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Chris A. Hostetler - One of the best experts on this subject based on the ideXlab platform.

  • improving estimates of pm2 5 concentration and chemical composition by application of high spectral resolution lidar hsrl and creating Aerosol Types from chemistry catch algorithm
    Atmospheric Environment, 2021
    Co-Authors: N Meskhidze, K. W. Dawson, Matthew S. Johnson, Chris A. Hostetler, Bethany Sutherland, Xinyi Ling, Barron H Henderson, Richard A. Ferrare
    Abstract:

    Abstract Improved characterization of ambient PM2.5 mass concentration and chemical speciation is a topic of interest in air quality and climate sciences. Over the past decades, considerable efforts have been made to improve ground-level PM2.5 using remotely sensed data. Here we present two new approaches for estimating atmospheric PM2.5 and chemical composition based on the High Spectral Resolution Lidar (HSRL)-retrieved Aerosol extinction values and Types and Creating Aerosol Types from Chemistry (CATCH)-derived Aerosol chemical composition. The first methodology (CMAQ-HSRL-CH) improves EPA’s Community Multiscale Air Quality (CMAQ) predictions by applying variable scaling factors derived using remotely-sensed information about Aerosol vertical distribution and Types and the CATCH algorithm. The second methodology (HSRL-CH) does not require regional model runs and can provide atmospheric PM2.5 mass concentration and chemical speciation using only the remotely sensed data and the CATCH algorithm. The resulting PM2.5 concentrations and chemical speciation derived for NASA DISCOVER-AQ (Deriving Information on Surface Conditions from COlumn and VERtically Resolved Observations Relevant to Air Quality) Baltimore-Washington, D.C. Corridor (BWC) Campaign (2011) are compared to surface measurements from EPA’s Air Quality Systems (AQS) network. The analysis shows that the CMAQ-HSRL-CH method leads to considerable improvement of CMAQ’s predicted PM2.5 concentrations (R2 value increased from 0.37 to 0.63, the root mean square error (RMSE) was reduced from 11.9 to 7.2 μg m-3, and the normalized mean bias (NMB) was lowered from -46.0 to 4.6%). The HSRL-CH method showed statistics (R2=0.75, RMSE=8.6 μgm-3, and NMB=24.0%), which were better than the CMAQ prediction of PM2.5 alone and analogous to CMAQ-HSRL-CH. In addition to mass concentration, HSRL-CH can also provide Aerosol chemical composition without specific model simulations. We expect that the HSRL-CH method will be able to make reliable estimates of PM2.5 concentration and chemical composition where HSRL data are available.

  • creating Aerosol Types from chemistry catch a new algorithm to extend the link between remote sensing and models
    Journal of Geophysical Research, 2017
    Co-Authors: K. W. Dawson, Nicholas Meskhidze, Matthew S. Johnson, Meloë Kacenelenbogen, S P Burton, Chris A. Hostetler
    Abstract:

    Current remote sensing methods can identify Aerosol Types within an atmospheric column, presenting an opportunity to incrementally bridge the gap between remote sensing and models. Here a new algorithm was designed for Creating Aerosol Types from CHemistry (CATCH). CATCH-derived Aerosol Types—dusty mix, maritime, urban, smoke, and fresh smoke—are based on first-generation airborne High Spectral Resolution Lidar (HSRL-1) retrievals during the Ship-Aircraft Bio-Optical Research (SABOR) campaign, July/August 2014. CATCH is designed to derive Aerosol Types from model output of chemical composition. CATCH-derived Aerosol Types are determined by multivariate clustering of model-calculated variables that have been trained using retrievals of Aerosol Types from HSRL-1. CATCH-derived Aerosol Types (with the exception of smoke) compare well with HSRL-1 retrievals during SABOR with an average difference in Aerosol optical depth (AOD) <0.03. Data analysis shows that episodic free tropospheric transport of smoke is underpredicted by the Goddard Earth Observing System- with Chemistry (GEOS-Chem) model. Spatial distributions of CATCH-derived Aerosol Types for the North American model domain during July/August 2014 show that Aerosol type-specific AOD values occurred over representative locations: urban over areas with large population, maritime over oceans, smoke, and fresh smoke over typical biomass burning regions. This study demonstrates that model-generated information on Aerosol chemical composition can be translated into Aerosol Types analogous to those retrieved from remote sensing methods. In the future, spaceborne HSRL-1 and CATCH can be used to gain insight into chemical composition of Aerosol Types, reducing uncertainties in estimates of Aerosol radiative forcing.

  • Creating Aerosol Types from CHemistry (CATCH): A New Algorithm to Extend the Link Between Remote Sensing and Models
    Journal of Geophysical Research: Atmospheres, 2017
    Co-Authors: K. W. Dawson, Nicholas Meskhidze, Sharon Burton, Matthew S. Johnson, Meloë Kacenelenbogen, Chris A. Hostetler
    Abstract:

    Current remote sensing methods can identify Aerosol Types within an atmospheric column, presenting an opportunity to incrementally bridge the gap between remote sensing and models. Here a new algorithm was designed for Creating Aerosol Types from CHemistry (CATCH). CATCH-derived Aerosol Types—dusty mix, maritime, urban, smoke, and fresh smoke—are based on first-generation airborne High Spectral Resolution Lidar (HSRL-1) retrievals during the Ship-Aircraft Bio-Optical Research (SABOR) campaign, July/August 2014. CATCH is designed to derive Aerosol Types from model output of chemical composition. CATCH-derived Aerosol Types are determined by multivariate clustering of model-calculated variables that have been trained using retrievals of Aerosol Types from HSRL-1. CATCH-derived Aerosol Types (with the exception of smoke) compare well with HSRL-1 retrievals during SABOR with an average difference in Aerosol optical depth (AOD)

  • Vertically resolved separation of dust and other Aerosol Types by a new lidar depolarization method.
    Optics express, 2015
    Co-Authors: Tao Luo, Chris A. Hostetler, Zhien Wang, Richard A. Ferrare, Renmin Yuan, Damao Zhang
    Abstract:

    This paper developed a new retrieval framework of external mixing of the dust and non-dust Aerosol to predict the lidar ratio of the external mixing Aerosols and to separate the contributions of non-spherical Aerosols by using different depolarization ratios among dust, sea salt, smoke, and polluted Aerosols. The detailed sensitivity tests and case study with the new method showed that reliable dust information could be retrieved even without prior information about the non-dust Aerosol Types. This new method is suitable for global dust retrievals with satellite observations, which is critical for better understanding global dust transportation and for model improvements.

  • Separating mixtures of Aerosol Types in airborne High Spectral Resolution Lidar data
    Atmospheric Measurement Techniques, 2014
    Co-Authors: Sharon Burton, M. A. Vaughan, R. A. Ferrare, Chris A. Hostetler
    Abstract:

    Abstract. Knowledge of Aerosol type is important for determining the magnitude and assessing the consequences of Aerosol radiative forcing, and can provide useful information for source attribution studies. However, atmospheric Aerosol is frequently not a single pure type, but instead occurs as a mixture of Types, and this mixing affects the optical and radiative properties of the Aerosol. This paper extends the work of earlier researchers by using the Aerosol intensive parameters measured by the NASA Langley Research Center airborne High Spectral Resolution Lidar (HSRL-1) to develop a comprehensive and unified set of rules for characterizing the external mixing of several key Aerosol intensive parameters: extinction-to-backscatter ratio (i.e., lidar ratio), backscatter color ratio, and depolarization ratio. We present the mixing rules in a particularly simple form that leads easily to mixing rules for the covariance matrices that describe Aerosol distributions, rather than just single values of measured parameters. These rules can be applied to infer mixing ratios from the lidar-observed Aerosol parameters, even for cases without significant depolarization. We demonstrate our technique with measurement curtains from three HSRL-1 flights which exhibit mixing between two Aerosol Types, urban pollution plus dust, marine plus dust, and smoke plus marine. For these cases, we infer a time-height cross-section of extinction mixing ratio along the flight track, and partition Aerosol extinction into portions attributed to the two pure Types.

D G Kaskaoutis - One of the best experts on this subject based on the ideXlab platform.

  • identification of key Aerosol Types and mixing states in the central indian himalayas during the gvax campaign the role of particle size in Aerosol classification
    Science of The Total Environment, 2021
    Co-Authors: U C Dumka, D G Kaskaoutis, N Mihalopoulos, Rahul Sheoran
    Abstract:

    Abstract Studies in Aerosol properties, Types and sources in the Himalayas are important for atmospheric and climatic issues due to high Aerosol loading in the neighboring plains. This study uses in situ measurements of Aerosol optical and microphysical properties obtained during the Ganges Valley Aerosol eXperiment (GVAX) at Nainital, India over the period June 2011–March 2012, aiming to identify key Aerosol Types and mixing states for two particle sizes (PM1 and PM10). Using a classification matrix based on SAE vs. AAE thresholds (scattering vs. absorption Angstrom exponents, respectively), seven Aerosol Types are identified, which are highly dependent on particle size. An Aerosol type named “large/BC mix” dominates in both PM1 (45.4%) and PM10 (46.9%) mass, characterized by aged BC mixed with other Aerosols, indicating a wide range of particle sizes and mixing states. Small particles with low spectral dependence of the absorption (AAE

  • In situ identification of Aerosol Types in Athens, Greece, based on long-term optical and on online chemical characterization
    Atmospheric Environment, 2021
    Co-Authors: D G Kaskaoutis, U C Dumka, Georgios Grivas, Iasonas Stavroulas, Eleni Liakakou, Konstantinos Dimitriou, Evangelos Gerasopoulos, N Mihalopoulos
    Abstract:

    Abstract Absorption Angstrom Exponent (AAE) and Scattering Angstrom Exponent (SAE) values, derived from aethalometer and nephelometer measurements during a period of 3 years at an urban background site in Athens, are combined for the first Aerosol type classification using in situ measurements in the eastern Mediterranean. In addition, single scattering albedo (SSA) and its wavelength dependence (dSSA), as well as the chemical composition of fine Aerosols and precursor gases from collocated measurements, are utilized to provide further insights on the optical-chemical characterization and related sources of seven identified Aerosol Types. Urban Aerosols are mostly characterized as Black Carbon (BC)-dominated (76.3%), representing a background atmosphere where fossil-fuel combustion is dominant throughout the year, while 14.3% of the cases correspond to the mixed Brown Carbon (BrC)-BC type, with a higher frequency in winter. The BrC type is associated with the highest scattering and absorption coefficients during winter nights, representing the impact from residential wood-burning emissions. Dust mixed with urban pollution (1.2%) and large particles mixed with BC (5.3%) have a higher frequency in spring. Furthermore, aging processes and BC coating with organic and inorganic species with weak spectral absorption (AAE

  • Identification of key Aerosol Types and mixing states in the central Indian Himalayas during the GVAX campaign: the role of particle size in Aerosol classification
    The Science of the total environment, 2020
    Co-Authors: U C Dumka, D G Kaskaoutis, N Mihalopoulos, Rahul Sheoran
    Abstract:

    Studies in Aerosol properties, Types and sources in the Himalayas are important for atmospheric and climatic issues due to high Aerosol loading in the neighboring plains. This study uses in situ measurements of Aerosol optical and microphysical properties obtained during the Ganges Valley Aerosol eXperiment (GVAX) at Nainital, India over the period June 2011-March 2012, aiming to identify key Aerosol Types and mixing states for two particle sizes (PM1 and PM10). Using a classification matrix based on SAE vs. AAE thresholds (scattering vs. absorption Angstrom exponents, respectively), seven Aerosol Types are identified, which are highly dependent on particle size. An Aerosol type named "large/BC mix" dominates in both PM1 (45.4%) and PM10 (46.9%) mass, characterized by aged BC mixed with other Aerosols, indicating a wide range of particle sizes and mixing states. Small particles with low spectral dependence of the absorption (AAE < 1) account for 31.6% and BC-dominated Aerosols for 14.8% in PM1, while in PM10, a large fraction (39%) corresponds to "large/low-absorbing" Aerosols and only 3.9% is characterized as "BC-dominated". The remaining Types consist of mixtures of dust and local emissions from biofuel burning and display very small fractions. The main optical properties e.g. spectral scattering, absorption, single scattering albedo, activation ratio, as well as seasonality and dependence on wind speed and direction of identified Types are examined, revealing a large influence of air masses originating from the Indo-Gangetic Plains. This indicates that Aerosols over the central Himalayas are mostly composed by mixtures of processed and transported polluted plumes from the plains. This is the first study that identifies key Aerosol populations in the central Indian Himalayas based on in situ measurements and the results are highly important for Aerosol-type inventories, chemical transport models and reducing the uncertainty in Aerosol radiative forcing over the third pole.

  • characterising the long range transport mechanisms of different Aerosol Types over athens greece during 2000 2005
    International Journal of Climatology, 2012
    Co-Authors: D G Kaskaoutis, P T Nastos, P G Kosmopoulos, H D Kambezidis
    Abstract:

    This study analyses the weather conditions, the main pathways and transport mechanisms favouring the presence of specific Aerosol Types over Athens, Greece. On the basis of the Aerosol optical depth at 550 nm (AOD550) and fine mode (FM) values from a Terra-MODIS dataset in the period 2000–2005, three main Aerosol Types are identified (urban/industrial, UI; clean maritime, CM; and desert dust, DD), each one corresponding to different optical characteristics and source regions. The UI Aerosols are associated with polluted air masses from Europe, the CM Aerosols with clean Atlantic air masses and the DD Aerosols with air masses from North African arid regions carrying significant amount of dust in certain cases. The comparison of the three Aerosol Types with the air masses from their favourable sector constitutes a first ‘quick-validation’ of the identification scheme. Thus, the incidence of transport from Europe explain 81% of the variability in the observed UI type, while the 73% of the Atlantic air masses correspond to the CM type; the 50% of the African air masses can be considered as DD Aerosols over Athens. The mean synoptic meteorological patterns, favouring the presence of each Aerosol type, are also investigated. Further analysing the air-mass trajectories at three altitudes, the transport mechanisms of the Aerosol Types are identified. The results clearly show that the UI Aerosols are mainly transported within the boundary layer, while the CM conditions are associated with Atlantic air masses at higher altitudes. Moreover, the DD Aerosols are transported either in the upper atmosphere or in the whole atmospheric column. This is among the first studies conducted over Athens aiming at investigating the weather conditions, pathways and transport mechanisms that favour the presence of Aerosols of different characteristics. Copyright © 2011 Royal Meteorological Society

  • Aerosol climatology: dependence of the Angstrom exponent on wavelength over four AERONET sites
    Atmospheric Chemistry and Physics Discussions, 2007
    Co-Authors: D G Kaskaoutis, P G Kosmopoulos, H D Kambezidis, N. Hatzianastassiou, K. V. S. Badarinath
    Abstract:

    The Ångström exponent, ?, is often used as a qualitative indicator of Aerosol particle size. In this study, Aerosol optical depth (AOD) and Ångström exponent (?) data were analyzed to obtain information about the adequacy of the simple use of the Ångström exponent for characterizing Aerosols, and for exploring possibilities for a more efficient characterization of Aerosols. This was made possible by taking advantage of the spectral variation of ?, the so-called curvature. The data were taken from four selected AERONET stations, which are representative of four Aerosol Types, i.e. biomass burning, pollution, desert dust and maritime. Using the least-squares method, the Ångström-? was calculated in the spectral interval 340?870 nm, along with the coefficients ?1 and ?2 of the second order polynomial fit to the plotted logarithm of AOD versus the logarithm of wavelength, and the second derivative of ?. The results show that the spectral curvature can provide important additional information about the different Aerosol Types, and can be effectively used to discriminate between them, since the fine-mode particles exhibit negative curvature, while the coarse-mode Aerosols positive. In addition, the curvature has always to be taken into account in the computations of Ångström exponent values in the spectral intervals 380?440 nm and 675?870 nm, since fine-mode Aerosols exhibit larger ?675?870 than ?380?440 values, and vice-versa for coarse-mode particles. A second-order polynomial fit simulates the spectral dependence of the AODs very well, while the associated constant term varies proportionally to the Aerosol type. The correlation between the coefficients ?1 and ?2 of the second-order polynomial fit and the Ångström exponent ?, and the atmospheric turbidity, is further investigated. The obtained results reveal important features, which can be used for better discriminating between different Aerosol Types.

A. Di Sarra - One of the best experts on this subject based on the ideXlab platform.

  • surface shortwave radiative forcing of different Aerosol Types in the central mediterranean
    Geophysical Research Letters, 2008
    Co-Authors: A. Di Sarra, G Pace, D Meloni, L De Silvestri, Salvatore Piacentino, F Monteleone
    Abstract:

    [1] Ground based measurements of Aerosol optical depth, τ, and shortwave irradiance at the Mediterranean island of Lampedusa during 2003 and 2004 were used to estimate the surface Aerosol shortwave radiative forcing. The shortwave forcing efficiency (FE) was derived at various solar zenith angles, θ, as the derivative of the shortwave irradiance with respect to τ. Values of FE for different classes of particles, namely desert dust, DD, biomass burning/industrial Aerosols, BU, and for the whole dataset are derived. At the summer solstice the daily average FE is −86.4 W/m2 for DD, −70.5 W/m2 for BU, and −94.0 W/m2 for the whole dataset. The daily Aerosol forcing of DD is much larger than for the other Aerosol classes due to the combination of larger forcing efficiency and largest optical depths. The estimated average daily forcing at the summer solstice and equinox for DD is −30 and −24 W/m2, respectively.

  • Aerosol optical properties at Lampedusa (Central Mediterranean). 2. Determination of single scattering albedo at two wavelengths for different Aerosol Types
    Atmospheric Chemistry and Physics, 2006
    Co-Authors: D. Meloni, A. Di Sarra, G. Pace, F. Monteleone
    Abstract:

    Aerosol optical properties were retrieved from direct and diffuse spectral irradiance measurements made by a multi-filter rotating shadowband radiometer (MFRSR) at the island of Lampedusa (35.5° N, 12.6° E), in the Central Mediterranean, in the period July 2001?September 2003. In a companion paper (Pace et al., 2006) the Aerosol optical depth (AOD) and Ångström exponent were used together with airmass backward trajectories to identify and classify different Aerosol Types. The MFRSR diffuse-to-direct ratio (DDR) at 415.6 nm and 868.7 nm for Aerosol classified as "biomass burning-urban/industrial", originating primarily from the European continent, and desert dust, originating from the Sahara, is used in this study to estimate the Aerosol single scattering albedo (SSA). A detailed radiative transfer model is initialised with the measured Aerosol optical depth; calculations are performed at the two wavelengths varying the SSA values until the modelled DDR matches the MFRSR observations. Sensitivity studies are performed to estimate how uncertainties on AOD, DDR, asymmetry factor (g), and surface albedo influence the retrieved SSA values. The results show that a 3% variation of AOD or DDR produce a change of about 0.02 in the retrieved SSA value at 415.6 and 868.7 nm; a ±0.06 variation of the asymmetry factor g produces a change of the estimated SSA of

  • Aerosol optical properties at Lampedusa (Central Mediterranean). 2. Determination of single scattering albedo at two wavelengths for different Aerosol Types
    Atmospheric Chemistry and Physics, 2006
    Co-Authors: D. Meloni, A. Di Sarra, G. Pace, F. Monteleone
    Abstract:

    Abstract. Aerosol optical properties were retrieved from direct and diffuse spectral irradiance measurements made by a multi-filter rotating shadowband radiometer (MFRSR) at the island of Lampedusa (35.5° N, 12.6° E), in the Central Mediterranean, in the period July 2001–September 2003. In a companion paper (Pace et al., 2006) the Aerosol optical depth (AOD) and Ångström exponent were used together with airmass backward trajectories to identify and classify different Aerosol Types. The MFRSR diffuse-to-direct ratio (DDR) at 415.6 nm and 868.7 nm for Aerosol classified as "biomass burning-urban/industrial", originating primarily from the European continent, and desert dust, originating from the Sahara, is used in this study to estimate the Aerosol single scattering albedo (SSA). A detailed radiative transfer model is initialised with the measured Aerosol optical depth; calculations are performed at the two wavelengths varying the SSA values until the modelled DDR matches the MFRSR observations. Sensitivity studies are performed to estimate how uncertainties on AOD, DDR, asymmetry factor (g), and surface albedo influence the retrieved SSA values. The results show that a 3% variation of AOD or DDR produce a change of about 0.02 in the retrieved SSA value at 415.6 and 868.7 nm; a ±0.06 variation of the asymmetry factor g produces a change of the estimated SSA of <0.04 at 415.6 nm, and <0.06 at 868.7 nm; finally, an increase of the assumed surface albedo of 0.05 causes very small changes (0.01–0.02) in the retrieved SSA. The calculations show that the SSA of desert dust (DD) increases with wavelength, from 0.81±0.05 at 415.6 nm to 0.94±0.05 at 868.7 nm; on the contrary, the SSA of urban/industrial (UN) Aerosols decreases from 0.96±0.02 at 415.6 nm to 0.87±0.07 at 868.7 nm; the SSA of biomass burning (BB) particles is 0.82±0.04 at 415.6 nm and 0.80±0.05 at 868.7 nm. Episodes of UN Aerosols occur usually in June and July; long lasting BB Aerosol episodes with large AOD are observed mainly in July and August, the driest months of the year, when the development of fires is frequent.

  • Aerosol optical properties at Lampedusa (Central Mediterranean) ? 2. Determination of single scattering albedo at two wavelengths for different Aerosol Types
    Atmospheric Chemistry and Physics Discussions, 2005
    Co-Authors: D. Meloni, A. Di Sarra, G. Pace, F. Monteleone
    Abstract:

    Aerosol optical properties were retrieved from direct and diffuse spectral irradiance measurements made by a multi-filter rotating shadowband radiometer (MFRSR) at the island of Lampedusa (35.5° N, 12.6° E), in the Central Mediterranean, in the period July 2001?September 2003. In a companion paper (Pace et al., 2005) the Aerosol optical depth (AOD) and Ångström exponent were used together with airmass backward trajectories to identify and classify different Aerosol Types. The MFRSR diffuse-to-direct ratio (DDR) at 415.6 nm and 868.7 nm for Aerosol classified as biomass burning-urban/industrial, originating primarily from the European continent, and desert dust, originating from the Sahara, is used in this study to estimate the Aerosol single scattering albedo (SSA). A detailed radiative transfer model is initialized with the measured Aerosol optical depth; calculations are performed at the two wavelengths varying the SSA values until the modelled DDR matches the MFRSR observations. Sensitivity studies are performed to estimate how uncertainties on AOD, DDR, asymmetry factor (g), and surface albedo influence the retrieved SSA values. The results show that a 3% variation of AOD or DDR produce a change of about 0.02 in the retrieved SSA value at 415.6 and 868.7 nm; a ±0.06 variation of the asymmetry factor g produces a change of the estimated SSA of

  • Aerosol optical properties at Lampedusa (Central Mediterranean) – 2. Determination of single scattering albedo at two wavelengths for different Aerosol Types
    2005
    Co-Authors: D. Meloni, A. Di Sarra, G. Pace, F. Monteleone
    Abstract:

    Abstract. Aerosol optical properties were retrieved from direct and diffuse spectral irradiance measurements made by a multi-filter rotating shadowband radiometer (MFRSR) at the island of Lampedusa (35.5° N, 12.6° E), in the Central Mediterranean, in the period July 2001–September 2003. In a companion paper (Pace et al., 2005) the Aerosol optical depth (AOD) and Ångström exponent were used together with airmass backward trajectories to identify and classify different Aerosol Types. The MFRSR diffuse-to-direct ratio (DDR) at 415.6 nm and 868.7 nm for Aerosol classified as biomass burning-urban/industrial, originating primarily from the European continent, and desert dust, originating from the Sahara, is used in this study to estimate the Aerosol single scattering albedo (SSA). A detailed radiative transfer model is initialized with the measured Aerosol optical depth; calculations are performed at the two wavelengths varying the SSA values until the modelled DDR matches the MFRSR observations. Sensitivity studies are performed to estimate how uncertainties on AOD, DDR, asymmetry factor (g), and surface albedo influence the retrieved SSA values. The results show that a 3% variation of AOD or DDR produce a change of about 0.02 in the retrieved SSA value at 415.6 and 868.7 nm; a ±0.06 variation of the asymmetry factor g produces a change of the estimated SSA of <0.04 at 415.6 nm, and <0.06 at 868.7 nm; finally, an increase of the assumed surface albedo of 0.05 gives very small changes (0.01–0.02) in the retrieved SSA. The calculations show that the SSA of desert dust (DD) increases with wavelength, from 0.81±0.05 at 415.6 nm to 0.94±0.05 at 868.7 nm; on the contrary, the SSA of urban/industrial (UN) Aerosols decreases from 0.96±0.02 at 415.6 nm to 0.87±0.07 at 868.7 nm; the SSA of biomass burning (BB) particles is 0.82±0.04 at 415.6 nm and 0.80±0.05 at 868.7 nm. Episodes of UN Aerosols occur usually in June and July; BB Aerosol episodes with large AOD and long duration are observed mainly in July and August, the driest months of the year, when the development of fires is favoured.

Jhoon Kim - One of the best experts on this subject based on the ideXlab platform.

  • Characteristics of Classified Aerosol Types in South Korea during the MAPS-Seoul Campaign
    Aerosol and Air Quality Research, 2018
    Co-Authors: Seoyoung Lee, Jhoon Kim, Jaemin Hong, Yeseul Cho, Myungje Choi, Sang Seo Park, Joon Young Ahn, Sang-kyun Kim, Kyung Jung Moon, Thomas F. Eck
    Abstract:

    During the Megacity Air Pollution Studies-Seoul (MAPS-Seoul) campaign from May to June 2015, Aerosol optical properties in Korea were obtained based on the AERONET sunphotometer measurement at five sites (Anmyon, Gangneung_WNU, Gosan_SNU, Hankuk_UFS, and Yonsei_University). Using this dataset, we examine regional Aerosol Types by applying a number of known Aerosol classification methods. We thoroughly utilize five different methods to categorize the regional Aerosol Types and evaluate the results from each method by inter-comparison. The differences and similarities among the results are also discussed, contingent upon the usage of AERONET inversion products, such as the single scattering albedo. Despite several small differences, all five methods suggest the same general features in terms of the regionally dominant Aerosol type: Fine-mode Aerosols with highly absorbing radiative properties dominate at Hankuk_UFS and Yonsei_University; non-absorbing fine-mode particles form a large portion of the Aerosol at Gosan_SNU; and coarse-mode particles cause some effects at Anmyon. The analysis of 3-day back-trajectories is also performed to determine the relationship between classified Types at each site and the regional transport pattern. In particular, the spatiotemporally short-scale transport appears to have a large influence on the local Aerosol properties. As a result, we find that the domestic emission in Korea significantly contributes to the high dominance of radiation-absorbing Aerosols in the Seoul metropolitan area and the air-mass transport from China largely affects the western coastal sites, such as Anmyon and Gosan_SNU.

  • Characteristics of Aerosol Types from AERONET sunphotometer measurements
    Atmospheric Environment, 2010
    Co-Authors: Jaehwa Lee, Jhoon Kim, Chul H. Song, S.b. Kim, Y. Chun, Byung-ju Sohn, Brent N. Holben
    Abstract:

    By using observations from the Aerosol Robotic Network (AERONET), Aerosol Types are classified according to dominant size mode and radiation absorptivity as determined by fine-mode fraction (FMF) and single-scattering albedo (SSA), respectively. The Aerosol type from anthropogenic sources is significantly different with regard to location and season, while dust Aerosol is observed persistently over North Africa and the Arabian Peninsula. For four reference locations where different Aerosol Types are observed, time series and optical properties for each Aerosol type are investigated. The results show that Aerosol Types are strongly affected by their sources and partly affected by relative humidity. The analysis and methodology of this study can be used to compare Aerosol classification results from satellite and chemical transport models, as well as to analyze Aerosol characteristics on a global scale over land for which satellite observations need to be improved.

  • Validation of Aerosol Type Classification from Satellite Remote Sensing
    2009
    Co-Authors: Jaehwa Lee, Jhoon Kim, Jungbin Mok, Yunjae Kim
    Abstract:

    Inter‐comparison of various satellite data is performed for the purpose of validation of Aerosol type classification algorithm from satellite remote sensing, so called, MODIS‐OMI algorithm (MOA hereafter). Infrared Optical Depth Index (IODI), correlation coefficient between carbon monoxide (CO) column density and black carbon (BC) Aerosol optical thickness (AOT), and Aerosol Types from 4‐channel algorithm and CALIOP measurements are used to validate dust, BC, and Aerosol type from MOA, respectively. The agreement of dust pixels between IODI and MOA ranges 0.1 to 0.6 with respect to AOT constraint, and it is inferred that IODI is less sensitive to optically thin dust layer. Increase of the correlation coefficient between AOT and CO column density when BC pixels are taken into account supports the performance of MOA to detect BC Aerosol. The agreement of Aerosol Types from MOA and 4 CA showed reasonable consistency, and the difference can be described by different absorptivity test and retrieval accuracy of...

  • Validation of Aerosol type classification from satellite remote sensing
    Remote Sensing of the Atmosphere and Clouds II, 2008
    Co-Authors: Jhoon Kim, Jaehwa Lee, Jungbin Mok, Yunjae Kim
    Abstract:

    Inter-comparison of various satellite data is performed for the purpose of validation of Aerosol type classification algorithm from satellite remote sensing, so called, MODIS-OMI algorithm (MOA hereafter). Infrared Optical Depth Index (IODI), correlation coefficient between carbon monoxide (CO) column density and black carbon (BC) Aerosol optical thickness (AOT), and Aerosol Types from 4-channel algorithm and CALIOP measurements are used to validate dust, BC, and Aerosol type from MOA, respectively. The agreement of dust pixels between IODI and MOA ranges 0.1 to 0.6 with respect to AOT constraint, and it is inferred that IODI is less sensitive to optically thin dust layer. Increase of the correlation coefficient between AOT and CO column density when BC pixels are taken into account supports the performance of MOA to detect BC Aerosol. The agreement of Aerosol Types from MOA and 4CA showed reasonable consistency, and the difference can be described by different absorptivity test and retrieval accuracy of AE. Intercomparison of Aerosol Types between MOA and CALIOP measurements represented reasonable consistency when AOT greater than 0.5, and height dependence of MOA is inferred from consistency analysis with respect to Aerosol layer height from CALIOP measurements. Inter-comparisons among different satellite data showed feasible future for validating Aerosol type classification algorithm from satellite remote sensing.

  • Detection of Aerosol type using satellite remote sensing
    2006
    Co-Authors: Jhoon Kim, J. H. Lee, J. M. Yoon, H. K. Cho
    Abstract:

    The effects of Aerosols on the Earth’s climate have been studied extensively by using observations and model studies. As the effects of Aerosol on the climate are different from one type to the other, Aerosol type detection from satellite remote sensing is very important. There have been several methods to classify Aerosol from satellite remote sensing (e.g. Higurashi and Nakajima, 2003; Jeong and Li, 2005 etc.). This study shows temporal and spatial distribution of four major Aerosol Types (dust, carbonaceous, seasalt and sulfate) retrieved by MODIS-OMI algorithm and 4-channel algorithm from Moderate Resolution Imaging Spectroradiometer (MODIS) and Ozone Monitoring Instrument (OMI) data over the South-East Asia region. Retrieved results show that there exist complex Types of Aerosol over the South-East Asia. In general, two different Aerosol classification algorithm make reasonably consistent results for most of the Aerosol Types. Dust type Aerosol usually occurred mixed with carbonaceous type Aerosol. It implies that the dust type Aerosol is loaded and transported with polluted air mass. The evidence of long distance transport of polluted air mass in the continent is also captured, that is, over the remote ocean area. Validation of the results with ground-based chemistry measurements or chemical transfer model (CTM) and separate estimation of the different Aerosol optical depths are desirable.

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  • Aerosol optical properties at Lampedusa (Central Mediterranean). 2. Determination of single scattering albedo at two wavelengths for different Aerosol Types
    Atmospheric Chemistry and Physics, 2006
    Co-Authors: D. Meloni, A. Di Sarra, G. Pace, F. Monteleone
    Abstract:

    Aerosol optical properties were retrieved from direct and diffuse spectral irradiance measurements made by a multi-filter rotating shadowband radiometer (MFRSR) at the island of Lampedusa (35.5° N, 12.6° E), in the Central Mediterranean, in the period July 2001?September 2003. In a companion paper (Pace et al., 2006) the Aerosol optical depth (AOD) and Ångström exponent were used together with airmass backward trajectories to identify and classify different Aerosol Types. The MFRSR diffuse-to-direct ratio (DDR) at 415.6 nm and 868.7 nm for Aerosol classified as "biomass burning-urban/industrial", originating primarily from the European continent, and desert dust, originating from the Sahara, is used in this study to estimate the Aerosol single scattering albedo (SSA). A detailed radiative transfer model is initialised with the measured Aerosol optical depth; calculations are performed at the two wavelengths varying the SSA values until the modelled DDR matches the MFRSR observations. Sensitivity studies are performed to estimate how uncertainties on AOD, DDR, asymmetry factor (g), and surface albedo influence the retrieved SSA values. The results show that a 3% variation of AOD or DDR produce a change of about 0.02 in the retrieved SSA value at 415.6 and 868.7 nm; a ±0.06 variation of the asymmetry factor g produces a change of the estimated SSA of

  • Aerosol optical properties at Lampedusa (Central Mediterranean). 2. Determination of single scattering albedo at two wavelengths for different Aerosol Types
    Atmospheric Chemistry and Physics, 2006
    Co-Authors: D. Meloni, A. Di Sarra, G. Pace, F. Monteleone
    Abstract:

    Abstract. Aerosol optical properties were retrieved from direct and diffuse spectral irradiance measurements made by a multi-filter rotating shadowband radiometer (MFRSR) at the island of Lampedusa (35.5° N, 12.6° E), in the Central Mediterranean, in the period July 2001–September 2003. In a companion paper (Pace et al., 2006) the Aerosol optical depth (AOD) and Ångström exponent were used together with airmass backward trajectories to identify and classify different Aerosol Types. The MFRSR diffuse-to-direct ratio (DDR) at 415.6 nm and 868.7 nm for Aerosol classified as "biomass burning-urban/industrial", originating primarily from the European continent, and desert dust, originating from the Sahara, is used in this study to estimate the Aerosol single scattering albedo (SSA). A detailed radiative transfer model is initialised with the measured Aerosol optical depth; calculations are performed at the two wavelengths varying the SSA values until the modelled DDR matches the MFRSR observations. Sensitivity studies are performed to estimate how uncertainties on AOD, DDR, asymmetry factor (g), and surface albedo influence the retrieved SSA values. The results show that a 3% variation of AOD or DDR produce a change of about 0.02 in the retrieved SSA value at 415.6 and 868.7 nm; a ±0.06 variation of the asymmetry factor g produces a change of the estimated SSA of <0.04 at 415.6 nm, and <0.06 at 868.7 nm; finally, an increase of the assumed surface albedo of 0.05 causes very small changes (0.01–0.02) in the retrieved SSA. The calculations show that the SSA of desert dust (DD) increases with wavelength, from 0.81±0.05 at 415.6 nm to 0.94±0.05 at 868.7 nm; on the contrary, the SSA of urban/industrial (UN) Aerosols decreases from 0.96±0.02 at 415.6 nm to 0.87±0.07 at 868.7 nm; the SSA of biomass burning (BB) particles is 0.82±0.04 at 415.6 nm and 0.80±0.05 at 868.7 nm. Episodes of UN Aerosols occur usually in June and July; long lasting BB Aerosol episodes with large AOD are observed mainly in July and August, the driest months of the year, when the development of fires is frequent.

  • Aerosol optical properties at Lampedusa (Central Mediterranean) ? 2. Determination of single scattering albedo at two wavelengths for different Aerosol Types
    Atmospheric Chemistry and Physics Discussions, 2005
    Co-Authors: D. Meloni, A. Di Sarra, G. Pace, F. Monteleone
    Abstract:

    Aerosol optical properties were retrieved from direct and diffuse spectral irradiance measurements made by a multi-filter rotating shadowband radiometer (MFRSR) at the island of Lampedusa (35.5° N, 12.6° E), in the Central Mediterranean, in the period July 2001?September 2003. In a companion paper (Pace et al., 2005) the Aerosol optical depth (AOD) and Ångström exponent were used together with airmass backward trajectories to identify and classify different Aerosol Types. The MFRSR diffuse-to-direct ratio (DDR) at 415.6 nm and 868.7 nm for Aerosol classified as biomass burning-urban/industrial, originating primarily from the European continent, and desert dust, originating from the Sahara, is used in this study to estimate the Aerosol single scattering albedo (SSA). A detailed radiative transfer model is initialized with the measured Aerosol optical depth; calculations are performed at the two wavelengths varying the SSA values until the modelled DDR matches the MFRSR observations. Sensitivity studies are performed to estimate how uncertainties on AOD, DDR, asymmetry factor (g), and surface albedo influence the retrieved SSA values. The results show that a 3% variation of AOD or DDR produce a change of about 0.02 in the retrieved SSA value at 415.6 and 868.7 nm; a ±0.06 variation of the asymmetry factor g produces a change of the estimated SSA of

  • Aerosol optical properties at Lampedusa (Central Mediterranean) – 2. Determination of single scattering albedo at two wavelengths for different Aerosol Types
    2005
    Co-Authors: D. Meloni, A. Di Sarra, G. Pace, F. Monteleone
    Abstract:

    Abstract. Aerosol optical properties were retrieved from direct and diffuse spectral irradiance measurements made by a multi-filter rotating shadowband radiometer (MFRSR) at the island of Lampedusa (35.5° N, 12.6° E), in the Central Mediterranean, in the period July 2001–September 2003. In a companion paper (Pace et al., 2005) the Aerosol optical depth (AOD) and Ångström exponent were used together with airmass backward trajectories to identify and classify different Aerosol Types. The MFRSR diffuse-to-direct ratio (DDR) at 415.6 nm and 868.7 nm for Aerosol classified as biomass burning-urban/industrial, originating primarily from the European continent, and desert dust, originating from the Sahara, is used in this study to estimate the Aerosol single scattering albedo (SSA). A detailed radiative transfer model is initialized with the measured Aerosol optical depth; calculations are performed at the two wavelengths varying the SSA values until the modelled DDR matches the MFRSR observations. Sensitivity studies are performed to estimate how uncertainties on AOD, DDR, asymmetry factor (g), and surface albedo influence the retrieved SSA values. The results show that a 3% variation of AOD or DDR produce a change of about 0.02 in the retrieved SSA value at 415.6 and 868.7 nm; a ±0.06 variation of the asymmetry factor g produces a change of the estimated SSA of <0.04 at 415.6 nm, and <0.06 at 868.7 nm; finally, an increase of the assumed surface albedo of 0.05 gives very small changes (0.01–0.02) in the retrieved SSA. The calculations show that the SSA of desert dust (DD) increases with wavelength, from 0.81±0.05 at 415.6 nm to 0.94±0.05 at 868.7 nm; on the contrary, the SSA of urban/industrial (UN) Aerosols decreases from 0.96±0.02 at 415.6 nm to 0.87±0.07 at 868.7 nm; the SSA of biomass burning (BB) particles is 0.82±0.04 at 415.6 nm and 0.80±0.05 at 868.7 nm. Episodes of UN Aerosols occur usually in June and July; BB Aerosol episodes with large AOD and long duration are observed mainly in July and August, the driest months of the year, when the development of fires is favoured.