PM 2.5 were determined, and aerosol scattering coefficient (b sp ) was synchronously measured. The daily PM 2.5 mass concentrations ranged from 21.0 to 213.6 μg m − 3 with an annual average of 76.8 ± 41.5 μg m − 3 . The highest seasonal average PM 2.5 was observed in winter (103.3 ± 50.1 μg m − 3 ) and the lowest in summer (38.6 ± 15.7 μg m − 3 ). Annual average PM 2.5 mass scattering efficiency (MSE) was 3.5 ± 0.9 m 2 g − 1 , with obvious seasonal variations in sequence of autumn (4.5 ± 0.2 m 2 g − 1 ) > winter (3.9 ± 0.5 m 2 g − 1 ) > spring (3.0 ± 0.4 m 2 g − 1 ) > summer (2.3 ± 0.3 m 2 g − 1 ). To determine the relationship between b sp and the chemical components of PM 2.5 , b sp was reconstructed in each season using the original IMPROVE formula with a modification of including sea salt aerosols. The estimated b sp using this method was 22 ± 28% smaller on annual average compared to the measurements. Multiple linear regression of measured b sp against (NH 4 ) 2 SO 4 , NH 4 NO 3 , OM (Organic Mass), SS (Sea Salt), FS (Fine Soil), and CM (Coarse Mass) were also performed in all the four seasons. The estimated b sp from using the regression equation was 4 ± 12% larger than the measured values. On average, (NH 4 ) 2 SO 4 , NH 4 NO 3 , OM, SS, FS and CM accounted for 50 ± 11%, 18 ± 10%, 19 ± 5%, 5 ± 4%, 3 ± 2% and 5 ± 6%, respectively, of the estimated b sp .

Lidar observations in Tomsk in January, 2010, recorded pronounced peaks of aerosol scattering in the stratosphere at heights from 14 to 24 km. Back trajectory calculations of air mass transport to Tomsk showed that enhanced aerosol scattering was directly associated with the cooling of air masses 6–12 h before their occurrence over Tomsk below temperature thresholds for polar stratospheric cloud formation. The back trajectory calculations showed that the polar stratospheric clouds recorded in Tomsk at heights of 16–24 km could have been formed over the Scandinavian mountains, and clouds at heights of 11–14 km could have been formed over the mountain ridges of the Polar Ural Mountains and Novaya Zemlya Archipelago. The presence of synoptic-scale stratospheric aerosol in these regions in January, 2010, was confirmed by data from the CALIOP satellite lidar.

Aerosol scattering characteristic is very important for atmospheric radiation and climate research.In order to study the aerosol particles scattering properties in different relative humidity,we firstly got the humidity polarization model based on the Mie scattering theory,then compared and analyzed the polarization properties of single particle and particle cluster of three aerosols in different humidity conditions.The results show that relative humidity have regularity impact on the polarization properties of aerosol particles,especially in the area between 120° to 150°.It means that the scattering light polarization degree of some backward scattering angel can effectively reflect the relative humidity's change of aerosol particles.

Aerosol optical properties were continuously measured at an urban site in Shanghai of China from December 2010 to March 2011, and aerosol scattering (σscat) and absorption (σabs) coefficients and single scattering albedo (SSA) were examined. During the entire period, mean σscat, σabs, SSA were 293 Mm− 1, 66 Mm− 1 and 0.81, respectively. Higher σscat and σabs occurred in December while relatively lower values were observed in March, and SSA was just opposite to them. σscat and σabs coefficients behaved an apparent bi-peak pattern in diurnal variation: maxima of 319, 76 Mm− 1 at 8:00 LT during traffic rush hours and sub-maxima of 280, 71 Mm− 1 at 20:00 LT. SSA also behaved a bi-peak diurnal cycle with maximum 0.85 at 13:00 LT and sub-maximum 0.82 at 4:00 LT. σscat and σabs coefficients showed a clear negative correlation with atmospheric visibility. PM2.5 and black carbon were major contributors to large optical parameters because their concentrations were 2 times higher during haze episode than in clean days. σscat and σabs were low in magnitude when northeasterly winds bring “clean” air from the China Yellow Sea arriving the observation site, and were relatively high when air masses from the north or northwest pass through continental areas or/and industrial regions, indicating impacts of various aerosol origins on aerosol optical properties.

The seasonal variations of the concentration of particles of different sizes in the atmospheric surface layer are studied on the basis of the data of daily measurements of atmospheric aerosol characteristics in the town of Dolgoprudny (20 km from the center of Moscow) carried out in 2006–2009. It is revealed that the steady variations of monthly mean aerosol concentration are observed within the particle diameter interval of 0.02–1 μm. The annual course of concentration of these particles has two maxima, in February-March and in September–October, and one minimum in June. The concentrations of particles with the size of 0.01–0.02 μm defined by the general atmospheric background and the concentrations of particles of >1 μm associated with the local sources do not have clearly pronounced seasonal variations. It is shown that the regularities of the annual concentration variations of particles with the size of 0.02–1 μm are mainly explained by the sign and value of the lapse rate in the layer up to 925 hPa that indicates the prevalence of the vertical mixing in the processes of aerosol scattering in the surface layer as compared with the horizontal transfer.

In this paper we present an approach to retrieve stratospheric aerosol number densities in the altitude range 10–40 km from SCIAMACHY limb radiance measurements in the spectral range of the O2 A absorption band, near 760 nm. Here, the characteristic light paths differ for the measured light in the O2 A-band and in the spectral continuum next to the absorption band. This difference is used to distinguish the effect of stratospheric aerosol scattering and ground reflection on the limb measurement. The capability to disentangle both effects is illustrated for SCIAMACHY limb observations over the Libyan desert, where the measurements are not affected by tropospheric clouds. Comparison of the SCIAMACHY retrieval and the SAGE II aerosol extinction product between 75° southern and northern latitude shows the clear need for prior knowledge of the mean size of the stratospheric aerosol for the SCIAMACHY retrieval. We found best agreement between SCIAMACHY and SAGE II aerosol extinction for the period 2003–2005 for a prior choice of the mean aerosol size radius of 0.2 μm. The overall agreement between both data sets is in the range

Atmospheric turbulence and aerosol scattering can produce the blurring of the remotely sensed image. The degrading effect is usually quantified by atmospheric modulation transfer function (MTF). However, this effect behaves differently with different remote sensors. The effort of this article is to study the different degrading effects of aerosol MTF and turbulence MTF between charge-coupled device (CCD) camera on China–Brazil Earth Resources Satellite-02b (CBERS-02b) and on Huan Jing-1A/1B satellite (HJ-1A/1B). Specifically, a corrected aerosol MTF model is established based on classical solution of small-angle approximation (SAA) model by considering the MTF and the effective instantaneous field of view (EIFOV) of CCD cameras. By assuming many different atmospheric conditions, the aerosol MTF and turbulence MTF for two CCD cameras are evaluated. It is found that the output aerosol MTF of CCD camera on HJ-1A/1B causes more degrading effect than that of CBERS-02b under the same atmospheric condition. Howe...

Aerosol scattering properties, near the surface (at about 10 m height), were measured during a period of seven years (2002–2008) at Évora, Portugal. The average (and median) scattering and backscattering coefficients, at the wavelength of 550 nm, were found to be 42.5 Mm−1 (29.9 Mm−1) and 5.9 Mm−1 (4.4 Mm−1), respectively. Also, the average and median scattering Ångström exponent (1.4 and 1.5) indicate that scattering was, in general, dominated by sub-micrometer particles. Both seasonal and daily cycles are shown, which were related to local production and transport of particles from elsewhere. Summer and winter average values of the scattering coefficient, at the wavelength of 550 nm (47 and 54 Mm−1, respectively), correspond to a significant increase in the aerosol particle concentration when compared with spring and fall (35 and 37 Mm−1, respectively). Also, the average increase in the Ångström exponent for summer and winter seasons is consistent with the input of sub-micrometer particles from anthropogenic origin in winter and forest fires in summer. Back-trajectory analysis indicated that the site was regularly under the influence of air masses from the Atlantic area, with low particle loads (low scattering coefficients), but as the influence of transport from the continent (Iberia Peninsula) increased, the aerosol particle load was observed to increase as well as the relative importance of fine particles over coarse ones, approaching the features observed at the site during European air masses influence.

A humidity controlled inlet system was developed to measure the hygroscopic growth of aerosol scattering coefficient in conjunction with nephelometry at an urban site of Chinese Academy of Meteorological Sciences (CAMS) in Beijing and a rural site at Shangdianzi Regional Background Air Pollution Monitoring Station (SDZ) outside Beijing during winter, from December 2005 to January 2006. Measurements were carried out at a wavelength of 525 nm with an Ecotech M9003 nephelometer. The hygroscopic growth function (or factor) of the aerosol scattering coefficient f (RH) increased continuously with increasing relative humidity (RH) and showed no obvious “step-like” deliquescent behavior at both sites during the experiment. The average growth factor f (RH) at the SDZ site could reach 1.5 when RH increased from less than 40% to 92%, and to 2.1 at the CAMS site when RH increased from less than 40% to 93%. The average hygroscopic growth factor at a relative humidity of 80%, f (RH = 80 ± 1%), was found to be about 1.26 ± 0.15 at CAMS and 1.24 ± 0.11 at SDZ. Further analysis indicated that under relatively polluted conditions, the average hygroscopic growth factor was higher at the CAMS site than that at the SDZ site. However, under relatively clean air conditions, the difference between the two sites was small, showing a hygroscopic growth behavior similar to those of burning biomass or blowing dust. These results reflected the different characteristics of aerosol types at the two sites.

The aerosol scattering properties were investigated at two continental sites in northern China in 2004. Aerosol light scattering coefficient (σsp) at 525 nm, PM10, and aerosol mass scattering efficiencies (α) at Dunhuang had a mean value of 165.1±148.8 M m−1, 157.6±270.0 μg m−3, and 2.30±3.41 m2 g−1, respectively, while these values at Dongsheng were, respectively, 180.2±151.9 M m−1, 119.0±112.9 μg m−3, and 1.87±1.41 m2 g−1. There existed a seasonal variability of aerosol scattering properties. In spring, at Dunhuang PM10, σsp, and α were 184.1±211.548 μg m−3, 126.3±89.6 M m−1, and 1.05±0.97 m2 g−1, respectively, and these values at Dongsheng were 146.4±142.1 μg m−3, 183.4±81.7 M m−1, and 1.98±1.52 m2 g−1, respectively. However, in winter at Dunhuang PM10, σsp, and α were 158.1±261.4 μg m−3, 303.3±165.2 M m−1, and 3.17±1.93 m2 g−1, respectively, and these values at Dongsheng were 155.7±170.1 μg m−3, 304.4±158.1 M m−1, and 2.90±1.72 m2 g−1, respectively. σsp and α in winter were higher than that in spring at both the sites, which coincides with the characteristics of dust aerosol and pollution aerosol. Overall, the dominant aerosol types in spring and winter at both sites in northern China are dust aerosol and pollution aerosol, respectively.

The transparency of a molecular gaseous medium comprising spherical aerosol particles is calculated. The characteristics of the transformed radiant energy that has passed through particles with different microphysical properties are analyzed. It is established that the joint effect of the molecular absorption and aerosol scattering in the IR range must be considered. Based on the characteristics of scattering particles, the boundary conditions are written that allow the molecular absorption and scattering to be considered separately.

The possibility of determining the Black Carbon (BC) concentration and its size distribution in submicron aerosol from data of polarization spectronephelometric measurements of angular aerosol scattering is demonstrated for the first time. The data of simultaneous nephelometric and aethalometric measurements of BC concentration in wood smoke are compared. The inverse problem is solved from measurements of 40 polarization components of spectral coefficients of angular scattering, and aerosol filling factors and the imaginary part of the complex refractive indexes are determined for subfractions of ultrafine- (radii of 30-100 nm), fine- (100-430 nm), and coarse-disperse (430-770 nm) particles. Then the total BC concentration, its size distribution, and BC fraction are estimated in the approximation of homogeneous volume internal mixture of BC and nonabsorbing matter. The analysis shows that at the long evolution of smoke aerosol, nephelometric and aethalometric estimates of the BC concentrations are in a good agreement. The discrepancy averages about 16% for concentrations varying in a range 30-1000 μg/m 3 .

The Langley Mobile Ozone Lidar (LMOL) is a compact mobile differential absorption lidar (DIAL) system that was developed at NASA Langley Research Center, Hampton, VA, USA to provide ozone, aerosol and cloud atmospheric measurements in a mobile trailer for ground-based atmospheric air quality campaigns. This lidar is part of the Tropospheric Ozone Lidar Network (TOLNet) currently made up of six other ozone lidars across the U.S and Canada. This lidar has been deployed to Denver, CO July 15-August 15, 2014 for the DISCOVER-AQ air quality campaign. Ozone and aerosol profiles were taken showing the influence of emissions from the Denver region. Results of ozone concentration, aerosol scattering ratio, boundary layer height and clouds will be presented with emphasis on regional air quality.

Recent studies revealed layers of enhanced aerosol scattering in the upper troposphere and lower stratosphere over Asia (Asian Tropopause Aerosol Layer (ATAL)) and North America (North American Tropospheric Aerosol Layer (NATAL)). We use a sectional aerosol model (Community Aerosol and Radiation Model for Atmospheres (CARMA)) coupled with the Community Earth System Model version 1 (CESM1) to explore the composition and optical properties of these aerosol layers. The observed aerosol extinction enhancement is reproduced by CESM1/CARMA. Both model and observations indicate a strong gradient of the sulfur-to-carbon ratio from Europe to the Asia on constant pressure surfaces. We found that the ATAL is mostly composed of sulfates, surface-emitted organics, and secondary organics; the NATAL is mostly composed of sulfates and secondary organics. The model also suggests that emission increases in Asia between 2000 and 2010 led to an increase of aerosol optical depth of the ATAL by 0.002 on average which is consistent with observations. Key Points The Asian Tropopause Aerosol Layer is composed of sulfate, primary organics, and secondary organics The North American Tropospheric Aerosol Layer is mostly composed of sulfate and secondary organics Aerosol Optical Depth of Asian Tropopause Aerosol Layer increases by 0.002 from 2000 to 2010

An aerosol lidar system was deployed on the NASA DC-8 and used to measure aerosol vertical profiles in the California Central Valley. The nadir-pointing Nd:YAG lidar operated at 532 and 1064 nm at 20 Hz. The resulting aerosol profiles were plotted in a unique three-dimensional format that allowed the visual observation of the aerosol scattering ratio profiles, the valley topography, and corresponding backward trajectory air masses. The accumulation of aerosols from the Bakersfield area can be seen in the southern end of the valley due to topography and prevailing winds.

This work is devoted to studies of the influence of the molecular-aerosol coupling on the scalar approximation-based aerosol satellite remote sensing procedures in the ultraviolet-near-infrared spectral range. It was found that the coupling error must be accounted in the aerosol remote sensing problems based on the analysis of the backscattered ultraviolet light.

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.

The inversion of aerosol characteristics over DDV (Dark Dense Vegetation) targets is an intermediate and important step whenever atmospheric correction over land for the Envisat/MERIS instrument is performed. We present here the results of an error budget for every step of this inversion. We show that the crucial step is DDV selection based on a threshold on the ARVI (Atmospherically Resistant Vegetation Index). The cornerstone of this inversion is aerosol climatology, as aerosol scattering properties depend on the aerosol refractive index. Finally, we conclude that the major source of uncertainty is the imaginary part of the aerosol refractive index. This is critical as the atmospheric correction over land algorithm handles it with difficulty.

Chemical measurements of CO, O3, non-methane hydrocarbons, aerosol chemistry, and aerosol scattering in air masses arriving at the west coast of North America demonstrate that a variety of chemical species can be transported across the Pacific from the Eurasian continent. In this paper, we analyze data from several ground sites in the Pacific Northwest and from aircraft observations in the region to identify six ‘new’ (i.e. previously unreported) episodes of trans-Pacific transport that occurred between 1993 and 2001. Of the six new episodes identified, one consisted of mineral dust combined with industrial emissions, while the other five appeared to consist of predominantly industrial emissions. In addition to gas and aerosol measurements, we calculated the Angstrom exponent, an indicator of the aerosol size distribution, to help identify the aerosol characteristics in 4 of the cases considered. Combining these data with previous reports, we find that there is a high degree of variability in these trans-Pacific episodes. In four episodes there were significant O3 enhancement, with mixing ratios sometimes exceeding 80 ppbv . However, O3 was only enhanced in episodes that were transported in the free troposphere and in the absence of mineral dust. In other words, transport in the boundary layer or transport of industrial emissions with mineral dust seems to preclude any significant O3 enhancement. Clarifying such patterns increases our understanding of not only trans-Pacific transport of air pollutants, but also intercontinental transport in general.

This paper focuses on the assessment of atmospheric aerosol optical properties at the surface and in atmospheric column during both desert dust and dust-free conditions over Granada, South-eastern Iberian Peninsula. Indeed, the spectral dependence of aerosol absorption and scattering properties are analyzed in detail. The analyzed period ranges from June 2008 to December 2010. On dusty days, the mean scattering Angström exponent value obtained in the atmospheric column (SAEcol) (0.5±0.3) was lower than the observed at the surface level (SAEis) (1.3±0.6), indicating higher contribution of coarse particles at high atmospheric level than at ground level during the analyzed dust events. In addition, it is noticed that the absorption Angström exponent in the atmospheric column (AAEcol) with mean value of 1.5±0.2 and at the surface (AAEis) with mean value of 1.3±0.2 obtained during dusty situations are indicative of mixture of desert dust and black carbon particles as dominant absorbers both in the atmospheric column and at the surface during dust intrusions over Granada. On the other hand, a non-parametric test (Kolmogorov-Smirnov) revealed that no significant statistical difference was found for AAEis between desert dust and free-dust conditions. This result may be due to the important contribution of urban absorbing aerosol (e.g. Black carbon) at ground level in the study location. Therefore, these parameters (AAEcol and AAEis) are not very useful to detect desert dust events without the use of other information (e.g., aerosol size) over urban area like Granada.A dust extreme event was analyzed in order to retrieve optical parameters during situation dominated by desert dust. The values of SAEcol and SAEis obtained during this extreme event were in agreement with the values showed above for the period 2008-2010, although the differences between dust-free and dust conditions are more noticeable in this special event Aerosol scattering and absorption Angström exponent as indicators of dust and dust-free days over Granada (Spain)., This work was supported by the Andalusia Regional Government through projects P12-RNM-2409 and P10-RNM-6299, by the Spanish Ministry of Science and Technology through projects CGL2010-18782, CSD2007-00067, CGL2011-29921-C02-01 and CGL2011-13580-E/CLI., Manuel Antón thanks the Ministerio de Ciencia e Innovación and Fondo Social Europeo for the award of a postdoctoral grant (Ramón y Cajal)., CIMEL Calibration was performed at the AERONET-EUROPE calibration center, supported by ACTRIS (European Union Seventh Framework Program (FP7/2007-2013) under grant agreement no. 262254.

Aerosol optical properties measured over several years at surface monitoring stations located at Bondville, Illinois (BND); Lamont, Oklahoma (SGP); Sable Island, Nova Scotia (WSA); and Barrow, Alaska (BRW), have been analyzed to determine the importance of the variability in aerosol optical properties to direct aerosol radiative forcing calculations. The amount of aerosol present is of primary importance and the aerosol optical properties are of secondary importance to direct aerosol radiative forcing calculations. The mean aerosol light absorption coefficient (σap) is 10 times larger and the mean aerosol scattering coefficient (σsp) is 5 times larger at the anthropogenically influenced site at BND than at BRW. The aerosol optical properties of single scattering albedo (ωo) and hemispheric backscatter fraction (b) have variability of approximately ± 3% and ± 8%, respectively, in mean values among the four stations. To assess the importance of the variability in ωo and b on top of the atmosphere a...

Different views of the significance of aerosol MTF have been reported. For example, one recent paper [OE, 52(4)/2013, pp. 046201] claims that the aerosol MTF "contrast reduction is approximately independent of spatial frequency, and image blur is practically negligible". On the other hand, another recent paper [JOSA A, 11/2013, pp. 2244-2252] claims that aerosols "can have a non-negligible effect on the atmospheric point spread function". We present clear experimental evidence of common significant aerosol blur and evidence that aerosol contrast reduction can be extremely significant. In the IR, it is more appropriate to refer to such phenomena as aerosol-absorption MTF. The role of imaging system instrumentation on such MTF is addressed too.

Size-resolved particle composition, mass and number concentrations, aerosol scattering coefficients, and prevailing meteorological conditions were measured at the Ellen Browning Scripps Memorial Pier located in La Jolla, California on 15 December 1998. Aerosol particles were sampled using a field transportable aerosol time-of-flight mass spectrometer, allowing for the continuous detection and characterization of single particles from a polydisperse sample. An extensive and rapid change in the chemical composition of aerosol particles with aerodynamic diameters between 1.0 and 2.5 μm has been observed during the onset of a Santa Ana Winds condition. Coincident with the observed change in meteorological conditions, a substantial decrease in sea salt particles corresponds to an increase in dust and carbon-containing particles. This paper examines observations of the rapid changes occurring in the chemical composition of single aerosol particles and demonstrates the new types of information that can be obtained by measuring single particle size and composition with high temporal resolution.

In this paper the atmospheric correction algorithms for two ocean color sensors, CZCS and SeaWiFS, were analyzed. Based upon the analysis, the 6S model was used to study the relationship between ρas( λ) and ρa(λ)+ρra(λ) and to develop a new e function. The new e3(λ, 865) function considered the aerosol scattering effect and the interaction between aerosols and atmospheric molecules as a whole. Using the e3(λ865) instead of the original SeaWiFS defined e(λ, 865) could avoid the converting between ρas(λ) and ρa(λ)+ρra(λ) and help to simplify the atmospheric correction algorithm to a great extent.

When measuring the aerosol scattering coefficient (ASC) with an integrating nephelometer, the instrumental “zero” value is established by passing filtered, particle-free air (zero air) through the instrument and setting the instrumental analog signal to zero. Ideally, the computer logged analog value of the zero air should also be zero. However, more commonly a non-zero analog value (zero offset) is obtained. This zero offset is normally regarded as a “blank” and the value is subtracted from the data values. During a one-month field experiment where we measured ASC, we consistently obtained a zero offset that ranged from 4 to 25 mV (equivalent to ASC values of 0.8 to 5×10-6 m-1). In this paper, we demonstrate that the zero offset we observed is in reality a threshold to the recorded analog data and that it should not be subtracted from the data record. Treating the zero offset as a blank could lead to an error in ASC data of as high as 21%. The zero offset observed in our experiment was not produced by the nephelometer. Rather, it was generated during the transmission of the analog signal from the instrument to an analog-to-digital converter. Thus, our results should serve as a caution for those who perform ASC or other measurements using analog data transmission.

The detected radiance of Channels 1 (0.58–0.68 μm) and 2 (0.725–1.10 μm) of the Advanced Very High Resolution Radiometer (AVHRR) on the NOAA‐14 polar‐orbiting satellite was used for the remote sensing of optical depth over South China Sea. Two aerosol scattering phase functions were used to retrieve the optical depth of the aerosols. One is the marine aerosol model by Shettle (Shettle et al. 1979) and the other is the two‐term Henyey‐Greenstein model (Durkee et al. 1991). In our computation, Channel 4 (10.5–11.3 μm) data were used for cloud test. The change in the optical depth over South China Sea are presented in this paper and the wind field images form NOAA‐14 are used to explain the possible meteorology‐induced changes.

During Diwali festival, extensive burning of crackers and fireworks is made. Weeklong intensive observational campaign for aerosol study was carried out at a representative urban location in the eastern Indo-Gangetic Plain (IGP), Varanasi (25.3°N, 83.0°E), from October 29 to November 04, 2005 (Diwali on November 01, 2005), to investigate behavioral change of aerosol properties and radiative forcing between firework affected and nonaffected periods. Results show a substantial increase (~27%) in aerosol optical depth, aerosol absorption coefficients, and aerosol scattering coefficients during affected period as compared to non-affected periods. Magnitudes of radiative forcing at top of atmosphere during affected and non-affected periods are found to be +10 ± 1 and +12 ± 1 Wm−2, respectively, which are −31 ± 7 and −17 ± 5 Wm−2, respectively, at surface. It suggests an additional cooling of ~20% at top of atmosphere, ~45% cooling at surface, and additional atmospheric heating of 0.23 Kday−1during fireworks affected period, which is ~30% higher than the non-affected period average.

This paper reports on the results of aircraft lidar studies of aerosol in the free troposphere in the Arctic and middle latitudes of Siberia in the summer of 1993. In the course of these studies, measurements were made of aerosol scattering and depolarization coefficients which characterize its optical thickness and phase state, as well as aerosol spatial distribution. Through analyzing the results obtained it has been established that tropospheric aerosol has a fine-cell and stratified structure. Its volume scattering and depolarization coefficients are within the limits of σ = (0.88−84) × 10−5 m−1 and δ = 0.01−0.15, respectively. The values of these parameters largely depend on atmospheric pollution, the geographical position of measurement sites in relation to industrial regions, and weather situation, particularly, air parcels transport direction and temperature distribution. In sub-inversion layers, and values are considerably higher than in the adjacent ones. The mean values of the scattering and depolarization coefficients obtained in these studies differ but insignificantly from those obtained in the same regions by other researchers.

Aerosol light scattering coefficients, the hemispheric σsp and the back-scattering coefficient σbsc, have been measured using a 3-wavelengths integrating nephelometer over two years (January 2006 to May 2008) at the monitoring station ESAT-El Arenosillo. This station is located in the coastal area of the province of Huelva, in the southwest of the Iberian, Peninsula. The Angstrom exponent α, has been also derived from the spectral dependence of σsp. All these parameters have been carefully analyzed to investigate their general characteristics and features, and diurnal variability. A general statistic gives mean values and std of σsp = 48.5 ±38.1 Mm−1 with a large range of variation showing moderate values of this rural and coastal site with marine prevalence but with significant influence of local sources of pollution. The daily cycle of σsp and α presents different behaviour depending on the season and is modulated by sea-land breeze regime.