scholarly journals Comparisons of spectral aerosol absorption in Seoul, South Korea

2017 ◽  
Author(s):  
Jungbin Mok ◽  
Nickolay A. Krotkov ◽  
Omar Torres ◽  
Hiren Jethva ◽  
Zhanqing Li ◽  
...  
Keyword(s):  
South Korea ◽  
Atmospheric Aerosol ◽  
Surface Albedo ◽  
Near Infrared ◽  
Single Scattering ◽  
Satellite Measurements ◽  
Absorption Properties ◽  
Invariant Surface ◽  
Aerosol Absorption ◽  
Gaseous Absorption

Abstract. Quantifying the aerosol absorption at ultraviolet (UV) wavelengths is important for monitoring air pollution using current (e.g., Aura/OMI) and future (e.g., TROPOMI, TEMPO, GEMS, and Sentinel-4) satellite measurements. Measurements of column atmospheric aerosol absorption (i.e., column effective imaginary refractive index (k), single scattering albedo (SSA), and aerosol absorption optical depth (AAOD)) are performed on the ground by the NASA AERONET in the visible (VIS) and near-infrared (NIR) wavelengths and in the UV-VIS-NIR by the SKYNET networks. Previous comparison studies have focused on visible and NIR wavelengths due to the lack of co-incident measurements of aerosol and gaseous absorption properties in the UV. This study compares the SKYNET-retrieved SSA in the UV with the SSA derived from a combination of AERONET, MFRSR, and Pandora (AMP) retrievals in Seoul, South Korea in spring and summer of 2016. The results show that the spectrally invariant surface albedo assumed in the SKYNET SSA retrievals leads to underestimated SSA compared to AMP values at near UV wavelengths. Re-processed SKYNET inversions using spectrally varying surface albedo, consistent with the AERONET retrieval improves agreement with AMP SSA. The combined AMP inversions allow for separating aerosol and gaseous (NO2 and O3) absorption and provides aerosol retrievals from the shortest UVB (305 nm) through visible to NIR wavelengths (870 nm).

scholarly journals Comparisons of spectral aerosol single scattering albedo in Seoul, South Korea

2018 ◽  
Vol 11 (4) ◽  
pp. 2295-2311 ◽  
Author(s):  
Jungbin Mok ◽  
Nickolay A. Krotkov ◽  
Omar Torres ◽  
Hiren Jethva ◽  
Zhanqing Li ◽  
...  
Keyword(s):  
South Korea ◽  
Surface Albedo ◽  
Near Infrared ◽  
Single Scattering ◽  
Single Scattering Albedo ◽  
Satellite Measurements ◽  
Absorption Properties ◽  
Invariant Surface ◽  
Aerosol Absorption ◽  
Gaseous Absorption

Abstract. Quantifying aerosol absorption at ultraviolet (UV) wavelengths is important for monitoring air pollution and aerosol amounts using current (e.g., Aura/OMI) and future (e.g., TROPOMI, TEMPO, GEMS, and Sentinel-4) satellite measurements. Measurements of column average atmospheric aerosol single scattering albedo (SSA) are performed on the ground by the NASA AERONET in the visible (VIS) and near-infrared (NIR) wavelengths and in the UV-VIS-NIR by the SKYNET networks. Previous comparison studies have focused on VIS and NIR wavelengths due to the lack of co-incident measurements of aerosol and gaseous absorption properties in the UV. This study compares the SKYNET-retrieved SSA in the UV with the SSA derived from a combination of AERONET, MFRSR, and Pandora (AMP) retrievals in Seoul, South Korea, in spring and summer 2016. The results show that the spectrally invariant surface albedo assumed in the SKYNET SSA retrievals leads to underestimated SSA compared to AMP values at near UV wavelengths. Re-processed SKYNET inversions using spectrally varying surface albedo, consistent with the AERONET retrieval improve agreement with AMP SSA. The combined AMP inversions allow for separating aerosol and gaseous (NO2 and O3) absorption and provide aerosol retrievals from the shortest UVB (305 nm) through VIS to NIR wavelengths (870 nm).

scholarly journals Critical surface albedo and its implications to aerosol remote sensing

2012 ◽  
Vol 5 (7) ◽  
pp. 1653-1665 ◽  
Author(s):  
F. C. Seidel ◽  
C. Popp
Keyword(s):  
Remote Sensing ◽  
Surface Albedo ◽  
Atmospheric Correction ◽  
Single Scattering ◽  
Small Range ◽  
Critical Surface ◽  
Aerosol Absorption ◽  
Sensing Applications ◽  
Aerosol Remote Sensing ◽  
Absorbing Aerosols

Abstract. We analyse the critical surface albedo (CSA) and its implications to aerosol remote sensing. CSA is defined as the surface albedo where the reflectance at top-of-atmosphere (TOA) does not depend on aerosol optical depth (AOD). AOD retrievals are therefore inaccurate at the CSA. The CSA is obtained by derivatives of the TOA reflectance with respect to AOD using a radiative transfer code. We present the CSA and the effect of surface albedo uncertainties on AOD retrieval and atmospheric correction as a function of aerosol single-scattering albedo, illumination and observation geometry, wavelength and AOD. In general, increasing aerosol absorption and increasing scattering angles lead to lower CSA. In contrast to the strict definition of the CSA, we show that the CSA can also slightly depend on AOD and therefore rather represent a small range of surface albedo values. This was often neglected in previous studies. The following implications to aerosol remote sensing applications were found: (i) surface albedo uncertainties result in large AOD retrieval errors, particularly close to the CSA; (ii) AOD retrievals of weakly or non-absorbing aerosols require dark surfaces, while strongly absorbing aerosols can be retrieved more accurately over bright surfaces; (iii) the CSA may help to estimate aerosol absorption; and (iv) the presented sensitivity of the reflectance at TOA to AOD provides error estimations to optimise AOD retrieval algorithms.

scholarly journals Combining POLDER-3 satellite observations and WRF-Chem numerical simulations to derive biomass burning aerosol properties over the Southeast Atlantic region

2021 ◽  
Author(s):  
Alexandre Siméon ◽  
Fabien Waquet ◽  
Jean-Christophe Péré ◽  
Fabrice Ducos ◽  
François Thieuleux ◽  
...  
Keyword(s):  
Numerical Simulations ◽  
Biomass Burning ◽  
Climate Models ◽  
Single Scattering ◽  
Satellite Observations ◽  
Biomass Combustion ◽  
Absorption Properties ◽  
Brown Carbon ◽  
Aerosol Absorption ◽  
Physico Chemical

Abstract. Aerosol absorption is a key property to assess the radiative impacts of aerosols on climate at both global and regional scales. The aerosol physico-chemical and optical properties remain not sufficiently constrained in climate models, with difficulties to properly represent both the aerosol load and their absorption properties in clear and cloudy scenes, especially for absorbing biomass burning aerosols (BBA). In this study we focus on biomass burning (BB) particle plumes transported above clouds over the Southeast Atlantic (SEA) region off the southwest coast of Africa, in order to improve the representation of their physico-chemical and absorption properties. The methodology is based on aerosol regional numerical simulations from the WRF-Chem coupled meteorology-chemistry model combined with a detailed inventory of BB emissions and various sets of innovative aerosol remote sensing observations, both in clear and cloudy skies from the POLDER-3/PARASOL space sensor. Current literature indicates that some organic aerosol compounds (OC) called "brown carbon" (BrOC), primarily emitted by biomass combustion absorb the ultraviolet-blue radiation more efficiently than pure black carbon (BC). We exploit this specificity by comparing the spectral dependence of the aerosol single scattering albedo (SSA) derived from the POLDER-3 satellite observations in the 443–1020 nm wavelength range with the SSA simulated for different proportions of BC, OC and BrOC at the source level, considering the homogeneous internal mixing state of particles. These numerical simulation experiments are based on two main constraints: maintaining a realistic aerosol optical depth both in clear and above cloudy scenes and a realistic BC/OC mass ratio. Modelling experiments are presented and discussed to link the chemical composition with the absorption properties of BBA and to provide estimates of the relative proportions of black, organic and brown carbon in the African BBA plumes transported over the SEA region for July 2008. The absorbing fraction of organic aerosols in the BBA plumes, i.e., BrOC, is estimated at 2 to 3 %. The simulated mean SSA are 0.81 (565 nm) and 0.84 (550 nm) in clear and above cloudy scenes respectively, in good agreement with those retrieved by POLDER-3 (0.85 ± 0.05 at 565 nm in clear-sky and at 550 nm above clouds) for the studied period.

scholarly journals Inferring the absorption properties of organic aerosol in biomass burning plumes from remote optical observations

2021 ◽  
Author(s):  
Igor B. Konovalov ◽  
Nikolai A. Golovushkin ◽  
Matthias Beekmann ◽  
Mikhail V. Panchenko ◽  
Meinrat O. Andreae
Keyword(s):  
Biomass Burning ◽  
Synthetic Data ◽  
Organic Aerosol ◽  
Single Scattering ◽  
Absorption Efficiency ◽  
Optical Observations ◽  
Annual Data ◽  
Observational Constraints ◽  
Absorption Properties ◽  
Aerosol Absorption

Abstract. Light-absorbing organic matter, known as brown carbon (BrC), has previously been found to significantly enhance the absorption of solar radiation by biomass burning (BB) aerosol. Previous studies also proposed methods aimed at constraining the BrC contribution to the overall aerosol absorption using the absorption Ångström exponents (AAEs) derived from the multi-wavelength remote observations at Aerosol Robotic Network (AERONET). However, representations of the BrC absorption in atmospheric models remain uncertain, particularly due to the high variability of the absorption properties of BB organic aerosol (OA). As a result, there is a need for stronger observational constraints on these properties. We extend the concept of the established AAE-based methods in the framework of our Bayesian method, which combines remote optical observations with Monte Carlo simulations of the aerosol absorption properties. We propose that the observational constraints on the absorption properties of BB OA can be enhanced by using the single scattering albedo (SSA) as part of the observation vector. The capabilities of our method were first examined by using synthetic data, which were intended to represent the absorption properties of BB aerosol originating from wildfires in Siberia. We found that observations of AAEs and SSA can provide efficient constraints not only on the BrC contribution to the total absorption but also on both the imaginary part of the refractive index and mass absorption efficiency of OA. As a result of the subsequent application of our method to the original multi-annual data from Siberian AERONET sites, we estimated that the average contribution of BrC to the overall light absorption by BB aerosol in Siberia at the 440 nm wavelength is about 15 %, although, in some cases, it can be more than 30 %. Based on the analysis of the AERONET data, we also derived simple nonlinear parameterizations for the absorption characteristics of BB OA in Siberia as functions of AAE.

scholarly journals Critical surface albedo and its implications to aerosol remote sensing

2011 ◽  
Vol 4 (6) ◽  
pp. 7725-7750 ◽  
Author(s):  
F. C. Seidel ◽  
C. Popp
Keyword(s):  
Remote Sensing ◽  
Surface Albedo ◽  
Atmospheric Correction ◽  
Single Scattering ◽  
Critical Surface ◽  
Aerosol Absorption ◽  
Sensing Applications ◽  
Aerosol Remote Sensing ◽  
Absorbing Aerosols ◽  
Observation Geometry

Abstract. We analyse the critical surface albedo (CSA) and its implications to aerosol remote sensing. CSA is defined as the surface albedo, where the reflectance at top-of-atmosphere (TOA) does not depend on aerosol optical depth (AOD). AOD retrievals are therefore inaccurate at the CSA. The CSA is obtained by derivatives of the TOA reflectance with respect to AOD using a radiative transfer code. We present the CSA and the effect of surface albedo uncertainties on AOD retrieval and atmospheric correction as a function of aerosol single-scattering albedo, illumination and observation geometry, wavelength and AOD. In general, increasing aerosol absorption and increasing scattering angles lead to lower CSA. We show that the CSA also depends on AOD, which was often neglected in previous studies. The following implications to aerosol remote sensing applications were found: (i) surface albedo uncertainties result in large AOD retrieval errors, particularly close to the CSA; (ii) AOD retrievals of non-absorbing aerosols require dark surfaces, while strong absorbing aerosols can be retrieved more accurately over bright surfaces; (iii) the CSA may help to estimate aerosol absorption; and (iv) the presented sensitivity of the reflectance at TOA to AOD provides error estimations to optimise AOD retrieval algorithms.

scholarly journals Analysis of aerosol absorption properties and transport over North Africa and the Middle East using AERONET data

2016 ◽  
Vol 34 (11) ◽  
pp. 1031-1044 ◽  
Author(s):  
Ashraf Farahat ◽  
Hesham El-Askary ◽  
Peter Adetokunbo ◽  
Abu-Tharr Fuad
Keyword(s):  
Middle East ◽  
North Africa ◽  
Geographic Location ◽  
Single Scattering ◽  
Transport Mechanisms ◽  
Absorption Properties ◽  
Data Set ◽  
Aerosol Absorption ◽  
Average Variation ◽  
Aerosol Types

Abstract. In this paper particle categorization and absorption properties were discussed to understand transport mechanisms at different geographic locations and possible radiative impacts on climate. The long-term Aerosol Robotic Network (AERONET) data set (1999–2015) is used to estimate aerosol optical depth (AOD), single scattering albedo (SSA), and the absorption Ångström exponent (αabs) at eight locations in North Africa and the Middle East. Average variation in SSA is calculated at four wavelengths (440, 675, 870, and 1020 nm), and the relationship between aerosol absorption and physical properties is used to infer dominant aerosol types at different locations. It was found that seasonality and geographic location play a major role in identifying dominant aerosol types at each location. Analyzing aerosol characteristics among different sites using AERONET Version 2, Level 2.0 data retrievals and the Hybrid Single Particle Lagrangian Integrated Trajectory model (HYSPLIT) backward trajectories shows possible aerosol particle transport among different locations indicating the importance of understanding transport mechanisms in identifying aerosol sources.

scholarly journals Combining POLDER-3 satellite observations and WRF-Chem numerical simulations to derive biomass burning aerosol properties over the southeast Atlantic region

2021 ◽  
Vol 21 (23) ◽  
pp. 17775-17805
Author(s):  
Alexandre Siméon ◽  
Fabien Waquet ◽  
Jean-Christophe Péré ◽  
Fabrice Ducos ◽  
François Thieuleux ◽  
...  
Keyword(s):  
Numerical Simulations ◽  
Biomass Burning ◽  
Climate Models ◽  
Single Scattering ◽  
Satellite Observations ◽  
Biomass Combustion ◽  
Absorption Properties ◽  
Brown Carbon ◽  
Aerosol Absorption ◽  
Physico Chemical

Abstract. Aerosol absorption is a key property to assess the radiative impacts of aerosols on climate at both global and regional scales. The aerosol physico-chemical and optical properties remain not sufficiently constrained in climate models, with difficulties to properly represent both the aerosol load and their absorption properties in clear and cloudy scenes, especially for absorbing biomass burning aerosols (BBA). In this study we focus on biomass burning (BB) particle plumes transported above clouds over the southeast Atlantic (SEA) region off the southwest coast of Africa, in order to improve the representation of their physico-chemical and absorption properties. The methodology is based on aerosol regional numerical simulations from the WRF-Chem coupled meteorology–chemistry model combined with a detailed inventory of BB emissions and various sets of innovative aerosol remote sensing observations, both in clear and cloudy skies from the POLDER-3/PARASOL space sensor. Current literature indicates that some organic aerosol compounds (OC), called brown carbon (BrOC), primarily emitted by biomass combustion absorb the ultraviolet-blue radiation more efficiently than pure black carbon (BC). We exploit this specificity by comparing the spectral dependence of the aerosol single scattering albedo (SSA) derived from the POLDER-3 satellite observations in the 443–1020 nm wavelength range with the SSA simulated for different proportions of BC, OC and BrOC at the source level, considering the homogeneous internal mixing state of particles. These numerical simulation experiments are based on two main constraints: maintaining a realistic aerosol optical depth both in clear and above cloudy scenes and a realistic BC/OC mass ratio. Modelling experiments are presented and discussed to link the chemical composition with the absorption properties of BBA and to provide estimates of the relative proportions of black, organic and brown carbon in the African BBA plumes transported over the SEA region for July 2008. The absorbing fraction of organic aerosols in the BBA plumes, i.e. BrOC, is estimated at 2 % to 3 %. The simulated mean SSA are 0.81 (565 nm) and 0.84 (550 nm) in clear and above cloudy scenes respectively, in good agreement with those retrieved by POLDER-3 (0.85±0.05 at 565 nm in clear sky and at 550 nm above clouds) for the studied period.

Study on the Near-infrared Absorption Properties of ZnGeP2 Single Crystals

2010 ◽  
Vol 25 (10) ◽  
pp. 1029-1033
Author(s):  
Shi-Xing XIA ◽  
Chun-Hui YANG ◽  
Chong-Qiang ZHU ◽  
Tian-Hui MA ◽  
Meng WANG ◽  
...  
Keyword(s):  
Single Crystals ◽  
Infrared Absorption ◽  
Near Infrared ◽  
Absorption Properties

scholarly journals The implication of the air quality pattern in South Korea after the COVID-19 outbreak

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Ja-Ho Koo ◽  
Jhoon Kim ◽  
Yun Gon Lee ◽  
Sang Seo Park ◽  
Seoyoung Lee ◽  
...  
Keyword(s):  
Air Quality ◽  
South Korea ◽  
Social Impact ◽  
Social Activity ◽  
Satellite Measurements ◽  
Ordinary Life ◽  
The Social ◽  
Regional Air Quality ◽  
Long Lifetime ◽  
Positive Effect

AbstractBy using multiple satellite measurements, the changes of the aerosol optical depth (AOD) and nitrogen dioxide (NO2) over South Korea were investigated from January to March 2020 to evaluate the COVID-19 effect on the regional air quality. The NO2 decrease in South Korea was found but not significant, which indicates the effects of spontaneous social distancing under the maintenance of ordinary life. The AODs in 2020 were normally high in January, but they became lower starting from February. Since the atmosphere over Eastern Asia was unusually stagnant in January and February 2020, the AOD decrease in February 2020 clearly reveals the positive effect of the COVID-19. Considering the insignificant NO2 decrease in South Korea and the relatively long lifetime of aerosols, the AOD decrease in South Korea may be more attributed to the improvement of the air quality in neighboring countries. In March, regional atmosphere became well mixed and ventilated over South Korea, contributing to large enhancement of air quality. While the social activity was reduced after the COVID-19 outbreak, the regional meteorology should be also examined significantly to avoid the biased evaluation of the social impact on the change of the regional air quality.

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