Angstrom Exponent Research Articles

Study of spectral characteristics of black carbon from biomass burning and source apportionment over Agartala in the northeastern India.

We have studied the black carbon (BC) mass concentrations, contributions from Fossil Fuels (FF), and Biomass burning (BB) to total BC mass concentrations using a 7-wavelength Aethalometer (Model, AE-31; Make, Magee Scientific, USA) at a rural continental location in the northeastern India. We have taken the continuous measurements of BC from January 2011 to December 2017 (excluding the year 2016 due to nonavailability of data). The annual mean BC concentration at 880 nm is observed maximum 12.56±5.06 µgm-3 in the year 2011 with a minimum of 7.26±2.76 µgm-3 during the year 2015." is the final sentence. BC, BCff, and BCbb mass concentrations show significant variation during morning, afternoon, evening, and night hours. The significant monthly, seasonal, and annual variabilities in the BC concentration, equivalent BC from FF and BB, are due to seasonal change in the emission sources, boundary layer dynamics, and dispersion and dilution conditions. The determination of Angstrom exponent (α) for the BC emitted during burning of different biofuels by performing a burning experiment is an important part of the present study. We have conducted a survey in and around the study location to know the different biofuels used by the people for daily household activities, and those biofuels are used in the burning experiment. As a result of biomass burning experiment to determine Angstrom exponent, we have found the α values to be ranging from 1.20 to 2.37 for flaming and a range from 1.59 to 2.33 for smoldering conditions for different biofuels. Annual mean contributions of BCff and BCbb to the total BC are found to be dominated by FF emissions during the whole study period. The percentage contribution of BCff and BCbb is found to be 56% and 44% during winter season due to increase in wood and biomass burning activities for various purposes. We have found the higher percentage contribution from BCff (85%) during monsoon season due to reduction in usage of biofuels.

Assessment of a new detection threshold for [formula omitted] concentrations linked to African dust events in the Caribbean Basin

The Lesser Antilles is an intermediate zone located between the Caribbean Sea and the Atlantic Ocean. This area is frequently affected by the major long range Saharan dust transportation from West African desert sources. The aerosols optical properties are provided by the AEronet Robotic NETwork (AERONET) measurement sites in Puerto Rico, Guadeloupe, and Barbados. Thus, Aerosols Optical Depth (AOD), Angstrom Exponent (AE), Volume Particle Size Distribution (VPSD), complex refractive indexes, and Single Scattering Albedo (SSA) were used to define the predominant type of atmospheric particles namely sea salt aerosols, mineral dust or aerosols mixture. Obtained results show that aerosols in the atmospheric column (AOD) and surface dust measurements (PM10) are well correlated with correlation coefficients of 0.72 and 0.81 respectively for Puerto Rico, and Guadeloupe. Detailed analysis of optical data associated to daily PM10 concentrations highlighted that dust phenomenon can be observable below PM10 threshold of 50 μg∕m3 given by the European directives to detect dust episodes. Indeed, for Caribbean islands, episodes of desert dust phenomenon have been detected from 35 μg∕m3. The climatological assessment of monthly dust events observed in Puerto Rico, Guadeloupe, and Martinique between 2006 and 2016 highlighted a low dust season from November to February and a high dust season from May to August. Both seasons are separated by two transition dust periods: March to April and September to October. Lastly, the day-to-day back trajectories (NOAA-HYSPLIT) illustrated the general atmospheric circulation and show three main dust transportation routes: the North West African Path (62.7%); the South West African Path (20.8%) ; and the North East Atlantic Path (15.1%). By computing the average PM10 concentrations bring from each path, we notice that South West African Path is the most loaded in mineral dust because he comes from one of the most persistently active and intense dust sources in the world, i.e. Bodélé Depression in northern Chad.

USING SATELLITE DATA DETECTION IN THE MARINE AND COASTAL REGIONS CONTAMINATED BY A FINE DISPERSED AEROSOL IN THE ATMOSPHERE

In the article the algorithm for revealing the polluted with fine aerosol atmospheric zones over the sea and coastal regions has been suggested. Algorithm is based on well-know regularity of inverse type variation of Angstrom exponent and optical density of aerosol, and formulated and solved optimization task. The operation capability of the algorithm is tested on the basis of know aerosol index maps, verified algorithm performance.

Aerosol classification in Europe, Middle East, North Africa and Arabian Peninsula based on AERONET Version 3

Abstract The aerosol optical properties from Version 3 (V3) of AERONET are used to classify the aerosol types in Europe, Middle East/North Africa (MENA) and Arabian Peninsula, during 2008–2017. Quality-assured data of Single Scattering Albedo (SSA), Fine Mode Fraction (FMF) and Angstrom Exponent (AE) from 39 stations are used to classify the aerosol types, based on threshold limits of these optical properties. The aerosol type depends on the location and the sources of each region of study; for example, in Atlantic, Arabian Peninsula and MENA, the dominant aerosol type is coarse absorbing due to dust from Sahara and Arabian deserts. However, in Arabian Peninsula, fine particles are also observed in autumn and winter. In addition, the lower percentages of coarse absorbing particles across MENA are observed in the East because of increased fine particle emissions from human activities. In the stations of the Group A of South Europe, a bimodal size distribution is revealed and the dominant aerosol types are the fine-slightly absorbing and non-absorbing, followed by coarse absorbing due to Sahara dust outbreaks. In the stations of the Group B of South Europe, fine slightly absorbing and non-absorbing particles are primarily observed since the stations are located in urban/industrial regions. In Central and East Europe, the prevailing aerosol type is fine-non absorbing which is followed by the fine slightly absorbing aerosols from urban/industrial sites. The results of the aerosol type characterization are presumed to give a better assessment of regional climate and local air pollution. The proposed method could be used to compare aerosol classification results from satellite and chemical transport models, as well as for the validation of satellite data and the improved performance of models and remote sensing algorithms in the future.

Lidar observations of Saharan dust loads above Sofia, Bulgaria: dust layers extending throughout the troposphere (a case study)

We report the lidar observations of a prolonged unusual event of atmospheric aerosol load extending up to about 15 km above the city of Sofia, Bulgaria. Based on the results obtained and air-transport modeling data, we show that the observed diffused aerosol layers consisted predominantly of Saharan mineral dust partly mixed with other aerosol types. We present retrieved time-averaged vertical profiles of the aerosol backscatter coefficient (at 532 and 1064 nm) in order to display the aerosol density height distribution, whereas the aerosol layering temporal dynamics is illustrated by color-coded maps of range-corrected lidar signals. We also calculated the profiles of the backscatter-related Angstrom exponent (BAE), which showed the domination of moderately coarse aerosol particle modes. Further, frequency count distributions of the BAE occurrences were obtained and analyzed statistically. Particular attention was paid to the revealed BAE distribution skewness, in view of better identifying and characterizing the aerosol size and composition changes. The results obtained enabled us to argue that the atmosphere above Sofia in the period considered had been strongly affected by intrusion of Saharan dust. Desert aerosols had perturbed or covered over the top of the atmospheric boundary layer and filled up the free troposphere, considerably influencing the local meteorological conditions. We also ascertained that aged volcanic aerosols had been likely present and detected at tropopause altitudes.

Pollution Trends in China from 2000 to 2017: A Multi-Sensor View from Space

Satellite sensors can provide unique views of global pollution information from space. In particular, a series of aerosol and trace gas monitoring instruments have been operating for more than a decade, providing the opportunity to analyze temporal trends of major pollutants on a large scale. In this study, we integrate aerosol products from MODIS (MODIS Resolution Imaging Spectroradiometer, all abbreviations and their definitions are listed alphabetically in Abbreviations) and MISR (Multi-angle Imaging Spectroradiometer), the AAI (Absorbing Aerosol Index) product from OMI (Ozone Monitoring Instrument), column SO2 and NO2 concentrations from OMI, and tropospheric column ozone concentration from OMI/MLS (Microwave Limb Sounder) to study temporal changes in major pollutants over China. MODIS and MISR consistently revealed that column AOD (Aerosol Optical Depth) increased from 2000, peaked around 2007, and started to decline afterward, except for northwest and northeast China, where a continuous upward trend was found. Extensive negative trends in both SO2 and NO2 have also been found over major pollution source regions since ~2005. On the other hand, the OMI AAI exhibited significant increases over north China, especially the northeast and northwest regions. These places also have a decreased Angstrom exponent as revealed by MISR, indicating an increased fraction of large particles. In general, summer had the largest AOD, SO2, and NO2 trends, whereas AAI trends were strongest for autumn and winter. A multi-regression analysis showed that much of the AOD variance over major pollution source regions could be explained by SO2, NO2, and AAI combined, and that the SO2 and NO2 reduction was likely to be responsible for the negative AOD trends, while the AOD increase over NE and NW China may be associated with an increase of coarse particles revealed by increased AAI and decreased AE. In contrast to aerosols, tropospheric ozone exhibited a steady increase from 2005 throughout China. This indicates that although the recent emission control effectively reduced aerosol pollutants, ozone remains a challenging issue and may dominate future air pollution.

High Efficiency of Solar Cell Model Based on Two Types of Nanoparticles

Climatology of aerosols, their trends and classification based on the long-term Moderate Resolution Imaging Spectroradiometer (MODIS) measurements (from February 2000 to July 2015) of aerosol optical depths at 550 nm (τ550) and Angstrom exponent (α470-660) using the wavelengths of 470 and 660nm in Nairobi, Skukuza and Ilorin AERONET stations were analyzed in this work. The level-2 collection-6 Deep Blue (L2 C006 DB) of the parameters listed above from the aqua- (MYD04) and terra- (MOD04) MODIS of the study area were statistically analyzed using SPSS. To be able to understand the temporal variation in the characteristics of aerosols in the three stations and during each season separately, MODIS measurements of τ, retrieved for the study area, were compared with AERONET τ. Overall, aqua-MODIS τ corroborate the AERONET measurements well in Nairobi and Ilorin stations with underestimation of 29.80 % and overestimation of 2.90 % respectively, whereas Skukuza station has terra-MODIS τ as the best representation of the AERONET measurements with underestimation of 1.90 %. ....

Aerosol Parameters During Winter and Summer Seasons and Meteorological Implications

The MICROTOPS II aerosol optical depth (AOD) and Moderate Resolution Imaging Spectroradiometer (MODIS) Aqua AOD and angstrom exponent (AE) were collected during December 2016 to May 2017. Higher AOD values were recorded during winter (December - February) and summer (March - May) Months. These values were observed by MICROTOPS II (0.35 - 1.279) and MODIS (0.222 - 1.904) during winter season. During summer AOD values were recorded by MICROTOPS II (0.272 – 1.744) and MODIS (0.227 – 1.33). Whereas MODIS AE (0.218 – 1.799) values were found high during winter season indicates about the dominance of fine particulates. During summer months MODIS AE (.001 – 1.648) values are indicating about the mixing of the aerosol particles. The relative humidity values during December and January months were found to be high, while its values were found decreasing during late February due to transition phase. Relative humidity values were recorded low during summer (36 – 86%) months in compare to the winter (50 - 100%) months.

Evaluation and Correction of the Ambient Particle Spectral Light Absorption Measured Using a Filter-based Aethalometer

ABSTRACT Spectral light-absorption properties measured using an aethalometer (AE, model AE33) are widely used for radiative forcing studies and source appointment tracing in China. However, considerable uncertainty regarding the measured absorption coefficient (σ_abs) exists because of the multiple scattering effects, loading effects, and filter tapes. In this study, evaluation of the σ_abs was conducted by comparing the σ_abs measured using an AE33 with tape 8050, an AE33 with tape 8060 (the material of tape 8060 is different from tape 8050) , and a three-wavelength photoacoustic soot spectrometer (PASS-3) during two field campaigns in Eastern China. Results indicated that the σ_abs measured by the AE33 for both tapes was approximately three-times larger than that measured by the PASS-3, mainly because of the multiple-scattering effect. Wavelength-independent multiple-scattering compensation factor (2.90), which varies slightly (±0.04) in Eastern China, was recommended for use over these regions. The σ_abs measured by the AE33 using tape 8050 was highly dependent on loading on the filter tape, which led to significant uncertainty and discontinuity of the absorption Angstrom exponent when compared with tape 8060. A method was proposed to effectively correct the historical datasets of σ_abs and the absorption Angstrom exponent by using the AE33 with tape 8050. This work provides insight into the data quality of measured absorption when filter-based measurement technology is used.

Comparison of Filter-based Absorption Measurements of Biomass Burning Aerosol and Background Aerosol at the Mt. Bachelor Observatory

ABSTRACT In this study we evaluate the recently upgraded aethalometer (AE33) and the newly released tricolor absorption photometer (TAP) with respect to their response to wildfire aerosol plumes during their deployment at the Mount Bachelor Observatory (MBO; 2763 m a.s.l.) in central Oregon, USA, during the summer of 2016. While both instruments use similar methodology (i.e., light extinction through an aerosol-laden filter), each has a unique set of correction schemes to address artifacts originating from filter loading, scattering from captured aerosol particles, and multiple scattering effects of the filter fibers. We also utilize a Single Particle Soot Photometer (SP2) to determine refractory black carbon (rBC) in these air masses. In addition to comparing the AE33 filter-loading correction methodology to previously published aethalometer correction schemes, we also compare the AE33 to the correction schemes used for the TAP and evaluate the degree to which the different correction factors influence the derived absorption Angstrom exponents (AAE) and mass absorption cross sections (MACs). We find that while the different correction factors for either the AE33 or TAP do exert an influence on the derived MACs, AAEs exhibit the most sensitivity to the correction schemes. Our study finds that using the AE33 manufacturer’s recommended settings results in aerosol light absorption coefficients that are 3.4 to 4 times greater than the aerosol light absorption coefficients reported by the TAP. We calculated a correction factor (Cf) of 4.35 for the AE33 by normalizing the AE33 to match the TAP. The uncorrected AE33 also gives equivalent black carbon (eBC) values that are approximately 2 times the rBC measured by the SP2 instrument. We also find that biomass burning aerosols result in significant MAC enhancements, particularly at lower wavelengths, which is attributable to brown carbon (BrC).

Aerosol Optical Radiation Properties in Kunming (the Low–Latitude Plateau of China) and Their Relationship to the Monsoon Circulation Index

Based on the Langley method and the EuroSkyRad (ESR) pack retrieval scheme, we carried out the retrieval of the aerosol properties for the CE–318 sunphotometer observation data from March 2012 to February 2014 in Kunming, China, and we explored the possible mechanisms of the seasonal variations. The seasonal variation of the aerosol optical depth (AOD) was unimodal and reached a maximum in summer. The retrieval analysis of the Angstrom exponent (α) showed the aerosol types were continental, biomass burning (BB), and urban/industrial (UI); the content of the desert dust (DD) was low, and it may have contained a sea–salt (SS) aerosol due to the influence of the summer monsoon. All the aerosol particle spectra in different seasons showed a bimodal structure. The maximum and submaximal values were located near 0.2 μm and 4 μm, respectively, and the concentration of the aerosol volume was the highest in summer. In summer, aerosol particles have a strong scattering power but a weak absorption power; this pattern is the opposite in winter. The synergistic effect of the East Asian monsoon and the South Asian monsoon seasonal oscillations can have an important impact on the variation of the aerosol properties. The oscillation variation characteristic of the total vertical columnar water vapor (CWV) and the monsoon index was completely consistent. The aerosol types and sources in the Yunnan–Kweichow Plateau and the optical radiation properties were closely related to the monsoon circulation activities during different seasons and were different from other regions in China.

Study of aerosol optical properties in the Middle East during 2013.

Aerosols affect the earth's atmospheric radiative fluxes via direct, semi-direct, and indirect mechanisms. Aerosols also are one of the main sources of uncertainty in climate models. In the Middle East, in addition to climate effects, various problems such as reduced visibility, human health hazards, and air pollution are caused by aerosols. Studying the optical and physical properties of aerosols on local and global scales helps reduce the uncertainties in climate forcing. In this study, aerosol optical properties, including Aerosol Optical Depth (AOD), Angstrom Exponent (AE), ASYmmetry parameter (ASY), Single Scattering Albedo (SSA), and phase function were analyzed. These properties were investigated over five sites in the Middle East during 2013 using the Aerosol Robotic NETwork (AERONET) data. The results revealed an inverse relationship between AOD and AE in all sites. A high AOD value and a low AE value were detected in spring and summer in all studied sites, suggestive of coarse mode dust particles. ASY initially decreased due to the dominance of absorbing type aerosols in the visible spectrum with the increase in wavelength. Afterwards, ASY increased with the increase in wavelength in the infrared region due to the dominance of the coarse mode particles. In most sites, SSA increased, particularly in spring and summer, with the increase in the wavelength because of the dominance of desert dust. In spring and summer, the phase function was high over all sites. High phase functions associated with small scattering angles were caused by the coarse mode particles.

Maritime Aerosol Optical and Microphysical Properties in the South China Sea Under Multi-source Influence

The South China Sea hosts a wide range of aerosol pollutants with the uneven development of socio-economic and complicated meteorology system. To fill the gap of the maritime aerosol characteristics over the sea, we selected the multi-year ground-based measurements of Taiping Site and Dongsha Site to investigate the optical and microphysical properties. In Taiping, the vast majority of aerosol optical depths (AODs) are less than 0.2, but that of Dongsha shows the wider distribution of AODs from 0 to 0.6. Angstrom Exponent frequency distribution in Taiping peaks at the range of 0.75–1.25 but that has the left-skewed distribution in Taiping Island. Moreover, there is a variation in the coarse-mode volume concentration in Taiping Island but less variation in the fine mode. The seasonal maritime aerosol properties of Taiping and Dongsha have been analyzed that can be employed as a maritime look up table (LUT) kernel in coupled atmospheric retrieval and correction algorithms.

AN AEROSOL TYPE CLASSIFICATION METHOD BASED ON REMOTE SENSING DATA IN GUANGDONG, CHINA

Abstract. This paper provides an aerosol classification method based on remote sensing data in Guangdong, China in year 2010 and 2011. Aerosol Optical Depth, Angstrom Exponent and Ultraviolet Aerosol Index, as important properties of aerosols, are introduced into classification. Data of these three aerosol properties are integrated to establish a 3-dimension dataset, and k-means clustering algorithm with Mahalanobis distance is used to find out four clusters of the dataset, which respectively represents four aerosol types of urban-industrial, dust, biomass burning and mixed type. Prior knowledge about the understanding of each aerosol type is involved to associate each cluster with aerosol type. Temporal variation of the aerosol properties shows similarities between these two years. The proportion of aerosol types in different cities of Guangdong Province is also calculated, and result shows that in most cities urban-industrial aerosols takes the largest proportion while the mixed type aerosols takes the second place. Classification results prove that k-means cluster algorithm with Mahalanobis distance is a brief and efficient method for aerosol classification.

Analysis of Atmospheric Aerosol Optical Properties in the Northeast Brazilian Atmosphere with Remote Sensing Data from MODIS and CALIOP/CALIPSO Satellites, AERONET Photometers and a Ground-Based Lidar

A 12-year analysis, from 2005 to 2016, of atmospheric aerosol optical properties focusing for the first time on Northeast Brazil (NEB) was performed based on four different remote sensing datasets: the Moderate Resolution Imaging Spectroradiometer (MODIS), the Aerosol Robotic Network (AERONET), the Cloud-Aerosol LIDAR with Orthogonal Polarization (CALIOP) and a ground-based Lidar from Natal. We evaluated and identified distinct aerosol types, considering Aerosol Optical Depth (AOD) and Angström Exponent (AE). All analyses show that over the NEB, a low aerosol scenario prevails, while there are two distinct seasons of more elevated AOD that occur every year, from August to October and January to March. According to MODIS, AOD values ranges from 0.04 to 0.52 over the region with a mean of 0.20 and occasionally isolated outliers of up to 1.21. Aerosol types were identified as sea spray, biomass burning, and dust aerosols mostly transported from tropical Africa. Three case studies on days with elevated AOD were performed. All cases identified the same aerosol types and modeled HYSPLIT backward trajectories confirmed their source-dependent origins. This analysis is motivated by the implementation of an atmospheric chemistry model with an advanced data assimilation system that will use the observational database over NEB with the model to overcome high uncertainties in the model results induced by still unvalidated emission inventories.

Aerosol Optical Characteristics During the Biomass Burning Season in Southeastern Mexico

In this paper, we present a characterization of the optical properties of the aerosols emitted during biomass burning (BB) season in the period 2005–2009. Trends of aerosol optical depth (AOD), Angstrom exponent (α), and precipitable water (PW) were analyzed using a 5-year dataset from AErosol RObotic NETwork (AERONET) observations over Tuxtla Gutierrez (TG), Chiapas. The overall mean AOD (500 nm) during the 2005–2009 period was 0.26 ± 0.18. However, monthly mean values of AOD > 0.5 during the spring months (April and May) would indicate the high load of particles emitted by fires. The overall mean of α (440–870 nm) was 1.40 ± 0.21, which confirms the presence of fine aerosols. Additionally, the combined analysis of the α with its spectral curvature δα, and the results from the spectral de-convolution algorithm (SDA) shows that fine-mode aerosols dominated AOD variability in TG. In this paper, the trajectories of air masses (400 and 1500 m, a.s.l.) arriving at the TG site were classified by using backward trajectory cluster analysis. Trajectory clustering results indicate a BB regional transport from Central America that affects the atmosphere in southeastern Mexico. We use observations of fire radiative power (FRP) from the Moderate Resolution Imaging Spectroradiometer (MODIS) to study the incidence of wildfires and to estimate the BB emissions from 2005 to 2009 in southeastern Mexico. The results indicated a gradual decrease in fires throughout the years. Campeche and Yucatan are the states in southeastern Mexico where BB produces the highest emissions of carbon dioxide (CO2), carbon monoxide (CO), black carbon (BC), and particulate material PM2.5. However, the largest emissions come from wildfires in Guatemala. Finally, to put in context the aerosol optical properties over southeastern Mexico, the sun photometric measurements in TG are compared with those retrieved from AERONET stations located in other tropical biomass burning regions (Brazil and Zambia).

Characteristics of airborne water-soluble organic carbon (WSOC) at a background site of the North China Plain

Abstract Water-soluble organic carbon (WSOC), a significant part of organic carbon (OC) in fine particles, can alter the hygroscopic properties of aerosols and affect global climate change. In this study, PM2.5 filter samples were collected in 2017 winter and summer to investigate the secondary formation, sources and light absorption properties of WSOC. The average WSOC/OC was 66% with the higher value in summer (74%). There are strong correlations between WSOC and secondary components like secondary organic carbon (SOC) and inorganic ions while the correlation between WSOC and EC was weak, indicating secondary formation contributed a dominant portion to WSOC at this site. Moreover, high aerosol liquid water (ALW) and particle acidity were found to enhance the secondary formation of WSOC. The sources of WSOC investigated with Positive Matrix Factorization model (PMF) demonstrated that secondary formation was dominated with 59.9% in winter and 77.9% in summer. The absorption Angstrom exponents (AAE) were 6.88 in winter and 9.15 in summer. The MAE365 in winter (1.32 m2 g−1) was higher than that in summer (0.38 m2 g−1), indicating the stronger light absorption ability of WSOC in winter. The radiative forcing of WSOC by light absorption corresponded to only 1–10% of that caused by EC. The potential source contribution function (PSCF) identified inland cities in Shandong province, eastern Henan and Jiangsu province as major source regions of WSOC. The findings from this study imply a critical role of secondary formation characteristics of WSOC at the regional background site of the North China Plain.

Impact of Urban Growth on Air Quality in Indian Cities Using Hierarchical Bayesian Approach

Several studies have found rising ambient particulate matter (PM 2.5 ) concentrations in urban areas across developing countries. For setting mitigation policies source-contribution is needed, which is calculated mostly through computationally intensive chemical transport models or manpower intensive source apportionment studies. Data based approach that use remote sensing datasets can help reduce this challenge, specially in developing countries which lack spatially and temporally dense air quality monitoring networks. Our objective was identifying relative contribution of urban emission sources to monthly PM 2.5 ambient concentrations and assessing whether urban expansion can explain rise of PM 2.5 ambient concentration from 2001 to 2015 in 15 Indian cities. We adapted the Intergovernmental Panel on Climate Change’s (IPCC) emission framework in a land use regression (LUR) model to estimate concentrations by statistically modeling the impact of urban growth on aerosol concentrations with the help of remote sensing datasets. Contribution to concentration from six key sources (residential, industrial, commercial, crop fires, brick kiln and vehicles) was estimated by inverse distance weighting of their emissions in the land-use regression model. A hierarchical Bayesian approach was used to account for the random effects due to the heterogeneous emitting sources in the 15 cities. Long-term ambient PM 2.5 concentration from 2001 to 2015, was represented by a indicator R (varying from 0 to 100), decomposed from MODIS (Moderate Resolution Imaging Spectroradiometer) derived AOD (aerosol optical depth) and angstrom exponent datasets. The model was trained on annual-level spatial land-use distribution and technological advancement data and the monthly-level emission activity of 2001 and 2011 over each location to predict monthly R. The results suggest that above the central portion of a city, concentration due to primary PM 2.5 emission is contributed mostly by residential areas (35.0 ± 11.9%), brick kilns (11.7 ± 5.2%) and industries (4.2 ± 2.8%). The model performed moderately for most cities (median correlation for out of time validation was 0.52), especially when assumed changes in seasonal emissions for each source reflected actual seasonal changes in emissions. The results suggest the need for policies focusing on emissions from residential regions and brick kilns. The relative order of the contributions estimated by this study is consistent with other recent studies and a contribution of up to 42.8 ± 14.1% is attributed to the formation of secondary aerosol, long-range transport and unaccounted sources in surrounding regions. The strength of this approach is to be able to estimate the contribution of urban growth to primary aerosols statistically with a relatively low computation cost compared to the more accurate but computationally expensive chemical transport based models. This remote sensing based approach is especially useful in locations without emission inventory.

The Effect of Varying Water Soluble Components on the Radiative Forcing of Continental Average Aerosols

This work embodies the results of the effect of the water soluble components on the radiative forcing of continental average aerosols, from aerosol data extracted from optical properties of aerosols and cloud (OPAC) 4.0 software package using FORTRAN program to model the effect of water soluble on optical depth, asymmetric parameter, scattering and absorption coefficients at the spectral range of (0.25-0.80µm) and at eight relative humidities (0%,50%,70%,80%,90%,95%,98% & 99%). The concentration of water soluble was varied while concentrations of water insoluble and soot were kept constant. The optical parameters were used to compute numerically the radiative forcing using the concept of chylek and wong, the Angstrom exponent (α), turbidity (β) and Curvature ....... Keywords: Angstrom exponent, Curvature, Optical depth, Radiative forcing, Turbidity. DOI: 10.7176/APTA/79-04 Publication date:September 30th 2019

Multiyear Typology of Long-Range Transported Aerosols over Europe

In this study, AERONET (Aerosol Robotic Network) and EARLINET (European Aerosol Research Lidar Network) data from 17 collocated lidar and sun photometer stations were used to characterize the optical properties of aerosol and their types for the 2008–2018 period in various regions of Europe. The analysis was done on six cluster domains defined using circulation types around each station and their common circulation features. As concluded from the lidar photometer measurements, the typical aerosol particles observed during 2008–2018 over Europe were medium-sized, medium absorbing particles with low spectral dependence. The highest mean values for the lidar ratio at 532 nm were recorded over Northeastern Europe and were associated with Smoke particles, while the lowest mean values for the Angstrom exponent were identified over the Southwest cluster and were associated with Dust and Marine particles. Smoke (37%) and Continental (25%) aerosol types were the predominant aerosol types in Europe, followed by Continental Polluted (17%), Dust (10%), and Marine/Cloud (10%) types. The seasonal variability was insignificant at the continental scale, showing a small increase in the percentage of Smoke during spring and a small increase of Dust during autumn. The aerosol optical depth (AOD) slightly decreased with time, while the Angstrom exponent oscillated between “hot and smoky” years (2011–2015) on the one hand and “dusty” years (2008–2010) and “wet” years (2017–2018) on the other hand. The high variability from year to year showed that aerosol transport in the troposphere became more and more important in the overall balance of the columnar aerosol load.