scholarly journals The Impact of Intense Winter Saharan Dust Events on PM and Optical Properties at Urban Sites in the Southeast of the Iberian Peninsula

Atmosphere ◽  
2021 ◽  
Vol 12 (11) ◽  
pp. 1469
Author(s):  
Alba López-Caravaca ◽  
Ramón Castañer ◽  
Alvaro Clemente ◽  
Eduardo Yubero ◽  
Nuria Galindo ◽  
...  
Keyword(s):  
Optical Properties ◽  
Iberian Peninsula ◽  
Fine Particles ◽  
Saharan Dust ◽  
Percentile Method ◽  
Angstrom Exponent ◽  
Ångström Exponent ◽  
Dust Events ◽  
The Impact ◽  
Ångstrom Exponent

The influence of three Saharan dust events (SDE) on particulate matter (PM) concentrations and aerosol optical properties (AOP) during February 2021 was studied. The physical characteristics of the African aerosol were different for each episode. Therefore, the impacts of the three events on PM and AOP were analyzed separately. The monitoring sites were placed in Elche, in the southeast of the Iberian Peninsula. The sites can be classified as urban background locations. The procedure used to obtain the contribution of SDE to PM10 mass concentrations was the 40th percentile method. Nearly half of the days during the study period were under the influence of Saharan air masses. The average contribution of mineral dust (MD) to the PM10 mean concentration was ~50%, which was the highest contribution during the month of February in the last 14 years. The results show that those events characterized by a high input of fine particles (PM1 and PM2.5) caused larger increases in the absorption (σap) and scattering (σsp) coefficients than SDE in which coarse particles predominated. Nevertheless, as expected, SAE (Scattering Angström Exponent) values were lowest during these episodes. AAE (Absorption Angström Exponent) values during SDE were slightly higher than those observed in the absence of African dust, suggesting some contribution from MD to the absorption process.

scholarly journals Detection of Saharan dust and biomass burning events using near real-time intensive aerosol optical properties in the northwestern Mediterranean

2016 ◽  
Author(s):  
M. Ealo ◽  
A. Alastuey ◽  
A. Ripoll ◽  
N. Pérez ◽  
M. C. Minguillón ◽  
...  
Keyword(s):  
Optical Properties ◽  
Biomass Burning ◽  
Mineral Dust ◽  
Organic Aerosol ◽  
Saharan Dust ◽  
Aerosol Optical Properties ◽  
Angstrom Exponent ◽  
Ångström Exponent ◽  
Dust Events ◽  
Ångstrom Exponent

Abstract. The study of Saharan dust events (SDE) and biomass burning (BB) emissions are both topic of great scientific interest since they are frequent and important polluting scenarios affecting air quality and climate. The main aim of this work is evaluating the feasibility of using near real-time in situ aerosol optical measurements for the detection of these atmospheric events in the Western Mediterranean Basin (WMB). With this aim, intensive aerosol optical properties (SAE: scattering Ångström exponent, AAE: absorption Ångström exponent, SSAAE: single scattering albedo Ångström exponent, and g: asymmetry parameter) were derived from multi-wavelength aerosol light scattering, hemispheric backscattering and absorption measurements performed at regional (Montseny; MSY, 720 m a.s.l.) and continental (Montsec; MSA, 1570 m a.s.l.) background sites in the WMB. A sensitivity study aiming at calibrating the measured intensive optical properties for SDE and BB detection is presented and discussed. The detection of Saharan dust events (SDE) by means of the SSAAE parameter and Ångström matrix depended on the altitude of the measurement station, and on SDE intensity. At MSA (mountain-top site) SSAAE detected around 85% of SDE compared with 50% at MSY station, where pollution episodes dominated by fine anthropogenic particles frequently masked the effect of mineral dust on optical properties during less intense SDE. Furthermore, an interesting feature of SSAAE was its capability to detect the presence of mineral dust after the end of SDE. Thus, resuspension processes driven by summer regional atmospheric circulations and dry conditions after SDE favored the accumulation of mineral dust at regional level having important consequences for air quality. On average, SAE, AAE and g ranged between -0.7 and 1, 1.3 and 2.5, and 0.5 and 0.75, respectively, during SDE. Based on the Aethalometer model, biomass burning (BB) contribution to equivalent black carbon (BC) accounted for 36% and 40% at MSY and MSA respectively. Linear relationships were found between AAE and %BCbb, with AAE values reaching around 1.5 when %BCbb was higher than 50%. BB contribution to organic matter (OM) at MSY was around 30%. Thus FF combustion sources showed important contributions to both BC and OM in the region under study. Results for OM source apportionment showed good agreement with simultaneous biomass burning organic aerosol (BBOA) and hydrocarbon-like organic aerosol (HOA) calculated from Positive Matrix Factorization (PMF) applied to simultaneous Aerosol Mass Spectrometer (ACSM) measurements. A wildfire episode was identified at MSY, showing AAE values up to 2 when daily BB contributions to BC and OM were 73% and 78% respectively.

scholarly journals Extreme Saharan dust event over the southern Iberian Peninsula in september 2007: active and passive remote sensing from surface and satellite

2009 ◽  
Vol 9 (4) ◽  
pp. 15673-15723
Author(s):  
J. L. Guerrero-Rascado ◽  
F. J. Olmo ◽  
I. Avilés-Rodríguez ◽  
F. Navas-Guzmán ◽  
D. Pérez-Ramírez ◽  
...  
Keyword(s):  
Remote Sensing ◽  
Iberian Peninsula ◽  
Aerosol Optical Depth ◽  
Optical Depth ◽  
Saharan Dust ◽  
Dust Event ◽  
Passive Remote Sensing ◽  
Angstrom Exponent ◽  
Ångström Exponent ◽  
Ångstrom Exponent

Abstract. This study investigates aerosol optical properties during the extreme Saharan dust event detected from 3 to 7 September 2007 over Granada, southern Iberian Peninsula, with both active and passive remote sensing instrumentation from surface and satellite. The intensity of the event was visualized on the aerosol optical depth series obtained by the sun-photometer Cimel CE 318-4 operated at Granada in the framework of AERONET from August 2004 until December 2008 (level 2 data). A combination of large aerosol optical depth (0.86–1.50) at 500 nm, and reduced Angström exponent (0.1–0.25) in the range 440–870 nm, was detected on 6 September during daytime. This Saharan dust event also affected other Iberian Peninsula stations included in AERONET (El Arenosillo and Évora stations). During the most intense stage, on 6 September, maximum aerosol backscatter values were a factor of 8 higher than other maxima during this Saharan dust event. Values up to 1.5×10−2 km−1 sr−1 at 355 and 532 nm were detected in the layer with the greatest aerosol load between 3–4 km a.s.l., although aerosol particles were also detected up to 5.5 km a.s.l. In this stage of the event, dust particles at these altitudes showed a backscatter-related Angström exponent between −0.44 and 0.53 for the two spectral intervals considered. The results from different measurements (active/passive and ground-based/satellite) reveal the importance of performing multi-instrumental measurements to properly characterize the contribution of different aerosol types from different sources during extreme events.

scholarly journals Ship-borne aerosol profiling with lidar over the Atlantic Ocean: From pure marine conditions to complex dust-smoke mixtures

2018 ◽  
Author(s):  
Stephanie Bohlmann ◽  
Holger Baars ◽  
Martin Radenz ◽  
Ronny Engelmann ◽  
Andreas Macke
Keyword(s):  
Optical Properties ◽  
Atlantic Ocean ◽  
Saharan Dust ◽  
Marine Aerosol ◽  
Angstrom Exponent ◽  
The Third ◽  
Depolarisation Ratio ◽  
Ångström Exponent ◽  
Lidar Ratio ◽  
Ångstrom Exponent

Abstract. The multiwavelength Raman lidar PollyXT have been regularly operated aboard the research vessel Polarstern on expeditions across the Atlantic Ocean from North to South and vice versa. The lidar measurements of the Polarstern cruises PS95 from Bremerhaven to Cape Town (November 2015) and PS98 from Punta Arenas to Bremerhaven (April/May 2016) are presented and analysed in detail. The latest setup of PollyXT allows improved coverage of the marine boundary layer (MBL) due to an additional near-range receiver. Three case studies provide an overview of the detected aerosol over the Atlantic Ocean. In the first case, marine conditions were observed near South Africa on the autumn cruise PS95. Values of optical properties (depolarisation ratios close to zero, lidar ratios of 23 sr at 355 nm and 532 nm) within the MBL indicate pure marine aerosol. A layer of dried marine aerosol, indicated by an increase of the particle depolarisation ratio to about 10 % at both wavelengths and thus confirming the non-sphericity of these particles, could be detected on the top the MBL. On the same cruise, an almost pure Saharan dust plume was observed near the Canary Islands, presented in the second case. The third case deals with several layers of Saharan dust partly mixed with biomass-burning smoke measured on PS98 near the Cape Verde Islands. While the MBL was partly mixed with dust in the pure Saharan dust case, an almost marine MBL was observed in the third case. A statistical analysis showed latitudinal differences in the optical properties within the MBL, caused by the down-mixing of dust in the tropics and anthropogenic influences in the northern latitudes whereas the optical properties of the MBL in the southern hemisphere correlate with typical marine values. The particle depolarisation ratio of dried marine layers ranged between 4–9 %. Night measurements from PS95 and PS98 were used to illustrate the potential of aerosol classification using lidar ratio, particle depolarisation ratio and Ångström exponent. Lidar ratio and particle depolarisation ratio have been found to be the main indicator for the particle type, whereas the Ångström exponent is rather variable.

scholarly journals Detection of Saharan dust and biomass burning events using near-real-time intensive aerosol optical properties in the north-western Mediterranean

2016 ◽  
Vol 16 (19) ◽  
pp. 12567-12586 ◽  
Author(s):  
Marina Ealo ◽  
Andrés Alastuey ◽  
Anna Ripoll ◽  
Noemí Pérez ◽  
María Cruz Minguillón ◽  
...  
Keyword(s):  
Optical Properties ◽  
Biomass Burning ◽  
Mineral Dust ◽  
Organic Aerosol ◽  
Western Mediterranean ◽  
Saharan Dust ◽  
Aerosol Optical Properties ◽  
Angstrom Exponent ◽  
Ångström Exponent ◽  
Ångstrom Exponent

Abstract. The study of Saharan dust events (SDEs) and biomass burning (BB) emissions are both topics of great scientific interest since they are frequent and important polluting scenarios affecting air quality and climate. The main aim of this work is evaluating the feasibility of using near-real-time in situ aerosol optical measurements for the detection of these atmospheric events in the western Mediterranean Basin (WMB). With this aim, intensive aerosol optical properties (SAE: scattering Ångström exponent, AAE: absorption Ångström exponent, SSAAE: single scattering albedo Ångström exponent and g: asymmetry parameter) were derived from multi-wavelength aerosol light scattering, hemispheric backscattering and absorption measurements performed at regional (Montseny; MSY, 720 m a.s.l.) and continental (Montsec; MSA, 1570 m a.s.l.) background sites in the WMB. A sensitivity study aiming at calibrating the measured intensive optical properties for SDEs and BB detection is presented and discussed. The detection of SDEs by means of the SSAAE parameter and Ångström matrix (made up by SAE and AAE) depended on the altitude of the measurement station and on SDE intensity. At MSA (mountain-top site) SSAAE detected around 85 % of SDEs compared with 50 % at the MSY station, where pollution episodes dominated by fine anthropogenic particles frequently masked the effect of mineral dust on optical properties during less intense SDEs. Furthermore, an interesting feature of SSAAE was its capability to detect the presence of mineral dust after the end of SDEs. Thus, resuspension processes driven by summer regional atmospheric circulations and dry conditions after SDEs favoured the accumulation of mineral dust at regional level having important consequences for air quality. On average, SAE, AAE and g ranged between −0.7 and 1, 1.3 and 2.5 and 0.5 and 0.75 respectively during SDEs. Based on the aethalometer model, BB contribution to equivalent black carbon (BC) accounted for 36 and 40 % at MSY and MSA respectively. Linear relationships were found between AAE and %BCbb, with AAE values reaching around 1.5 when %BCbb was higher than 50 %. BB contribution to organic matter (OM) at MSY was around 30 %. Thus fossil fuel (FF) combustion sources showed important contributions to both BC and OM in the region under study. Results for OM source apportionment showed good agreement with simultaneous biomass burning organic aerosol (BBOA) and hydrocarbon-like organic aerosol (HOA) obtained by applying a positive matrix factorization model (PMF) to simultaneous Aerosol Chemical Speciation Monitor (ACSM) measurements. A wildfire episode was identified at MSY, showing AAE values up to 2 when daily BB contributions to BC and OM were 73 and 78 % respectively.

scholarly journals Effects of different correction algorithms on absorption coefficient – a comparison of three optical absorption photometers at a boreal forest site

2021 ◽  
Vol 14 (10) ◽  
pp. 6419-6441
Author(s):  
Krista Luoma ◽  
Aki Virkkula ◽  
Pasi Aalto ◽  
Katrianne Lehtipalo ◽  
Tuukka Petäjä ◽  
...  
Keyword(s):  
Optical Properties ◽  
Absorption Coefficient ◽  
Boreal Forest ◽  
Single Scattering ◽  
Forest Site ◽  
Angstrom Exponent ◽  
Ångström Exponent ◽  
Boreal Environment ◽  
Absorption Photometer ◽  
Ångstrom Exponent

Abstract. We present a comparison between three absorption photometers that measured the absorption coefficient (σabs) of ambient aerosol particles in 2012–2017 at SMEAR II (Station for Measuring Ecosystem–Atmosphere Relations II), a measurement station located in a boreal forest in southern Finland. The comparison included an Aethalometer (AE31), a multi-angle absorption photometer (MAAP), and a particle soot absorption photometer (PSAP). These optical instruments measured particles collected on a filter, which is a source of systematic errors, since in addition to the particles, the filter fibers also interact with light. To overcome this problem, several algorithms have been suggested to correct the AE31 and PSAP measurements. The aim of this study was to research how the different correction algorithms affected the derived optical properties. We applied the different correction algorithms to the AE31 and PSAP data and compared the results against the reference measurements conducted by the MAAP. The comparison between the MAAP and AE31 resulted in a multiple-scattering correction factor (Cref) that is used in AE31 correction algorithms to compensate for the light scattering by filter fibers. Cref varies between different environments, and our results are applicable to a boreal environment. We observed a clear seasonal cycle in Cref, which was probably due to variations in aerosol optical properties, such as the backscatter fraction and single-scattering albedo, and also due to variations in the relative humidity (RH). The results showed that the filter-based absorption photometers seemed to be rather sensitive to the RH even if the RH was kept below the recommended value of 40 %. The instruments correlated well (R≈0.98), but the slopes of the regression lines varied between the instruments and correction algorithms: compared to the MAAP, the AE31 underestimated σabs only slightly (the slopes varied between 0.96–1.00) and the PSAP overestimated σabs only a little (the slopes varied between 1.01–1.04 for a recommended filter transmittance >0.7). The instruments and correction algorithms had a notable influence on the absorption Ångström exponent: the median absorption Ångström exponent varied between 0.93–1.54 for the different algorithms and instruments.

scholarly journals Measurements of optical properties of atmospheric aerosols in Northern Finland

2005 ◽  
Vol 5 (6) ◽  
pp. 11703-11728 ◽  
Author(s):  
V. Aaltonen ◽  
H. Lihavainen ◽  
V.-M. Kerminen ◽  
M. Komppula ◽  
J. Hatakka ◽  
...  
Keyword(s):  
Optical Properties ◽  
Size Distribution ◽  
Seasonal Pattern ◽  
Late Summer ◽  
Aerosol Optical Properties ◽  
Air Masses ◽  
Angstrom Exponent ◽  
Northern Border ◽  
Ångström Exponent ◽  
Ångstrom Exponent

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

scholarly journals Estimating cloud condensation nuclei number concentrations using aerosol optical properties: role of particle number size distribution and parameterization

2019 ◽  
Vol 19 (24) ◽  
pp. 15483-15502 ◽  
Author(s):  
Yicheng Shen ◽  
Aki Virkkula ◽  
Aijun Ding ◽  
Krista Luoma ◽  
Helmi Keskinen ◽  
...  
Keyword(s):  
Optical Properties ◽  
Size Distribution ◽  
Cloud Condensation Nuclei ◽  
Size Distributions ◽  
Condensation Nuclei ◽  
Aerosol Optical Properties ◽  
Average Bias ◽  
Angstrom Exponent ◽  
Ångström Exponent ◽  
Ångstrom Exponent

Abstract. The concentration of cloud condensation nuclei (CCN) is an essential parameter affecting aerosol–cloud interactions within warm clouds. Long-term CCN number concentration (NCCN) data are scarce; there are a lot more data on aerosol optical properties (AOPs). It is therefore valuable to derive parameterizations for estimating NCCN from AOP measurements. Such parameterizations have already been made, and in the present work a new parameterization is presented. The relationships between NCCN, AOPs, and size distributions were investigated based on in situ measurement data from six stations in very different environments around the world. The relationships were used for deriving a parameterization that depends on the scattering Ångström exponent (SAE), backscatter fraction (BSF), and total scattering coefficient (σsp) of PM10 particles. The analysis first showed that the dependence of NCCN on supersaturation (SS) can be described by a logarithmic fit in the range SS <1.1 %, without any theoretical reasoning. The relationship between NCCN and AOPs was parameterized as NCCN≈((286±46)SAE ln(SS/(0.093±0.006))(BSF − BSFmin) + (5.2±3.3))σsp, where BSFmin is the minimum BSF, in practice the 1st percentile of BSF data at a site to be analyzed. At the lowest supersaturations of each site (SS ≈0.1 %), the average bias, defined as the ratio of the AOP-derived and measured NCCN, varied from ∼0.7 to ∼1.9 at most sites except at a Himalayan site where the bias was >4. At SS >0.4 % the average bias ranged from ∼0.7 to ∼1.3 at most sites. For the marine-aerosol-dominated site Ascension Island the bias was higher, ∼1.4–1.9. In other words, at SS >0.4 % NCCN was estimated with an average uncertainty of approximately 30 % by using nephelometer data. The biases were mainly due to the biases in the parameterization related to the scattering Ångström exponent (SAE). The squared correlation coefficients between the AOP-derived and measured NCCN varied from ∼0.5 to ∼0.8. To study the physical explanation of the relationships between NCCN and AOPs, lognormal unimodal particle size distributions were generated and NCCN and AOPs were calculated. The simulation showed that the relationships of NCCN and AOPs are affected by the geometric mean diameter and width of the size distribution and the activation diameter. The relationships of NCCN and AOPs were similar to those of the observed ones.

scholarly journals Optical properties of different aerosol types: seven years of combined Raman-elastic backscatter lidar measurements in Thessaloniki, Greece

2010 ◽  
Vol 3 (3) ◽  
pp. 569-578 ◽  
Author(s):  
E. Giannakaki ◽  
D. S. Balis ◽  
V. Amiridis ◽  
C. Zerefos
Keyword(s):  
Saharan Dust ◽  
Downward Movement ◽  
Angstrom Exponent ◽  
Lidar Measurements ◽  
Ångström Exponent ◽  
Lidar Ratio ◽  
Local Path ◽  
Aerosol Types ◽  
Lidar Observations ◽  
Ångstrom Exponent

Abstract. We present our combined Raman/elastic backscatter lidar observations which were carried out at the EARLINET station of Thessaloniki, Greece, during the period 2001–2007. The largest optical depths are observed for Saharan dust and smoke aerosol particles. For local and continental polluted aerosols the measurements indicate high aerosol loads. However, measurements associated with the local path indicate enhanced aerosol load within the Planetary Boundary Layer. The lowest value of aerosol optical depth is observed for continental aerosols, from West directions with less free tropospheric contribution. The largest lidar ratios, of the order of 70 sr, are found for biomass burning aerosols. A significant and distinct correlation between lidar ratio and backscatter related Ångström exponent values were estimated for different aerosol categories. Scatter plot between lidar ratio values and Ångström exponent values for local and continental polluted aerosols does not show a significant correlation, with a large variation in both parameters possibly due to variable absorption characteristics of these aerosols. Finally for continental aerosols with west and northwest directions that follow downward movement when arriving at our site constantly low lidar ratios almost independent of size are found.

scholarly journals Optical properties of different aerosol types: seven years of combined Raman- elastic backscatter lidar measurements in Thessaloniki, Greece

2009 ◽  
Vol 2 (6) ◽  
pp. 3027-3054
Author(s):  
E. Giannakaki ◽  
D. S. Balis ◽  
V. Amiridis ◽  
C. Zerefos
Keyword(s):  
Saharan Dust ◽  
Scatter Plot ◽  
Angstrom Exponent ◽  
Lidar Measurements ◽  
Ångström Exponent ◽  
Lidar Ratio ◽  
Local Path ◽  
Aerosol Types ◽  
Lidar Observations ◽  
Ångstrom Exponent

Abstract. We present our combined Raman/elastic backscatter lidar observations which were carried out at the EARLINET station of Thessaloniki, Greece, during the period 2001–2007. The largest optical depths are observed for Saharan dust and smoke aerosol loads. For "local" and "continental polluted" aerosols the measurements indicate moderate aerosol loads. However, measurements associated with the "local" path show lower values of free tropospheric contribution (37% versus 46% for "continental polluted") and thus, enhanced aerosol load within the Planetary Boundary Layer. The lowest value of aerosol optical depth is observed for "continental clean" aerosols. The largest lidar ratios, of the order of 70 sr are found for biomass burning aerosols. A significant and distinct correlation between lidar ratio and backscatter related Ångström exponent values was estimated for well defined aerosol categories, which provides a statistical measure of the lidar ratio's dependency on aerosol-size, which is a useful tool for elastic lidar systems. Scatter plot between lidar ratio values and Ångström exponent values for "local" and "continental polluted" aerosols does not show a significant correlation, with a large variation in both parameters possibly due to variable absorption characteristics of these aerosols. Finally for "clean continental" aerosols we found constantly low lidar ratios almost independent of size.

scholarly journals CARACTERIZAÇÃO ESPECTRAL DE PROPRIEDADES ÓPTICAS DE AEROSSÓIS EM REGIÃO DE FLORESTA TROPICAL

Nativa ◽  
2018 ◽  
Vol 6 (5) ◽  
pp. 451
Author(s):  
Jorge Almeida de Menezes ◽  
Rafael Da Silva Palácios ◽  
Evanízio Marinho Menezes Júnior ◽  
Amazonino Soares Júnior ◽  
José De Souza Nogueira
Keyword(s):  
Optical Properties ◽  
Global Network ◽  
Angstrom Exponent ◽  
The Earth ◽  
Forest Region ◽  
Ångström Exponent ◽  
Forest Regions ◽  
Suspended Dust ◽  
Ångstrom Exponent

Aerossóis atmosféricos desempenham um papel importante no equilíbrio de energia do sistema Terra-atmosfera. Medidas de aerossóis foram realizadas em área de floresta tropical utilizando fotômetro solar da rede global AERONET. Dados de 4 anos permitiram classificar as propriedades óticas dos aerossóis, definindo a climatologia para área de floresta tropical. Neste trabalho a profundidade óptica de aerossol (AOD) e expoente Ångström, α(440-870), foram utilizados para a análise espectral de aerossol. Médias de AOD(440nm) de 0,22 (±0,40), com média correspondente de α 1,27(±0,39).  A AOD(440nm) mostra picos distintos para estação seca e chuvosa, sendo que podem estar relacionados com padrões sazonais de aerossóis característicos dessas regiões. O α (440-870) apresentou modos de frequência que se relacionam com os principais tipos de aerossóis presentes em regiões de Floresta. Um cenário principal de aerossóis foi definido como aerossóis oriundos de queima de biomassa, com forte influência de fontes locais de aerossóis poluídos. Mistura de aerossóis estão presentes, enquanto que poeira em suspensão tem uma ocorrência pouco relevante.Palavras-chave: AOD, expoente Ångström, climatologia. SPECTRAL CHARACTERIZATION OF OPTICAL PROPERTIES OF AEROSOLS IN FOREST REGION ABSTRACT:Atmospheric aerosols play an important role in the energy balance of the Earth-atmosphere system. Aerosol measurements were performed in rainforest area, Manaus_Embrapa site using solar photometer from the AERONET global network. Data from 4 years allowed to classify the optical properties of the aerosols, defining the climatology for the site. In this work, the aerosol optical depth (AOD) and Ångström exponent, α (440-870), were used for aerosol spectral analysis. Mean AOD (440nm) of 0,22 (± 0.40), with corresponding mean of α 1,27 (± 0.39). AOD (440nm) shows distinct peaks for dry and rainy season, and may be related to seasonal aerosol patterns characteristic of these regions. The α (440-870) presented frequency modes that relate to the main types of aerosols present in Forest regions. A major aerosol scenario was defined as biomass-based aerosols, with strong influence from local sources of polluted aerosols. Mixtures of aerosols are present, while suspended dust has a slightly relevant occurrence.Keywords: AOD, Ångström exponent, climatology.

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