Columnar Aerosol Research Articles

Global trends of columnar and vertically distributed properties of aerosols with emphasis on dust, polluted dust and smoke - inferences from 10-year long CALIOP observations

In this paper, the decadal datasets available from the space-borne lidar, Cloud Aerosol Lidar with Orthogonal Polarization (CALIOP) onboard Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) are analyzed in order to understand the spatial and vertical distributions of aerosols at a global scale. Decadal (September 2006–August 2016) Level 3 night time Standard All-sky data products, created using quality controlled Level 2 datasets are utilized in the study. Columnar aerosol properties are discussed in conjugation with vertical properties of the three major aerosol types i.e. dust, polluted dust and smoke. It is found that the global mean aerosol optical depth (AOD) amounts to 0.10, with AOD values of 0.13 and 0.09 for land and ocean respectively, during the last decade. Mean aerosol extinction coefficients are also reported for four altitude bins i.e. 0–1 km, 1–2 km, 2–3 km and 3–4 km above mean sea level (a.m.s.l.). It is observed that dust and smoke particles have stronger vertical transport compared to polluted dust particles, which are generally found to be confined within the lower altitudes. In order to observe the changes in aerosol loading over different parts of the globe, de-seasonalized trends of AOD and vertical extinction coefficients are computed using linear regression technique. Globally, the total columnar particle load shows a significant negative trend during the last decade. In particular, trends of total particle loading (AOD and extinction) are decreasing over North America, South America, East China and Australia. However, the smoke emissions (columnar and vertically distributed) have increased over India, Russia, North America, Australia and Central Africa. This is of concern in the context of rising temperatures accompanied with increasing wildfires throughout the globe. Additionally, enhanced levels of polluted dust over the developing regions of Africa and Asia are also revealed.

Long-term aerosol climatology over Indo-Gangetic Plain: Trend, prediction and potential source fields

Long-term aerosol climatology is derived using Terra MODIS (Collection 6) enhanced Deep Blue (DB) AOD retrieval algorithm to investigate decadal trend (2006–2015) in columnar aerosol loading, future scenarios and potential source fields over the Indo-Gangetic Plain (IGP), South Asia. Satellite based aerosol climatology was analyzed in two contexts: for the entire IGP considering area weighted mean AOD and for nine individual stations located at upper (Karachi, Multan, Lahore), central (Delhi, Kanpur, Varanasi, Patna) and lower IGP (Kolkata, Dhaka). A comparatively high aerosol loading (AOD: 0.50 ± 0.25) was evident over IGP with a statistically insignificant increasing trend of 0.002 year−1. Analysis highlights the existing spatial and temporal gradients in aerosol loading with stations over central IGP like Varanasi (decadal mean AOD±SD; 0.67 ± 0.28) and Patna (0.65 ± 0.30) exhibit the highest AOD, followed by stations over lower IGP (Kolkata: 0.58 ± 0.21; Dhaka: 0.60 ± 0.24), with a statistically significant increasing trend (0.0174–0.0206 year−1). In contrast, stations over upper IGP reveal a comparatively low aerosol loading, having an insignificant increasing trend. Variation in AOD across IGP is found to be mainly influenced by seasonality and topography. A distinct “aerosol pool” region over eastern part of Ganges plain is identified, where meteorology, topography, and aerosol sources favor the persistence of airborne particulates. A strong seasonality in aerosol loading and types is also witnessed, with high AOD and dominance of fine particulates over central to lower IGP, especially during post-monsoon and winter. The time series analyses by autoregressive integrated moving average (ARIMA) indicate contrasting patterns in randomness of AOD over individual stations with better performance especially over central IGP. Concentration weighted trajectory analyses identify the crucial contributions of western dry regions and partial contributions from central Highlands and north-eastern India, in regulating AOD over stations across IGP. Although our analyses provide some attributes to the observed changes in aerosol loading, we conclude that the spatial and temporal pattern of aerosol properties is highly complex and dynamic over IGP, and require further investigation in order to reduce uncertainty in aerosol-climate model.

Assessment of column aerosol optical properties using ground-based sun-photometer at urban Harbin, Northeast China

Aerosol plays a key role in determining radiative balance, regional climate and human health. Severe air pollution over Northeast China in recent years urges more comprehensive studies to figure out the adverse effects caused by excessive aerosols. In this study, column aerosol measurements over urban Harbin, a metropolis located at the highest latitude in Northeast China, during May 2016 to March 2017 were conducted using a CIMEL sun-photometer to analyze local aerosol properties and its variation from different aspects. According to the observations, aerosol optical depth at 440nm (AOD440) ranges from 0.07 up to 1.54, and the large variability in both AOD440 and Angstrom Exponent (AE440–870) indicates the frequent change of aerosol types due of different emission sources. Coarse mode particles dominated Harbin during the studying period because of the long-range transported dust and probably the suspended snow crystals in winter. As the wavelength increases, relatively consistent decrease trends of single scattering albedo (SSA) and asymmetry factor (ASY) were observed in spring, autumn, and winter, indicating the presence of absorbing polluted aerosols. Mixed type (MIX) aerosol dominated the study region with a total percentage of 34%, and biomass burning and urban industry (BB/UI), clean continental (CC), and desert dust (DD) aerosols were found to be 31%, 27%, and 8%, respectively. The current work fills up the optical characteristics of aerosols in Harbin, and will contribute to the in-depth understanding of local aerosol variation and regional climate change over Northeast China.

Light-absorbing aerosol properties retrieved from the sunphotometer observation over the Yangtze River Delta, China.

In this study, aerosol optical depth (AOD) and extinction Ångström exponent (EAE) are derived from ground-based sunphotometer observations between 2007 and 2014 at urban sites of Nanjing over the Yangtze River Delta. In addition, the present study aims to investigate aerosol light-absorbing properties such as single-scattering albedo (SSA), absorption Ångström exponent (AAE), and the aerosol-absorbing optical depth (AAOD). The retrieval of aerosol properties is compared with AERONET inversion products. The results demonstrate that the retrieved AOD has a good agreement with the AERONET Level 1.5 data, with the root mean square error being 0.068, 0.065, and 0.026 for total, fine mode, and coarse mode at 440nm, respectively. The SSA values indicate similar accuracies in the results, which are about 0.003, -0.009, -0.008, and 0.010 different from AERONET at 440, 670, 870, and 1020nm, respectively. The occurrence frequency of background level AOD (AOD<0.10) at 440nm in this region is limited (1%). Monthly mean AOD, SSA, the effective radius (Reff), and the volume concentration at 440nm were 0.6-1.3, 0.85-0.92, 0.24-0.40μm, and 0.18-0.28 μm3 μm-2, respectively. The mean value of AAOD at 440nm (AAOD440) was the highest in both summer (0.095±0.041) and autumn (0.094±0.042), but was the lowest in winter (0.079±0.036). It was also noted that SSA was found to be higher during summer (0.89±0.05). The spectral variation of SSA was observed to be strongly wavelength-dependent during all seasons. The seasonal mean AAE440-870 is the highest in winter (0.86±0.41) and lowest in spring (0.49±0.29). In winter, the cumulative frequency for AAE between 1.0 and 1.2 was about 87%. The peak in the AAE distribution was close to 1.0, indicating that the aerosol column was dominated by urban-industrial aerosols and absorption species other than black carbon. Analysis of the relationship between EAE and SSA showed that the aerosol populations could be classified as "mixed" aerosol, including a mixture of both anthropogenic particles and secondary organic aerosol with highly variable sphericity fraction.

The optical properties, physical properties and direct radiative forcing of urban columnar aerosols in the Yangtze River Delta, China

Abstract. The optical and physical properties as well as the direct radiative forcings (DRFs) of fractionated aerosols in the urban area of the western Yangtze River Delta (YRD) are investigated with measurements from a Cimel sun photometer combined with a radiation transfer model. Ground-based observations of aerosols have much higher temporal resolutions than satellite retrievals. An initial analysis reveals the characteristics of the optical properties of different types of fractionated aerosols in the western YRD. The total aerosols, mostly composed of scattering components (93.8 %), have mean optical depths of 0.65 at 550 nm and refractive index of 1.44 + 0.0084i at 440 nm. The fine aerosols are approximately four times more abundant and have very different compositions from coarse aerosols. The absorbing components account for only ∼ 4.6 % of fine aerosols and 15.5 % of coarse aerosols and have smaller sizes than the scattering aerosols within the same mode. Therefore, fine particles have stronger scattering than coarse ones, simultaneously reflecting the different size distributions between the absorbing and scattering aerosols. The relationships among the optical properties quantify the aerosol mixing and imply that approximately 15 and 27.5 % of the total occurrences result in dust- and black-carbon-dominating mixing aerosols, respectively, in the western YRD. Unlike the optical properties, the size distributions of aerosols in the western YRD are similar to those found at other sites over eastern China on a climatological scale, peaking at radii of 0.148 and 2.94 µm. However, further analysis reveals that the coarse-dominated particles can also lead to severe haze pollution over the YRD. Observation-based estimations indicate that both fine and coarse aerosols in the western YRD exert negative DRFs, and this is especially true for fine aerosols (−11.17 W m−2 at the top of atmosphere, TOA). A higher absorption fraction leads directly to the negative DRF being further offset for coarse aerosols (−0.33 W m−2) at the TOA. Similarly, the coarse-mode DRF contributes to only 13.3 % of the total scattering aerosols but &gt; 33.7 % to the total absorbing aerosols. A sensitivity analysis states that aerosol DRFs are not highly sensitive to their profiles in clear-sky conditions. Most of the aerosol properties and DRFs have substantial seasonality in the western YRD. The results further reveal the contributions of each component of the different size particles to the total aerosol optical depths (AODs) and DRFs. Additionally, these results can be used to improve aerosol modelling performance and the modelling of aerosol effects in the eastern regions of China.

EarthCARE Aerosol and Cloud Layer and Column Products

We introduce the development of EarthCARE Level 2 layer products derived from profile measurements of the high-spectral-resolution lidar ATLID and column products obtained from combined information of ATLID and the Multi-Spectral Imager (MSI). Layer products include cloud top height as well as aerosol layer boundaries and mean optical properties along the satellite nadir track. Synergistic column products comprise cloud top height, Ångström exponent, and aerosol type both along-track and across the MSI swath.

Aerosol characterization from active and passive ground measurements and satellite data

One year records of AErosolROboticNEtwork (AERONET) sun photometer measurements were analyzed to investigate the seasonal and daily variations of columnar aerosol optical depth. Some irregularities of this time series are associated with aerosol intrusions. The aerosol layers indicated by these irregularities are identified and characterized using the extensive optical data from coincident CALIPSO satellite observations and ground based LIDAR.

Effect of Heat Wave Conditions on Aerosol Optical Properties Derived from Satellite and Ground-Based Remote Sensing over Poland

During an exceptionally warm September in 2016, unique and stable weather conditions contributed to a heat wave over Poland, allowing for observations of aerosol optical properties, using a variety of ground-based and satellite remote sensors. The data set collected during 11–16 September 2016 was analysed in terms of aerosol transport (HYbrid Single-Particle Lagrangian Integrated Trajectory model (HYSPLIT)), aerosol load model simulations (Copernicus Atmosphere Monitoring Service (CAMS), Navy Aerosol Analysis and Prediction System (NAAPS), Global Environmental Multiscale-Air Quality (GEM-AQ), columnar aerosol load measured at ground level (Aerosol Robotic NETwork (AERONET), Polish Aerosol Research Network (PolandAOD)) and from satellites (Spinning Enhanced Visible and Infrared Imager (SEVIRI), Moderate Resolution Imaging Spectroradiometer (MODIS)), as well as with 24/7 PollyXT Raman Lidar observations at the European Aerosol Research Lidar Network (EARLINET) site in Warsaw. Analyses revealed a single day of a relatively clean background aerosol related to an Arctic air-mass inflow, surrounded by a few days with a well increased aerosol load of differing origin: pollution transported from Germany and biomass burning from Ukraine. Such conditions proved excellent to test developed-in-house algorithms designed for near real-time aerosol optical depth (AOD) derivation from the SEVIRI sensor. The SEVIRI AOD maps derived over the territory of Poland, with an exceptionally high resolution (every 15 min; 5.5 × 5.5 km2), revealed on an hourly scale, very low aerosol variability due to heat wave conditions. Comparisons of SEVIRI with NAAPS and CAMS AOD maps show strong qualitative similarities; however, NAAPS underestimates AOD and CAMS tends to underestimate it on relatively clean days (&lt;0.2), and overestimate it for a high aerosol load (&gt;0.4). A slight underestimation of the SEVIRI AOD is reported for pixel-to-column comparisons with AODs of several radiometers (AERONET, PolandAOD) and Lidar (EARLINET) with high correlation coefficients (r2 of 0.8–0.91) and low root-mean-square error (RMSE of 0.03–0.05). A heat wave driven increase of the boundary layer height of 10% is accompanied with the AOD increase of 8–12% for an urban site dominated by anthropogenic pollution. Contrary trend, with an AOD decrease of around 4% for a rural site dominated by a long-range transported biomass burning aerosol is reported. There is a positive feedback of heat wave conditions on local and transported pollution and an extenuating effect on transported biomass burning aerosol. The daytime mean SEVIRI PM2.5 converted from the SEVIRI AODs at a pixel representative for Warsaw is in agreement with the daily mean PM2.5 surface measurements, whereby SEVIRI PM2.5 and Lidar-derived Ångström exponent are anti-correlated.

Toward understanding atmospheric physics impacting the relationship between columnar aerosol optical depth and near-surface PM2.5 mass concentrations in Nevada and California, U.S.A., during 2013

Determining the relationship between columnar aerosol optical depth (τext) and surface particulate matter concentrations (PM2.5) is desired to estimate surface aerosol concentrations over broad spatial and temporal scales using satellite remote sensing. However, remote sensing studies incur challenges when surface aerosol pollution (i.e. PM2.5) is not correlated with columnar conditions (i.e., τext). PM2.5 data fusion models that rely on satellite data and statistical relationships of τext and PM2.5 may not be able to capture the physical conditions impacting the relationships that cause columnar and surface aerosols to not be correlated in the western U.S. Therefore, an extensive examination of the atmospheric conditions is required to improve surface estimates of PM2.5 that rely on columnar aerosol measurements. This investigation uses datasets from both routine monitoring networks and models of meteorological variables and aerosol physical parameters to understand the atmospheric conditions under which surface aerosol pollution can be explained by column measurements in California and Nevada during 2013. A novel quadrant method, that utilizes statistical analysis, was developed to investigate the relationship between τext and PM2.5. The results from this investigation show that τext and PM2.5 had a positive association (τext and PM2.5 increase together) when local sources of pollution or wildfires dominated aerosol pollution in the presence of a deep and well-mixed planetary boundary layer (PBL). Moreover, τext and PM2.5 had no association (where the variables are not related) when stable conditions, long-range transport, or entrainment of air from above the PBL were observed. It was found that seasonal categorization of the relationship between τext and PM2.5, an approach commonly used in statistical models to estimate surface concentrations with satellite remote sensing, may not be enough to account for the atmospheric conditions that drive the relationships between τext and PM2.5. For all stations, winter showed the maximum average PM2.5 concentrations (14.1 μg m−3, σ = 11.6 μg m−3) meanwhile, τext reached minimum values (0.06 μg m−3, σ = 0.04) during the same season. Conversely, spring presented the minimum average PM2.5 concentrations (9.4 μg m−3, σ = 6.9 μg m−3) and the average values of τext during spring had the second highest values (0.11, σ = 0.06) averaged for all stations.

Dependence of columnar aerosol size distribution, optical properties, and chemical components on regional transport in Beijing

Seasonal dependence of the columnar aerosol optical and chemical properties on regional transport in Beijing over 10 years (from January 2005 to December 2014) were analyzed by using the ground-based remote sensing combined with backward trajectory analysis. Daily air mass backward trajectories terminated in Beijing were computed with HYSPLIT-4 model and were categorized into five clusters. The columnar mass concentrations of black carbon (BC), brown carbon (BrC), dust (DU), aerosol water content (AW), and ammonium sulfate like aerosol (AS) of each cluster were retrieved from the optical data obtained from the Aerosol Robotic NETwork (AERONET) with five-component model. It was found that the columnar aerosol properties in different seasons were changed, and they were related to the air mass origins. In spring, aerosol was dominated by coarse particles. Summer was characterized by higher single scattering albedo (SSA), lower real part of complex refractive index ( n ), and obvious hygroscopic growth due to humid air from the south. During autumn and winter, there was an observable increase in absorption aerosol optical thickness (AAOT) and the imaginary part of complex refraction ( k ), with high levels of retrieved BC and BrC. However, concentrations of BC showed less dependence on the clusters during the two seasons owing to the widely spread coal heating in north China.

Impact of drought and normal monsoon scenarios on aerosol induced radiative forcing and atmospheric heating in Varanasi over middle Indo-Gangetic Plain

Observations on aerosols with specific emphasis to black carbon (BC) are reported for an urban site over middle Indo-Gangetic Plain (IGP), South Asia. Emphases are made to evaluate variation in BC concentrations during typical monsoon season (June-September, JJAS) from 2009 to 2011, and to recognize its impact on aerosol radiative forcing (ARF) and atmospheric heating. Almost entire Indian sub-continent experienced a drought year in 2009 before achieving a normal monsoon in 2010 and 2011. The ground monitoring station in Varanasi over middle-IGP experienced minimum monsoonal rain during 2009 drought year (total monsoon rain: 437.3mm), which gradually increased during 2010 (deficit monsoon, 613.4mm), before achieving a normal monsoon in year 2011 (1207.0mm). The BC mass loading during drought year was relatively high (mean ± SD: 7.0 ± 3.3; range: 5.3–8.8μgm−3) compared to 2010 (4.9 ± 2.1, 3.7–5.8μgm−3) and 2011 (4.6 ± 2.1, 3.2–5.2μgm−3). The increase in BC aerosols especially during drought year was associated to lower wind speed and reduced rate of wet removal, which potentially enhanced BC loading in comparison to years with normal monsoon. Columnar aerosol loading in terms of aerosol optical depth (AOD) was retrieved from space-borne MODerate resolution Imaging Spectroradiometer (MODIS) sensor on-board Terra satellite. It has revealed high AOD over Varanasi during drought (2009: 1.03 ± 0.15) and deficit monsoon (2010: 1.07 ± 0.53) before being reduced during 2011 (0.89 ± 0.20). Conclusively, a radiative transfer model was run to estimate the ARF for composite aerosols for both surface (SUF), atmosphere (ATM) and top of the atmosphere (TOA). The 2009 drought year was found to have reasonably higher ATM and SUF forcing (ATM: 105; SUF: − 122Wm−2) in comparison to deficit (ATM: 61; SUF: − 88Wm−2) and normal (ATM: 67; SUF: − 89Wm−2) monsoon scenarios. The lower atmosphere heating rates during 2009 monsoon was also recorded to be as high as 2.9K day−1 in comparison to 2010 (1.7K day−1) and 2011 (1.9K day−1). Such findings provide meaningful outcomes in terms of climatic effects of BC aerosols and their associated inference on Indian summer monsoon. CapsuleBC induced aerosol radiative forcing during 2009 drought year was higher in comparison to deficit (2010) and normal (2011) monsoon scenarios over middle IGP.

Multi year aerosol characterization in the tropical Andes and in adjacent Amazonia using AERONET measurements

This work focuses on the analysis of columnar aerosol properties in the complex geophysical tropical region of South America within 10–20° South and 50–70° West. The region is quite varied and encompasses a significant part of Amazonia (lowlands) as well as high mountains in the Andes (highlands,∼4000 m a.s.l.). Several AERONET stations were included to study the aerosol optical characteristics of the lowlands (Rio Branco, Ji Parana and Cuiaba in Brazil and Santa Cruz in Bolivia) and the highlands (La Paz, Bolivia) during the 2000–2014 period. Biomass-burning is by far the most important source of aerosol in the lowlands, particularly during the dry season (August–October). Multi-annual variability was investigated and showed very strong burning activity in 2005, 2006, 2007 and 2010. This resulted in smoke characterized by correspondingly strong, above-average AODs (aerosol optical depths) and homogeneous single scattering albedo (SSA) across all the stations (∼0.93). For other years, however, SSA differences arise between the northern stations (Rio Branco and Ji Parana) with SSAs of ∼0.95 and the southern stations (Cuiaba and Santa Cruz) with lower SSAs of ∼0.85. Such differences are explained by the different types of vegetation burned in the two different regions. In the highlands, however, the transport of biomass burning smoke is found to be sporadic in nature. This sporadicity results in highly variable indicators of aerosol load and type (Angstrom exponent and fine mode fraction) with moderately significant increases in both. Regional dust and local pollution are the background aerosol in this highland region, whose elevation places it close to the free troposphere. Transported smoke particles were generally found to be more optical absorbing than in the lowlands: the hypothesis to explain this is the significantly higher amount of water vapor in Amazonia relative to the high mountain areas. The air-mass transport to La Paz was investigated using the HYSPLIT air-concentration five-days back trajectories. Two different patterns were clearly differentiated: westerly winds from the Pacific that clean the atmosphere and easterly winds favoring the transport of particles from Amazonia.

Seasonal variation of columnar aerosol optical properties and radiative forcing over Beijing, China

Long-term seasonal characteristics of aerosol optical properties and radiative forcing at Beijing (during March 2001–March 2015) were investigated using a combination of ground-based Sun/sky radiometer retrievals from the AERONET and a radiative transfer model. Aerosol optical depth (AOD) showed a distinct seasonal variation with higher values in spring and summer, and relatively lower values in fall and winter. Average Angstrom exponent (AE) in spring was lower than other seasons, implying the significant impact of dust episodes on aerosol size distribution. AE mainly distributed between 1.0 and 1.4 with an obvious uni-peak pattern in each season. The observation data showed that high AODs (>1.0) were clustered in the fine mode growth wing and the coarse mode. Compared to AOD, seasonal variation in single scattering albedo (SSA) showed an opposite pattern with larger values in summer and spring, and smaller ones in winter and fall. The highest volume size distribution and median radius of fine mode particles occurred in summer, while those of coarse mode particles in spring. The averaged aerosol radiative forcing (ARF) at the top of the atmosphere (TOA) in spring, summer, fall and winter were −33 ± 22 W m-2, -35 ± 22 W m-2, -28 ± 20 W m-2, and -24 ± 23 W m-2 respectively, and these differences were mainly due to the SSA seasonal variation. The largest positive ARF within atmosphere occurred in spring, implying strong warming in the atmosphere. The low heating ratio in summer was caused by the increase in water vapor content, which enhanced light scattering capacity (i.e., increased SSA).

Temporal characteristics of columnar aerosol optical properties and radiative forcing (2011–2015) measured at AERONET’s Pretoria_CSIR_DPSS site in South Africa

Ground-based observations of the spectral aerosol optical depths (AODs) revealed that the northwest of South Africa (SA) possessed large aerosol loading and still remained unexplored as none of the authors have been extensively studied. The characteristics of aerosol optical, physical, and radiative properties, as well as their relationships presented in this paper, were derived from the direct sun and sky radiances measured at Pretoria during August 2011–December 2015 using the AERONET's (CE-318) automatic sun/sky radiometer. The annual mean AOD440, AE440-870, and SSA-T440 estimated at Pretoria during the study period were 0.23 ± 0.13, 1.50 ± 0.26, and 0.91 ± 0.04, respectively. The mean AOD440 (AE440-870) for the study period appeared higher during the spring and summer seasons (summer), suggest dominance of fine mode particles attributed to biomass burning activities and seasonal influence of meteorology. Analysis of frequency occurrences of AOD and AE also indicate that this region is richly populated with fine mode particles. Further, the AOD-AE relationship was studied at Pretoria and the result concluded that the mixed type aerosols contributed more among the others followed by the urban/industrial-biomass burning and clean continental (background) aerosols. The high summertime SSA-T440 and fine mode radius of AVSD could be associated with the hygroscopic growth of water-soluble aerosols under high water vapor (absorbing aerosols). The positive (negative) values of aerosol radiative forcing (ARF) were observed in all the months, an indication of significant heating (cooling) within the atmosphere (top of the atmosphere (TOA) and bottom of the atmosphere (BOA)) were due to strong absorption (scattering) of radiation. Further, the efficiency derived between ARF and AOD440 indicated that ARF is a strong function of AOD at the BOA noted with a high degree of correlation coefficient (r = 0.93).

Classification of key aerosol types and their frequency distributions based on satellite remote sensing data at an industrially polluted city in the Yangtze River Delta, China

ABSTRACTIn the present study, characterization of columnar aerosol optical properties and classifying the major aerosol types was investigated at an urban–industrial city, Nanjing in the Yangtze River Delta (YRD) region over East China using simultaneous data sets retrieved from the MODerate resolution Imaging Spectroradiometer (MODIS) and Ozone Monitoring Instrument (OMI) sensors during 2004–2015. A notable spatiotemporal heterogeneity was observed in the optical properties of aerosols on the seasonal scale over East China. Aerosol optical depth at 550 nm (AOD550) exhibited pronounced seasonal variability over Nanjing in the YRD, with higher values during summer and spring seasons and lower in winter. Ångström exponent (AE470–660) found higher in summer indicating the relative abundance of fine mode aerosols over the coarse mode. We also used the Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) model for presenting cluster trajectory analysis which revealed that the airmasses from different source regions contributed greatly to aerosol loading during the study period. In addition, we followed two techniques for studying classification of major aerosol types based on the predefined thresholds. Using the AOD–AE method (here called as Technique‐I), five major aerosol types were identified via, continental clean (CC), marine (MA), biomass burning/urban–industrial (BU), desert dust (DD), and mixed (MX). In all the seasons, MX is the dominant aerosol type followed by the BU and DD type aerosols during summer and spring seasons, respectively. Further, the sub‐classification of aerosol types was carried out considering into account of the characteristics of absorbing aerosol index (AAI) (here called as Technique‐II). The two clustering techniques showed reasonable consistency in the obtained results. The various aerosol types (absorbing and non‐absorbing) and their change over a region are highly helpful in fine tuning the models to decrease the uncertainty in the radiative and climatic effects of aerosols.

Efficient transport of tropospheric aerosol into the stratosphere via the Asian summer monsoon anticyclone

An enhanced aerosol layer near the tropopause over Asia during the June-September period of the Asian summer monsoon (ASM) was recently identified using satellite observations. Its sources and climate impact are presently not well-characterized. To improve understanding of this phenomenon, we made in situ aerosol measurements during summer 2015 from Kunming, China, then followed with a modeling study to assess the global significance. The in situ measurements revealed a robust enhancement in aerosol concentration that extended up to 2 km above the tropopause. A climate model simulation demonstrates that the abundant anthropogenic aerosol precursor emissions from Asia coupled with rapid vertical transport associated with monsoon convection leads to significant particle formation in the upper troposphere within the ASM anticyclone. These particles subsequently spread throughout the entire Northern Hemispheric (NH) lower stratosphere and contribute significantly (∼15%) to the NH stratospheric column aerosol surface area on an annual basis. This contribution is comparable to that from the sum of small volcanic eruptions in the period between 2000 and 2015. Although the ASM contribution is smaller than that from tropical upwelling (∼35%), we find that this region is about three times as efficient per unit area and time in populating the NH stratosphere with aerosol. With a substantial amount of organic and sulfur emissions in Asia, the ASM anticyclone serves as an efficient smokestack venting aerosols to the upper troposphere and lower stratosphere. As economic growth continues in Asia, the relative importance of Asian emissions to stratospheric aerosol is likely to increase.

Characteristics of columnar aerosol optical and microphysical properties retrieved from the sun photometer and its impact on radiative forcing over Skukuza (South Africa) during 1999-2010.

The detailed analysis of columnar optical and microphysical properties of aerosols obtained from the AErosol RObotic NETwork (AERONET) Cimel sun photometer operated at Skukuza (24.98° S, 31.60° E, 150m above sea level), South Africa was carried out using the level 2.0 direct sun and inversion products measured during 1999-2010. The observed aerosol optical depth (AOD) was generally low over the region, with high values noted in late winter (August) and mid-spring (September and October) seasons. The major aerosol types found during the study period were made of 3.74, 69.63, 9.34, 8.83, and 8.41% for polluted dust (PD), polluted continental (PC), non-absorbing (NA), slightly absorbing (SA), and moderately absorbing (MA) aerosols, respectively. Much attention was given to the aerosol fine- and coarse-modes deduced from the particle volume concentration, effective radius, and fine-mode volume fraction. The aerosol volume size distribution pattern was found to be bimodal with the fine-mode showing predominance relative to coarse-mode during the winter and spring seasons, owing to the onset of the biomass burning season. The mean values of total, fine-, and coarse-mode volume particle concentrations were 0.07±0.04, 0.03±0.03, and 0.04±0.02μm3μm-2, respectively, whereas the mean respective effective radii observed at Skukuza for the abovementioned modes were 0.35±0.17, 0.14±0.02, and 2.08±0.02μm. The averaged shortwave direct aerosol radiative forcing (ARF) observed within the atmosphere was found to be positive (absorption or heating effect), whereas the negative forcing in the surface and TOA depicted significant cooling effect due to more scattering type particles.

역궤적 이동경로별 용인지역의 컬럼에어로졸 특성

역궤적 이동경로별 용인지역의 컬럼에어로졸 특성

Evaluation of the Multi-Angle Implementation of Atmospheric Correction (MAIAC) Aerosol Algorithm through Intercomparison with VIIRS Aerosol Products and AERONET.

The Multi-Angle Implementation of Atmospheric Correction (MAIAC) algorithm is under evaluation for use in conjunction with the Geostationary Coastal and Air Pollution Events (GEO-CAPE) mission. Column aerosol optical thickness (AOT) data from MAIAC are compared against corresponding data from the Visible Infrared Imaging Radiometer Suite (VIIRS) instrument over North America during 2013. Product coverage and retrieval strategy, along with regional variations in AOT through comparison of both matched and un-matched seasonally gridded data are reviewed. MAIAC shows extended coverage over parts of the continent when compared to VIIRS, owing to its pixel selection process and ability to retrieve aerosol information over brighter surfaces. To estimate data accuracy, both products are compared with AERONET Level 2 measurements to determine the amount of error present and discover if there is any dependency on viewing geometry and/or surface characteristics. Results suggest that MAIAC performs well over this region with a relatively small bias of -0.01; however there is a tendency for greater negative biases over bright surfaces and at larger scattering angles. Additional analysis over an expanded area and longer time period are likely needed to determine a comprehensive assessment of the products capability over the Western Hemisphere.

Enhanced gold recovery based on joint ore and waste processing

The authors present the gravity concentration-and-flotation technology for joint processing of gold ore and placer gold mining waste ensuring high gold recovery. The research is carried out using samples of ore from a primary gold deposit under mining and from waste of gold placer mining in the Yano- Kolyma gold province in the Russian Federation. The feature of the technology is the use of bullion gold in the gold flotation circuit. Bullion gold is recovered from gold placer mining waste by gravity concentration. The ore and waste processing by gravity concentration and flotation is based on the jet flow of feed material and rough concentrate. The second flotation stream circuit uses the technology of aerosol column flotation. The efficiency of investment to joint processing of gold ore and placer gold mine waste is evaluated.