WorldWideScience

Sample records for csphot aerosol optical

  1. Cimel Sunphotometer (CSPHOT) Handbook

    Energy Technology Data Exchange (ETDEWEB)

    Gregory, L

    2011-01-17

    The Cimel sunphotometer (CSPHOT) is a multi-channel, automatic sun-and-sky scanning radiometer that measures the direct solar irradiance and sky radiance at the Earth’s surface. Measurements are taken at pre-determined discrete wavelengths in the visible and near-IR parts of the spectrum to determine atmospheric transmission and scattering properties. This instrument is weather-proof and requires little maintenance during periods of adverse weather conditions. It takes measurements only during daylight hours (sun above horizon).

  2. SMEX02 Atmospheric Aerosol Optical Properties Data

    Data.gov (United States)

    National Aeronautics and Space Administration — This data set consists of observations of atmospheric parameters including spectral aerosol optical depths, precipitable water, sky radiance distributions and...

  3. Study of Aerosol Chemical Composition Based on Aerosol Optical Properties

    Science.gov (United States)

    Berry, Austin; Aryal, Rudra

    2015-03-01

    We investigated the variation of aerosol absorption optical properties obtained from the CIMEL Sun-Photometer measurements over three years (2012-2014) at three AERONET sites GSFC; MD Science_Center and Tudor Hill, Bermuda. These sites were chosen based on the availability of data and locations that can receive different types of aerosols from land and ocean. These absorption properties, mainly the aerosol absorption angstrom exponent, were analyzed to examine the corresponding aerosol chemical composition. We observed that the retrieved absorption angstrom exponents over the two sites, GSFC and MD Science Center, are near 1 (the theoretical value for black carbon) and with low single scattering albedo values during summer seasons indicating presence of black carbon. Strong variability of aerosol absorption properties were observed over Tudor Hill and will be analyzed based on the air mass embedded from ocean side and land side. We will also present the seasonal variability of these properties based on long-range air mass sources at these three sites. Brent Holben, NASA GSFC, AERONET, Jon Rodriguez.

  4. Optical trapping of gold aerosols

    DEFF Research Database (Denmark)

    Schmitt, Regina K.; Pedersen, Liselotte Jauffred; Taheri, S. M.

    2015-01-01

    Aerosol trapping has proven challenging and was only recently demonstrated.1 This was accomplished by utilizing an air chamber designed to have a minimum of turbulence and a laser beam with a minimum of aberration. Individual gold nano-particles with diameters between 80 nm and 200 nm were trappe...

  5. Optical closure experiments for biomass smoke aerosols

    Directory of Open Access Journals (Sweden)

    L. E. Mack

    2010-03-01

    Full Text Available The FLAME experiments were a series of laboratory studies of the chemical, physical, and optical properties of fresh smokes from the combustion of wildland fuels that are burned annually in the western and southeastern US. The burns were conducted in the combustion chamber of the USFS Fire Sciences Laboratory in Missoula, Montana. Here we discuss the retrieval of optical properties for a variety of fuels burned in FLAME 2, using nephelometer-measured scattering coefficients, photoacoustically-measured aerosol absorption coefficients, and size distribution measurements. Uncertainties are estimated from the various instrument characteristics and from instrument calibration studies. Our estimates of single scattering albedo for different dry smokes varied from 0.43–0.99, indicative of the wide variations in smoke aerosol chemical composition that were observed. In selected case studies, we retrieved the complex refractive index from the measurements, but show that these are highly sensitive to the uncertainties in measured size distributions.

  6. Optical closure experiments for biomass smoke aerosols

    Directory of Open Access Journals (Sweden)

    L. A. Mack

    2010-09-01

    Full Text Available A series of laboratory experiments at the Fire Laboratory at Missoula (FLAME investigated chemical, physical, and optical properties of fresh smoke samples from combustion of wildland fuels that are burned annually in the western and southeastern US The burns were conducted in the combustion chamber of the US Forest Service Fire Sciences Laboratory in Missoula, Montana. Here we discuss retrieval of optical properties for a variety of fuels burned in FLAME 2, using nephelometer-measured scattering coefficients, photoacoustically-measured aerosol absorption coefficients, and size distribution measurements. Uncertainties are estimated from various instrument characteristics and instrument calibration studies. Our estimates of single scattering albedo for different dry smoke samples varied from 0.428 to 0.990, indicative of observed wide variations in smoke aerosol chemical composition. In selected case studies, we retrieved the complex refractive index from measurements but show that these are highly sensitive to uncertainties in measured size distributions.

  7. Black carbon aerosol mixing state, organic aerosols and aerosol optical properties over the UK

    Science.gov (United States)

    McMeeking, G. R.; Morgan, W. T.; Flynn, M.; Highwood, E. J.; Turnbull, K.; Haywood, J.; Coe, H.

    2011-05-01

    Black carbon (BC) aerosols absorb sunlight thereby leading to a positive radiative forcing and a warming of climate and can also impact human health through their impact on the respiratory system. The state of mixing of BC with other aerosol species, particularly the degree of internal/external mixing, has been highlighted as a major uncertainty in assessing its radiative forcing and hence its climate impact, but few in situ observations of mixing state exist. We present airborne single particle soot photometer (SP2) measurements of refractory BC (rBC) mass concentrations and mixing state coupled with aerosol composition and optical properties measured in urban plumes and regional pollution over the UK. All data were obtained using instrumentation flown on the UK's BAe-146-301 large Atmospheric Research Aircraft (ARA) operated by the Facility for Airborne Atmospheric Measurements (FAAM). We measured sub-micron aerosol composition using an aerosol mass spectrometer (AMS) and used positive matrix factorization to separate hydrocarbon-like (HOA) and oxygenated organic aerosols (OOA). We found a higher number fraction of thickly coated rBC particles in air masses with large OOA relative to HOA, higher ozone-to-nitrogen oxides (NOx) ratios and large concentrations of total sub-micron aerosol mass relative to rBC mass concentrations. The more ozone- and OOA-rich air masses were associated with transport from continental Europe, while plumes from UK cities had higher HOA and NOx and fewer thickly coated rBC particles. We did not observe any significant change in the rBC mass absorption efficiency calculated from rBC mass and light absorption coefficients measured by a particle soot absorption photometer despite observing significant changes in aerosol composition and rBC mixing state. The contributions of light scattering and absorption to total extinction (quantified by the single scattering albedo; SSA) did change for different air masses, with lower SSA observed in

  8. Black carbon aerosol mixing state, organic aerosols and aerosol optical properties over the United Kingdom

    Science.gov (United States)

    McMeeking, G. R.; Morgan, W. T.; Flynn, M.; Highwood, E. J.; Turnbull, K.; Haywood, J.; Coe, H.

    2011-09-01

    Black carbon (BC) aerosols absorb sunlight thereby leading to a positive radiative forcing and a warming of climate and can also impact human health through their impact on the respiratory system. The state of mixing of BC with other aerosol species, particularly the degree of internal/external mixing, has been highlighted as a major uncertainty in assessing its radiative forcing and hence its climate impact, but few in situ observations of mixing state exist. We present airborne single particle soot photometer (SP2) measurements of refractory BC (rBC) mass concentrations and mixing state coupled with aerosol composition and optical properties measured in urban plumes and regional pollution over the United Kingdom. All data were obtained using instrumentation flown on the UK's BAe-146-301 large Atmospheric Research Aircraft (ARA) operated by the Facility for Airborne Atmospheric Measurements (FAAM). We measured sub-micron aerosol composition using an aerosol mass spectrometer (AMS) and used positive matrix factorization to separate hydrocarbon-like (HOA) and oxygenated organic aerosols (OOA). We found a higher number fraction of thickly coated rBC particles in air masses with large OOA relative to HOA, higher ozone-to-nitrogen oxides (NOx) ratios and large concentrations of total sub-micron aerosol mass relative to rBC mass concentrations. The more ozone- and OOA-rich air masses were associated with transport from continental Europe, while plumes from UK cities had higher HOA and NOx and fewer thickly coated rBC particles. We did not observe any significant change in the rBC mass absorption efficiency calculated from rBC mass and light absorption coefficients measured by a particle soot absorption photometer despite observing significant changes in aerosol composition and rBC mixing state. The contributions of light scattering and absorption to total extinction (quantified by the single scattering albedo; SSA) did change for different air masses, with lower SSA

  9. Black carbon aerosol mixing state, organic aerosols and aerosol optical properties over the United Kingdom

    Directory of Open Access Journals (Sweden)

    G. R. McMeeking

    2011-09-01

    Full Text Available Black carbon (BC aerosols absorb sunlight thereby leading to a positive radiative forcing and a warming of climate and can also impact human health through their impact on the respiratory system. The state of mixing of BC with other aerosol species, particularly the degree of internal/external mixing, has been highlighted as a major uncertainty in assessing its radiative forcing and hence its climate impact, but few in situ observations of mixing state exist. We present airborne single particle soot photometer (SP2 measurements of refractory BC (rBC mass concentrations and mixing state coupled with aerosol composition and optical properties measured in urban plumes and regional pollution over the United Kingdom. All data were obtained using instrumentation flown on the UK's BAe-146-301 large Atmospheric Research Aircraft (ARA operated by the Facility for Airborne Atmospheric Measurements (FAAM. We measured sub-micron aerosol composition using an aerosol mass spectrometer (AMS and used positive matrix factorization to separate hydrocarbon-like (HOA and oxygenated organic aerosols (OOA. We found a higher number fraction of thickly coated rBC particles in air masses with large OOA relative to HOA, higher ozone-to-nitrogen oxides (NOx ratios and large concentrations of total sub-micron aerosol mass relative to rBC mass concentrations. The more ozone- and OOA-rich air masses were associated with transport from continental Europe, while plumes from UK cities had higher HOA and NOx and fewer thickly coated rBC particles. We did not observe any significant change in the rBC mass absorption efficiency calculated from rBC mass and light absorption coefficients measured by a particle soot absorption photometer despite observing significant changes in aerosol composition and rBC mixing state. The contributions of light scattering and absorption to total extinction (quantified by the single scattering albedo; SSA did change for

  10. Aerosol Optical Properties over Northwestern European Seas

    Science.gov (United States)

    Avgousta Floutsi, Athina; Korras Carraca, Marios Bruno; Matsoukas, Christos; Riva, Riccardo; Biskos, George

    2017-04-01

    Atmospheric aerosols, both natural and anthropogenic, can affect the regional and global climate through their direct, indirect, and semi-direct effects on the radiative energy budget of the Earth-atmosphere system. In order to quantify these effects it is necessary to determine the aerosol load. An effective way to do this is by measuring the aerosol optical depth (AOD). Besides AOD, the Fine mode Fraction (AOD of particles smaller than 1 μm / total AOD, FF) is a useful parameter for the characterization of the aerosol and provides a good proxy for particle size. In this study, we investigate the spatial and temporal variability of the AOD and FF over the Western and Northwestern European Seas (43° N - 67° N, 10° W - 31° E), where significant sources of both natural and anthropogenic particles are located. Anthropogenic particles (mostly fine mode) originate from ship activity, or from urban-industrial and biomass-burning processes in the European countries. The natural, coarse mode particles are primarily sea salt. The study is performed using Collection 006 Level-3 mean daily aerosol data from the Moderate Resolution Imaging Spectroradiometer (MODIS) instrument on board Aqua satellite, available in 1° × 1° resolution (ca. 100 km × 100 km) over the period 2002- 2014. Our results indicate significant spatial variability of the aerosol load over the study region. The highest AOD values (up to 0.32 on annual level) are observed over the English Channel and the coasts of the Netherlands and Germany. In these regions the highest FF values are also observed (up to 0.77), indicating a relatively large contribution of anthropogenic particles to the aerosol load. Offshore, both AOD and FF are lower compared to coastal regions, indicating the predominance of maritime aerosols (sea salt). The data also show a clear seasonal cycle, with larger aerosol load during spring and summer (AOD up to 0.60), and lower during autumn and winter (AOD up to 0.30). A similar

  11. Multiwavelength multistatic optical scattering for aerosol characterization

    Science.gov (United States)

    Brown, Andrea M.

    The main focus of this research is the development of a technique to remotely characterize aerosol properties, such as particle size distribution, concentration, and refractive index as a function of wavelength, through the analysis of optical scattering measurements. The proposed technique is an extension of the multistatic polarization ratio technique that has been developed by prior students at the Penn State Lidar Lab to include multiple wavelengths. This approach uses the ratio of polarized components of the scattering phase functions at multiple wavelengths across the visible region of the electromagnetic spectrum to extract the microphysical and optical properties of aerosols. The scattering intensities at each wavelength are vertically separated across the face of the imager using a transmission diffraction grating, so that scattering intensities for multiple wavelengths at many angles are available for analysis in a single image. The ratio of the scattering phase function intensities collected using parallel and perpendicular polarized light are formed for each wavelength and analysis of the ratio is used to determine the microphysical properties of the aerosols. One contribution of the present work is the development of an inversion technique based on a genetic algorithm that retrieves lognormal size distributions from scattering measurements by minimizing the squared error between measured polarization ratios and polarization ratios calculated using the Mie solution to Maxwell's equations. The opportunities and limitations of using the polarization ratio are explored, and a genetic algorithm is developed to retrieve single mode and trimodal lognormal size distributions from multiwavelength, angular scattering data. The algorithm is designed to evaluate particles in the diameter size range of 2 nm to 60 im, and uses 1,000 linear spaced diameters within this range to compute the modeled polarization ratio. The algorithm returns geometric mean radii and

  12. Climatology of Aerosol Optical Properties in Southern Africa

    Science.gov (United States)

    Queface, Antonio J.; Piketh, Stuart J.; Eck, Thomas F.; Tsay, Si-Chee

    2011-01-01

    A thorough regionally dependent understanding of optical properties of aerosols and their spatial and temporal distribution is required before we can accurately evaluate aerosol effects in the climate system. Long term measurements of aerosol optical depth, Angstrom exponent and retrieved single scattering albedo and size distribution, were analyzed and compiled into an aerosol optical properties climatology for southern Africa. Monitoring of aerosol parameters have been made by the AERONET program since the middle of the last decade in southern Africa. This valuable information provided an opportunity for understanding how aerosols of different types influence the regional radiation budget. Two long term sites, Mongu in Zambia and Skukuza in South Africa formed the core sources of data in this study. Results show that seasonal variation of aerosol optical thicknesses at 500 nm in southern Africa are characterized by low seasonal multi-month mean values (0.11 to 0.17) from December to May, medium values (0.20 to 0.27) between June and August, and high to very high values (0.30 to 0.46) during September to November. The spatial distribution of aerosol loadings shows that the north has high magnitudes than the south in the biomass burning season and the opposite in none biomass burning season. From the present aerosol data, no long term discernable trends are observable in aerosol concentrations in this region. This study also reveals that biomass burning aerosols contribute the bulk of the aerosol loading in August-October. Therefore if biomass burning could be controlled, southern Africa will experience a significant reduction in total atmospheric aerosol loading. In addition to that, aerosol volume size distribution is characterized by low concentrations in the non biomass burning period and well balanced particle size contributions of both coarse and fine modes. In contrast high concentrations are characteristic of biomass burning period, combined with

  13. Climatology of Aerosol Optical Properties in Southern Africa

    Science.gov (United States)

    Queface, Antonio J.; Piketh, Stuart J.; Eck, Thomas F.; Tsay, Si-Chee

    2011-01-01

    A thorough regionally dependent understanding of optical properties of aerosols and their spatial and temporal distribution is required before we can accurately evaluate aerosol effects in the climate system. Long term measurements of aerosol optical depth, Angstrom exponent and retrieved single scattering albedo and size distribution, were analyzed and compiled into an aerosol optical properties climatology for southern Africa. Monitoring of aerosol parameters have been made by the AERONET program since the middle of the last decade in southern Africa. This valuable information provided an opportunity for understanding how aerosols of different types influence the regional radiation budget. Two long term sites, Mongu in Zambia and Skukuza in South Africa formed the core sources of data in this study. Results show that seasonal variation of aerosol optical thicknesses at 500 nm in southern Africa are characterized by low seasonal multi-month mean values (0.11 to 0.17) from December to May, medium values (0.20 to 0.27) between June and August, and high to very high values (0.30 to 0.46) during September to November. The spatial distribution of aerosol loadings shows that the north has high magnitudes than the south in the biomass burning season and the opposite in none biomass burning season. From the present aerosol data, no long term discernable trends are observable in aerosol concentrations in this region. This study also reveals that biomass burning aerosols contribute the bulk of the aerosol loading in August-October. Therefore if biomass burning could be controlled, southern Africa will experience a significant reduction in total atmospheric aerosol loading. In addition to that, aerosol volume size distribution is characterized by low concentrations in the non biomass burning period and well balanced particle size contributions of both coarse and fine modes. In contrast high concentrations are characteristic of biomass burning period, combined with

  14. Optical closure study on light-absorbing aerosols

    Science.gov (United States)

    Petzold, Andreas; Bundke, Ulrich; Freedman, Andrew; Onasch, Timothy B.; Massoli, Paola; Andrews, Elizabeth; Hallar, Anna G.

    2014-05-01

    The in situ measurement of atmospheric aerosol optical properties is an important component of quantifying climate change. In particular, the in-situ measurement of the aerosol single-scattering albedo (SSA), which is the ratio of aerosol scattering to aerosol extinction, is identified as a key challenge in atmospheric sciences and climate change research. Ideally, the complete set of aerosol optical properties is measured through optical closure studies which simultaneous measure aerosol extinction, scattering and absorption coefficients. The recent development of new optical instruments have made real-time in situ optical closure studies attainable, however, many of these instruments are state-of-the-art but not practical for routine monitoring. In our studies we deployed a suit of well-established and recently developed instruments including the cavity attenuated phase shift (CAPS) method for aerosol light extinction, multi-angle absorption photometer (MAAP) and particle soot absorption photometer (PSAP) for aerosol light absorption, and an integrating nephelometer (NEPH) for aerosol light scattering measurements. From these directly measured optical properties we calculated light absorption from extinction minus scattering (difference method), light extinction from scattering plus absorption, and aerosol single-scattering albedo from combinations CAPS + MAAP, NEPH + PSAP, NEPH + MAAP, CAPS + NEPH. Closure studies were conducted for laboratory-generated aerosols composed of various mixtures of black carbon (Regal 400R pigment black, Cabot Corp.) and ammonium sulphate, urban aerosol (Billerica, MA), and background aerosol (Storm Peak Lab.). Key questions addressed in our closure studies are: (1) how well can we measure aerosol light absorption by various methods, and (2) how well can we measure the aerosol single-scattering albedo by various instrument combinations? In particular we investigated (3) whether the combination of a CAPS and NEPH provides a reasonable

  15. An investigation of aerosol optical properties: Atmospheric implications and influences

    Science.gov (United States)

    Penaloza-Murillo, Marcos A.

    An experimental, observational, and theoretical investigation of aerosol optical properties has been made in this work to study their implications and influences on the atmosphere. In the laboratory the scientific and instrumental methodology consisted of three parts, namely, aerosol generation, optical and mass concentration measurements, and computational calculations. In particular the optical properties of ammonium sulfate and caffeine aerosol were derived from measurements made with a transmissometer cell-reciprocal- integrating nephelometer (TCRIN), equipped with a laser beam at 632.8 nm, and by applying a Mie theory computer code The aerosol generators, optical equipment and calibration procedures were reviewed. The aerosol shape and size distribution were studied by means of scanning electron microscopy and the Gumprecht- Sliepcevich/Lipofsky-Green extinction-sedimentation method. In particular the spherical and cylindrical shape were considered. During this investigation, an alternative method for obtaining the optical properties of monodisperse spherical non-absorbing aerosol using a cell-transmissometer, which is based on a linearisation of the Lambert-Beer law, was found. In addition, adapting the TCRIN to electrooptical aerosol studies, the optical properties of a circular-cylindrical aerosol of caffeine were undertaken under the condition of random orientation in relation with the laser beam, and perpendicular orientation to it. A theoretical study was conducted to assess the sensitivity of aerosol to a change of shape under different polarisation modes. The aerosol optical properties, obtained previously in the laboratory, were then used to simulate the direct radiative forcing. The calculations and results were obtained by applying a one- dimensional energy-balance box model. The influence of atmospheric aerosol on the sky brightness due to a total solar eclipse was studied using the photometric and meteorological observations made during the

  16. Hyperspectral aerosol optical depths from TCAP flights

    Energy Technology Data Exchange (ETDEWEB)

    Shinozuka, Yohei [NASA Ames Research Center (ARC), Moffett Field, Mountain View, CA (United States); Bay Area Environmental REsearch Institute; Johnson, Roy R [NASA Ames Research Center (ARC), Moffett Field, Mountain View, CA (United States); Flynn, Connor J [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Russell, Philip B [NASA Ames Research Center (ARC), Moffett Field, Mountain View, CA (United States); Schmid, Beat [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

    2016-06-01

    4STAR (Spectrometer for Sky-Scanning, Sun-Tracking Atmospheric Research), a hyperspectral airborne sunphotometer, acquired aerosol optical depths (AOD) at 1 Hz during all July 2012 flights of the Two Column Aerosol Project (TCAP). Root-mean-square differences from AERONET ground-based observations were 0.01 at wavelengths between 500-1020 nm, 0.02 at 380 and 1640 nm and 0.03 at 440 nm in four clear-sky fly-over events, and similar in ground side-by-side comparisons. Changes in the above-aircraft AOD across 3- km-deep spirals were typically consistent with integrals of coincident in situ (on DOE Gulfstream 1 with 4STAR) and lidar (on NASA B200) extinction measurements within 0.01, 0.03, 0.01, 0.02, 0.02, 0.02 at 355, 450, 532, 550, 700, 1064 nm, respectively, despite atmospheric variations and combined measurement uncertainties. Finer vertical differentials of the 4STAR measurements matched the in situ ambient extinction profile within 14% for one homogeneous column. For the AOD observed between 350-1660 nm, excluding strong

  17. Using the OMI aerosol index and absorption aerosol optical depth to evaluate the NASA MERRA Aerosol Reanalysis

    Science.gov (United States)

    Buchard, V.; da Silva, A. M.; Colarco, P. R.; Darmenov, A.; Randles, C. A.; Govindaraju, R.; Torres, O.; Campbell, J.; Spurr, R.

    2015-05-01

    A radiative transfer interface has been developed to simulate the UV aerosol index (AI) from the NASA Goddard Earth Observing System version 5 (GEOS-5) aerosol assimilated fields. The purpose of this work is to use the AI and aerosol absorption optical depth (AAOD) derived from the Ozone Monitoring Instrument (OMI) measurements as independent validation for the Modern Era Retrospective analysis for Research and Applications Aerosol Reanalysis (MERRAero). MERRAero is based on a version of the GEOS-5 model that is radiatively coupled to the Goddard Chemistry, Aerosol, Radiation, and Transport (GOCART) aerosol module and includes assimilation of aerosol optical depth (AOD) from the Moderate Resolution Imaging Spectroradiometer (MODIS) sensor. Since AI is dependent on aerosol concentration, optical properties and altitude of the aerosol layer, we make use of complementary observations to fully diagnose the model, including AOD from the Multi-angle Imaging SpectroRadiometer (MISR), aerosol retrievals from the AErosol RObotic NETwork (AERONET) and attenuated backscatter coefficients from the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) mission to ascertain potential misplacement of plume height by the model. By sampling dust, biomass burning and pollution events in 2007 we have compared model-produced AI and AAOD with the corresponding OMI products, identifying regions where the model representation of absorbing aerosols was deficient. As a result of this study over the Saharan dust region, we have obtained a new set of dust aerosol optical properties that retains consistency with the MODIS AOD data that were assimilated, while resulting in better agreement with aerosol absorption measurements from OMI. The analysis conducted over the southern African and South American biomass burning regions indicates that revising the spectrally dependent aerosol absorption properties in the near-UV region improves the modeled-observed AI comparisons

  18. High resolution aerosol optical thickness retrieval over the Pearl River Delta region with improved aerosol modelling

    Institute of Scientific and Technical Information of China (English)

    WONG; ManSing; NICHOL; Janet; LEE; Kwon; Ho

    2009-01-01

    Aerosol retrieval algorithms for the MODerate Resolution Imaging Spectroradiometer (MODIS) have been developed to estimate aerosol and microphysical properties of the atmosphere, which help to address aerosol climatic issues at global scale. However, higher spatial resolution aerosol products for urban areas have not been well researched mainly due to the difficulty of differentiating aerosols from bright surfaces in urban areas. Here, a new aerosol retrieval algorithm using the MODIS 500 m resolution images is described, to retrieve aerosol properties over Hong Kong and the Pearl River Delta region. The rationale of our technique is to first estimate the aerosol reflectance by decomposing the top-of-atmosphere reflectance from surface reflectance and Rayleigh path reflectance. For the determination of surface reflectance, a modified Minimum Reflectance Technique (MRT) is used, and MRT images are computed for different seasons. A strong correlation is shown between the surface reflectance of MRT images and MODIS land surface reflectance products (MOD09), with a value of 0.9. For conversion of aerosol reflectance to Aerosol Optical Thickness (AOT), comprehensive Look Up Tables (LUT) are constructed, in which aerosol properties and sun-viewing geometry in the radiative transfer calculations are taken into account. Four aerosol types, namely mixed urban, polluted urban, dust, and heavy pollution, were derived using cluster analysis on three years of AERONET measurements in Hong Kong. Their aerosol properties were input for LUT calculation. The resulting 500 m AOT images are highly correlated (r = 0.89) with AERONET sunphotometer observations in Hong Kong. This study demonstrates the applicability of aerosol retrieval at fine resolution scale in urban areas, which can assist the study of aerosol loading distribution and the impact of localized and transient pollution on urban air quality. In addition, the MODIS 500 m AOT images can be used to study cross

  19. High resolution aerosol optical thickness retrieval over the Pearl River Delta region with improved aerosol modelling

    Institute of Scientific and Technical Information of China (English)

    WONG ManSing; NICHOL Janet; LEE Kwon Ho; LI ZhanQing

    2009-01-01

    Aerosol retrieval algorithms for the MODerate Resolution Imaging Spectroradiometer (MODIS) have been developed to estimate aerosol and microphysical properties of the atmosphere, which help to address aerosol climatic issues at global scale. However, higher spatial resolution aerosol products for urban areas have not been well researched mainly due to the difficulty of differentiating aerosols from bright surfaces in urban areas. Here, a new aerosol retrieval algorithm using the MODIS 500 m resolu-tion images is described, to retrieve aerosol properties over Hong Kong and the Pearl River Delta re-gion. The rationale of our technique is to first estimate the aerosol reflectance by decomposing the top-of-atmosphere reflectance from surface reflectance and Rayleigh path reflectance. For the deter-mination of surface reflectance, a modified Minimum Reflectance Technique (MRT) is used, and MRT images are computed for different seasons. A strong correlation is shown between the surface reflec-tance of MRT images and MODIS land surface reflectance products (MOD09), with a value of 0.9. For conversion of aerosol reflectance to Aerosol Optical Thickness (AOT), comprehensive Look Up Tables (LUT) are constructed, in which aerosol properties and sun-viewing geometry in the radiative transfer calculations are taken into account. Four aerosol types, namely mixed urban, polluted urban, dust, and heavy pollution, were derived using cluster analysis on three years of AERONET measurements in Hong Kong. Their aerosol properties were input for LUT calculation. The resulting 500 m AOT images are highly correlated (r=0.89) with AERONET sunphotometer observations in Hong Kong. This study demonstrates the applicability of aerosol retrieval at fine resolution scale in urban areas, which can assist the study of aerosol loading distribution and the impact of localized and transient pollution on urban air quality. In addition, the MODIS 500 m AOT images can be used to study cross

  20. Effect of Aerosol Size and Hygroscopicity on Aerosol Optical Depth in the Southeastern United States

    Science.gov (United States)

    Brock, Charles; Wagner, Nick; Gordon, Timothy

    2016-04-01

    Aerosol optical depth (AOD) is affected by the size, optical characteristics, and hygroscopicity of particles, confounding attempts to link remote sensing observations of AOD to measured or modeled aerosol mass concentrations. In situ airborne observations of aerosol optical, chemical, microphysical and hygroscopic properties were made in the southeastern United States in the daytime in summer 2013. We use these observations to constrain a simple model that is used to test the sensitivity of AOD to the various measured parameters. As expected, the AOD was found to be most sensitive to aerosol mass concentration and to aerosol water content, which is controlled by aerosol hygroscopicity and the ambient relative humidity. However, AOD was also fairly sensitive to the mean particle diameter and the width of the size distribution. These parameters are often prescribed in global models that use simplified modal parameterizations to describe the aerosol, suggesting that the values chosen could substantially bias the calculated relationship between aerosol mass and optical extinction, AOD, and radiative forcing.

  1. Estimating aerosol emissions by assimilating observed aerosol optical depth in a global aerosol model

    Directory of Open Access Journals (Sweden)

    N. Huneeus

    2012-01-01

    Full Text Available This study estimates the emission fluxes of a range of aerosol species and aerosol precursor at the global scale. These fluxes are estimated by assimilating daily total and fine mode aerosol optical depth (AOD at 550 nm from the Moderate Resolution Imaging Spectroradiometer (MODIS into a global aerosol model of intermediate complexity. Monthly emissions are fitted homogenously for each species over a set of predefined regions. The performance of the assimilation is evaluated by comparing the AOD after assimilation against the MODIS observations and against independent observations. The system is effective in forcing the model towards the observations, for both total and fine mode AOD. Significant improvements for the root mean square error and correlation coefficient against both the assimilated and independent datasets are observed as well as a significant decrease in the mean bias against the assimilated observations. The assimilation is more efficient over land than over ocean. The impact of the assimilation of fine mode AOD over ocean demonstrates potential for further improvement by including fine mode AOD observations over continents. The Angström exponent is also improved in African, European and dusty stations. The estimated emission flux for black carbon is 14.5 Tg yr−1, 119 Tg yr−1 for organic matter, 17 Pg yr−1 for sea salt, 82.7 TgS yr−1 for SO2 and 1383 Tg yr−1 for desert dust. They represent a difference of +45%, +40%, +26%, +13% and −39% respectively, with respect to the a priori values. The initial errors attributed to the emission fluxes are reduced for all estimated species.

  2. Estimating aerosol emissions by assimilating observed aerosol optical depth in a global aerosol model

    Directory of Open Access Journals (Sweden)

    N. Huneeus

    2012-05-01

    Full Text Available This study estimates the emission fluxes of a range of aerosol species and one aerosol precursor at the global scale. These fluxes are estimated by assimilating daily total and fine mode aerosol optical depth (AOD at 550 nm from the Moderate Resolution Imaging Spectroradiometer (MODIS into a global aerosol model of intermediate complexity. Monthly emissions are fitted homogenously for each species over a set of predefined regions. The performance of the assimilation is evaluated by comparing the AOD after assimilation against the MODIS observations and against independent observations. The system is effective in forcing the model towards the observations, for both total and fine mode AOD. Significant improvements for the root mean square error and correlation coefficient against both the assimilated and independent datasets are observed as well as a significant decrease in the mean bias against the assimilated observations. These improvements are larger over land than over ocean. The impact of the assimilation of fine mode AOD over ocean demonstrates potential for further improvement by including fine mode AOD observations over continents. The Angström exponent is also improved in African, European and dusty stations. The estimated emission flux for black carbon is 15 Tg yr−1, 119 Tg yr−1 for particulate organic matter, 17 Pg yr−1 for sea salt, 83 TgS yr−1 for SO2 and 1383 Tg yr−1 for desert dust. They represent a difference of +45 %, +40 %, +26 %, +13 % and −39 % respectively, with respect to the a priori values. The initial errors attributed to the emission fluxes are reduced for all estimated species.

  3. Aerosol Optical Depth Value-Added Product Report

    Energy Technology Data Exchange (ETDEWEB)

    Koontz, A; Hodges, G; Barnard, J; Flynn, C; Michalsky, J

    2013-03-17

    This document describes the process applied to retrieve aerosol optical depth (AOD) from multifilter rotating shadowband radiometers (MFRSR) and normal incidence multifilter radiometers (NIMFR) operated at the ARM Climate Research Facility’s ground-based facilities.

  4. Aerosol optical depths and their contributing sources in Taiwan

    Science.gov (United States)

    Chan, K. L.; Chan, K. L.

    2017-01-01

    In this paper, we present a quantitative investigation of the contributions of different aerosols to the aerosol optical depths (AODs) in Taiwan using a global chemical transport model (GEOS-Chem) and remote sensing measurements. The study focus is on the period from June 2012 to October 2013. Five different types of aerosols are investigated: sea salt, dust, sulfate, organic carbon and black carbon. Three of these aerosols, namely sulfate, organic carbon and black carbon, have significant anthropogenic sources. Model simulation results were compared with both ground based sun photometer measurements and MODerate resolution Imaging Spectroradiometer (MODIS) satellite observations. The model data shows good agreement with satellite observations (R = 0.72) and moderate correlation with sun photometer measurements (R = 0.52). Simulation results show the anthropogenic aerosols contribute ∼65% to the total AOD in Taipei, while natural originated aerosols only show a minor impact (∼35%). Among all the aerosols, sulfate is the dominating species, contributing 62.4% to the annual average total AOD. Organic carbon and black carbons respectively contribute 7.3% and 1.5% to the annual averaged total AOD. The annual average contributions of sea salt and dust aerosols to the total AOD are 26.4% and 2.4%, respectively. A sensitivity study was performed to identify the contributions of anthropogenic aerosol sources in each region to the AODs in Taipei. North-East Asia was identified as the major contributing source region of anthropogenic aerosols to Taipei, accounting for more than 50% of total sulfate, 32% of total organic carbon and 51% of total black carbon aerosols. South-East Asia is the second largest contributing source region, contributing 35%, 24% and 34% of total sulfate, organic carbon and black carbon aerosols, respectively. The aerosols from continents other than Asia only show minor impacts to the aerosol load in Taipei. In addition, a case study of a biomass

  5. Path radiance technique for retrieving aerosol optical thickness over land

    Energy Technology Data Exchange (ETDEWEB)

    Wen, Guoyong [Joint Center for Earth Systems Technology, University of Maryland, Baltimore County, Catonsville (United States); Tsay, Si-Chee [NASA Goddard Space Flight Center, Greenbelt, Maryland (United States); Cahalan, Robert F. [Joint Center for Earth Systems Technology, University of Maryland, Baltimore County, Catonsville (United States); NASA Goddard Space Flight Center, Greenbelt, Maryland (United States); Oreopoulos, Lazaros [Joint Center for Earth Systems Technology, University of Maryland, Baltimore County, Catonsville (United States)

    1999-12-27

    The key issue in retrieving aerosol optical thickness over land from shortwave satellite radiances is to identify and separate the signal due to scattering by a largely transparent aerosol layer from the noise due to reflection by the background surface, where the signal is relatively uniform compared to the highly inhomogeneous surface contribution. Sensitivity studies in aerosol optical thickness retrievals reveal that the apparent reflectance at the top of the atmosphere is very susceptible to the surface reflectance, especially when aerosol optical thickness is small. Uncertainties associated with surface reflectance estimation can greatly amplify the error of the aerosol optical thickness retrieval. To reduce these uncertainties, we have developed a ''path radiance'' method to retrieve aerosol optical thickness over land by extending the traditional technique that uses the ''dark object'' approach to extract the aerosol signal. This method uses the signature of the correlation of visible and middle-IR reflectance at the surface and couples the correlation with the atmospheric effect. We have applied this method to a Landsat TM (Thematic Mapper) image acquired over the Oklahoma southern Great Plains site of the Department of Energy Atmospheric Radiation Measurement (ARM) program on September 27, 1997, a very clear day (aerosol optical thickness of 0.07 at 0.5 {mu}m) during the first Landsat Intensive Observation Period. The retrieved mean aerosol optical thickness for TM band 1 at 0.49 {mu}m and band 3 at 0.66 {mu}m agree very well with the ground-based Sun photometer measurements at the ARM site. The ability to retrieve small aerosol optical thickness makes this path radiance technique promising. More importantly, the path radiance is relatively insensitive to surface inhomogeneity. The retrieved mean path radiances in reflectance units have very small standard deviations for both TM blue and red bands. This small

  6. Influence of semi-volatile aerosol on physical and optical properties of aerosol in Kathmandu valley

    Science.gov (United States)

    Shrestha, Sujan; Praveen, Ps; Adhikary, Bhupesh; Shrestha, Kundan; Panday, Arnico

    2016-04-01

    A field study was conducted in the urban atmosphere of Kathmandu valley to study the influence of the semi-volatile aerosol fraction on physical and optical properties of aerosols. The study was carried out during the 2015 pre-monsoon period. Experimental setup consisted of air from an ambient air inlet being split to two sets of identical sampling instruments. The first instrument received the ambient sample directly, while the second instrument received the air sample through a thermodenuder (TDD). Four sets of experiments were conducted to understand aerosol number, size distribution, scattering and absorption properties using Condensation Particle Counter (CPC), Scanning Mobility Particle Sizer (SMPS), Aethalometer (AE33) and Nephelometer. The influence of semi-volatile aerosols was calculated from the fraction of particles evaporated in the TDD at set temparetures: room temperature, 50°C, 100°C, 150°C, 200°C, 250°C and 300°C. Results show that, with increasing temperature, the evaporated fraction of semi-volatile aerosol also increased. At room temperature the fraction of semi-volatile aerosols was 12% while at 300°C it was as high as to 49%. Aerosol size distribution analysis shows that with an increase in TDD temperature from 50°C to 300°C, peak mobility diameter of particles shifted from around 60nm to 40nm. However we found little change in effective diameter of aerosol size distribution with increase in set TDD temperature. The change in size of aerosols due to loss of semi-volatile component has a stronger influence (~70%) in higher size bins when compared to at lower size bins (~20%). Studies using the AE33 showed that absorption by black carbon (BC) is amplified due to influence of semi-volatile aerosols by upto 37% at 880nm wavelength. Similarly nephelometer measurements showed that upto 71% of total scattering was found to be contributed by semi-volatile aerosol fraction. The scattering Angstrom Exponent (SAE) of semi-volatile aerosol

  7. [Effects of aerosol optical thickness on the optical remote sensing imaging quality].

    Science.gov (United States)

    Hu, Xin-Li; Gu, Xing-Fa; Yu, Tao; Zhang, Zhou-Wei; Li, Juan; Luan, Hai-Jun

    2014-03-01

    In recent years, due to changes in atmospheric environment, atmospheric aerosol affection on optical sensor imaging quality is increasingly considered by the load developed departments. Space-based remote sensing system imaging process, atmospheric aerosol makes optical sensor imaging quality deterioration. Atmospheric medium causing image degradation is mainly forward light scattering effect caused by the aerosol turbid medium. Based on the turbid medium radiation transfer equation, the point spread function models were derived contained aerosol optical properties of atmosphere in order to analyze and evaluate the atmospheric blurring effect on optical sensor imaging system. It was found that atmospheric aerosol medium have effect on not only energy decay of atmospheric transmittance, but also the degradation of image quality due to the scattering effect. Increase of atmospheric aerosol optical thickness makes aerosol scattering intensity enhanced, variation of aerosol optical thickness is also strongly influences the point spread function of the spatial distribution. it is because the degradation of aerosol in spatial domain, which reduces the quality of remote sensing image, in particularly reduction of the sharpness of image. Meanwhile, it would provide a method to optimize and improve simulation of atmospheric chain.

  8. Assessment of error in aerosol optical depth measured by AERONET due to aerosol forward scattering

    Science.gov (United States)

    Sinyuk, Alexander; Holben, Brent N.; Smirnov, Alexander; Eck, Thomas F.; Slutsker, Ilya; Schafer, Joel S.; Giles, David M.; Sorokin, Mikhail

    2012-12-01

    We present an analysis of the effect of aerosol forward scattering on the accuracy of aerosol optical depth (AOD) measured by CIMEL Sun photometers. The effect is quantified in terms of AOD and solar zenith angle using radiative transfer modeling. The analysis is based on aerosol size distributions derived from multi-year climatologies of AERONET aerosol retrievals. The study shows that the modeled error is lower than AOD calibration uncertainty (0.01) for the vast majority of AERONET level 2 observations, ∼99.53%. Only ∼0.47% of the AERONET database corresponding mostly to dust aerosol with high AOD and low solar elevations has larger biases. We also show that observations with extreme reductions in direct solar irradiance do not contribute to level 2 AOD due to low Sun photometer digital counts below a quality control cutoff threshold.

  9. Spatial Correlations of Aerosol Optical Depth Over Land

    Science.gov (United States)

    Radkevich, A. V.; Trishchenko, A. P.

    2009-05-01

    The accurate atmospheric correction of historical satellite long-term data is required to make them suitable for climate change application. This is essential to properly identify the impacts caused by changing surface properties, such as vegetation, soil and snow cover, rather than atmospheric effects, cloud contamination and artefacts. The correction of satellite data over land for aerosol effect constitutes the most challenging part of the processing. While a good progress in aerosol retrievals has been achieved in recent years using the Moderate Resolution Imaging Spectroradiometer (MODIS) and the Multi-angle Imaging Spectroradiometer (MISR), the aerosol properties and their associated impact on atmospheric correction for historical data over land from the Advanced Very High Resolution Radiometer (AVHRR) onboard NOAA satellites for pre-MODIS period is still not adequately addressed. It seems promising to develop the AVHRR atmospheric correction algorithm based on the synthesis of aerosol retrievals over dark targets and optimum interpolation technique based on aerosol spatio-temporal statistics. The implementation of this approach requires the knowledge of aerosol spatial correlation function. The estimates of aerosol optical depth (AOD) spatial correlation function were obtained in this study using different data sources: MODIS level 2 and level 3 aerosol products, daily averages of ground sun photometer aerosol retrievals from Aerosol Robotic Network (AERONET) and the global chemistry and aerosol atmospheric transport model results from NASA's GOCART. The AOD correlation properties obtained from different types of MODIS aerosol products were found in reasonably good agreement with each other. The AOD correlation radius for different types of MODIS data varied from 418 km to 900 km. The AOD correlation radius obtained from AERONET data was found to be close to 500km. Substantial differences were detected between AOD spatial correlation function derived from

  10. Sources of optically active aerosol particles over the Amazon forest

    Science.gov (United States)

    Guyon, Pascal; Graham, Bim; Roberts, Gregory C.; Mayol-Bracero, Olga L.; Maenhaut, Willy; Artaxo, Paulo; Andreae, Meinrat O.

    taken into account when modeling the physical and optical properties of aerosols in forested regions such the Amazon Basin.

  11. Estimation of aerosol optical properties from all-sky imagers

    Science.gov (United States)

    Kazantzidis, Andreas; Tzoumanikas, Panagiotis; Salamalikis, Vasilios; Wilbert, Stefan; Prahl, Christoph

    2015-04-01

    Aerosols are one of the most important constituents in the atmosphere that affect the incoming solar radiation, either directly through absorbing and scattering processes or indirectly by changing the optical properties and lifetime of clouds. Under clear skies, aerosols become the dominant factor that affect the intensity of solar irradiance reaching the ground. It has been shown that the variability in direct normal irradiance (DNI) due to aerosols is more important than the one induced in global horizontal irradiance (GHI), while the uncertainty in its calculation is dominated by uncertainties in the aerosol optical properties. In recent years, all-sky imagers are used for the detection of cloud coverage, type and velocity in a bouquet of applications including solar irradiance resource and forecasting. However, information about the optical properties of aerosols could be derived with the same instrumentation. In this study, the aerosol optical properties are estimated with the synergetic use of all-sky images, complementary data from the Aerosol Robotic Network (AERONET) and calculations from a radiative transfer model. The area of interest is Plataforma Solar de Almería (PSA), Tabernas, Spain and data from a 5 month period are analyzed. The proposed methodology includes look-up-tables (LUTs) of diffuse sky radiance of Red (R), Green (G) and Blue (B) channels at several zenith and azimuth angles and for different atmospheric conditions (Angström α and β, single scattering albedo, precipitable water, solar zenith angle). Based on the LUTS, results from the CIMEL photometer at PSA were used to estimate the RGB radiances for the actual conditions at this site. The methodology is accompanied by a detailed evaluation of its robustness, the development and evaluation of the inversion algorithm (derive aerosol optical properties from RGB image values) and a sensitivity analysis about how the pre-mentioned atmospheric parameters affect the results.

  12. Retrieval of aerosol aspect ratio from optical measurements in Vienna

    Science.gov (United States)

    Kocifaj, M.; Horvath, H.; Gangl, M.

    The phase function and extinction coefficient measured simultaneously are interpreted in terms of surface distribution function and mean effective aspect ratio of aerosol particles. All optical data were collected in the atmosphere of Vienna during field campaign in June 2005. It is shown that behavior of aspect ratio of Viennese aerosols has relation to relative humidity in such a way, that nearly spherical particles (with aspect ratio ɛ≈1) might became aspherical with ɛ≈1.3-1.6 under low relative humidity conditions. Typically, >80% of all Viennese aerosols have the aspect ratio Vienna.

  13. A characterization of Arctic aerosols on the basis of aerosol optical depth and black carbon measurements

    Directory of Open Access Journals (Sweden)

    R. S. Stone

    2014-06-01

    Full Text Available Abstract Aerosols, transported from distant source regions, influence the Arctic surface radiation budget. When deposited on snow and ice, carbonaceous particles can reduce the surface albedo, which accelerates melting, leading to a temperature-albedo feedback that amplifies Arctic warming. Black carbon (BC, in particular, has been implicated as a major warming agent at high latitudes. BC and co-emitted aerosols in the atmosphere, however, attenuate sunlight and radiatively cool the surface. Warming by soot deposition and cooling by atmospheric aerosols are referred to as “darkening” and “dimming” effects, respectively. In this study, climatologies of spectral aerosol optical depth AOD (2001–2011 and Equivalent BC (EBC (1989–2011 from three Arctic observatories and from a number of aircraft campaigns are used to characterize Arctic aerosols. Since the 1980s, concentrations of BC in the Arctic have decreased by more than 50% at ground stations where in situ observations are made. AOD has increased slightly during the past decade, with variations attributed to changing emission inventories and source strengths of natural aerosols, including biomass smoke and volcanic aerosol, further influenced by deposition rates and airflow patterns.

  14. Photoacoustic measurements of photokinetics in single optically trapped aerosol droplets

    Science.gov (United States)

    Covert, Paul; Cremer, Johannes; Signorell, Ruth; Thaler, Klemens; Haisch, Christoph

    2017-04-01

    It is well established that interaction of light with atmospheric aerosols has a large impact on the Earth's climate. However, uncertainties in the magnitude of this impact remain large, due in part to broad distributions of aerosol size, composition, and chemical reactivity. In this context, photoacoustic spectroscopy is commonly used to measure light absorption by aerosols. Here, we present photoacoustic measurements of single, optically-trapped nanodroplets to reveal droplet size-depencies of photochemical and physical processes. Theoretical considerations have pointed to a size-dependence in the magnitude and phase of the photoacoustic response from aerosol droplets. This dependence is thought to originate from heat transfer processes that are slow compared to the acoustic excitation frequency. In the case of a model aerosol, our measurements of single particle absorption cross-section versus droplet size confirm these theoretical predictions. In a related study, using the same model aerosol, we also demonstrate a droplet size-dependence of photochemical reaction rates [1]. Within sub-micron sized particles, photolysis rates were observed to be an order of magnitude greater than those observed in larger droplets. [1] J. W. Cremer, K. M. Thaler, C. Haisch, and R. Signorell. Photoacoustics of single laser-trapped nanodroplets for the direct observation of nanofocusing in aerosol photokinetics. Nat. Commun., 7:10941, 2016.

  15. Toward Investigating Optically Trapped Organic Aerosols with CARS Microspectroscopy

    Science.gov (United States)

    Voss, L. F.

    2009-12-01

    The Intergovernmental Panel on Climate Change notes the huge uncertainty in the effect that atmospheric aerosols play in determining overall global temperature, specifically in their ability to nucleate clouds. To better understand aerosol chemistry, the novel coupling of gradient force optical trapping with broad bandwidth coherent anti-Stokes Raman scattering (CARS) spectroscopy is being developed to study single particles suspended in air. Building on successful designs employed separately for the techniques, this hybrid technology will be used to explain how the oxidation of organic compounds changes the chemical and physical properties of aerosols. By trapping the particles, an individual aerosol can be studied for up to several days. Using a broad bandwidth pulse for one of the incident beams will result in a Raman vibrational spectrum from every laser pulse. Combined with signal enhancement due to resonance and coherence of nonlinear CARS spectroscopy, this technique will allow for acquisition of data on the millisecond time scale, facilitating the study of dynamic processes. This will provide insights on how aerosols react with and absorb species from the gas phase. These experiments will increase understanding of aerosol oxidation and growth mechanisms and the effects that aerosols have on our atmosphere and climate. Progress in efforts developing this novel technique to study model systems is presented.

  16. Variability of aerosol optical depth and aerosol radiative forcing over Northwest Himalayan region

    Science.gov (United States)

    Saheb, Shaik Darga; Kant, Yogesh; Mitra, D.

    2016-05-01

    In recent years, the aerosol loading in India is increasing that has significant impact on the weather/climatic conditions. The present study discusses the analysis of temporal (monthly and seasonal) variation of aerosol optical depth(AOD) by the ground based observations from sun photometer and estimate the aerosol radiative forcing and heating rate over selected station Dehradun in North western Himalayas, India during 2015. The in-situ measurements data illustrate that the maximum seasonal average AOD observed during summer season AOD at 500nm ≍ 0.59+/-0.27 with an average angstrom exponent, α ≍0.86 while minimum during winter season AOD at 500nm ≍ 0.33+/-0.10 with angstrom exponent, α ≍1.18. The MODIS and MISR derived AOD was also compared with the ground measured values and are good to be in good agreement. Analysis of air mass back trajectories using HYSPLIT model reveal that the transportation of desert dust during summer months. The Optical Properties of Aerosols and clouds (OPAC) model was used to compute the aerosol optical properties like single scattering albedo (SSA), Angstrom coefficient (α) and Asymmetry(g) parameter for each day of measurement and they are incorporated in a Discrete Ordinate Radiative Transfer model, i.e Santa Barbara DISORT Atmospheric Radiative Transfer (SBDART) to estimate the direct short-wave (0.25 to 4 μm) Aerosol Radiative forcing at the Surface (SUR), the top-of-atmosphere (TOA) and Atmosphere (ATM). The maximum Aerosol Radiative Forcing (ARF) was observed during summer months at SUR ≍ -56.42 w/m2, at TOA ≍-21.62 w/m2 whereas in ATM ≍+34.79 w/m2 with corresponding to heating rate 1.24°C/day with in lower atmosphere.

  17. Optical Properties of Polymers Relevant to Secondary Organic Aerosols

    Science.gov (United States)

    Marrero-Ortiz, W.; Gomez-Hernandez, M. E.; Xu, W.; Guo, S.; Zhang, R.

    2014-12-01

    Atmospheric aerosols play a critical role in climate directly by scattering and absorbing solar radiation and indirectly by modifying the cloud formation. Currently, the direct and indirect effects of aerosols represent the largest uncertainty in climate predictions models. Some aerosols are directly emitted, but the majority are formed in the atmosphere by the oxidation of gaseous precursors. However, the formation of aerosols at the molecular level is not fully characterized. Certain category of secondary organic aerosols (SOA), which represent a significant fraction of the total aerosol burden, can be light-absorbing, also known as brown carbon. However, the overall contribution of SOA to the brown carbon and the related climate forcing is poorly understood. Such incomplete understanding is due in part to the chemical complexity of SOA and the lack of knowledge regarding SOA formation, transformation, and optical properties. Based on previous laboratory experiments, field measurements, and modeling studies, it has been suggested that the polymers and oligomers play an important role in the SOA formation. Atmospheric polymers could be produced by the hydration or heterogeneous reactions of epoxides and small α-dicarbonyls. Their aqueous chemistry products have been shown to give light-absorbing and high molecular weight oligomeric species, which increase the SOA mass production and alter the direct and indirect effect of aerosols. In this paper, the aerosol chemistry of small α-dicarbonyl compounds with amines is investigated and the associated optical properties are measured using spectroscopic techniques. The differences between primary, secondary and tertiary amines with glyoxal and methylglyoxal are evaluated in terms of SOA browning efficiency. Atmospheric implications of our present work for understanding the formation of light-absorbing SOA will be presented, particularly in terms of the product distribution of light-absorbing SOA formed by aqueous phase

  18. The Two-Column Aerosol Project: Phase I - Overview and Impact of Elevated Aerosol Layers on Aerosol Optical Depth

    Energy Technology Data Exchange (ETDEWEB)

    Berg, Larry K.; Fast, Jerome D.; Barnard, James C.; Burton, Sharon; Cairns, Brian; Chand, Duli; Comstock, Jennifer M.; Dunagan, Stephen; Ferrare, Richard A.; Flynn, Connor J.; Hair, John; Hostetler, Chris A.; Hubbe, John M.; Jefferson, Anne; Johnson, Roy; Kassianov, Evgueni I.; Kluzek, Celine D.; Kollias, Pavlos; Lamer, Katia; Lantz, K.; Mei, Fan; Miller, Mark A.; Michalsky, Joseph; Ortega, Ivan; Pekour, Mikhail S.; Rogers, Ray; Russell, P.; Redemann, Jens; Sedlacek, Art; Segal Rozenhaimer, Michal; Schmid, Beat; Shilling, John E.; Shinozuka, Yohei; Springston, Stephen R.; Tomlinson, Jason M.; Tyrrell, Megan; Wilson, Jacqueline; Volkamer, Rainer M.; Zelenyuk, Alla; Berkowitz, Carl M.

    2016-01-08

    The Two-Column Aerosol Project (TCAP), which was conducted from June 2012 through June 2013, was a unique field study that was designed to provide a comprehensive data set that can be used to investigate a number of important climate science questions, including those related to aerosol mixing state and aerosol radiative forcing. The study was designed to sample the atmosphere at a number of altitudes, from near the surface to as high as 8 km, within two atmospheric columns; one located near the coast of North America (over Cape Cod, MA) and a second over the Atlantic Ocean several hundred kilometers from the coast. TCAP included the yearlong deployment of the U.S. Department of Energy’s (DOE) Atmospheric Radiation Measurement (ARM) Mobile Facility (AMF) that was located at the base of the Cape Cod column, as well as summer and winter aircraft intensive observation periods of the ARM Aerial Facility. One important finding from TCAP is the relatively common occurrence (on four of six nearly cloud-free flights) of elevated aerosol layers in both the Cape Cod and maritime columns that were detected using the nadir pointing second-generation NASA high-spectral resolution lidar (HSRL-2). These layers contributed up to 60% of the total aerosol optical depth (AOD) observed in the column. Many of these layers were also intercepted by the aircraft configured for in situ sampling, and the aerosol in the layers was found to have increased amounts of biomass burning aerosol and nitrate compared to the aerosol found near the surface.

  19. Model of optical response of marine aerosols to Forbush decreases

    Directory of Open Access Journals (Sweden)

    T. Bondo

    2009-10-01

    Full Text Available In order to elucidate the effect of galactic cosmic rays on cloud formation, we investigate the optical response of marine aerosols to Forbush decreases – abrupt decreases in galactic cosmic rays – by means of modeling. We vary the nucleation rate of new aerosols, in a sectional coagulation and condensation model, according to changes in ionization by the Forbush decrease. From the resulting size distribution we then calculate the aerosol optical thickness and Angstrom exponent, for the wavelength pairs 350, 450 nm and 550, 900 nm. For the shorter wavelength pair we observe a change in Angstrom exponent, following the Forbush Decrease, of −6 to +3% in the cases with atmospherically realistic output parameters. For some parameters we also observe a delay in the change of Angstrom exponent, compared to the maximum of the Forbush decrease, which is caused by different sensitivities of the probing wavelengths to changes in aerosol number concentration and size. For the long wavelengths these changes are generally smaller. The types and magnitude of change is investigated for a suite of nucleation rates, condensable gas production rates, and aerosol loss rates. Furthermore we compare the model output with observations of 5 of the largest Forbush decreases after year 2000. For the 350, 450 nm pair we use AERONET data and find a comparable change in signal while the Angstrom Exponent is lower in the model than in the data, due to AERONET being mainly sampled over land. For 550, 900 nm we compare with both AERONET and MODIS and find little to no response in both model and observations. In summary our study shows that the optical properties of aerosols show a distinct response to Forbush Decreases, assuming that the nucleation of fresh aerosols is driven by ions. Shorter wavelengths seem more favorable for observing these effects and great care should be taken when analyzing observations, in order to avoid the signal being drowned out by noise.

  20. Model of optical response of marine aerosols to Forbush decreases

    Directory of Open Access Journals (Sweden)

    T. Bondo

    2010-03-01

    Full Text Available In order to elucidate the effect of galactic cosmic rays on cloud formation, we investigate the optical response of marine aerosols to Forbush decreases – abrupt decreases in galactic cosmic rays – by means of modeling. We vary the nucleation rate of new aerosols, in a sectional coagulation and condensation model, according to changes in ionization by the Forbush decrease. From the resulting size distribution we then calculate the aerosol optical thickness and Angstrom exponent, for the wavelength pairs 350, 450 nm and 550, 900 nm. In the cases where the output parameters from the model seem to compare best with atmospheric observations we observe, for the shorter wavelength pair, a change in Angstrom exponent, following the Forbush Decrease, of −6 to +3%. In some cases we also observe a delay in the change of Angstrom exponent, compared to the maximum of the Forbush decrease, which is caused by different sensitivities of the probing wavelengths to changes in aerosol number concentration and size. For the long wavelengths these changes are generally smaller. The types and magnitude of change is investigated for a suite of nucleation rates, condensable gas production rates, and aerosol loss rates. Furthermore we compare the model output with observations of 5 of the largest Forbush decreases after year 2000. For the 350, 450 nm pair we use AERONET data and find a comparable change in signal while the Angstrom Exponent is lower in the model than in the data, due to AERONET being mainly sampled over land. For 550, 900 nm we compare with both AERONET and MODIS and find little to no response in both model and observations. In summary our study shows that the optical properties of aerosols show a distinct response to Forbush Decreases, assuming that the nucleation of fresh aerosols is driven by ions. Shorter wavelengths seem more favorable for observing these effects and great care should be taken when analyzing observations, in order to avoid

  1. Aerosol physical and optical properties in the Eastern Mediterranean Basin, Crete, from Aerosol Robotic Network data

    Directory of Open Access Journals (Sweden)

    A. Fotiadi

    2006-01-01

    Full Text Available In this study, we investigate the aerosol optical properties, namely aerosol extinction optical thickness (AOT, Angström parameter and size distribution over the Eastern Mediterranean Basin, using spectral measurements from the recently established FORTH (Foundation for Research and Technology-Hellas AERONET station in Crete, for the two-year period 2003–2004. The location of the FORTH-AERONET station offers a unique opportunity to monitor aerosols from different sources. Maximum values of AOT are found primarily in spring, which together with small values of the Angström parameter indicate dust transported from African deserts, whereas the minimum values of AOT occur in winter. In autumn, large AOT values observed at near-infrared wavelengths arise also from dust transport. In summer, large AOT values at ultraviolet (340 nm and visible wavelengths (500 nm, together with large values of the Angström parameter, are associated with transport of fine aerosols of urban/industrial and biomass burning origin. The Angström parameter values vary on a daily basis within the range 0.05–2.20, and on a monthly basis within the range 0.68–1.9. This behaviour, together with broad frequency distributions and back-trajectory analyses, indicates a great variety of aerosol types over the study region including dust, urban-industrial and biomass-burning pollution, and maritime, as well as mixed aerosol types. Large temporal variability is observed in AOT, Angström parameter, aerosol content and size. The fine and coarse aerosol modes persist throughout the year, with the coarse mode dominant except in summer. The highest values of AOT are related primarily to southeasterly winds, associated with coarse aerosols, and to a less extent to northwesterly winds associated with fine aerosols. The results of this study show that the FORTH AERONET station in Crete is well suited for studying the transport and mixing of different types of aerosols from a variety

  2. Optical response of marine aerosols to Forbush Decreases

    DEFF Research Database (Denmark)

    Enghoff, Martin Andreas Bødker

    A tempting approach to investigate the link between cosmic rays and climate is to explore Forbush decreases - sudden drops in the amount of galactic cosmic rays reaching Earth, caused by large Coronal Mass Ejections from the sun. Due to the sudden nature of these events effects from other solar...... parameters, such as total irradiance or UV can be ruled out. There has previously been several papers using observations to gauge the impact of Forbush decreases on cloud cover, but with no definitive conclusion. In this study we model the response of the optical parameters of marine aerosols – precursors...... for cloud drops. We are specifically looking at the Angstrom exponent and the optical thickness. The goal is to elucidate the sensitivity of the type and magnitude of response in these parameters during a Forbush decrease, to changes in aerosol production, condensable gases, and primary aerosols....

  3. Electro-Optical Aerosol Phase Function Database PFNDAT2005

    Science.gov (United States)

    2005-11-01

    Pollack, J.B.; Khare, B.N. Optical Constants of Several Atmospheric Aerosol Species, Ammonium Sulphate , Aluminum Oxide and Sodium Chloride. J. of...16 Table 12. Precipitation rates, number...rain at three precipitation rates (drizzle, moderate, and heavy); and two classes of snow, “dry” and “wet”. Dusts are treated under four categories

  4. Sensitivity of aerosol optical thickness and aerosol direct radiative effect to relative humidity

    Directory of Open Access Journals (Sweden)

    H. Bian

    2008-07-01

    Full Text Available We present a sensitivity study on the effects of spatial and temporal resolution of atmospheric relative humidity (RH on calculated aerosol optical thickness (AOT and the aerosol direct radiative effects (DRE in a global model. Using the same aerosol fields simulated in the Global Modeling Initiative (GMI model, we find that, on a global average, the calculated AOT from RH in 1° latitude by 1.25° longitude spatial resolution is 11% higher than that in 2° by 2.5° resolution, and the corresponding DRE at the top of the atmosphere is 8–9% higher for total aerosols and 15% higher for only anthropogenic aerosols in the finer spatial resolution case. The difference is largest over surface escarpment regions (e.g. >200% over the Andes Mountains where RH varies substantially with surface terrain. The largest zonal mean AOT difference occurs at 50–60°N (16–21%, where AOT is also relatively larger. A similar increase is also found when the time resolution of RH is increased. This increase of AOT and DRE with the increase of model resolution is due to the highly non-linear relationship between RH and the aerosol mass extinction efficiency (MEE at high RH (>80%. Our study suggests that caution should be taken in a multi-model comparison (e.g. AeroCom since the comparison usually deals with results coming from different spatial/temporal resolutions.

  5. Aerosol Optical Depth over Africa retrieved from AATSR

    Science.gov (United States)

    Sogacheva, Larisa; de Leeuw, Gerrit; Kolmonen, Pekka; Sundström, Anu-Maija; Rodriques, Edith

    2010-05-01

    Aerosols produced over the African continent have important consequences for climate. In particular, large amounts of desert dust are produced over the Sahara and transported across the North Atlantic where desert dust deposition influences the eco system by iron fertilization, and further North over Europe with outbreaks as far as Scandinavia. Biomass burning occurs in most of the African continent south of the Sahara and causes a net positive radiating forcing resulting in local warming of the atmosphere layers. These effects have been studied during large field campaigns. Satellites can systematically provide information on aerosols over a large area such as Africa and beyond. To this end, we retrieved the Aerosol Optical Depth (AOD) at three wavelengths (555nm, 670nm, and 1600nm) over Africa from the reflectance measured at the top of the atmosphere by the AATSR (Advances Along Track Scanning Radiometer) flying on ENVISAT, for one year (1 May 2008 to 30 April 2009) to obtain information on the seasonal and spatial behaviour of the AOD, episodes of high AOD events and connect the retrieved AOD with the ground-based aerosol measurements. The AOD retrieval algorithm, which is applied to cloud-free pixels over land, is based on the comparison of the measured and modeled reflectance at the top of the atmosphere (TOA). The algorithm uses look-up-tables (LUTs) to compute the modeled TOA reflectance. For AOD retrieval, an aerosol in the atmosphere is assumed to be an external mixture of fine and coarse mode particles. The two aerosol types are mixed such that the spectral behavior of the reflectance due to aerosol best fits the measurements. Comparison with AERONET (Aerosol Roboric NETwork), which is a network of ground-based sun photometers which measure atmospheric aerosol properties, shows good agreement but with some overestimation of the AATSR retrieved AOD. Different aerosol models have been used to improve the comparison. The lack of AERONET stations in Africa

  6. Variability of aerosol optical properties in the Western Mediterranean Basin

    Science.gov (United States)

    Pandolfi, M.; Cusack, M.; Alastuey, A.; Querol, X.

    2011-08-01

    Aerosol light scattering, absorption and particulate matter (PM) concentrations were measured at Montseny, a regional background site in the Western Mediterranean Basin (WMB) which is part of the European Supersite for Atmospheric Aerosol Research (EUSAAR). Off line analyses of 24 h PM filters collected with Hi-Vol instruments were performed for the determination of the main chemical components of PM. Mean scattering and hemispheric backscattering coefficients (@ 635 nm) were 26.6±23.2 Mm-1 and 4.3±2.7 Mm-1, respectively and the mean aerosol absorption coefficient (@ 637 nm) was 2.8±2.2 Mm-1. Mean values of Single Scattering Albedo (SSA) and Ångström exponent (å) (calculated from 450 nm to 635 nm) at MSY were 0.90±0.05 and 1.3±0.5 respectively. A clear relationship was observed between the PM1/PM10 and PM2.5/PM10 ratios as a function of the calculated Ångström exponents. Mass scattering cross sections (MSC) for fine mass and sulfate at 635 nm were 2.8±0.5 m2 g-1 and 11.8±2.2 m2 g-1, respectively, while the mean aerosol absorption cross section (MAC) was 10.4±2.0 m2 g-1. The variability in aerosol optical properties in the WMB were largely explained by the origin and ageing of air masses over the measurement site. The MAC values appear dependent of particles aging: similar to the expected absorption cross-section for fresh emissions under Atlantic Advection episodes and higher under aerosol pollution episodes. The analysis of the Ångström exponent as a function of the origin the air masses revealed that polluted winter anticyclonic conditions and summer recirculation scenarios typical of the WMB led to an increase of fine particles in the atmosphere (å = 1.5±0.1) while the aerosol optical properties under Atlantic Advection episodes and Saharan dust outbreaks were clearly dominated by coarser particles (å = 1.0±0.4). The sea breeze played an important role in transporting pollutants from the developed WMB coastlines towards inland rural areas

  7. Sensitivity of aerosol optical thickness and aerosol direct radiative effect to relative humidity

    Directory of Open Access Journals (Sweden)

    H. Bian

    2009-04-01

    Full Text Available We present a sensitivity study of the effects of spatial and temporal resolution of atmospheric relative humidity (RH on calculated aerosol optical thickness (AOT and the aerosol direct radiative effects (DRE in a global model. We carry out different modeling experiments using the same aerosol fields simulated in the Global Modeling Initiative (GMI model at a resolution of 2° latitude by 2.5° longitude, using time-averaged fields archived every three hours by the Goddard Earth Observation System Version 4 (GEOS-4, but we change the horizontal and temporal resolution of the relative humidity fields. We find that, on a global average, the AOT calculated using RH at a 1°×1.25° horizontal resolution is 11% higher than that using RH at a 2°×2.5° resolution, and the corresponding DRE at the top of the atmosphere is 8–9% and 15% more negative (i.e., more cooling for total aerosols and anthropogenic aerosol alone, respectively, in the finer spatial resolution case. The difference is largest over surface escarpment regions (e.g. >200% over the Andes Mountains where RH varies substantially with surface terrain. The largest zonal mean AOT difference occurs at 50–60° N (16–21%, where AOT is also relatively larger. A similar impact is also found when the time resolution of RH is increased. This increase of AOT and aerosol cooling with the increase of model resolution is due to the highly non-linear relationship between RH and the aerosol mass extinction efficiency (MEE at high RH (>80%. Our study is a specific example of the uncertainty in model results highlighted by multi-model comparisons such as AeroCom, and points out one of the many inter-model differences that can contribute to the overall spread among models.

  8. Investigation of aerosol optical properties for remote sensing through DRAGON (distributed regional aerosol gridded observation networks) campaign in Korea

    Science.gov (United States)

    Lim, Jae-Hyun; Ahn, Joon Young; Park, Jin-Soo; Hong, You-Deok; Han, Jin-Seok; Kim, Jhoon; Kim, Sang-Woo

    2014-11-01

    Aerosols in the atmosphere, including dust and pollutants, scatters/absorbs solar radiation and change the microphysics of clouds, thus influencing the Earth's energy budget, climate, air quality, visibility, agriculture and water circulation. Pollutants have also been reported to threaten the human health. The present research collaborated with the U.S. NASA and the U.S. Aerosol Robotic Network (AERONET) is to study the aerosol characteristics in East Asia and improve the long-distance transportation monitoring technology by analyzing the observations of aerosol characteristics in East Asia during Distributed Regional Aerosol Gridded Observation Networks (DRAGON) Campaign (March 2012-May 2012). The sun photometers that measure the aerosol optical characteristics were placed evenly throughout the Korean Peninsula and concentrated in Seoul and the metropolitan area. Observation data are obtained from the DRAGON campaign and the first year (2012) observation data (aerosol optical depth and aerosol spatial distribution) are analyzed. Sun photometer observations, including aerosol optical depth (AOD), are utilized to validate satellite observations from Geostationary Ocean Color Imager (GOCI) and Moderate Resolution Imaging Spectroradiometer (MODIS). Additional analysis is performed associated with the Northeast Asia, the Korean Peninsula in particular, to determine the spatial distribution of the aerosol.

  9. SPATIAL INTERPOLATION OF AEROSOL OPTICAL DEPTH POLLUTION: COMPARISON OF METHODS FOR THE DEVELOPMENT OF AEROSOL DISTRIBUTION

    Directory of Open Access Journals (Sweden)

    S. Safarpour

    2017-09-01

    Full Text Available Air pollution is a growing problem arising from domestic heating, high density of vehicle traffic, electricity production, and expanding commercial and industrial activities, all increasing in parallel with urban population. Monitoring and forecasting of air quality parameters are important due to health impact. One widely available metric of aerosol abundance is the aerosol optical depth (AOD. The AOD is the integrated light extinction coefficient over a vertical atmospheric column of unit cross section, which represents the extent to which the aerosols in that vertical profile prevent the transmission of light by absorption or scattering. Seasonal aerosol optical depth (AOD values at 550 nm derived from the Moderate Resolution Imaging Spectroradiometer (MODIS sensor onboard NASA’s Terra satellites, for the 10 years period of 2000 - 2010 were used to test 7 different spatial interpolation methods in the present study. The accuracy of estimations was assessed through visual analysis as well as independent validation based on basic statistics, such as root mean square error (RMSE and correlation coefficient. Based on the RMSE and R values of predictions made using measured values from 2000 to 2010, Radial Basis Functions (RBFs yielded the best results for spring, summer and winter and ordinary kriging yielded the best results for fall.

  10. Optical characterization of continental and biomass-burning aerosols over Bozeman, Montana: A case study of the aerosol direct effect

    Science.gov (United States)

    Nehrir, Amin R.; Repasky, Kevin S.; Reagan, John A.; Carlsten, John L.

    2011-11-01

    Atmospheric aerosol optical properties were observed from 21 to 27 September 2009 over Bozeman, Montana, during a transitional period in which background polluted rural continental aerosols and well-aged biomass-burning aerosols were the dominant aerosol types of extremely fresh biomass-burning aerosols resulting from forest fires burning in the northwestern United States and Canada. Aerosol optical properties and relative humidity profiles were retrieved using an eye-safe micropulse water vapor differential absorption lidar (DIAL) (MP-DIAL), a single-channel backscatter lidar, a CIMEL solar radiometer as part of the Aerosol Robotic Network (AERONET), a ground-based integrating nephelometer, and aerosol products from Moderate Resolution Imaging Spectroradiometer (MODIS) Terra and Aqua. Aerosol optical depths (AODs) measured during the case study ranged between 0.03 and 0.17 (0.015 and 0.075) at 532 nm (830 nm) as episodic combinations of fresh and aged biomass-burning aerosols dominated the optical depth of the pristinely clean background air. Here, a pristinely clean background refers to very low AOD conditions, not that the aerosol scattering and absorption properties are necessarily representative of a clean aerosol type. Diurnal variability in the aerosol extinction to backscatter ratio (Sa) of the background atmosphere derived from the two lidars, which ranged between 55 and 95 sr (50 and 90 sr) at 532 nm (830 nm), showed good agreement with retrievals from AERONET sun and sky measurements over the same time period but were consistently higher than some aerosol models had predicted. Sa measured during the episodic smoke events ranged on average from 60 to 80 sr (50 to 70 sr) at 532 nm (830 nm) while the very fresh biomass-burning aerosols were shown to exhibit significantly lower Sa ranging between 20 and 40 sr. The shortwave direct radiative forcing that was due to the intrusion of biomass-burning aerosols was calculated to be on average -10 W/m2 and was

  11. Vertically Resolved Aerosol Optical Properties over the ARM SGP Site

    Science.gov (United States)

    Schmid, B.; Jonsson, H.; Strawa, A.; Provencal, B.; Covert, D.; Arnott, P.; Bucholtz, A.; Pilewskie, P.; Pommier, J.; Rissman, T.

    2003-01-01

    In order to meet one of its goals - to relate observations of radiative fluxes and radiances to the atmospheric composition - the Department of Energy's Atmospheric Radiation Measurement (ARM) program has pursued measurements and modeling activities that attempt to determine how aerosols impact atmospheric radiative transfer, both directly and indirectly. However, significant discrepancies between aerosol properties measured in situ or remotely remain. To this end, the ARM program will conduct an Aerosol Intensive Operational Period (IOP) in May 2003 at the ARM Southern Great Plains (SGP) site in north central Oklahoma. The IOP involves airborne measurements from two airplanes over the heavily instrumented SGP site. We will give an overview of early airborne results obtained aboard Center for Interdisciplinary Remotely-Piloted Aircraft Studies (CIRPAS) Twin Otter aircraft. The aircraft will carry instrumentation to perform in-situ measurements of aerosol absorption, scattering, extinction and particle size including such novel techniques as the photoacoustic and cavity ring-down methods. Aerosol optical depth and extinction will be measured with the NASA Ames Airborne Tracking 14-channel sunphotometer. Furthermore up- and downwelling solar (broadband and spectral) and infrared radiation will be measured using three different instruments. The up-looking radiation instruments will be mounted on a newly developed stabilized platform, which will keep the instruments level up to aircraft pitch and roll angles of 10 degrees. Additional effort will be directed toward measurement of cloud condensation nucleus concentration as a function of supersaturation and relating CCN concentration to aerosol composition and size distribution. This relation is central to description of the aerosol indirect effect.

  12. Aerosols, light, and water: Measurements of aerosol optical properties at different relative humidities

    Science.gov (United States)

    Orozco, Daniel

    The Earth's atmosphere is composed of a large number of different gases as well as tiny suspended particles, both in solid and liquid state. These tiny particles, called atmospheric aerosols, have an immense impact on our health and on our global climate. Atmospheric aerosols influence the Earth's radiation budget both directly and indirectly. In the direct effect, aerosols scatter and absorb sunlight changing the radiative balance of the Earth-atmosphere system. Aerosols indirectly influence the Earth's radiation budget by modifying the microphysical and radiative properties of clouds as well as their water content and lifetime. In ambient conditions, aerosol particles experience hygroscopic growth due to the influence of relative humidity (RH), scattering more light than when the particles are dry. The quantitative knowledge of the RH effect and its influence on the light scattering coefficient and, in particular, on the phase function and polarization of aerosol particles is of substantial importance when comparing ground based observations with other optical aerosol measurements techniques such satellite and sunphotometric retrievals of aerosol optical depth and their inversions. This dissertation presents the aerosol hygroscopicity experiment investigated using a novel dryer-humidifier system, coupled to a TSI-3563 nephelometer, to obtain the light scattering coefficient (sp) as a function of relative humidity (RH) in hydration and dehydration modes. The measurements were performed in Porterville, CA (Jan 10-Feb 6, 2013), Baltimore, MD (Jul 3-30, 2013), and Golden, CO (Jul 12-Aug 10, 2014). Observations in Porterville and Golden were part of the NASA-sponsored DISCOVER-AQ project. The measured sp under varying RH in the three sites was combined with ground aerosol extinction, PM2:5mass concentrations, particle composition measurements, and compared with airborne observations performed during campaigns. The enhancement factor, f(RH), defined as the ratio of sp

  13. Seasonal variability of aerosol optical depth over Indian subcontinent

    Science.gov (United States)

    Prasad, A.K.; Singh, R.P.; Singh, A.; Kafatos, M.

    2005-01-01

    Ganga basin extends 2000 km E-W and about 400 km N-S and is bounded by Himalayas in the north. This basin is unequivocally found to be affected by high aerosols optical depth (AOD) (>0.6) throughout the year. Himalayas restricts movement of aerosols toward north and as a result dynamic nature of aerosol is seen over the Ganga basin. High AOD in this region has detrimental effects on health of more than 460 million people living in this part of India besides adversely affecting clouds formation, monsoonal rainfall pattern and Normalized Difference Vegetation Index (NDVI). Severe drought events (year 2002) in Ganga basin and unexpected failure of monsoon several times, occurred in different parts of Indian subcontinent. Significant rise in AOD (18.7%) over the central part of basin (Kanpur region) have been found to cause substantial decrease in NDVI (8.1%) since 2000. A negative relationship is observed between AOD and NDVI, magnitude of which differs from region to region. Efforts have been made to determine general distribution of AOD and its dominant departure in recent years spatially using Moderate Resolution Imaging Spectroradiometer (MODIS) data. The seasonal changes in aerosol optical depth over the Indo-Gangetic basin is found to very significant as a result of the increasing dust storm events in recent years. ?? 2005 IEEE.

  14. Characterisation of coated aerosols using optical tweezers and neutron reflectometry

    Science.gov (United States)

    Jones, S. H.; Ward, A.; King, M. D.

    2013-12-01

    Thin organic films are believed to form naturally on the surface of aerosols [1,2] and influence aerosol properties. Cloud condensation nuclei formation and chemical reactions such as aerosol oxidation are effected by the presence of thin films [3]. There is a requirement to characterise the physical properties of both the core aerosol and its organic film in order to fully understand the contribution of coated aerosols to the indirect effect. Two complementary techniques have been used to study the oxidation of thin organic films on the surface of aerosols; laser optical tweezers and neutron reflectometry. Micron sized polystyrene beads coated in oleic acid have been trapped in air using two counter propagating laser beams. Polystyrene beads are used as a proxy for solid aerosol. The trapped aerosol is illuminated with a white LED over a broadband wavelength range and the scattered light collected to produce a Mie spectrum [4]. Analysis of the Mie spectrum results in determination of the core polystyrene bead radius, the oleic acid film thickness and refractive index dispersion of the core and shell [5]. A flow of ozone gas can then be introduced into the aerosol environment to oxidise the thin film of oleic acid and the reaction followed by monitoring the changes in the Mie spectrum. The results demonstrate complete removal of the oleic acid film. We conclude that the use of a counter propagating optical trap combined with white light Mie spectroscopy can be used to study a range of organic films on different types of aerosols and their oxidation reactions. Neutron reflectometry has been used as a complementary technique to study the oxidation of monolayer films at the air-water interface in order to gain information on reaction kinetics. The oxidation of an oleic acid film at the air-water interface by the common tropospheric oxidant ozone has been studied using a Langmuir trough. Results indicate complete removal of the oleic acid film with ozone in agreement

  15. Cloud-Driven Changes in Aerosol Optical Properties - Final Technical Report

    Energy Technology Data Exchange (ETDEWEB)

    Ogren, John A.; Sheridan, Patrick S.; Andrews, Elisabeth

    2007-09-30

    The optical properties of aerosol particles are the controlling factors in determining direct aerosol radiative forcing. These optical properties depend on the chemical composition and size distribution of the aerosol particles, which can change due to various processes during the particles’ lifetime in the atmosphere. Over the course of this project we have studied how cloud processing of atmospheric aerosol changes the aerosol optical properties. A counterflow virtual impactor was used to separate cloud drops from interstitial aerosol and parallel aerosol systems were used to measure the optical properties of the interstitial and cloud-scavenged aerosol. Specifically, aerosol light scattering, back-scattering and absorption were measured and used to derive radiatively significant parameters such as aerosol single scattering albedo and backscatter fraction for cloud-scavenged and interstitial aerosol. This data allows us to demonstrate that the radiative properties of cloud-processed aerosol can be quite different than pre-cloud aerosol. These differences can be used to improve the parameterization of aerosol forcing in climate models.

  16. Columnar Aerosol Optical Properties during "El Arenosillo 2004 Summer Campaign"

    Energy Technology Data Exchange (ETDEWEB)

    Prats, N.; Cachorro, V. E.; Sorribas, M.; Mogo, S.; Berjon, A.; Toledano, C.; de Frutos, A. M.; de la Rosa, J.; Laulainen, Nels S.; de la Morena, B. A.

    2008-04-14

    A detailed analysis of the microphysical and radiative columnar aerosol parameters has been carried out for data collected during the “El Arenosillo 2004” summer campaign. These data are derived from a Cimel sun-photometer, as part of the PHOTONS-AERONET network at the El Arenosillo site in south-western Spain, over the period 1 June to 31 October 2004. The aim of this campaign was to obtain a more complete set of data on aerosol microphysical, optical/radiative, and chemical properties for use in closure studies. Previous papers addressed the climatology of the AOD-alpha parameters at this site. In this paper, we focus on the characterization of the particle size distribution and associated microphysical parameters, such as volume concentration, effective radius, etc., in order to define the features and ranges of these physical parameters associated with both fine and coarse particle modes. The requirement of high AOD values for using the optical inversion technique puts significant constraints on the estimation of these parameters and, thus, necessitates great care in the analysis. As a result, only the characterizations for desert dust events are considered reliable. Moreover, summer 2004 had the most frequent desert dust intrusions, including the most intense event, ever recorded at the El Arensillo site. We summarize the results for the intensive summer campaign in terms of the range of values of the physical and optical parameters of the mixed aerosol types present in this area of Spain.

  17. Evaluating UVA aerosol optical depth using a smartphone camera.

    Science.gov (United States)

    Igoe, Damien P; Parisi, Alfio V; Carter, Brad

    2013-01-01

    This research evaluates a smartphone complementary metal oxide semiconductor (CMOS) image sensor's ability to detect and quantify incident solar UVA radiation and subsequently, aerosol optical depth at 340 and 380 nm. Earlier studies revealed that the consumer grade CMOS sensor has inherent UVA sensitivities, despite attenuating effects of the lens. Narrow bandpass and neutral density filters were used to protect the image sensor and to not allow saturation of the solar images produced. Observations were made on clear days, free from clouds. The results of this research demonstrate that there is a definable response to changing solar irradiance and aerosol optical depth can be measured within 5% and 10% error margins at 380 and 340 nm respectively. The greater relative error occurs at lower wavelengths (340 nm) due to increased atmospheric scattering effects, particularly at higher air masses and due to lower signal to noise ratio in the image sensor. The relative error for solar irradiance was under 1% for observations made at 380 nm. The results indicate that the smartphone image sensor, with additional external narrow bandpass and neutral density filters can be used as a field sensor to evaluate solar UVA irradiance and aerosol optical depth. © 2013 The American Society of Photobiology.

  18. AeroCom INSITU Project: Comparing modeled and measured aerosol optical properties

    Science.gov (United States)

    Andrews, Elisabeth; Schmeisser, Lauren; Schulz, Michael; Fiebig, Markus; Ogren, John; Bian, Huisheng; Chin, Mian; Easter, Richard; Ghan, Steve; Kokkola, Harri; Laakso, Anton; Myhre, Gunnar; Randles, Cynthia; da Silva, Arlindo; Stier, Phillip; Skeie, Ragnehild; Takemura, Toshihiko; van Noije, Twan; Zhang, Kai

    2016-04-01

    AeroCom, an open international collaboration of scientists seeking to improve global aerosol models, recently initiated a project comparing model output to in-situ, surface-based measurements of aerosol optical properties. The model/measurement comparison project, called INSITU, aims to evaluate the performance of a suite of AeroCom aerosol models with site-specific observational data in order to inform iterative improvements to model aerosol modules. Surface in-situ data has the unique property of being traceable to physical standards, which is an asset in accomplishing the overall goal of bettering the accuracy of aerosols processes and the predicative capability of global climate models. Here we compare dry, in-situ aerosol scattering and absorption data from ~75 surface, in-situ sites from various global aerosol networks (including NOAA, EUSAAR/ACTRIS and GAW) with a simulated optical properties from a suite of models participating in the AeroCom project. We report how well models reproduce aerosol climatologies for a variety of time scales, aerosol characteristics and behaviors (e.g., aerosol persistence and the systematic relationships between aerosol optical properties), and aerosol trends. Though INSITU is a multi-year endeavor, preliminary phases of the analysis suggest substantial model biases in absorption and scattering coefficients compared to surface measurements, though the sign and magnitude of the bias varies with location. Spatial patterns in the biases highlight model weaknesses, e.g., the inability of models to properly simulate aerosol characteristics at sites with complex topography. Additionally, differences in modeled and measured systematic variability of aerosol optical properties suggest that some models are not accurately capturing specific aerosol behaviors, for example, the tendency of in-situ single scattering albedo to decrease with decreasing aerosol extinction coefficient. The endgoal of the INSITU project is to identify specific

  19. Interference of Heavy Aerosol Loading on the VIIRS Aerosol Optical Depth (AOD Retrieval Algorithm

    Directory of Open Access Journals (Sweden)

    Yang Wang

    2017-04-01

    Full Text Available Aerosol optical depth (AOD has been widely used in climate research, atmospheric environmental observations, and other applications. However, high AOD retrieval remains challenging over heavily polluted regions, such as the North China Plain (NCP. The Visible Infrared Imaging Radiometer Suite (VIIRS, which was designed as a successor to the Moderate Resolution Imaging Spectroradiometer (MODIS, will undertake the aerosol observations mission in the coming years. Using the VIIRS AOD retrieval algorithm as an example, we analyzed the influence of heavy aerosol loading through the 6SV radiative transfer model (RTM with a focus on three aspects: cloud masking, ephemeral water body tests, and data quality estimation. First, certain pixels were mistakenly screened out as clouds and ephemeral water bodies because of heavy aerosols, resulting in the loss of AOD retrievals. Second, the greenness of the surface could not be accurately identified by the top of atmosphere (TOA index, and the quality of the aggregation data may be artificially high. Thus, the AOD retrieval algorithm did not perform satisfactorily, indicated by the low availability of data coverage (at least 37.97% of all data records were missing according to ground-based observations and overestimation of the data quality (high-quality data increased from 63.42% to 80.97% according to radiative simulations. To resolve these problems, the implementation of a spatial variability cloud mask method and surficial index are suggested in order to improve the algorithm.

  20. Reconciling satellite aerosol optical thickness and surface fine particle mass through aerosol liquid water

    Science.gov (United States)

    Nguyen, Thien Khoi V.; Ghate, Virendra P.; Carlton, Annmarie G.

    2016-11-01

    Summertime aerosol optical thickness (AOT) over the southeast U.S. is sharply enhanced over wintertime values. This seasonal pattern is unique and of particular interest because temperatures there have not warmed over the past 100 years. Patterns in surface fine particle mass are inconsistent with satellite reported AOT. In this work, we attempt to reconcile the spatial and temporal distribution of AOT over the U.S. with particle mass measurements at the surface by examining trends in aerosol liquid water (ALW), a particle constituent that scatters radiation and affects satellite AOT but is removed in mass measurements at routine surface monitoring sites. We employ the thermodynamic model ISORROPIAv2.1 to estimate ALW mass concentrations at Interagency Monitoring of PROtected Visual Environments sites using measured ion mass concentrations and North American Regional Reanalysis meteorological data. Excellent agreement between Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations AOT and estimated ALW provides a plausible explanation for the discrepancies in the geographical patterns of AOT and aerosol mass measurements.

  1. Optical and Hygroscopic Studies of Aerosols In Simulated Planetary Atmospheres

    Science.gov (United States)

    Hasenkopf, Christa A.

    2011-08-01

    Basic characteristics of the early Earth climate, the only known environment in the Universe in which life has been known to emerge and thrive, remain a mystery. In particular, little is understood about the Earth's atmosphere 2.8 billion years ago. From climate models and laboratory studies, it is postulated that an organic haze, much like that found on Saturn's largest moon Titan, covered the early Earth. This haze, generated from photolysis of carbon dioxide (CO2) and methane (CH4), may have had profound climatic consequences. Climate models of the early Earth that include this haze have had to rely upon optical properties of a Titan laboratory analog. Titan haze, though thought to be similar, is formed from a different combination of precursor gases and by different energy sources than early Earth haze. This thesis examines the direct and indirect radiative effects of aerosol on early Earth climate by studying the optical and hygroscopic properties of a laboratory analog. A Titan analog is studied for comparison and to better understand spacecraft-retrieved haze chemical and optical properties from Titan. The properties of the laboratory analogs, generated in a flowing reactor cell with a continuum ultraviolet (UV) light source, were primarily measured using cavity ringdown aerosol extinction spectroscopy and UV-visible (UV-Vis) transmission spectroscopy. We find that the optical properties of our early Earth analog are significantly different than those of the Titan analog from Khare et al. (1984). In both the UV and visible, when modeled as fractals, particles with the optical properties of the early Earth analog have approximately 30% larger extinction efficiencies than particles with Khare et al. (1984) values. This result implies our early Earth haze analog would provide a more efficient UV shield and have a stronger antigreenhouse effect than the Khare et al. (1984) Titan analog. Our Titan analog has significantly smaller imaginary refractive index values

  2. Variability of aerosol optical thickness and atmospheric turbidity in Tunisia

    Science.gov (United States)

    Masmoudi, M.; Chaabane, M.; Medhioub, K.; Elleuch, F.

    The aerosol optical thickness (AOT) τa computed from the spectral sun photometer in Thala (Tunisia) exhibited variability ranging from approximately 0.03 to greater than 2.0 at 870 nm for March-October 2001. These measurements are compared to the aerosol optical thickness computed in Ouagadougou (Burkina-Faso), Banizoumbou (Niger), IMC Oristano (Sardinia) and Rome Tor Vergata (Italy). Analysis of τa data from this observation network suggests that there is a high temporal and spatial variability of τa in the different sites. The Angström wavelength exponent α was found to vary with the magnitude of the aerosol optical thickness, with values as high as 1.5 for very low τa, and values of -0.1 for high τa situations. The relationship between the two parameters τa and α is investigated. Values of the turbidity coefficient β have been determined in Thala (Tunisia) for 8 months in 2001 based on a direct fitting method of the Angström power law expression using sun photometer data. The monthly averaged values of the turbidity coefficient β vary between 0.15 and 0.33. The months of July and October experienced the highest turbidity, while April experienced the lowest aerosol loading on average. The turbidity shows a maximum and minimum values for the Southwest and the Northwest wind directions, respectively. The single scattering albedo ωo for the 870 nm wavelength obtained from solar aureole data in Thala is analysed according to the particles' origin.

  3. Optical Properties of Mixed Black Carbon, Inorganic and Secondary Organic Aerosols

    Energy Technology Data Exchange (ETDEWEB)

    Paulson, S E

    2012-05-30

    Summarizes the achievements of the project, which are divided into four areas: 1) Optical properties of secondary organic aerosols; 2) Development and of a polar nephelometer to measure aerosol optical properties and theoretical approaches to several optical analysis problems, 3) Studies on the accuracy of measurements of absorbing carbon by several methods, and 4) Environmental impacts of biodiesel.

  4. Aerosol Optical Properties During The SAMUM-2 Experiment

    Science.gov (United States)

    Toledano, C.; Freudenthaler, V.; Gross, S.; Seefeldner, M.; Gasteiger, J.; Garhammer, M.; Esselborn, M.; Wiegner, M.; Koepke, P.

    2009-03-01

    A field campaign of the Saharan Mineral Dust Experiment (SAMUM-2) took place in the Cape Verde islands in January-February 2008, to investigate the properties of long-range transported dust over the Atlantic. The Meteorological Institute of the University of Munich deployed a set of active and passive remote sensing instruments: one sun photometer, for the measurement of the direct sun irradiance and sky radiances; a broad-band UV radiometer; and 2 tropospheric lidar systems. The measurements were made in close cooperation with the other participating groups. During the measurement period the aerosol scenario over Cape Verde mostly consisted of a dust layer below 2 km and a smoke layer above 2 km height. The Saharan dust arrived in the site from the NE, whereas the smoke originated in the African equatorial region is transported from the SE. The aerosol load was also very variable over this area, with AOD (500 nm) ranging from 0.04 to 0.74. The optical properties of the layers are shown: extinction and particle depolarization ratio profiles at 3 wavelengths, as well as aerosol optical depth (in the range 340-1550 nm), Ångström exponent, size distribution and single scattering albedo.

  5. Climatology of aerosol optical properties in Northern Norway and Svalbard

    Directory of Open Access Journals (Sweden)

    Y.-C. Chen

    2012-10-01

    Full Text Available We present comparisons between estimates of the aerosol optical thickness and the Ångström exponent in Northern Norway and Svalbard based on data from AERONET stations at Andenes (69° N, 16° E, 379 m altitude and Hornsund (77° N, 15° E, 10 m altitude for the period 2008–2010. The three-year annual mean values for the aerosol optical thickness at 500 nm τ(500 at Andenes and Hornsund were 0.11 and 0.10, respectively. At Hornsund, there was less variation of the monthly mean value of τ(500 than at Andenes. The annual mean values of the Ångström exponent α at Andenes and Hornsund were 1.18 and 1.37, respectively. At Andenes and Hornsund α was found to be larger than 1.0 in 68% and 93% of the observations, respectively, indicating that fine-mode particles were dominating at both sites. Both sites had a similar seasonal variation of the aerosol size distribution although one site is in an Arctic area while the other site is in a sub-arctic area.

  6. Optical and microphysical properties of atmospheric aerosols in Moldova

    Science.gov (United States)

    Aculinin, Alexandr; Smicov, Vladimir

    2010-05-01

    Measurements of aerosol properties in Kishinev, Moldova are being carried out within the framework of the international AERONET program managed by NASA/GSFC since 1999. Direct solar and sky diffuse radiances are measured by using of sunphotometer Cimel-318. Aerosol optical properties are retrieved from measured radiances by using of smart computational procedures developed by the AERONET's team. The instrument is situated at the ground-based solar radiation monitoring station giving the opportunity to make simultaneous spectral (win sunphotometer) and broadband (with the set of sensors from radiometric complex) solar radiation. Detailed description of the station and investigations in progress can be found at the http://arg.phys.asm.md. Ground station is placed in an urban environment of Kishinev city (47.00N; 28.56E; 205 m a.s.l). Summary of aerosol optical and microphysical properties retrieved from direct solar and diffuse sky radiance observations at Moldova site from September 1999 to June 2009 are presented below. Number of measurements (total): 1695 Number of measurements (for ?o, n, k): 223 Range of aerosol optical depth (AOD) @440 nm: 0.03 =0.25 Range of Ångström parameter : 0.14 (440/670/870/1020): 0.93/0.92/0.90/0.89 ±0.04 Parameters of volume particle size distribution function: (fine mode) volume median radius r v,f , μm: 0.17 ± 0.06 particle volume concentration Cv,f, μm3/μm2: 0.04 ± 0.03 (coarse mode) volume median radius rv,c , μm: 3.08 ± 0.64 particle volume concentration Cv,c, μm3/μm2: 0.03 ± 0.03 Climatic norms of AOD@500 nm and Ångström parameter at the site of observation are equal to 0.21 ± 0.06 and 1.45 ± 0.14, respectively. The aerosol type in Moldova may be considered as 'urban-industrial and mixed' in accordance with the classification of aerosol type models systematized and developed by AERONET team (O.Dubovik et al., 2002, J. Atmosph. Sci., 59, 590-608) on the basis of datasets acquired from worldwide observations at the

  7. Variability of aerosol optical properties in the Western Mediterranean Basin

    Directory of Open Access Journals (Sweden)

    M. Pandolfi

    2011-08-01

    Full Text Available Aerosol light scattering, absorption and particulate matter (PM concentrations were measured at Montseny, a regional background site in the Western Mediterranean Basin (WMB which is part of the European Supersite for Atmospheric Aerosol Research (EUSAAR. Off line analyses of 24 h PM filters collected with Hi-Vol instruments were performed for the determination of the main chemical components of PM. Mean scattering and hemispheric backscattering coefficients (@ 635 nm were 26.6±23.2 Mm−1 and 4.3±2.7 Mm−1, respectively and the mean aerosol absorption coefficient (@ 637 nm was 2.8±2.2 Mm−1. Mean values of Single Scattering Albedo (SSA and Ångström exponent (å (calculated from 450 nm to 635 nm at MSY were 0.90±0.05 and 1.3±0.5 respectively. A clear relationship was observed between the PM1/PM10 and PM2.5/PM10 ratios as a function of the calculated Ångström exponents. Mass scattering cross sections (MSC for fine mass and sulfate at 635 nm were 2.8±0.5 m2 g−1 and 11.8±2.2 m2 g−1, respectively, while the mean aerosol absorption cross section (MAC was 10.4±2.0 m2 g−1. The variability in aerosol optical properties in the WMB were largely explained by the origin and ageing of air masses over the measurement site. The MAC values appear dependent of particles aging: similar to the expected absorption cross-section for fresh emissions under Atlantic Advection episodes and higher under aerosol pollution episodes. The analysis of the Ångström exponent as a function of the origin the air masses revealed that polluted winter anticyclonic conditions and summer recirculation scenarios typical of the WMB led to an increase of fine particles in the atmosphere (å = 1.5±0.1 while the aerosol optical properties under Atlantic Advection episodes and Saharan dust outbreaks were clearly

  8. Modeling of optical binding of submicron aerosol particles in counterpropagating Bessel beams

    Science.gov (United States)

    Thanopulos, I.; Luckhaus, D.; Signorell, R.

    2017-06-01

    We theoretically investigate the interparticle force between a pair of spherical aerosol nanoparticles in a dual counterpropagating Bessel beam configuration. We study the dependence of optical binding in the aerosol phase on the wavelength of the electromagnetic radiation, the particle radius, and the refractive index, including the cases of weak, moderate, and strong light absorption by the particles. We also investigate the relation between optical binding and the time-averaged intensity of the incident and scattered light. Our results show that optical binding in the aerosol phase depends strongly on the specific values of these parameters. This explains some of the difficulties associated with optical binding experiments with aerosol nanoparticles.

  9. Sensitivity test of GOCI dust aerosol index with aerosol absorptivity by using radiative transfer simulation and comparison with AERONET aerosol optical properties

    Science.gov (United States)

    Choi, M.; Kim, J.; Lee, J.; Park, Y. J.

    2016-12-01

    For the monitoring of aerosol properties in East Asia using the Geostationary Ocean Color Imager (GOCI), the GOCI Yonsei aerosol retrieval (YAER) algorithm was developed and has been improved continuously since 2011. GOCI YAER algorithm contains several aerosol models consisted of various optical properties such as aerosol optical depth (AOD), fine-mode fraction (FMF), and single scattering albedo (SSA) for assuming every possible aerosol status. Then, AOD at 550 nm is retrieved from selected aerosol models which show least difference between observed top-of-atmosphere (TOA) reflectance and simulated TOA reflectance in terms of spectral AODs. Current inversion method is optimized for spectral AODs, especially AOD at 550 nm. Therefore, GOCI YAER AOD, FMF, and Angstrom exponent show reliable accuracy with ground-based AERONET and satellite-based MODIS and VIIRS products. However, SSA shows least accuracy (R = 0.2) with AERONET SSA, which is different from AOD, FMF, and AE. To improve accuracy of SSA retrieval, the inversion method should reflect a characteristic of aerosol absorptivity well, not only in the aerosol model construction as forward modeling. UV aerosol index from TOMS and OMI measurements, calculated by using 354 and 388 nm, provides the extent of aerosol absorptivity, which can be used for the improvement of aerosol model quality between absorbing and non-absorbing aerosol model. Instead of UV index, a dust aerosol index (DAI) can be calculated using two visible channels such as 412 and 443 (or 490) nm. Heavy dust plume, which is coarse and absorbing aerosol, in 47 April 2012 show DAI of 5, but heavy haze plume, which is fine and non-absorbing aerosol, in 6 May 2012 shows DAI close to 0. To find relationship between DAI and aerosol absorptivity properties, sensitivity is tested by using radiative transfer model (RTM), and retrieved GOCI DAI from observed TOA reflectance is compared with ground-based AERONET SSA and other optical properties. Both of

  10. Spatiotemporal variability and contribution of different aerosol types to the aerosol optical depth over the Eastern Mediterranean

    Science.gov (United States)

    Georgoulias, Aristeidis K.; Alexandri, Georgia; Kourtidis, Konstantinos A.; Lelieveld, Jos; Zanis, Prodromos; Pöschl, Ulrich; Levy, Robert; Amiridis, Vassilis; Marinou, Eleni; Tsikerdekis, Athanasios

    2016-11-01

    This study characterizes the spatiotemporal variability and relative contribution of different types of aerosols to the aerosol optical depth (AOD) over the Eastern Mediterranean as derived from MODIS (Moderate Resolution Imaging Spectroradiometer) Terra (March 2000-December 2012) and Aqua (July 2002-December 2012) satellite instruments. For this purpose, a 0.1° × 0.1° gridded MODIS dataset was compiled and validated against sun photometric observations from the AErosol RObotic NETwork (AERONET). The high spatial resolution and long temporal coverage of the dataset allows for the determination of local hot spots like megacities, medium-sized cities, industrial zones and power plant complexes, seasonal variabilities and decadal averages. The average AOD at 550 nm (AOD550) for the entire region is ˜ 0.22 ± 0.19, with maximum values in summer and seasonal variabilities that can be attributed to precipitation, photochemical production of secondary organic aerosols, transport of pollution and smoke from biomass burning in central and eastern Europe and transport of dust from the Sahara and the Middle East. The MODIS data were analyzed together with data from other satellite sensors, reanalysis projects and a chemistry-aerosol-transport model using an optimized algorithm tailored for the region and capable of estimating the contribution of different aerosol types to the total AOD550. The spatial and temporal variability of anthropogenic, dust and fine-mode natural aerosols over land and anthropogenic, dust and marine aerosols over the sea is examined. The relative contribution of the different aerosol types to the total AOD550 exhibits a low/high seasonal variability over land/sea areas, respectively. Overall, anthropogenic aerosols, dust and fine-mode natural aerosols account for ˜ 51, ˜ 34 and ˜ 15 % of the total AOD550 over land, while, anthropogenic aerosols, dust and marine aerosols account ˜ 40, ˜ 34 and ˜ 26 % of the total AOD550 over the sea, based on

  11. Probing into the aging dynamics of biomass burning aerosol by using satellite measurements of aerosol optical depth and carbon monoxide

    Science.gov (United States)

    Konovalov, Igor B.; Beekmann, Matthias; Berezin, Evgeny V.; Formenti, Paola; Andreae, Meinrat O.

    2017-04-01

    Carbonaceous aerosol released into the atmosphere from open biomass burning (BB) is known to undergo considerable chemical and physical transformations (aging). However, there is substantial controversy about the nature and observable effects of these transformations. A shortage of consistent observational evidence on BB aerosol aging processes under different environmental conditions and at various temporal scales hinders development of their adequate representations in chemistry transport models (CTMs). In this study, we obtain insights into the BB aerosol dynamics by using available satellite measurements of aerosol optical depth (AOD) and carbon monoxide (CO). The basic concept of our method is to consider AOD as a function of the BB aerosol photochemical age (that is, the time period characterizing the exposure of BB aerosol emissions to atmospheric oxidation reactions) predicted by means of model tracers. We evaluate the AOD enhancement ratio (ER) defined as the ratio of optical depth of actual BB aerosol with respect to that of a modeled aerosol tracer that is assumed to originate from the same fires as the real BB aerosol but that is not affected by any aging processes. To limit possible effects of model transport errors, the AOD measurements are normalized to CO column amounts that are also retrieved from satellite measurements. The method is applied to the analysis of the meso- and synoptic-scale evolution of aerosol in smoke plumes from major wildfires that occurred in Siberia in summer 2012. AOD and CO retrievals from MODIS and IASI measurements, respectively, are used in combination with simulations performed with the CHIMERE CTM. The analysis indicates that aging processes strongly affected the evolution of BB aerosol in the situation considered, especially in dense plumes (with spatial average PM2. 5 concentration exceeding 100 µg m-3). For such plumes, the ER is found to increase almost 2-fold on the scale of ˜ 10 h of daytime aerosol evolution

  12. Retrieving Aerosol Optical Depth over Turbid Coastal Water

    Science.gov (United States)

    Wang, Y.; Wang, J.; Xu, X.; Levy, R. C.

    2016-12-01

    We present an approach to retrieve Aerosol Optical Depth (AOD) over turbid coastal water where operational MODerate Resolution Imaging Spectroradiometer (MODIS) Dark Target (DT) aerosol retrieval algorithm is not applied due to high water leaving radiance. Filling the coastal water AOD gap is significant because 60% of human population lives in the coastal zone. In this study, the Top of Atmosphere (TOA) reflectance at 2.1 μm observed from MODIS is used to retrieve AOD over turbid coastal water through look up table method as water leaving radiance is negligible at the band. During the retrieval process, aerosol model is substituted by the counterpart of the closest pixel retrieved through MODIS ocean DT algorithm. AOD retrievals over turbid coastal water are validated against observations from six AERONET sites at coastal region in one month. The monthly mean AERONET 440-870 nm Ångström exponent ranges from 0.597 to 1.842 for the six sites, thus they can represent from coarse-mode dominated to fine-mode dominated scenes. AOD retrievals in this study are more in agreement with AERONET observations than operational MODIS AOD (over land or clean coastal water) in terms of bias, and root-mean-square error.

  13. War Induced Aerosol Optical, Microphysical and Radiative Effects

    Science.gov (United States)

    Munshi, Pavel; Tiwari, Shubhansh

    2017-01-01

    The effect of war on air pollution and climate is assessed in this communication. War today in respect of civil wars and armed conflict in the Middle East area is taken into consideration. Impacts of war are not only in loss of human life and property, but also in the environment. It is well known that war effects air pollution and in the long run contribute to anthropogenic climate change, but general studies on this subject are few because of the difficulties of observations involved. In the current scenario of the ongoing conflict in the Middle East regions, deductions in parameters of atmosphere are discussed. Aerosol Optical Depth, Aerosol loads, Black Carbon, Ozone,Dust, regional haze and many more are analyzed using various satellite data. Multi-model analysis is also studied to verify the analysis. Type segregation of aerosols, in-depth constraints to atmospheric chemistry, biological effects and particularly atmospheric physics in terms of radiative forcing, etc. are discussed. Undergraduate in Earth Sciences.

  14. Seasonal differences in the vertical profiles of aerosol optical properties over rural Oklahoma

    Directory of Open Access Journals (Sweden)

    E. Andrews

    2011-04-01

    Full Text Available A small airplane made more than 450 aerosol optical property (light absorption and light scattering vertical profile measurements (up to 4 km over a rural Oklahoma site between March 2000 and July 2005. These profiles suggest significant seasonal differences in aerosol properties. The highest amounts of scattering and absorbing aerosol are observed during the summer, while the relative contribution of aerosol absorption is highest in the winter (i.e., single scattering albedo is lowest in winter. Aerosol absorption generally decreased with altitude below ∼1.5 km and then was relatively constant above that. Aerosol scattering decreased sharply with altitude below ∼1.5 km but, unlike absorption, also decreased at higher altitudes, albeit less sharply. The seasonal variability observed for aerosol loading is consistent with other aerosol measurements in the region including AERONET aerosol optical depth (AOD, CALIPSO vertical profiles, and IMPROVE aerosol mass. The column averaged single scattering albedo derived from in situ airplane measurements shows a similar seasonal cycle as the AERONET single scattering albedo inversion product, but a comparison of aerosol asymmetry parameter from airplane and AERONET platforms suggests differences in seasonal variability. The observed seasonal cycle of aerosol loading corresponds with changes in air mass back trajectories: the aerosol scattering was higher when transport was from polluted areas (e.g., the Gulf Coast and lower when the air came from cleaner regions and/or the upper atmosphere.

  15. Characteristics of spectral aerosol optical depths over India during ICARB

    Indian Academy of Sciences (India)

    S Naseema Beegum; K Krishna Moorthy; Vijayakumar S Nair; S Suresh Babu; S K Satheesh; V Vinoj; R Ramakrishna Reddy; K Rama Gopal; K V S Badarinath; K Niranjan; Santosh Kumar Pandey; M Behera; A Jeyaram; P K Bhuyan; M M Gogoi; Sacchidanand Singh; P Pant; U C Dumka; Yogesh Kant; J C Kuniyal; Darshan Singh

    2008-07-01

    Spectral aerosol optical depth (AOD) measurements, carried out regularly from a network of observatories spread over the Indian mainland and adjoining islands in the Bay of Bengal and Arabian Sea, are used to examine the spatio-temporal and spectral variations during the period of ICARB (March to May 2006). The AODs and the derived Ångström parameters showed considerable variations across India during the above period. While at the southern peninsular stations the AODs decreased towards May after a peak in April, in the north Indian regions they increased continuously from March to May. The Ångström coefficients suggested enhanced coarse mode loading in the north Indian regions, compared to southern India. Nevertheless, as months progressed from March to May, the dominance of coarse mode aerosols increased in the columnar aerosol size spectrum over the entire Indian mainland, maintaining the regional distinctiveness. Compared to the above, the island stations showed considerably low AODs, so too the northeastern station Dibrugarh, indicating the prevalence of cleaner environment. Long-range transport of aerosols from the adjoining regions leads to remarkable changes in the magnitude of the AODs and their wavelength dependencies during March to May. HYSPLIT back-trajectory analysis shows that enhanced long-range transport of aerosols, particularly from the west Asia and northwest coastal India, contributed significantly to the enhancement of AOD and in the flattening of the spectra over entire regions; if it is the peninsular regions and the island Minicoy are more impacted in April, the north Indian regions including the Indo Gangetic Plain get affected the most during May, with the AODs soaring as high as 1.0 at 500 nm. Over the islands, the Ångström exponent () remained significantly lower (∼1) over the Arabian Sea compared to Bay of Bengal (BoB) (∼1.4) as revealed by the data respectively from Minicoy and Port Blair. Occurrences of higher values of

  16. MODIS Retrieval of Aerosol Optical Depth over Turbid Coastal Water

    Directory of Open Access Journals (Sweden)

    Yi Wang

    2017-06-01

    Full Text Available We present a new approach to retrieve Aerosol Optical Depth (AOD using the Moderate Resolution Imaging Spectroradiometer (MODIS over the turbid coastal water. This approach supplements the operational Dark Target (DT aerosol retrieval algorithm that currently does not conduct AOD retrieval in shallow waters that have visible sediments or sea-floor (i.e., Class 2 waters. Over the global coastal water regions in cloud-free conditions, coastal screening leads to ~20% unavailability of AOD retrievals. Here, we refine the MODIS DT algorithm by considering that water-leaving radiance at 2.1 μm to be negligible regardless of water turbidity, and therefore the 2.1 μm reflectance at the top of the atmosphere is sensitive to both change of fine-mode and coarse-mode AODs. By assuming that the aerosol single scattering properties over coastal turbid water are similar to those over the adjacent open-ocean pixels, the new algorithm can derive AOD over these shallow waters. The test algorithm yields ~18% more MODIS-AERONET collocated pairs for six AERONET stations in the coastal water regions. Furthermore, comparison of the new retrieval with these AERONET observations show that the new AOD retrievals have equivalent or better accuracy than those retrieved by the MODIS operational algorithm’s over coastal land and non-turbid coastal water product. Combining the new retrievals with the existing MODIS operational retrievals yields an overall improvement of AOD over those coastal water regions. Most importantly, this refinement extends the spatial and temporal coverage of MODIS AOD retrievals over the coastal regions where 60% of human population resides. This expanded coverage is crucial for better understanding of impact of anthropogenic aerosol particles on coastal air quality and climate.

  17. Optical characteristics of the aerosol in Spain and Austria and its effect on radiative forcing

    Science.gov (United States)

    Horvath, H.; Alados Arboledas, L.; Olmo, F. J.; Jovanović, O.; Gangl, M.; Kaller, W.; SáNchez, C.; Sauerzopf, H.; Seidl, S.

    2002-10-01

    The horizontal and vertical attenuation of the aerosol, the sky radiance, and the light absorption coefficient of the aerosol have been determined at wavelengths in the visible. From this set of data the following optical characteristics of the atmospheric aerosol could be derived: vertical optical depth, horizontal extinction and absorption coefficient, scattering phase function, asymmetry parameter, and single scattering albedo. Campaigns have been performed in Almería, Spain, and Vienna, Austria. The aerosol undergoes a considerable variation, as experienced by many other studies. Sometimes the vertical and the horizontal measurements gave similar data; on other days the aerosol at the surface and the aerosol aloft were completely different. The "clearest" aerosol always had the smallest single scattering albedo and thus relatively the highest light absorption. The optical characteristics of the aerosol in the two very different locations were very similar. Using the measured optical data, a radiative transfer calculation was performed, and the radiation reaching the ground was calculated. Comparing the values for the clear aerosol and the days with higher aerosol load, the radiative forcing due to the additional aerosol particles could be determined. The forcing of the aerosol at the ground is always negative, and at the top of the atmosphere it is close to zero or slightly negative. Its dependence on wavelength and zenith angle is presented. The preindustrial aerosol in Europe was estimated, and the forcing due to the present-day aerosol was determined. At the surface it is negative, but at the top of the atmosphere it is close to zero or positive. This is caused by the light absorption of the European aerosol, which is higher than in most other locations.

  18. Comparison of near surface and column-integrated atmospheric aerosol optical properties

    Science.gov (United States)

    Aryal, Rudra Prasad

    Optical and chemical properties of size-resolved aerosols in near-surface air at Tudor Hill, Bermuda were measured between July 2006 and June 2009. Vertical distributions of aerosol backscattering and column-averaged aerosol optical properties were characterized with a Micro-pulse lidar (MPL) and a CIMEL automated sun-sky radiometer. The chemical species in size-segregated aerosols in marine air were compared with the surface level aerosol optical properties. The aerosol concentration, along with chemical components, was compared with the surface level wind speed and showed a significant correlation with the sea salt components. The non-sea salt components such as non-sea salt sulfate and ammonium did not show a correlation with the surface level wind speed. A comparison between scattering data at surface level with the extinction coefficient at the lowest altitude bin (75m) from the lidar inversion shows a consistent correlation but is quantitatively different. This quantitative discrepancy was explained based on the hygroscopic growth due to differences in relative humidity in measurement conditions. Aerosol optical properties measured near the surface were often significantly correlated with those averaged over the column. These include scattering by near-surface bulk aerosol at 530 nm versus column aerosol optical depth (AOD), near-surface sub-microm scattering fraction versus column averaged sub-microm scattering fraction, and the average angstrom exponent over column and lidar ratio derived using column integrated size distribution and complex refractive index. We also found that the single scattering albedo (ω o) measured at the surface by combining daily averages of the aerosol absorption and aerosol light scattering were in the same range as the instantaneous ω o retrieved for the column. The relative contribution of submicron aerosol light scattering to total aerosol light scattering is slightly higher in the column relative to the surface. Surface

  19. Estimates of the aerosol optical depth over Pretoria using the CSIR mobile lidar

    CSIR Research Space (South Africa)

    Shikwambana, L

    2013-09-01

    Full Text Available This study shows the estimates of aerosol optical depth measured over Pretoria, South Africa, using the CSIR-NLC mobile LIDAR. The measurements are also compared with observations from the Level-3 MODIS aerosol optical depth (AOD) data...

  20. Calibrated sky imager for aerosol optical properties determination

    Directory of Open Access Journals (Sweden)

    A. Cazorla

    2008-11-01

    Full Text Available The calibrated ground-based sky imager developed in the Marine Physical Laboratory, the Whole Sky Imager (WSI, has been tested to determine optical properties of the atmospheric aerosol. Different neural network-based models calculate the aerosol optical depth (AOD for three wavelengths using the radiance extracted from the principal plane of sky images from the WSI as input parameters. The models use data from a CIMEL CE318 photometer for training and validation and the wavelengths used correspond to the closest wavelengths in both instruments. The spectral dependency of the AOD, characterized by the Ångström exponent α in the interval 440–870, is also derived using the standard AERONET procedure and also with a neural network-based model using the values obtained with a CIMEL CE318. The deviations between the WSI derived AOD and the AOD retrieved by AERONET are within the nominal uncertainty assigned to the AERONET AOD calculation (±0.01, in 80% of the cases. The explanation of data variance by the model is over 92% in all cases. In the case of α, the deviation is within the uncertainty assigned to the AERONET α (±0.1 in 50% for the standard method and 84% for the neural network-based model. The explanation of data variance by the model is 63% for the standard method and 77% for the neural network-based model.

  1. AERONET-based microphysical and optical properties of smoke-dominated aerosol near source regions and transported over oceans, and implications for satellite retrievals of aerosol optical depth

    Science.gov (United States)

    Sayer, A. M.; Hsu, N. C.; Eck, T. F.; Smirnov, A.; Holben, B. N.

    2013-09-01

    Smoke aerosols from biomass burning are an important component of the global aerosol cycle. Analysis of Aerosol Robotic Network (AERONET) retrievals of size distribution and refractive index reveals variety between biomass burning aerosols in different global source regions, in terms of aerosol particle size and single scatter albedo (SSA). Case studies of smoke transported to coastal/island AERONET sites also mostly lie within the range of variability at near-source sites. Two broad ''families'' of aerosol properties are found, corresponding to sites dominated by boreal forest burning (larger, broader fine mode, with midvisible SSA ∼0.95), and those influenced by grass, shrub, or crop burning with additional forest contributions (smaller, narrower particles with SSA ∼0.88-0.9 in the midvisible). The strongest absorption is seen in southern African savannah at Mongu (Zambia), with average SSA ∼0.85 in the midvisible. These can serve as candidate sets of aerosol microphysical/optical properties for use in satellite aerosol optical depth (AOD) retrieval algorithms. The models presently adopted by these algorithms over ocean are often insufficiently absorbing to represent these biomass burning aerosols. A corollary of this is an underestimate of AOD in smoke outflow regions, which has important consequences for applications of these satellite datasets.

  2. Influence of observed diurnal cycles of aerosol optical depth on aerosol direct radiative effect

    Directory of Open Access Journals (Sweden)

    A. Arola

    2013-08-01

    Full Text Available The diurnal variability of aerosol optical depth (AOD can be significant, depending on location and dominant aerosol type. However, these diurnal cycles have rarely been taken into account in measurement-based estimates of aerosol direct radiative forcing (ADRF or aerosol direct radiative effect (ADRE. The objective of our study was to estimate the influence of diurnal aerosol variability at the top of the atmosphere ADRE estimates. By including all the possible AERONET sites, we wanted to assess the influence on global ADRE estimates. While focusing also in more detail on some selected sites of strongest impact, our goal was to also see the possible impact regionally. We calculated ADRE with different assumptions about the daily AOD variability: taking the observed daily AOD cycle into account and assuming diurnally constant AOD. Moreover, we estimated the corresponding differences in ADREs, if the single AOD value for the daily mean was taken from the the Moderate Resolution Imaging Spectroradiometer (MODIS Terra or Aqua overpass times, instead of accounting for the true observed daily variability. The mean impact of diurnal AOD variability on 24 h ADRE estimates, averaged over all AERONET sites, was rather small and it was relatively small even for the cases when AOD was chosen to correspond to the Terra or Aqua overpass time. This was true on average over all AERONET sites, while clearly there can be much stronger impact in individual sites. Examples of some selected sites demonstrated that the strongest observed AOD variability (the strongest morning afternoon contrast does not typically result in a significant impact on 24 h ADRE. In those cases, the morning and afternoon AOD patterns are opposite and thus the impact on 24 h ADRE, when integrated over all solar zenith angles, is reduced. The most significant effect on daily ADRE was induced by AOD cycles with either maximum or minimum AOD close to local noon. In these cases, the impact on

  3. Influence of Observed Diurnal Cycles of Aerosol Optical Depth on Aerosol Direct Radiative Effect

    Science.gov (United States)

    Arola, A.; Eck, T. F.; Huttunen, J.; Lehtinen, K. E. J.; Lindfors, A. V.; Myhre, G.; Smirinov, A.; Tripathi, S. N.; Yu, H.

    2013-01-01

    The diurnal variability of aerosol optical depth (AOD) can be significant, depending on location and dominant aerosol type. However, these diurnal cycles have rarely been taken into account in measurement-based estimates of aerosol direct radiative forcing (ADRF) or aerosol direct radiative effect (ADRE). The objective of our study was to estimate the influence of diurnal aerosol variability at the top of the atmosphere ADRE estimates. By including all the possible AERONET sites, we wanted to assess the influence on global ADRE estimates. While focusing also in more detail on some selected sites of strongest impact, our goal was to also see the possible impact regionally.We calculated ADRE with different assumptions about the daily AOD variability: taking the observed daily AOD cycle into account and assuming diurnally constant AOD. Moreover, we estimated the corresponding differences in ADREs, if the single AOD value for the daily mean was taken from the the Moderate Resolution Imaging Spectroradiometer (MODIS) Terra or Aqua overpass times, instead of accounting for the true observed daily variability. The mean impact of diurnal AOD variability on 24 h ADRE estimates, averaged over all AERONET sites, was rather small and it was relatively small even for the cases when AOD was chosen to correspond to the Terra or Aqua overpass time. This was true on average over all AERONET sites, while clearly there can be much stronger impact in individual sites. Examples of some selected sites demonstrated that the strongest observed AOD variability (the strongest morning afternoon contrast) does not typically result in a significant impact on 24 h ADRE. In those cases, the morning and afternoon AOD patterns are opposite and thus the impact on 24 h ADRE, when integrated over all solar zenith angles, is reduced. The most significant effect on daily ADRE was induced by AOD cycles with either maximum or minimum AOD close to local noon. In these cases, the impact on 24 h ADRE was

  4. Aerosol absorption measurement with a sinusoidal phase modulating fiber optic photo thermal interferometer

    Science.gov (United States)

    Li, Shuwang; Shao, Shiyong; Mei, Haiping; Rao, Ruizhong

    2016-10-01

    Aerosol light absorption plays an important role in the earth's atmosphere direct and semi-direct radiate forcing, simultaneously, it also has a huge influence on the visibility impairment and laser engineering application. Although various methods have been developed for measuring aerosol light absorption, huge challenge still remains in precision, accuracy and temporal resolution. The main reason is that, as a part of aerosol light extinction, aerosol light absorption always generates synchronously with aerosol light scattering, and unfortunately aerosol light scattering is much stronger in most cases. Here, a novel photo-thermal interferometry is proposed only for aerosol absorption measurement without disturbance from aerosol scattering. The photo-thermal interferometry consists of a sinusoidal phase-modulating single mode fiber-optic interferometer. The thermal dissipation, caused by aerosol energy from photo-thermal conversion when irritated by pump laser through interferometer, is detected. This approach is completely insensitive to aerosol scattering, and the single mode fiber-optic interferometer is compact, low-cost and insensitive to the polarization shading. The theory of this technique is illustrated, followed by the basic structure of the sinusoidal phase-modulating fiber-optic interferometer and demodulation algorithms. Qualitative and quantitative analysis results show that the new photo-thermal interference is a potential approach for aerosol absorption detection and environmental pollution detection.

  5. Preliminary results of the aerosol optical depth retrieval in Johor, Malaysia

    Science.gov (United States)

    Lim, H. Q.; Kanniah, K. D.; Lau, A. M. S.

    2014-02-01

    Monitoring of atmospheric aerosols over the urban area is important as tremendous amounts of pollutants are released by industrial activities and heavy traffic flow. Air quality monitoring by satellite observation provides better spatial coverage, however, detailed aerosol properties retrieval remains a challenge. This is due to the limitation of aerosol retrieval algorithm on high reflectance (bright surface) areas. The aim of this study is to retrieve aerosol optical depth over urban areas of Iskandar Malaysia; the main southern development zone in Johor state, using Moderate Resolution Imaging Spectroradiometer (MODIS) 500 m resolution data. One of the important steps is the aerosol optical depth retrieval is to characterise different types of aerosols in the study area. This information will be used to construct a Look Up Table containing the simulated aerosol reflectance and corresponding aerosol optical depth. Thus, in this study we have characterised different aerosol types in the study area using Aerosol Robotic Network (AERONET) data. These data were processed using cluster analysis and the preliminary results show that the area is consisting of coastal urban (65%), polluted urban (27.5%), dust particles (6%) and heavy pollution (1.5%) aerosols.

  6. An analysis of the collection 5 MODIS over-ocean aerosol optical depth product for its implication in aerosol assimilation

    Directory of Open Access Journals (Sweden)

    Y. Shi

    2011-01-01

    Full Text Available As an update to our previous use of the collection 4 Moderate Resolution Imaging Spectroradiometer (MODIS over-ocean aerosol optical depth (AOD data, we examined ten years of Terra and eight years of Aqua collection 5 data for its potential usage in aerosol assimilation. Uncertainties in the over-ocean MODIS AOD were studied as functions of observing conditions, such as surface characteristics, aerosol optical properties, and cloud artifacts. Empirical corrections and quality assurance procedures were developed and compared to collection 4 data. After applying these procedures, the Root-Mean-Square-Error (RMSE in the MODIS Terra and Aqua AOD are reduced by 30% and 10–20%, respectively, with respect to AERONET data. Ten years of Terra and eight years of Aqua quality-assured level 3 MODIS over-ocean aerosol products were produced. The newly developed MODIS over-ocean aerosol products will be used in operational aerosol assimilation and aerosol climatology studies, as well as other research based on MODIS products.

  7. Validation of MODIS aerosol optical depth over the Mediterranean Coast

    Science.gov (United States)

    Díaz-Martínez, J. Vicente; Segura, Sara; Estellés, Víctor; Utrillas, M. Pilar; Martínez-Lozano, J. Antonio

    2013-04-01

    Atmospheric aerosols, due to their high spatial and temporal variability, are considered one of the largest sources of uncertainty in different processes affecting visibility, air quality, human health, and climate. Among their effects on climate, they play an important role in the energy balance of the Earth. On one hand they have a direct effect by scattering and absorbing solar radiation; on the other, they also have an impact in precipitation, modifying clouds, or affecting air quality. The application of remote sensing techniques to investigate aerosol effects on climate has advanced significatively over last years. In this work, the products employed have been obtained from the Moderate Resolution Imaging Spectroradiometer (MODIS). MODIS is a sensor located onboard both Earth Observing Systems (EOS) Terra and Aqua satellites, which provide almost complete global coverage every day. These satellites have been acquiring data since early 2000 (Terra) and mid 2002 (Aqua) and offer different products for land, ocean and atmosphere. Atmospheric aerosol products are presented as level 2 products with a pixel size of 10 x 10 km2 in nadir. MODIS aerosol optical depth (AOD) is retrieved by different algorithms depending on the pixel surface, distinguishing between land and ocean. For its validation, ground based sunphotometer data from AERONET (Aerosol Robotic Network) has been employed. AERONET is an international operative network of Cimel CE318 sky-sunphotometers that provides the most extensive aerosol data base globally available of ground-based measurements. The ground sunphotometric technique is considered the most accurate for the retrieval of radiative properties of aerosols in the atmospheric column. In this study we present a validation of MODIS C051 AOD employing AERONET measurements over different Mediterranean coastal sites centered over an area of 50 x 50 km2, which includes both pixels over land and ocean. The validation is done comparing spatial

  8. Field Studies of Broadband Aerosol Optical Extinction in the Ultraviolet Spectral Region

    Science.gov (United States)

    Washenfelder, R. A.; Attwood, A.; Brock, C. A.; Brown, S. S.

    2013-12-01

    Aerosols influence the Earth's radiative budget by scattering and absorbing incoming solar radiation. The optical properties of aerosols vary as a function of wavelength, but few measurements have reported the wavelength dependence of aerosol extinction cross sections and complex refractive indices. In the case of brown carbon, its wavelength-dependent absorption in the ultraviolet spectral region has been suggested as an important component of aerosol radiative forcing. We describe a new field instrument to measure aerosol optical extinction as a function of wavelength, using cavity enhanced spectroscopy with a broadband light source. The instrument consists of two broadband channels which span the 360-390 and 385-420 nm spectral regions using two light emitting diodes (LED) and a grating spectrometer with charge-coupled device (CCD) detector. We deployed this instrument during the Fire Lab at Missoula Experiment during Fall 2012 to measure biomass burning aerosol, and again during the Southern Oxidant and Aerosol Study in summer 2013 to measure organic aerosol in the Southeastern U.S. In both field experiments, we determined aerosol optical extinction as a function of wavelength and can interpret this together with size distribution and composition measurements to characterize the aerosol optical properties and radiative forcing.

  9. ModelE2-TOMAS development and evaluation using aerosol optical depths, mass and number concentrations

    Directory of Open Access Journals (Sweden)

    Y. H. Lee

    2014-09-01

    Full Text Available The TwO-Moment Aerosol Sectional microphysics model (TOMAS has been integrated into the state-of-the-art general circulation model, GISS ModelE2. TOMAS has the flexibility to select a size resolution as well as the lower size cutoff. A computationally efficient version of TOMAS is used here, which has 15 size bins covering 3 nm to 10 μm aerosol dry diameter. For each bin, it simulates the total aerosol number concentration and mass concentrations of sulphate, pure elementary carbon (hydrophobic, mixed elemental carbon (hydrophilic, hydrophobic organic matter, hydrophilic organic matter, sea salt, mineral dust, ammonium, and aerosol-associated water. This paper provides a detailed description of the ModelE2-TOMAS model and evaluates the model against various observations including aerosol precursor gas concentrations, aerosol mass and number concentrations, and aerosol optical depths. Additionally, global budgets in ModelE2-TOMAS are compared with those of other global aerosol models, and the TOMAS model is compared to the default aerosol model in ModelE2, which is a bulk aerosol model. Overall, the ModelE2-TOMAS predictions are within the range of other global aerosol model predictions, and the model has a reasonable agreement with observations of sulphur species and other aerosol components as well as aerosol optical depth. However, ModelE2-TOMAS (as well as the bulk aerosol model cannot capture the observed vertical distribution of sulphur dioxide over the Pacific Ocean possibly due to overly strong convective transport. The TOMAS model successfully captures observed aerosol number concentrations and cloud condensation nuclei concentrations. Anthropogenic aerosol burdens in the bulk aerosol model running in the same host model as TOMAS (ModelE2 differ by a few percent to a factor of 2 regionally, mainly due to differences in aerosol processes including deposition, cloud processing, and emission parameterizations. Larger differences are found

  10. Parameterization of the Optical Properties of Sulfate Aerosols.

    Science.gov (United States)

    Li, J.; Wong, J. G. D.; Dobbie, J. S.; Chýlek, P.

    2001-01-01

    Parameterizations of the shortwave optical properties of ammonium sulfate [(NH4)2SO4], ammonium bisulfate (NH4HSO4), and sulfuric acid (H2SO4) are provided as functions of relative humidity for high and low spectral resolution band models. The optical property parameterization is simple in form and in its dependence on relative humidity. The growth of the aerosol particles is based on equilibrium saturation theory, and the optical properties are computed from Mie theory. The optical properties necessary for the most commonly used radiative transfer methods are provided.Results show that when relative humidity effects are included in the backscatter fraction the radiative forcing is found to be a more sensitive function of near infrared wavelengths compared to visible wavelengths. For increasing relative humidity, sulfuric acid is found to have a larger effect on radiative forcing compared to the forcing by ammonium sulfate or ammonium bisulfate. Also, as relative humidity increases, forcing increases to higher values for smaller mode size distributions compared to forcing by larger mode distributions. These parameterizations will enable climate forcing studies to be performed with radiative transfer schemes that more accurately represent sulfate influences on the radiation balance.

  11. Ground-based measurements of aerosol optical properties and radiative forcing in North China

    Institute of Scientific and Technical Information of China (English)

    Hongbin Chen; Xiangao Xia; Pucai Wang; Wenxing Zhang

    2007-01-01

    In order to gain an insight into the aerosol properties and their climatic effect over the continental source regions of China, it is of significance to carry out long-term ground-based measurements of aerosol optical properties and radiative forcing. A couple of temporary and permanent Aerosol Robotic Network (AERONET) sites and three comprehensive radiative sites were established in China as a result of international cooperation in recent years. Heavy aerosol loading and significant temporal and spatial variation over North China are revealed by the AERONET data.Aerosol-induced reductions in surface radiation budget are examined on the basis of collocated observations by sun photometers and pyranometers.

  12. Climatology of aerosol optical properties near the New England coast: preparation for the Two Column Aerosol Program (TCAP) field campaign

    Science.gov (United States)

    Berkowitz, C. M.; Chand, D.; Berg, L.; Kassianov, E.; Chapman, E.

    2011-12-01

    A key objective of the U.S. Department of Energy's Two Column Aerosol Project (TCAP) is to provide observations with which to evaluate the uncertainty in model simulations of aerosol optical depth (AOD) and their relation to estimates of aerosol radiative forcing and hence, to climate. To meet this objective, detailed ground-based aerosol measurements will be made via deployment of the ARM Mobile Facility (AMF) and the Mobile Aerosol Observing System (MAOS) at Cape Cod, Massachusetts for a 12-month period starting in the summer of 2012. These measurements will be supported by two scheduled aircraft campaigns using the ARM Aerial Facility's (AAF) G-1 aircraft and the NASA B-200 aircraft in July 2012 and again in February 2013. Each campaign will include sampling within two atmospheric columns using the aircrafts; one column will be located directly over, or very close to, Cape Cod, while the second will be over a relatively remote maritime location. This preliminary study presented here is designed to select the optimum location of the second, remote maritime atmospheric column using the mean and standard deviation of previously observed AODs from surface and space. An area with the large variability in AOD will be considered as a potential location for evaluation of the outputs from atmospheric models. In this study, we present regional climatological values of (1) AOD from the Moderate Resolution Imaging Spectrometer (MODIS) on Terra and Aqua satellite platforms; (2) single scattering albedo from the Multi-angle Imaging SpectroRadiometer (MISR) satellite; (3) the vertical distribution of aerosol layers from the Cloud Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) satellite; and (4) the long term aerosol optical properties from the Aerosol Robotic Network (AERONET) surface sunphotometer at Martha's Vineyard, MA. Seasonal and geographical variations in these quantities will be analyzed and possible explanations will be presented based on

  13. Aerosol optical depth trend over the Middle East

    KAUST Repository

    Klingmüller, Klaus

    2016-04-22

    We use the combined Dark Target/Deep Blue aerosol optical depth (AOD) satellite product of the moderate-resolution imaging spectroradiometer (MODIS) collection 6 to study trends over the Middle East between 2000 and 2015. Our analysis corroborates a previously identified positive AOD trend over large parts of the Middle East during the period 2001 to 2012. We relate the annual AOD to precipitation, soil moisture and surface winds to identify regions where these attributes are directly related to the AOD over Saudi Arabia, Iraq and Iran. Regarding precipitation and soil moisture, a relatively small area in and surrounding Iraq turns out to be of prime importance for the AOD over these countries. Regarding surface wind speed, the African Red Sea coastal area is relevant for the Saudi Arabian AOD. Using multiple linear regression we show that AOD trends and interannual variability can be attributed to soil moisture, precipitation and surface winds, being the main factors controlling the dust cycle. Our results confirm the dust driven AOD trends and variability, supported by a decreasing MODIS-derived Ångström exponent and a decreasing AERONET-derived fine mode fraction that accompany the AOD increase over Saudi Arabia. The positive AOD trend relates to a negative soil moisture trend. As a lower soil moisture translates into enhanced dust emissions, it is not needed to assume growing anthropogenic aerosol and aerosol precursor emissions to explain the observations. Instead, our results suggest that increasing temperature and decreasing relative humidity in the last decade have promoted soil drying, leading to increased dust emissions and AOD; consequently an AOD increase is expected due to climate change.

  14. Deriving atmospheric visibility from satellite retrieved aerosol optical depth

    Science.gov (United States)

    Riffler, M.; Schneider, Ch.; Popp, Ch.; Wunderle, S.

    2009-04-01

    Atmospheric visibility is a measure that reflects different physical and chemical properties of the atmosphere. In general, poor visibility conditions come along with risks for transportation (e.g. road traffic, aviation) and can negatively impact human health since visibility impairment often implies the presence of atmospheric pollution. Ambient pollutants, particulate matter, and few gaseous species decrease the perceptibility of distant objects. Common estimations of this parameter are usually based on human observations or devices that measure the transmittance of light from an artificial light source over a short distance. Such measurements are mainly performed at airports and some meteorological stations. A major disadvantage of these observations is the gap between the measurements, leaving large areas without any information. As aerosols are one of the most important factors influencing atmospheric visibility in the visible range, the knowledge of their spatial distribution can be used to infer visibility with the so called Koschmieder equation, which relates visibility and atmospheric extinction. In this study, we evaluate the applicability of satellite aerosol optical depth (AOD) products from the Advanced Very High Resolution Radiometer (AVHRR) and Moderate Resolution Imaging Spectroradiometer (MODIS) to infer atmospheric visibility on large spatial scale. First results applying AOD values scaled with the planetary boundary layer height are promising. For the comparison we use a full automated and objective procedure for the estimation of atmospheric visibility with the help of a digital panorama camera serving as ground truth. To further investigate the relation between the vertical measure of AOD and the horizontal visibility data from the Aerosol Robotic Network (AERONET) site Laegeren (Switzerland), where the digital camera is mounted, are included as well. Finally, the derived visibility maps are compared with synoptical observations in central

  15. Optical Properties and Aging of Light Absorbing Secondary Organic Aerosol

    Science.gov (United States)

    Liu, J.; Lin, P.; Laskin, A.; Laskin, J.; Kathmann, S. M.; Wise, M.; Caylor, R.; Imholt, F.; Selimovic, V.; Shilling, J.

    2016-12-01

    The light-absorbing organic aerosol (OA), commonly referred to as "brown carbon (BrC)", has attracted considerable attention in recent years because of its potential to affect atmospheric radiation balance, especially in the ultraviolet region and thus impact photochemical processes. A growing amount of data has indicated that BrC is prevalent in the atmosphere, which has motivated numerous laboratory and field studies; however, our understanding of the relationship between the chemical composition and optical properties of BrC remains limited. We conducted chamber experiments to investigate the effect of various VOC precursors, NOx concentrations, photolysis time and relative humidity (RH) on the light absorption of selected secondary organic aerosols (SOA). Light absorption of chamber generated SOA samples, especially aromatic SOA, was found to increase with NOx concentration, at moderate RH, and for the shortest photolysis aging times. The highest mass absorption coefficients (MAC) value is observed from toluene SOA products formed under high NOx conditions at moderate RH, in which nitro-aromatics were previously identified as the major light absorbing compounds. BrC light absorption is observed to decrease with photolysis time, correlated with a decline of the organonitrate fraction of SOA. SOA formed from mixtures of aromatics and isoprene absorb less visible and UV light than SOA formed from aromatic precursors alone on a mass basis. The inherent changes in chemical compositions and the relationship with the light absorption will be discussed in detail.

  16. A 10-year global gridded Aerosol Optical Thickness Reanalysis for climate and applied applications

    Science.gov (United States)

    Lynch, P.; Reid, J. S.; Zhang, J.; Westphal, D. L.; Campbell, J. R.; Curtis, C. A.; Hegg, D.; Hyer, E. J.; Sessions, W.; Shi, Y.; Turk, J.

    2013-12-01

    While standalone satellite and model aerosol products see wide utilization, there is a significant need of a best-available fused product on a regular grid for numerous climate and applied applications. Remote sensing and modeling technologies have now advanced to a point where aerosol data assimilation is an operational reality at numerous centers. It is inevitable that, like meteorological reanalyses, aerosol reanalyses will see heavy use in the near future. A first long term, 2003-2012 global 1x1 degree and 6-hourly aerosol optical thickness (AOT) reanalysis product has been generated. The goal of this effort is not only for climate applications, but to generate a dataset that can be used by the US Navy to understand operationally hindering aerosol events, aerosol impacts on numerical weather prediction, and application of electro-optical technologies. The reanalysis utilizes Navy Aerosol Analysis and Prediction System (NAAPS) at its core and assimilates quality controlled collection 5 Moderate Resolution Imaging Spectroradiometer (MODIS) AOD with minor corrections from Multi-angle Imaging SpectroRaditometer (MISR). A subset of this product includes Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) lidar assimilation since its launch in mid-2006. Surface aerosol sources, including dust and smoke, in the aerosol model have been regionally tuned so that fine and coarse mode AOTs best match those resolve by ground-based Aerosol Robotic Network (AERONET). The AOT difference between the model and satellite AOT is then used to adjust other aerosol processes, eg., sources, dry deposition, etc. Aerosol wet deposition is constrained with satellite-retrieved precipitation. The final AOT reanalysis is shown to exhibit good agreement with AERONET. Here we review the development of the reanalysis and consider issues particular to aerosol reanalyses that make them distinct from standard meteorological reanalyses. Considerations are also made for extending such work

  17. Classification of Aerosol over Central Europe by Cluster Analysis of Aerosol Columnar Optical Properties and Backward Trajectory Statistics

    Science.gov (United States)

    Szkop, Artur; Pietruczuk, Aleksander; Posyniak, Michał

    2016-12-01

    A cluster analysis is applied to the Aerosol Robotic Network (AERONET) data obtained at Belsk, Poland, as well as three nearby Central European stations (Leipzig, Minsk and Moldova) for estimation of atmospheric aerosol types. Absorption Ångstrom exponent (AAE), aerosol optical thickness (AOT) and extinction Ångstrom exponent (EAE) parameters are used. Clustering in both 2D (AOT, EAE) and 3D (AOT, EAE, AAE) is investigated. A method of air mass backward trajectory analysis is then proposed, with the receptor site at Belsk, to determine possible source regions for each cluster. Four dominant aerosol source regions are identified. The biomass burning aerosol source is localized in the vicinity of Belarusian-Ukrainian border. Slovakia and northern Hungary are found to be the source of urban/industrial pollutants. Western Poland and eastern Germany are the main sources of polluted continental aerosols. The most differentiated source region of Scandinavia, Baltic Sea and Northern Atlantic, associated with lowest values of AOT, corresponds to clean continental and possibly maritime type aerosols.

  18. Optical Properties and Aging of Light Absorbing Secondary Organic Aerosol

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Jiumeng; Lin, Peng; Laskin, Alexander; Laskin, Julia; Kathmann, Shawn M.; Wise, Matthew E.; Caylor, Ryan; Imholt, Felisha; Selimovic, Vanessa; Shilling, John E.

    2016-10-14

    The light-absorbing organic aerosol (OA), commonly referred to as “brown carbon (BrC)”, has attracted considerable attention in recent years because of its potential to affect atmospheric radiation balance, especially in the ultraviolet region and thus impact photochemical processes. A growing amount of data has indicated that BrC is prevalent in the atmosphere, which has motivated numerous laboratory and field studies; however, our understanding of the relationship between the chemical composition and optical properties of BrC remains limited. We conducted chamber experiments to investigate the effect of various VOC precursors, NOx concentrations, photolysis time and relative humidity (RH) on the light absorption of selected secondary organic aerosols (SOA). Light absorption of chamber generated SOA samples, especially aromatic SOA, was found to increase with NOx concentration, at moderate RH, and for the shortest photolysis aging times. The highest mass absorption coefficients (MAC) value is observed from toluene SOA products formed under high NOx conditions at moderate RH, in which nitro-aromatics were previously identified as the major light absorbing compounds. BrC light absorption is observed to decrease with photolysis time, correlated with a decline of the organonitrate fraction of SOA. SOA formed from mixtures of aromatics and isoprene absorb less visible and UV light than SOA formed from aromatic precursors alone on a mass basis. However, the mixed-SOA absorption was underestimated when optical properties were predicted using a two-product SOA formation model, as done in many current climate models. Further investigation, including analysis on detailed mechanisms, are required to explain the discrepancy.

  19. Morphology and Optical Properties of Mixed Aerosol Particles

    Science.gov (United States)

    Fard, Mehrnoush M.; Krieger, Ulrich; Rudich, Yinon; Marcolli, Claudia; Peter, Thomas

    2016-04-01

    Experiments and modeling studies have shown that deliquesced aerosols can exist not only as one-phase system containing organics, inorganic salts and water, but often as two-phase systems consisting of a predominantly organic and a predominantly inorganic aqueous phase (1,2). Recent laboratory studies conducted with model mixtures representing tropospheric aerosols (1,2,3), secondary organic aerosol (SOA) from smog chamber experiments (4), and field measurements (5) suggest that liquid-liquid phase separations (LLPS) is indeed a common phenomenon in mixed organic/ inorganic particles. During LLPS, particles may adopt different morphologies mainly core-shell and partially engulfed. A core-shell configuration will have consequences for heterogeneous chemistry and hygroscopicity and as a result will alter the optical properties of the particles in particular for organic phases containing absorbing molecules, e.g. brown carbon. The primary objective of this project is to establish a method for investigating the morphology of mixed inorganic and absorbing organic compounds of atmospheric relevance and study their radiative properties before, during, and after phase transitions mainly during LLPS. This will be the first study looking into the radiative effect of LLPS in detail. Our ternary model system consist of ammonium sulfate (AS)/ Polyethylene Glycol (PEG)/ and water (H2O). Carminic acid (CA) was added as a proxy for an absorbing organic compound to the system. The behavior of single droplets of above ternary mixture was monitored during relative humidity (RH) cycles using optical microscopy. The same ternary mixture particle was levitated in an electrodynamic balance (EDB) and the change in its absorption properties was measured at varying RH. In addition, Mie-code modeling is used to predict the absorption efficiency of the same ternary system and the result will be compared with the data obtained from EDB experiment. We also intend to determine the occurrence of

  20. Organic component vapor pressures and hygroscopicities of aqueous aerosol measured by optical tweezers

    OpenAIRE

    Cai, Chen; Stewart, David J.; Reid, Jonathan P; Zhang, Yun Hong; Ohm, Peter; Dutcher, Cari S.; Clegg, Simon L.

    2015-01-01

    Measurements of the hygroscopic response of aerosol and the particle-to-gas partitioning of semivolatile organic compounds are crucial for providing more accurate descriptions of the compositional and size distributions of atmospheric aerosol. Concurrent measurements of particle size and composition (inferred from refractive index) are reported here using optical tweezers to isolate and probe individual aerosol droplets over extended timeframes. The measurements are shown to allow accurate re...

  1. Assessing the Role of Brewer Spectrophotometer in Determining Aerosol Optical Properties in the UK and Tropics.

    OpenAIRE

    Kumharn, Wilawan

    2010-01-01

    Aerosol effects are one of the major uncertainties in assessing global climate change, ecosystem processes and human health. This is because they critically change the balance between the radiation entering and leaving the atmosphere, as well as influencing cloud formation and having direct effects on biological systems e.g. through the respiratory system. It is the direct radiative effects of aerosol that are the focus of this work. The Aerosol Optical Depth (AOD) is a measure of the extinc...

  2. Global error maps of aerosol optical properties: an error propagation analysis

    Directory of Open Access Journals (Sweden)

    K. Tsigaridis

    2008-08-01

    Full Text Available Among the numerous atmospheric constituents, aerosols play a unique role on climate, due to their scattering and absorbing capabilities, visibility degradation and their effect on incoming and outgoing radiation. The most important optical properties are the aerosol optical depth (AOD, the asymmetry parameter (g and the single scattering albedo (SSA. Uncertainties in aerosol microphysics in global models, which in turn affect their optical properties, propagate to uncertainties on the effect of aerosols on climate. This study aims to estimate the uncertainty of AOD, g and SSA attributable to the aerosol representation in models, namely mixing state, aerosol size and aerosol associated water. As a reference, the monthly mean output of the general circulation model LMDz-INCA from the international comparison exercise AEROCOM B was used. For the optical properties calculations, aerosols were considered either externally mixed, homogeneously internally mixed or coated spheres. The radius was allowed to vary by ±20% (with 2% intervals and the aerosol water content by ±50% (with 5% intervals with respect to the reference model output. All of these possible combinations were assumed to be equally likely and the optical properties were calculated for each one of them. A probability density function (PDF was constructed at each model grid point for AOD, g and SSA. From this PDF, the 1σ and 2σ uncertainties of the AOD, g and SSA were calculated and are available as global maps for each month. For the range of the cases studied, we derive a maximum 2σ uncertainty range in AOD of 70%, while for g and SSA the maxima reach 18% and 28% respectively. The mixing state was calculated to be important, with the aerosol absorption and SSA being the most affected properties when absorbing aerosols are present.

  3. Aerosol optical properties and radiative effects over Manora Peak in the Himalayan foothills: seasonal variability and role of transported aerosols

    Energy Technology Data Exchange (ETDEWEB)

    Srivastava, A.K. [Indian Institute of Tropical Meteorology (Branch), Prof Ramnath Vij Marg, New Delhi (India); Ram, K. [Institute of Environment and Sustainable Development, Banaras Hindu University, Varanasi (India); Singh, Sachchidanand, E-mail: ssingh@nplindia.org [Radio and Atmospheric Sciences Division, CSIR-National Physical Laboratory, New Delhi (India); Kumar, Sanjeev [Radio and Atmospheric Sciences Division, CSIR-National Physical Laboratory, New Delhi (India); Tiwari, S. [Indian Institute of Tropical Meteorology (Branch), Prof Ramnath Vij Marg, New Delhi (India)

    2015-01-01

    The higher altitude regions of Himalayas and Tibetan Plateau are influenced by the dust and black carbon (BC) aerosols from the emissions and long-range transport from the adjoining areas. In this study, we present impacts of advection of polluted air masses of natural and anthropogenic emissions, on aerosol optical and radiative properties at Manora Peak (∼ 2000 m amsl) in central Himalaya over a period of more than two years (February 2006–May 2008). We used the most updated and comprehensive data of chemical and optical properties available in one of the most climatically sensitive region, the Himalaya, to estimate atmospheric radiative forcing and heating rate. Aerosol optical depth (AOD) was found to vary from 0.04 to 0.45 with significantly higher values in summer mainly due to an increase in mineral dust and biomass burning aerosols due to transport. In contrast, single scattering albedo (SSA) varied from 0.74 to 0.88 with relatively lower values during summer, suggesting an increase in absorbing BC and mineral dust aerosols. As a result, a large positive atmospheric radiative forcing (about 28 ± 5 Wm{sup −2}) and high values of corresponding heating rate (0.80 ± 0.14 Kday{sup −1}) has been found during summer. During the entire observation period, radiative forcing at the top of the atmosphere varied from − 2 to + 14 Wm{sup −2} and from − 3 to − 50 Wm{sup −2} at the surface whereas atmospheric forcing was in the range of 3 to 65 Wm{sup −2} resulting in a heating rate of 0.1–1.8 Kday{sup −1}. - Highlights: • Aerosol chemical and optical properties at Manora Peak, in central Himalaya, were significantly affected by dust and black carbon (BC) aerosols from the emissions and long-range transport from the adjoining areas. • Elevated AOD and lower SSA values were observed at Manora Peak during summer. • Enhancement in absorbing aerosols was observed during summer. • Large aerosol radiative forcing and heating rate was observed

  4. A merged aerosol dataset based on MODIS and MISR Aerosol Optical Depth products

    Science.gov (United States)

    Singh, Manoj K.; Gautam, Ritesh; Venkatachalam, Parvatham

    2016-05-01

    Aerosol Optical Depth (AOD) products available from MODIS and MISR observations are widely used for aerosol characterization, and global/environmental change studies. These products are based on different retrieval-algorithms, resolutions, sampling, and cloud-screening schemes, which have led to global/regional biases. Thus a merged product is desirable which bridges this gap by utilizing strengths from each of the sensors. In view of this, we have developed a "merged" AOD product based on MODIS and MISR AOD datasets, using Bayesian principles which takes error distributions from ground-based AOD measurements (from AERONET). Our methodology and resulting dataset are especially relevant in the scenario of combining multi-sensor retrievals for satellite-based climate data records; particularly for long-term studies involving AOD. Specifically for MISR AOD product, we also developed a methodology to produce a gap-filled dataset, using geostatistical methods (e.g. Kriging), taking advantage of available MODIS data. Merged and spatially-complete AOD datasets are inter-compared with other satellite products and with AERONET data at three stations- Kanpur, Jaipur and Gandhi College, in the Indo-Gangetic Plains. The RMSE of merged AOD (0.08-0.09) is lower than MISR (0.11-0.20) and MODIS (0.15-0.27). It is found that merged AOD has higher correlation with AERONET data (r within 0.92-0.95), compared to MISR (0.74-0.86) and MODIS (0.69-0.84) data. In terms of Expected Error, the accuracy of valid merged AOD is found to be superior as percent of merged AOD within error envelope are larger (71-92%), compared to MISR (43-61%) and MODIS (50-70%).

  5. Aerosol Composition, Size Distribution and Optical Properties during SEAC4RS Simulated by a Sectional Aerosol Model

    Science.gov (United States)

    Yu, P.; Toon, O. B.; Bardeen, C.; Wiedinmyer, C.; Jimenez, J. L.; Campuzano Jost, P.; Froyd, K. D.; Ziemba, L. D.; Schwarz, J. P.; Perring, A. E.; Wagner, N.; Neely, R. R., III

    2014-12-01

    Studies of Emissions and Atmospheric Composition, Clouds and Climate Coupling by Regional Surveys (SEAC4RS) field mission in August and September 2013 provided large aerosol/gas datasets over the Southeastern U.S. We use a sectional microphysics model (CARMA) coupled with CAM-Chem to study the aerosol composition, size distribution, vertical distribution and optical properties during the SEAC4RS campaign. Our simulations are within the observational error bars for the mass of organics, sulfate and black carbon from the boundary layer to upper-troposphere. CARMA, as a sectional model, provides detailed aerosol size distributions from nano-meters to tens of microns, which is important to determine optical properties. We investigate how the aerosol size distribution varies with altitude. Modeled spatial gradients of [O]:[C] and [OC]:[SO4-2] ratios are compared with the AMS and PALMS data collected over forests, fires and cities. These ratios are important to constrain the budget of secondary organic aerosols. We will discuss the values of these ratios over the U.S. and the rest of the world.

  6. Analysis of intensive aerosol optical properties measured at the Jungfraujoch station

    Energy Technology Data Exchange (ETDEWEB)

    Li, F.; Nyeki, S.; Baltensperger, U.; Weingartner, E.; Lugauer, M. [Paul Scherrer Inst. (PSI), Villigen (Switzerland)

    1997-09-01

    Characterisation of atmospheric aerosol optical properties at the Jungfraujoch has been conducted to deliver basic data for comparison with those from NOAA baseline atmospheric monitoring stations. (author) 2 figs., 2 refs.

  7. Case study of modeled aerosol optical properties during the SAFARI 2000 campaign.

    Science.gov (United States)

    Kuzmanoski, Maja; Box, Michael A; Schmid, Beat; Russell, Philip B; Redemann, Jens

    2007-08-01

    We present modeled aerosol optical properties (single scattering albedo, asymmetry parameter, and lidar ratio) in two layers with different aerosol loadings and particle sizes, observed during the Southern African Regional Science Initiative 2,000 (SAFARI 2,000) campaign. The optical properties were calculated from aerosol size distributions retrieved from aerosol layer optical thickness spectra, measured using the NASA Ames airborne tracking 14-channel sunphotometer (AATS-14) and the refractive index based on the available information on aerosol chemical composition. The study focuses on sensitivity of modeled optical properties in the 0.3-1.5 microm wavelength range to assumptions regarding the mixing scenario. We considered two models for the mixture of absorbing and nonabsorbing aerosol components commonly used to model optical properties of biomass burning aerosol: a layered sphere with absorbing core and nonabsorbing shell and the Maxwell-Garnett effective medium model. In addition, comparisons of modeled optical properties with the measurements are discussed. We also estimated the radiative effect of the difference in aerosol absorption implied by the large difference between the single scattering albedo values (approximately 0.1 at midvisible wavelengths) obtained from different measurement methods for the case with a high amount of biomass burning particles. For that purpose, the volume fraction of black carbon was varied to obtain a range of single scattering albedo values (0.81-0.91 at lambda=0.50 microm). The difference in absorption resulted in a significant difference in the instantaneous radiative forcing at the surface and the top of the atmosphere (TOA) and can result in a change of the sign of the aerosol forcing at TOA from negative to positive.

  8. Intercomparison and closure calculations using measurements of aerosol species and optical properties during the Yosemite Aerosol Characterization Study

    Science.gov (United States)

    Malm, William C.; Day, Derek E.; Carrico, Christian; Kreidenweis, Sonia M.; Collett, Jeffrey L.; McMeeking, Gavin; Lee, Taehyoung; Carrillo, Jacqueline; Schichtel, Bret

    2005-07-01

    Physical and optical properties of inorganic aerosols have been extensively studied, but less is known about carbonaceous aerosols, especially as they relate to the non-urban settings such as our nation's national parks and wilderness areas. Therefore an aerosol characterization study was conceived and implemented at one national park that is highly impacted by carbonaceous aerosols, Yosemite. The primary objective of the study was to characterize the physical, chemical, and optical properties of a carbon-dominated aerosol, including the ratio of total organic matter weight to organic carbon, organic mass scattering efficiencies, and the hygroscopic characteristics of a carbon-laden ambient aerosol, while a secondary objective was to evaluate a variety of semi-continuous monitoring systems. Inorganic ions were characterized using 24-hour samples that were collected using the URG and Interagency Monitoring of Protected Visual Environments (IMPROVE) monitoring systems, the micro-orifice uniform deposit impactor (MOUDI) cascade impactor, as well as the semi-continuous particle-into-liquid sampler (PILS) technology. Likewise, carbonaceous material was collected over 24-hour periods using IMPROVE technology along with the thermal optical reflectance (TOR) analysis, while semi-continuous total carbon concentrations were measured using the Rupprecht and Patashnick (R&P) instrument. Dry aerosol number size distributions were measured using a differential mobility analyzer (DMA) and optical particle counter, scattering coefficients at near-ambient conditions were measured with nephelometers fitted with PM10 and PM2.5 inlets, and "dry" PM2.5 scattering was measured after passing ambient air through Perma Pure Nafion® dryers. In general, the 24-hour "bulk" measurements of various aerosol species compared more favorably with each other than with the semi-continuous data. Semi-continuous sulfate measurements correlated well with the 24-hour measurements, but were biased low by

  9. Aerosol Optical Properties Measured Onboard the Ronald H. Brown During ACE Asia as a Function of Aerosol Chemical Composition and Source Region

    Science.gov (United States)

    Quinn, P. K.; Coffman, D. J.; Bates, T. S.; Welton, E. J.; Covert, D. S.; Miller, T. L.; Johnson, J. E.; Maria, S.; Russell, L.; Arimoto, R.

    2004-01-01

    During the ACE Asia intensive field campaign conducted in the spring of 2001 aerosol properties were measured onboard the R/V Ronald H. Brown to study the effects of the Asian aerosol on atmospheric chemistry and climate in downwind regions. Aerosol properties measured in the marine boundary layer included chemical composition; number size distribution; and light scattering, hemispheric backscattering, and absorption coefficients. In addition, optical depth and vertical profiles of aerosol 180 deg backscatter were measured. Aerosol within the ACE Asia study region was found to be a complex mixture resulting from marine, pollution, volcanic, and dust sources. Presented here as a function of air mass source region are the mass fractions of the dominant aerosol chemical components, the fraction of the scattering measured at the surface due to each component, mass scattering efficiencies of the individual components, aerosol scattering and absorption coefficients, single scattering albedo, Angstrom exponents, optical depth, and vertical profiles of aerosol extinction. All results except aerosol optical depth and the vertical profiles of aerosol extinction are reported at a relative humidity of 55 +/- 5%. An over-determined data set was collected so that measured and calculated aerosol properties could be compared, internal consistency in the data set could be assessed, and sources of uncertainty could be identified. By taking into account non-sphericity of the dust aerosol, calculated and measured aerosol mass and scattering coefficients agreed within overall experimental uncertainties. Differences between measured and calculated aerosol absorption coefficients were not within reasonable uncertainty limits, however, and may indicate the inability of Mie theory and the assumption of internally mixed homogeneous spheres to predict absorption by the ACE Asia aerosol. Mass scattering efficiencies of non-sea salt sulfate aerosol, sea salt, submicron particulate organic

  10. Analysis of aerosol optical and microphysical properties observed during the DC3 field study

    Science.gov (United States)

    Chen, G.; Schuster, G. L.; Anderson, B. E.; Jimenez, J. L.; Campuzano Jost, P.; Dibb, J. E.; Scheuer, E. M.; Ziemba, L. D.; Beyersdorf, A. J.; Thornhill, K. L.; Moore, R.; Winstead, E.; Markovic, M. Z.

    2013-12-01

    The Deep Convective Clouds and Chemistry Experiment (DC3) consisted of 18 research flights from Salina, KS. During cloud inflow and outflow surveys, various aged aerosol layers and plumes, including biomass burning, were sampled by the NASA DC-8 aircraft which was equipped with a broad suite of instruments for aerosol optical, microphysical, and chemical properties. As a result, the DC3 dataset includes detailed aerosol number size distribution, bulk aerosol mass concentration, black carbon mass concentration, and mass size distribution for sulfate, nitrate, ammonium and organics, together with scattering and absorption coefficients. We use this comprehensive dataset to perform a detailed closure analysis to examine the consistency between the observed aerosol properties and the literature reported aerosol refractive index values. In this context, we report aerosol observations, and comparisons between the aerosol mass and number size distribution for various aerosol layers. Closure tests will also be presented in terms of the impact of the aerosol composition and size distribution on the scattering and absorption.

  11. The surface aerosol optical properties in the urban area of Nanjing, west Yangtze River Delta, China

    Science.gov (United States)

    Zhuang, Bingliang; Wang, Tijian; Liu, Jane; Li, Shu; Xie, Min; Han, Yong; Chen, Pulong; Hu, Qiduo; Yang, Xiu-qun; Fu, Congbin; Zhu, Jialei

    2017-01-01

    Observational studies of aerosol optical properties are useful for reducing uncertainties in estimations of aerosol radiative forcing and forecasting visibility. In this study, the observed near-surface aerosol optical properties in urban Nanjing are analysed from March 2014 to February 2016. Results show that near-surface urban aerosols in Nanjing are mainly from local emissions and the surrounding regions. They have lower loadings but are more scattering than aerosols in most cities in China. The annual mean aerosol extinction coefficient (EC), single-scattering albedo (SSA) and asymmetry parameter (ASP) at 550 nm are 381.96 Mm-1, 0.9 and 0.57, respectively. The aerosol absorption coefficient (AAC) is about 1 order of magnitude smaller than its scattering coefficient (SC). However, the absorbing aerosol has a larger Ångström exponent (AAE) value, 1.58 at 470/660 nm, about 0.2 larger than the scattering aerosols (SAE). All the aerosol optical properties follow a near-unimodal pattern, and their values are mostly concentrated around their averages, accounting for more than 60 % of the total samplings. Additionally, they have substantial seasonality and diurnal variations. High levels of SC and AAC all appear in winter due to higher aerosol and trace gas emissions. AAE (ASP) is the smallest (largest) in summer, possibly because of high relative humidity (RH) which also causes considerably larger SC and smaller SAE, although intensive gas-to-particle transformation could produce a large number of finer scattering aerosols in this season. Seasonality of EC is different from the columnar aerosol optical depth. Larger AACs appear during the rush hours of the day while SC and back-scattering coefficient (Bsp) only peak in the early morning. Aerosols are fresher in the daytime than at night-time, leading to their larger Ångström exponent and smaller ASP. Different temporal variations between AAC and SC cause the aerosols to be more absorbing (smaller SSA) in autumn

  12. Aerosol optical depth as observed by the Mars Science Laboratory REMS UV photodiodes

    Science.gov (United States)

    Smith, Michael D.; Zorzano, María-Paz; Lemmon, Mark; Martín-Torres, Javier; Mendaza de Cal, Teresa

    2016-12-01

    Systematic observations taken by the REMS UV photodiodes on a daily basis throughout the landed Mars Science Laboratory mission provide a highly useful tool for characterizing aerosols above Gale Crater. Radiative transfer modeling is used to model the approximately 1.75 Mars Years of observations taken to date taking into account multiple scattering from aerosols and the extended field of view of the REMS UV photodiodes. The retrievals show in detail the annual cycle of aerosol optical depth, which is punctuated with numerous short timescale events of increased optical depth. Dust deposition onto the photodiodes is accounted for by comparison with aerosol optical depth derived from direct imaging of the Sun by Mastcam. The effect of dust on the photodiodes is noticeable, but does not dominate the signal. Cleaning of dust from the photodiodes was observed in the season around Ls=270°, but not during other seasons. Systematic deviations in the residuals from the retrieval fit are indicative of changes in aerosol effective particle size, with larger particles present during periods of increased optical depth. This seasonal dependence of aerosol particle size is expected as dust activity injects larger particles into the air, while larger aerosols settle out of the atmosphere more quickly leading to a smaller average particle size over time.

  13. Aerosol Optical Depth as Observed by the Mars Science Laboratory REMS UV Photodiodes

    Science.gov (United States)

    Smith, M. D.; Zorzano, M.-P.; Lemmon, M.; Martin-Torres, J.; Mendaza de Cal, T.

    2017-01-01

    Systematic observations taken by the REMS UV photodiodes on a daily basis throughout the landed Mars Science Laboratory mission provide a highly useful tool for characterizing aerosols above Gale Crater. Radiative transfer modeling is used to model the approximately two Mars Years of observations taken to date taking into account multiple scattering from aerosols and the extended field of view of the REMS UV photodiodes. The retrievals show in detail the annual cycle of aerosol optical depth, which is punctuated with numerous short timescale events of increased optical depth. Dust deposition onto the photodiodes is accounted for by comparison with aerosol optical depth derived from direct imaging of the Sun by Mastcam. The effect of dust on the photodiodes is noticeable, but does not dominate the signal. Cleaning of dust from the photodiodes was observed in the season around Ls=270deg, but not during other seasons. Systematic deviations in the residuals from the retrieval fit are indicative of changes in aerosol effective particle size, with larger particles present during periods of increased optical depth. This seasonal dependence of aerosol particle size is expected as dust activity injects larger particles into the air, while larger aerosols settle out of the atmosphere more quickly leading to a smaller average particle size over time. A full description of these observations, the retrieval algorithm, and the results can be found in Smith et al. (2016).

  14. Model Analysis of Influences of Aerosol Mixing State upon Its Optical Properties in East Asia

    Institute of Scientific and Technical Information of China (English)

    HAN Xiao; ZHANG Meigen; ZHU Lingyun; XU Liren

    2013-01-01

    The air quality model system RAMS (Regional Atmospheric Modeling System)-CMAQ (Models-3 Community Multi-scale Air Quality) coupled with an aerosol optical/radiative module was applied to investigate the impact of different aerosol mixing states (i.e.,externally mixed,half externally and half internally mixed,and internally mixed) on radiative forcing in East Asia.The simulation results show that the aerosol optical depth (AOD) generally increased when the aerosol mixing state changed from externally mixed to internally mixed,while the single scattering albedo (SSA) decreased.Therefore,the scattering and absorption properties of aerosols can be significantly affected by the change of aerosol mixing states.Comparison of simulated and observed SSAs at five AERONET (Aerosol Robotic Network) sites suggests that SSA could be better estimated by considering aerosol particles to be internally mixed.Model analysis indicates that the impact of aerosol mixing state upon aerosol direct radiative forcing (DRF) is complex.Generally,the cooling effect of aerosols over East Asia are enhanced in the northern part of East Asia (Northern China,Korean peninsula,and the surrounding area of Japan) and are reduced in the southern part of East Asia (Sichuan Basin and Southeast China) by internal mixing process,and the variation range can reach ±5 W m-2.The analysis shows that the internal mixing between inorganic salt and dust is likely the main reason that the cooling effect strengthens.Conversely,the internal mixture of anthropogenic aerosols,including sulfate,nitrate,ammonium,black carbon,and organic carbon,could obviously weaken the cooling effect.

  15. Influence of aerosol vertical profile variability on retrievals of aerosol optical thickness from NOAA AVHRR measurements in the Baltic region

    Directory of Open Access Journals (Sweden)

    Anna Rozwadowska

    2007-06-01

    Full Text Available The expected influence of variability in atmospheric aerosolprofiles on retrievals of aerosol optical thickness (AOTfrom NOAA AVHRR measurements is analysed. In particular, thebias in the AOT retrieval due to the assumption of a climatologicalaerosol profile in the retrieval algorithm is studied. The biasis defined as the difference between AOT retrieved with analgorithm using a climatological aerosol profile, and the actual AOTemployed in the calculations of radiances at the top of the atmosphere(TOA. The TOA radiances are simulated by means of the MODTRANcode for different aerosol profiles. Atmospheric conditions andsolar and satellite angles used in the bias simulations are typicalof the Baltic region. In the simulations, the maximum absolutevalue of the bias amounts to nearly 40% in channel 2 and 14%in channel 1 of AVHRR.

  16. Aerosol optical depth trend over the Middle East

    Science.gov (United States)

    Klingmueller, Klaus; Pozzer, Andrea; Metzger, Swen; Abdelkader, Mohamed; Stenchikov, Georgiy; Lelieveld, Jos

    2016-04-01

    We use the combined Dark Target/Deep Blue aerosol optical depth (AOD) satellite product of the Moderate-resolution Imaging Spectroradiometer (MODIS) collection 6 to study trends over the Middle East between 2000 and 2015. Our analysis corroborates a previously identified positive AOD trend over large parts of the Middle East during the period 2001 to 2012. By relating the annual AOD to precipitation, soil moisture and surface wind, being the main factors controlling the dust cycle, we identify regions where these attributes are significantly correlated to the AOD over Saudi Arabia, Iraq and Iran. The Fertile Crescent turns out to be of prime importance for the AOD trend over these countries. Using multiple linear regression we show that AOD trend and interannual variability can be attributed to the above mentioned dust cycle parameters, confirming that the AOD increase is predominantly driven by dust. In particular, the positive AOD trend relates to a negative soil moisture trend. This suggests that increasing temperature and decreasing relative humidity in the last decade have promoted soil drying, leading to increased dust emissions and AOD; consequently an AOD increase is expected due to climate change. Based on simulations using the ECHAM/MESSy atmospheric chemistry-climate model (EMAC), we interpret the correlations identified in the observational data in terms of causal relationships.

  17. On the variation of aerosol properties over Finland based on the optical columnar measurements

    Science.gov (United States)

    Aaltonen, V.; Rodriguez, E.; Kazadzis, S.; Arola, A.; Amiridis, V.; Lihavainen, H.; de Leeuw, G.

    2012-10-01

    Long-range aerosol transport over Finland has been studied using ground-based sunphotometer measurements of aerosol optical properties. Cimel sunphotometers were used at an urban site (Helsinki), a rural site (Hyytiälä) and a semiurban site (Kuopio) and PFR sunphotometer measurements were made at two rural sites, Jokioinen and Sodankylä. The CIMEL measurements are part of the AERONET (Aerosol robotic network) network and Jokioinen and Sodankylä are GAW-PFR (Global Atmosphere Watch-Precision Filter Radiometer) Associate Stations. Sunphotometers provide information on local columnar aerosol properties such as aerosol optical depth (AOD) and Ångström exponent (ÅE) that were used to investigate the aerosol content and aerosol type in this region. A set of representative event days, i.e. days with high turbidity, covering the time period between March 2006 and June 2010 has been selected for further analysis. For these days the AOD results were combined with air mass back trajectories to provide information about the air mass origin, especially for cases with moderate turbidity produced by long-range transported aerosols from mid latitudes to Finland. As expected, episodes with high AOD are connected with the transport of polluted air masses originating from the east or southeast or from industrial areas in Central Europe. We distinguished events with long range transported air pollution from cases where pollution was accumulated in the area due to the local meteorological factors.

  18. Assessment of 10 Year Record of Aerosol Optical Depth from OMI UV Observations

    Science.gov (United States)

    Ahn, Changwoo; Torres, Omar; Jethva, Hiren

    2014-01-01

    The Ozone Monitoring Instrument (OMI) onboard the EOS-Aura satellite provides information on aerosol optical properties by making use of the large sensitivity to aerosol absorption in the near-ultraviolet (UV) spectral region. Another important advantage of using near UV observations for aerosol characterization is the low surface albedo of all terrestrial surfaces in this spectral region that reduces retrieval errors associated with land surface reflectance characterization. In spite of the 13 × 24 square kilometers coarse sensor footprint, the OMI near UV aerosol algorithm (OMAERUV) retrieves aerosol optical depth (AOD) and single-scattering albedo under cloud-free conditions from radiance measurements at 354 and 388 nanometers. We present validation results of OMI AOD against space and time collocated Aerosol Robotic Network measured AOD values over multiple stations representing major aerosol episodes and regimes. OMAERUV's performance is also evaluated with respect to those of the Aqua-MODIS Deep Blue and Terra-MISR AOD algorithms over arid and semi-arid regions in Northern Africa. The outcome of the evaluation analysis indicates that in spite of the "row anomaly" problem, affecting the sensor since mid-2007, the long-term aerosol record shows remarkable sensor stability.

  19. Optical properties and source analysis of aerosols over a desert area in Dunhuang, Northwest china

    Science.gov (United States)

    Ma, Yongjing; Xin, Jinyuan; Ma, Yining; Kong, Lingbin; Zhang, Kequan; Zhang, Wenyu; Wang, Yuesi; Wang, Xiuqin; Zhu, Yongfeng

    2017-08-01

    Aerosol observational data for 2012 obtained from Dunhuang Station of CARE-China (Campaign on Atmospheric Aerosol Research Network of China) were analyzed to achieve in-depth knowledge of aerosol optical properties over Dunhuang region. The results showed that the annual average aerosol optical depth (AOD) at 500 nm was 0.32±0.06, and the Ångström exponent ( α) was 0.73 ± 0.27. Aerosol optical properties revealed significant seasonal characteristics. Frequent sandstorms in MAM (March-April-May) resulted in the seasonal maximum AOD, 0.41 ± 0.04, and a relatively smaller α value, 0.44±0.04. The tourism seasons, JJA (June-July-August) and SON (September-October-November) coincide with serious emissions of small anthropogenic aerosols. While in DJF (December-January-February), the composition of the atmosphere was a mixture of dust particles and polluted aerosols released by domestic heating; the average AOD and α were 0.29 ± 0.02 and 0.66 ± 0.17, respectively. Different air masses exhibited different degrees of influence on the aerosol concentration over Dunhuang in different seasons. During MAM, ranges of AOD (0.11-1.18) and α (0.06-0.82) were the largest under the dust influence of northwest-short-distance air mass in the four trajectories. Urban aerosols transported by northwest-short-distance air mass accounted for a very large proportion in JJA and the mixed aerosols observed in SON were mainly conveyed by air masses from the west. In DJF, the similar ranges of AOD and α under the three air mass demonstrated the analogous diffusion effects on regional pollutants over Dunhuang.

  20. Aerosol optical, microphysical and radiative properties at regional background insular sites in the western Mediterranean

    Science.gov (United States)

    Sicard, Michaël; Barragan, Rubén; Dulac, François; Alados-Arboledas, Lucas; Mallet, Marc

    2016-09-01

    In the framework of the ChArMEx (the Chemistry-Aerosol Mediterranean Experiment; http://charmex.lsce.ipsl.fr/) program, the seasonal variability of the aerosol optical, microphysical and radiative properties derived from AERONET (Aerosol Robotic Network; http://aeronet.gsfc.nasa.gov/) is examined in two regional background insular sites in the western Mediterranean Basin: Ersa (Corsica Island, France) and Palma de Mallorca (Mallorca Island, Spain). A third site, Alborán (Alborán Island, Spain), with only a few months of data is considered for examining possible northeast-southwest (NE-SW) gradients of the aforementioned aerosol properties. The AERONET dataset is exclusively composed of level 2.0 inversion products available during the 5-year period 2011-2015. AERONET solar radiative fluxes are compared with ground- and satellite-based flux measurements. To the best of our knowledge this is the first time that AERONET fluxes are compared with measurements at the top of the atmosphere. Strong events (with an aerosol optical depth at 440 nm greater than 0.4) of long-range transport aerosols, one of the main drivers of the observed annual cycles and NE-SW gradients, are (1) mineral dust outbreaks predominant in spring and summer in the north and in summer in the south and (2) European pollution episodes predominant in autumn. A NE-SW gradient exists in the western Mediterranean Basin for the aerosol optical depth and especially its coarse-mode fraction, which all together produces a similar gradient for the aerosol direct radiative forcing. The aerosol fine mode is rather homogeneously distributed. Absorption properties are quite variable because of the many and different sources of anthropogenic particles in and around the western Mediterranean Basin: North African and European urban areas, the Iberian and Italian peninsulas, most forest fires and ship emissions. As a result, the aerosol direct forcing efficiency, more dependent to absorption than the absolute

  1. Model of optical response of marine aerosols to Forbush decreases

    DEFF Research Database (Denmark)

    Bondo, Torsten; Enghoff, Martin Andreas Bødker; Svensmark, Henrik

    2010-01-01

    by different sensitivities of the probing wavelengths to changes in aerosol number concentration and size. For the long wavelengths these changes are generally smaller. The types and magnitude of change is investigated for a suite of nucleation rates, condensable gas production rates, and aerosol loss rates...

  2. Evaluating the representation of aerosol optical properties using an online coupled model over the Iberian Peninsula

    Science.gov (United States)

    Palacios-Peña, Laura; Baró, Rocío; Guerrero-Rascado, Juan Luis; Alados-Arboledas, Lucas; Brunner, Dominik; Jiménez-Guerrero, Pedro

    2017-01-01

    The effects of atmospheric aerosol particles on the Earth's climate mainly depend on their optical, microphysical and chemical properties, which modify the Earth's radiative budget. The aerosol radiative effects can be divided into direct and semi-direct effects, produced by the aerosol-radiation interactions (ARIs), and indirect effects, produced by aerosol-cloud interactions (ACIs). In this sense the objective of this work is to assess whether the inclusion of aerosol radiative feedbacks in the online coupled WRF-Chem model improves the modelling outputs over the Iberian Peninsula (IP) and surrounding water areas. For this purpose, the methodology is based on the evaluation of modelled aerosol optical properties under different simulation scenarios. The evaluated data come from two WRF-Chem simulations for the IP differing in the inclusion/no-inclusion of ARIs and ACIs (RF/NRF simulations). The case studies cover two episodes with different aerosol types over the IP in 2010, namely a Saharan dust outbreak and a forest fire episode. The evaluation uses observational data from AERONET (Aerosol Robotic Network) stations and MODIS (Moderate Resolution Imaging Spectroradiometer) sensor, including aerosol optical depth (AOD) and Ångström exponent (AE). Experimental data of aerosol vertical distribution from the EARLINET (European Aerosol Research Lidar Network) Granada station are used for checking the models. The results indicate that for the spatial distribution the best-represented variable is AOD and the largest improvements when including the aerosol radiative feedbacks are found for the vertical distribution. In the case of the dust outbreak, a slight improvement (worsening) is produced over the areas with medium (high/low) levels of AOD(-9 % / +12 % of improvement) when including the aerosol radiative feedbacks. For the wildfire episode, improvements of AOD representation (up to 11 %) over areas further away from emission sources are estimated, which

  3. Broadband optical properties of biomass-burning aerosol and identification of brown carbon chromophores: OPTICAL AND CHEMICAL PROPERTIES OF BROWN CARBON AEROSOLS

    Energy Technology Data Exchange (ETDEWEB)

    Bluvshtein, Nir [Department of Earth and Planetary Sciences, Weizmann Institute of Science, Rehovot Israel; Lin, Peng [Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland Washington USA; Flores, J. Michel [Department of Earth and Planetary Sciences, Weizmann Institute of Science, Rehovot Israel; Segev, Lior [Department of Earth and Planetary Sciences, Weizmann Institute of Science, Rehovot Israel; Mazar, Yinon [Department of Earth and Planetary Sciences, Weizmann Institute of Science, Rehovot Israel; Tas, Eran [The Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot Israel; Snider, Graydon [Department of Physics and Atmospheric Science, Dalhousie University, Halifax Nova Scotia Canada; Weagle, Crystal [Department of Chemistry, Dalhousie University, Halifax Nova Scotia Canada; Brown, Steven S. [Cooperative Institute for Research in Environmental Sciences, University of Colorado Boulder, Boulder Colorado USA; Chemical Sciences Division, Earth System Research Laboratory, National Oceanic and Atmospheric Administration, Boulder Colorado USA; Laskin, Alexander [Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland Washington USA; Rudich, Yinon [Department of Earth and Planetary Sciences, Weizmann Institute of Science, Rehovot Israel

    2017-05-23

    The radiative effects of biomass burning aerosols on regional and global scale is substantial. Accurate modeling of the radiative effects of smoke aerosols require wavelength-dependent measurements and parameterizations of their optical properties in the UV and visible spectral ranges along with improved description of their chemical composition. To address this issue, we used a recently developed approach to retrieve the time- and spectral-dependent optical properties of ambient biomass burning aerosols between 300 and 650 nm wavelength during a regional bonfire festival in Israel. During the biomass burning event, the overall absorption at 400 nm increased by about two orders of magnitude, changing the size-weighted single scattering albedo from a background level of 0.95 to 0.7. Based on the new retrieval method, we provide parameterizations of the wavelength-dependent effective complex refractive index from 350 to 650 nm for freshly emitted and aged biomass burning aerosols. In addition, PM2.5 filter samples were collected for detailed off-line chemical analysis of the water soluble organics that contribute to light absorption. Nitrophenols were identified as the main organic species responsible for the increased absorption at 400-500 nm. These include species such as 4- nitrocatechol, 4-nitrophenol, nitro-syringol and nitro-guaiacol; oxidation-nitration products of methoxyphenols, known products of lignin pyrolysis. Our findings emphasize the importance of both primary and secondary organic aerosol from biomass burning in absorption of solar radiation and in effective radiative forcing.

  4. Laboratory measurements of the optical properties of sea salt aerosol

    Directory of Open Access Journals (Sweden)

    R. Irshad

    2009-01-01

    Full Text Available The extinction spectra of laboratory generated sea salt aerosols have been measured from 1 μm to 20 μm using a Bruker 66v/S FTIR spectrometer. Concomitant measurements include temperature, pressure, relative humidity and the aerosol size distribution. The refractive indices of the sea salt aerosol have been determined using a simple harmonic oscillator band model (Thomas et al., 2004 for aerosol with relative humidities at eight different values between 0.4% to 86%. The resulting refractive index spectra show significant discrepancies when compared to existing sea salt refractive indices calculated using volume mixing rules (Shettle and Fenn, 1979. Specifically, an additional band is found in the refractive indices of dry sea salt aerosol and the new data shows increased values of refractive index at almost all wavelengths. This implies that the volume mixing rules, currently used to calculate the refractive indices of wet sea salt aerosols, are inadequate. Furthermore, the existing data for the real and imaginary parts of the refractive indices of dry sea salt aerosol are found not to display the Kramers-Kronig relationship. This implies that the original data used for the volume mixing calculations is also inaccurate.

  5. MODIS Aerosol Optical Depth Bias Adjustment Using Machine Learning Algorithms

    Science.gov (United States)

    Albayrak, A.; Wei, J. C.; Petrenko, M.; Lary, D. J.; Leptoukh, G. G.

    2011-12-01

    Over the past decade, global aerosol observations have been conducted by space-borne sensors, airborne instruments, and ground-base network measurements. Unfortunately, quite often we encounter the differences of aerosol measurements by different well-calibrated instruments, even with a careful collocation in time and space. The differences might be rather substantial, and need to be better understood and accounted for when merging data from many sensors. The possible causes for these differences come from instrumental bias, different satellite viewing geometries, calibration issues, dynamically changing atmospheric and the surface conditions, and other "regressors", resulting in random and systematic errors in the final aerosol products. In this study, we will concentrate on the subject of removing biases and the systematic errors from MODIS (both Terra and Aqua) aerosol product, using Machine Learning algorithms. While we are assessing our regressors in our system when comparing global aerosol products, the Aerosol Robotic Network of sun-photometers (AERONET) will be used as a baseline for evaluating the MODIS aerosol products (Dark Target for land and ocean, and Deep Blue retrieval algorithms). The results of bias adjustment for MODIS Terra and Aqua are planned to be incorporated into the AeroStat Giovanni as part of the NASA ACCESS funded AeroStat project.

  6. Monitoring and tracking the trans-Pacific transport of aerosols using multi-satellite aerosol optical depth retrievals

    Directory of Open Access Journals (Sweden)

    A. R. Naeger

    2015-10-01

    Full Text Available The primary goal of this study was to generate a near-real time (NRT aerosol optical depth (AOD product capable of providing a comprehensive understanding of the aerosol spatial distribution over the Pacific Ocean in order to better monitor and track the trans-Pacific transport of aerosols. Therefore, we developed a NRT product that takes advantage of observations from both low-earth orbiting and geostationary satellites. In particular, we utilize AOD products from the Moderate Resolution Imaging Spectroradiometer (MODIS and Suomi National Polar-orbiting Partnership (NPP Visible Infrared Imaging Radiometer Suite (VIIRS satellites. Then, we combine these AOD products with our own retrieval algorithms developed for the NOAA Geostationary Operational Environmental Satellite (GOES-15 and Japan Meteorological Agency (JMA Multi-functional Transport Satellite (MTSAT-2 to generate a NRT daily AOD composite product. We present examples of the daily AOD composite product for a case study of trans-Pacific transport of Asian pollution and dust aerosols in mid-March 2014. Overall, the new product successfully tracks this aerosol plume during its trans-Pacific transport to the west coast of North America. However, we identify several areas across the domain of interest from Asia to North America where the new product can encounter significant uncertainties due to the inclusion of the geostationary AOD retrievals. The uncertainties associated with geostationary AOD retrievals are expected to be minimized after the successful launch of the next-generation advanced NOAA GOES-R and recently launched JMA Himawari satellites. Observations from these advanced satellites will ultimately provide an enhanced understanding of the spatial and temporal distribution of aerosols over the Pacific.

  7. Modeling the spectral optical properties of ammonium sulfate and biomass burning aerosols

    Energy Technology Data Exchange (ETDEWEB)

    Grant, K.E.; Chuang, C.C.; Grossman, A.S.; Penner, J.E. [Michigan Univ., Ann Arbor, MI (United States)

    1997-09-01

    The importance of including the global and regional radiative effects of aerosols in climate models has increasingly been realized. Accurate modeling of solar radiative forcing due to aerosols from anthropogenic sulfate and biomass burning emissions requires adequate spectral resolution and treatment of spatial and temporal variability. The variation of aerosol spectral optical properties with local relative humidity and dry aerosol composition must be considered. Because the cost of directly including Mie calculations within a climate model is prohibitive, parameterizations from offline calculations must be used. Starting from a log-normal size distribution of dry ammonium sulfate, we developed optical properties for tropospheric sulfate aerosol at 15 relative humidities up to 99 percent. The resulting aerosol size distributions were then used to calculate bulk optical properties at wavelengths between 0.175 {micro}m and 4 {micro}m. Finally, functional fits of optical properties were made for each of 12 wavelength bands as a function of relative humidity. Significant variations in optical properties occurred across the total solar spectrum. Relative increases in specific extinction and asymmetry factor with increasing relative humidity became larger at longer wavelengths. Significant variation in single-scattering albedo was found only in the longest near-IR band. This is also the band with the lowest albedo. A similar treatment was done for aerosols from biomass burning. In this case, size distributions were taken as having two carbonaceous size modes and a larger dust mode. The two carbonaceous modes were considered to be humidity dependent. Equilibrium size distributions and compositions were calculated for 15 relative humidities and five black carbon fractions. Mie calculations and Chandrasekhar averages of optical properties were done for each of the resulting 75 cases. Finally, fits were made for each of 12 spectral bands as functions of relative humidity

  8. Columnar aerosol optical properties at AERONET sites in northern, central and southern Mexico

    Science.gov (United States)

    Carabali, Giovanni; Estévez, Hector; Florean-Cruz, Claudia; Navarro-Medina, Abigail; Valdés-Barrón, Mauro; Bonifaz-Alfonzo, Roberto; Riveros-Rosas, David; Velasco-Herrera, Víctor; Vázquez-Gálvez, Felipe

    2017-04-01

    The column-integrated optical properties of aerosol in the north, central and southern Mexico were investigated based on Sun/sky radiometer measurements made at Aerosol Robotic Network (AERONET) sites. Characterization of aerosol properties in these Mexico regions is important due to natural and anthropogenic significant events that occurred: dust storms from Sonora desert, biomass burning from south forest areas and urban/industrial from Mexico City due to the increases in fossil fuel combustion. Some cities in northern Mexico located near desert areas are affected by the dust from Sonora and Chihuahua deserts. These particles are suspended in the atmosphere due to strong wind activity that creates dust storms. In the central part of the Mexican territory, urban air pollution is one of the biggest problems. Mexico City is the most important urban area that face seriously environmental problem generated by daily anthropogenic emissions from activities of some 21 million people and the vast amount of industry. On the other hand, biomass burning in the Yucatan Peninsula, Southern Mexico, and Guatemala is an important source of anthropogenic aerosol in the troposphere (Crutzen and Andrade, 1990). The pollution from these fires affects air quality locally and is transported over the Gulf of Mexico to the United States (Wang et al., 2006). The aim of this work is to study the optical properties of different types of aerosols by analyzing a 5-year (2005-2010) data set from AErosol RObotic NETwork (AERONET). Time series of Angstrom exponent (α) and aerosol optical depth (τ) in 7 wavelengths from 340 to 1020 nm are shown. Additionally, a graphical framework to classify aerosol properties using direct sun-photometer observations in the different regions of Mexico is presented. That aerosol classification was made by applying the method described by Gobbi et al (2007), which relies on the combined analysis of α and its spectral curvature δα.

  9. Aerosol Optical Properties and Its Radiative Forcing over Yulin, China in 2001 and 2002

    Institute of Scientific and Technical Information of China (English)

    CHE Huizheng; ZHANG Xiaoye; Stephane ALFRARO; Bernadette CHATENET; Laurent GOMES; ZHAO Jianqi

    2009-01-01

    The aerosol optical properties and direct radiative forcing over the Mu Us desert of northern China, acquired through a CE318 sunphotometer of the ground-bascd Aerosol Robotic Network (AERONET), are analyzed. The seasonal variations in the aerosol optical properties are examined. The effect of meteorological elements (pressure, temperature, water vapor pressure, relative humidity and wind speed) on the aerosol optical properties is also studied. Then, the sources and optical properties under two different cases, a dust event and a pollution event, are compared. The results show that the high aerosol optical depth (AOD) found in Yulin was mostly attributed to the occurrence of dust events in spring from the Mu Us desert and deserts of West China and Mongolia, as well as the impacts of anthropogenic pollutant particles from the middle part of China in the other seasons. The seasonal variation and the probability distribution of the radiative forcing and the radiative forcing efficiency at the surface and the top of the atmosphere are analyzed and regressed using the linear and Gaussian regression methods.

  10. Urban Aerosol Optical Properties Measurement by Elastic Counter-Look Lidar

    OpenAIRE

    Wang X.; Boselli A.; He Y; Sannino A.; Song C.; Spinelli N.

    2016-01-01

    The new developed elastic lidar system utilizes two identical elastic lidars, in counter-look configuration, to measure aerosol backscattering and extinction coefficients without any hypotheses. Compared to elastic-Raman lidar and high spectral resolution lidar, the proposed counter-look elastic lidar can use low power eyesafe laser and all available wavelengths. With this prototype lidar system, urban aerosol optical properties and their spatial distribution have been directly measured, incl...

  11. Simultaneous retrieval of aerosol optical thickness and chlorophyll concentration from multiwavelength measurement over East China Sea

    Science.gov (United States)

    Shi, Chong; Nakajima, Teruyuki; Hashimoto, Makiko

    2016-12-01

    A flexible inversion algorithm is proposed for simultaneously retrieving aerosol optical thickness (AOT) and surface chlorophyll a (Chl) concentration from multiwavelength observation over the ocean. In this algorithm, forward radiation calculation is performed by an accurate coupled atmosphere-ocean model with a comprehensive bio-optical ocean module. Then, a full-physical nonlinear optimization approximation approach is used to retrieve AOT and Chl. For AOT retrieval, a global three-dimensional spectral radiation-transport aerosol model is used as the a priori constraint to increase the retrieval accuracy of aerosol. To investigate the algorithm's availability, the retrieval experiment is conducted using simulated radiance data to demonstrate that the relative errors in simultaneously determining AOT and Chl can be mostly controlled to within 10% using multiwavelength and angle covering in and out of sunglint. Furthermore, the inversion results are assessed using the actual satellite observation data obtained from Cloud and Aerosol Imager (CAI)/Greenhouse gas Observation SATellite GOSAT and MODerate resolution Imaging Spectroradiometer (MODIS)/Aqua instruments through comparison to Aerosol Robotic Network (AERONET) aerosol and ocean color (OC) products over East China Sea. Both the retrieved AOT and Chl compare favorably to the reported AERONET values, particularly when using the CASE 2 ocean module in turbid water, even when the retrieval is performed in the presence of high aerosol loading and sunglint. Finally, the CAI and MODIS images are used to jointly retrieve the spatial distribution of AOT and Chl in comparison to the MODIS AOT and OC products.

  12. A new approach for retrieving the UV-vis optical properties of ambient aerosols

    Science.gov (United States)

    Bluvshtein, Nir; Flores, J. Michel; Segev, Lior; Rudich, Yinon

    2016-08-01

    Atmospheric aerosols play an important part in the Earth's energy budget by scattering and absorbing incoming solar and outgoing terrestrial radiation. To quantify the effective radiative forcing due to aerosol-radiation interactions, researchers must obtain a detailed understanding of the spectrally dependent intensive and extensive optical properties of different aerosol types. Our new approach retrieves the optical coefficients and the single-scattering albedo of the total aerosol population over 300 to 650 nm wavelength, using extinction measurements from a broadband cavity-enhanced spectrometer at 315 to 345 nm and 390 to 420 nm, extinction and absorption measurements at 404 nm from a photoacoustic cell coupled to a cavity ring-down spectrometer, and scattering measurements from a three-wavelength integrating nephelometer. By combining these measurements with aerosol size distribution data, we retrieved the time- and wavelength-dependent effective complex refractive index of the aerosols. Retrieval simulations and laboratory measurements of brown carbon proxies showed low absolute errors and good agreement with expected and reported values. Finally, we implemented this new broadband method to achieve continuous spectral- and time-dependent monitoring of ambient aerosol population, including, for the first time, extinction measurements using cavity-enhanced spectrometry in the 315 to 345 nm UV range, in which significant light absorption may occur.

  13. Biogenic Aerosols Over the Amazon Basin: Optical Properties and Relationship With Elemental and Ionic Composition

    Science.gov (United States)

    Artaxo, P.; Martin, S. T.; Andreae, M. O.; Godoy, J. M.; Godoy, M. L.; Rizzo, L. V.; Paixao, M.

    2008-12-01

    We investigated the optical properties of natural biogenic aerosol particles over the central Amazon Basin near Manaus during the wet season in February and March 2008. The measurements were conducted as part of the AMAZE-08 (Amazonian Aerosol Characterization Experiment) sampling campaign. Light absorption was determined with the use of an Aethalometer and an MAAP (Multi Angle Absorption Photometer). Light scattering was measured with a 3 wavelength TSI nephelometer and an Ecotech nephelometer. The elemental composition was measured trough PIXE and IC. Single scattering albedo shows relatively low values varying from 0.86 to 0.95. Very low fine mode aerosol mass was measured, and coarse mode particles are responsible for a significant fraction of scattering and absorption. Sulfur was observed in very low concentrations, and most of the aerosol mass was organic. Long range transport of soil dust from Sahara were observed and reflected in the light scattering coefficient. Wavelength dependence of absorption indicates the strong influence of coarse mode aerosol. Aerosol optical thickness shows low values, but with significant single scattering albedo values, showing strong absorption properties of these biogenic aerosols. Size distribution measurements shows consistence with the scattering coefficients measured, if the coarse mode particles are taken into account.

  14. Airborne in situ characterization of dry urban aerosol optical properties around complex topography

    Science.gov (United States)

    Targino, Admir Créso; Noone, Kevin J.

    2006-02-01

    In situ data from the 1997 Southern California Ozone Study—NARSTO were used to describe the aerosol optical properties in an urban area whose aerosol distribution is modified as the aerosols are advected over the surrounding topography. The data consist of measurements made with a nephelometer and absorption photometer onboard the Center for Interdisciplinary Remotely-Piloted Aircraft Studies (CIRPAS) Pelican aircraft. The cases investigated in this study include vertical profiles flown over coastal sites as well as sites located along some important mountain ranges in southern California. The vertical distribution of the aerosol in the Los Angeles Basin showed a complex configuration, directly related with the local meteorological circulations and the surrounding topography. High spatial and temporal variability in air pollutant concentrations within a relatively small area was found, as indicated by the aerosol scattering and absorption coefficient data. The results suggest that in areas with such complex terrain, a high spatial resolution is required in order to adequately describe the aerosol optical quantities. Principal components analysis (PCA) has been applied to aerosol chemical samples in order to identify the major aerosol types in the Los Angeles Basin. The technique yielded four components that accounted for 78% of the variance in the data set. These were indicative of marine aerosols, urban aerosols, trace elements and secondary aerosol components of traffic emissions and agricultural activities. A Monte Carlo radiation transfer model has been employed to simulate the effects that different aerosol vertical profiles have on the attenuation of solar energy. The cases examined were selected using the results of the PCA and in situ data were used to describe the atmospheric optical properties in the model. These investigations comprise a number of sensitivity tests to evaluate the effects on the results of the location of the aerosol layers as well as

  15. Relationship between wind speed and aerosol optical depth over remote ocean

    Directory of Open Access Journals (Sweden)

    R. G. Grainger

    2009-11-01

    Full Text Available The effect of wind speed on aerosol optical depth (AOD at 550 nm over remote ocean regions is investigated. Remote ocean regions are defined by the combination of AOD from satellite observation and wind direction from ECMWF. According to our definition, many oceanic regions cannot be taken as remote ocean regions due to long-range transportation of aerosols from continents. Highly correlated linear relationships are found in remote ocean regions with a wind speed range of 4–20 ms−1. The enhancement of AOD at high wind speed is explained as the increase of sea salt aerosol production.

  16. Multi-wavelength optical measurement to enhance thermal/optical analysis for carbonaceous aerosol

    Directory of Open Access Journals (Sweden)

    L.-W. A. Chen

    2014-09-01

    Full Text Available A thermal/optical carbon analyzer equipped with seven-wavelength light source/detector (405–980 nm for monitoring spectral reflectance (R and transmittance (T of filter samples allows "thermal spectral analysis (TSA" and wavelength (λ-dependent organic carbon (OC-elemental carbon (EC measurements. Optical sensing is calibrated with transfer standards traceable to absolute R and T measurements and adjusted for loading effects to determine spectral light absorption (as absorption optical depth [τa, λ] using diesel exhaust samples as a reference. Tests on ambient and source samples show OC and EC concentrations equivalent to those from conventional carbon analysis when based on the same wavelength (~635 nm for pyrolysis adjustment. TSA provides additional information that evaluates black carbon (BC and brown carbon (BrC contributions and their optical properties in the near-IR to the near-UV parts of the solar spectrum. The enhanced carbon analyzer can add value to current aerosol monitoring programs and provide insight into more accurate OC and EC measurements for climate, visibility, or health studies.

  17. Aerosol optical properties retrieved from Sun photometer measurements over Shanghai, China

    Science.gov (United States)

    He, Qianshan; Li, Chengcai; Geng, Fuhai; Yang, Hequn; Li, Peiren; Li, Tingting; Liu, Dongwei; Pei, Zhen

    2012-08-01

    Using a CIMEL Sun photometer, we conducted continuous observations over the urban area of Shanghai (31°14'N, 121°32'E) from 18 April 2007 to 31 January 2009. The aerosol optical depth (AOD), Angstrom wavelength exponent, single scattering albedo (ω0), and aerosol particle size distribution were derived from the observational data. The monthly mean AOD reached a maximum value of 1.20 in June and a minimum value of 0.43 in January. The monthly averaged Angstrom wavelength exponent reached a minimum value of 1.15 in April and a maximum value of 1.41 in October. The frequencies of the AOD and Angstrom wavelength exponent presented lognormal distributions. The averaged ω0 at 550 nm was 0.94 throughout the observation period, indicating that the aerosols over Shanghai are composed mainly of scattering particles. The concentrations of coarse mode and accumulation mode aerosols over Shanghai were highest in spring compared with other seasons, especially for those particles with radii between 1.0 and 2.0 μm. The median radius of monthly averaged accumulation mode aerosols increased with increasing AOD, and fine particles accounted for the majority of the aerosol volume concentration. The ratios of the monthly averaged volume concentration of accumulation mode and coarse mode aerosols (Vf/Vc) were over 0.6 for all months studied and reached up to 1.94 in August. The volumes of the two modes changed with AOD, but their correlations presented different sensitivities, that is, the volume concentration of accumulation mode aerosols was more sensitive to variations in AOD than that of coarse mode aerosols. The aerosol volume concentration decreased with increasing ω0, indicating that the higher the volume concentration of aerosols, the higher the absorption in particle extinction properties. The increase in absorption was caused primarily by secondary species coated on black carbon (BC) and primary organic carbon (POC) particles.

  18. Weekly periodicities of aerosol optical thickness over Central Europe – evidence of an anthropogenic direct aerosol effect

    Directory of Open Access Journals (Sweden)

    B. Vogel

    2007-08-01

    Full Text Available Statistical analyses of data from 14 ground-based sun photometer stations all over Central Europe are presented. All stations are part of the Aerosol Robotic Network (AERONET, and only data of the highest data quality level 2.0 had been applied. The averages by weekday of aerosol optical thickness (AOT at a wavelength of 440 nm of 12 of the 14 stations show a weekly periodicity with lowest values on Sunday and Monday, but greatest values from Wednesday until Saturday, that is significant at least on a 90% level. The stations in Germany and in Greater Paris show weekly cycles with ranges of about 20% on average. In Northern Italy and Switzerland this range is about 10% on average. The corresponding weekly cycle of anthropogenic gaseous and particulate emissions leads us to the conclusion of the anthropogenic origin of the weekly AOT cycle. Since these AOT patterns are derived from the reduction of the direct sun radiation by the columnar atmospheric aerosol, this result represents strong evidence for an anthropogenic direct aerosol effect on shortwave radiation. Furthermore, this study makes a first contribution to the understanding and explanation of recently observed weekly periodicities in meteorological variables as temperature in Germany.

  19. Observationally-constrained estimates of aerosol optical depths (AODs) over East Asia via data assimilation techniques

    Science.gov (United States)

    Lee, K.; Lee, S.; Song, C. H.

    2015-12-01

    Not only aerosol's direct effect on climate by scattering and absorbing the incident solar radiation, but also they indirectly perturbs the radiation budget by influencing microphysics and dynamics of clouds. Aerosols also have a significant adverse impact on human health. With an importance of aerosols in climate, considerable research efforts have been made to quantify the amount of aerosols in the form of the aerosol optical depth (AOD). AOD is provided with ground-based aerosol networks such as the Aerosol Robotic NETwork (AERONET), and is derived from satellite measurements. However, these observational datasets have a limited areal and temporal coverage. To compensate for the data gaps, there have been several studies to provide AOD without data gaps by assimilating observational data and model outputs. In this study, AODs over East Asia simulated with the Community Multi-scale Air Quality (CMAQ) model and derived from the Geostationary Ocean Color Imager (GOCI) observation are interpolated via different data assimilation (DA) techniques such as Cressman's method, Optimal Interpolation (OI), and Kriging for the period of the Distributed Regional Aerosol Gridded Observation Networks (DRAGON) Campaign (March - May 2012). Here, the interpolated results using the three DA techniques are validated intensively by comparing with AERONET AODs to examine the optimal DA method providing the most reliable AODs over East Asia.

  20. Quantification of black carbon mixing state from traffic: implications for aerosol optical properties

    Science.gov (United States)

    Willis, Megan D.; Healy, Robert M.; Riemer, Nicole; West, Matthew; Wang, Jon M.; Jeong, Cheol-Heon; Wenger, John C.; Evans, Greg J.; Abbatt, Jonathan P. D.; Lee, Alex K. Y.

    2016-04-01

    The climatic impacts of black carbon (BC) aerosol, an important absorber of solar radiation in the atmosphere, remain poorly constrained and are intimately related to its particle-scale physical and chemical properties. Using particle-resolved modelling informed by quantitative measurements from a soot-particle aerosol mass spectrometer, we confirm that the mixing state (the distribution of co-emitted aerosol amongst fresh BC-containing particles) at the time of emission significantly affects BC-aerosol optical properties even after a day of atmospheric processing. Both single particle and ensemble aerosol mass spectrometry observations indicate that BC near the point of emission co-exists with hydrocarbon-like organic aerosol (HOA) in two distinct particle types: HOA-rich and BC-rich particles. The average mass fraction of black carbon in HOA-rich and BC-rich particle classes was < 0.1 and 0.8, respectively. Notably, approximately 90 % of BC mass resides in BC-rich particles. This new measurement capability provides quantitative insight into the physical and chemical nature of BC-containing particles and is used to drive a particle-resolved aerosol box model. Significant differences in calculated single scattering albedo (an increase of 0.1) arise from accurate treatment of initial particle mixing state as compared to the assumption of uniform aerosol composition at the point of BC injection into the atmosphere.

  1. Aerosol data assimilation in the chemical transport model MOCAGE during the TRAQA/ChArMEx campaign: aerosol optical depth

    Science.gov (United States)

    Sič, Bojan; El Amraoui, Laaziz; Piacentini, Andrea; Marécal, Virginie; Emili, Emanuele; Cariolle, Daniel; Prather, Michael; Attié, Jean-Luc

    2016-11-01

    In this study, we describe the development of the aerosol optical depth (AOD) assimilation module in the chemistry transport model (CTM) MOCAGE (Modèle de Chimie Atmosphérique à Grande Echelle). Our goal is to assimilate the spatially averaged 2-D column AOD data from the National Aeronautics and Space Administration (NASA) Moderate-resolution Imaging Spectroradiometer (MODIS) instrument, and to estimate improvements in a 3-D CTM assimilation run compared to a direct model run. Our assimilation system uses 3-D-FGAT (first guess at appropriate time) as an assimilation method and the total 3-D aerosol concentration as a control variable. In order to have an extensive validation dataset, we carried out our experiment in the northern summer of 2012 when the pre-ChArMEx (CHemistry and AeRosol MEditerranean EXperiment) field campaign TRAQA (TRAnsport à longue distance et Qualité de l'Air dans le bassin méditerranéen) took place in the western Mediterranean basin. The assimilated model run is evaluated independently against a range of aerosol properties (2-D and 3-D) measured by in situ instruments (the TRAQA size-resolved balloon and aircraft measurements), the satellite Spinning Enhanced Visible and InfraRed Imager (SEVIRI) instrument and ground-based instruments from the Aerosol Robotic Network (AERONET) network. The evaluation demonstrates that the AOD assimilation greatly improves aerosol representation in the model. For example, the comparison of the direct and the assimilated model run with AERONET data shows that the assimilation increased the correlation (from 0.74 to 0.88), and reduced the bias (from 0.050 to 0.006) and the root mean square error in the AOD (from 0.12 to 0.07). When compared to the 3-D concentration data obtained by the in situ aircraft and balloon measurements, the assimilation consistently improves the model output. The best results as expected occur when the shape of the vertical profile is correctly simulated by the direct model. We

  2. Studies of aerosol optical depth with use of Microtops sun photometers and MODIS detectors

    Science.gov (United States)

    Makuch, Przemyslaw; Zawadzka, Olga; Markowicz, Krzystof M.; Zielinski, Tymon; Petelski, Tomasz; Strzalkowska, Agata; Rozwadowska, Anna; Gutowska, Dorota

    2013-04-01

    We would like to describe the results of a research campaign aimed at the studies of aerosol optical properties in the regions of the open Baltic Sea as well as coastal areas. During the campaign we carried out simultaneous measurements of aerosol optical depth at 4 stations with use of the hand-held Microtops II sunphotometers. The studies were complemented with the MODIS aerosol data. In order to obtain the full picture of the aerosol situation over the study area we added air mass back-trajectories at various altitudes and wind fields. Such complex information facilitated the proper conclusions regarding aerosol optical depth and Angstroem exponent for the four locations and discussion of the changes of aerosol properties with distance and meteorological factors. We show that Microtops II sunphotometers are reliable instruments for field campaigns. They are easy to operate and provide good quality results. Acknowledgements: The support for this study was provided by the project Satellite Monitoring of the Baltic Sea Environment - SatBałtyk founded by European Union through European Regional Development Fund contract No. POIG 01.01.02-22-011/09.

  3. [Aerosol optical properties during different air-pollution episodes over Beijing].

    Science.gov (United States)

    Shi, Chan-Zhen; Yu, Xing-Na; Zhou, Bin; Xiang, Lei; Nie, Hao-Hao

    2013-11-01

    Based on the 2005-2011 data from Aerosol Robotic Network (AERONET), this study conducted analysis on aerosol optical properties over Beijing during different air-pollution episodes (biomass burning, CNY firework, dust storm). The aerosol optical depth (AOD) showed notable increases in the air-pollution episodes while the AOD (at 440 nm) during dust storm was 4. 91, 4. 07 and 2.65 times higher as background, biomass burning and firework aerosols. AOD along with Angstrom exponent (alpha) can be used to determine the aerosol types. The dust aerosol had the highest AOD and the lowest alpha. The alpha value of firework (1.09) was smaller than biomass burning (1.21) and background (1.27), indicating that coarse particles were dominant in the former type. Higher AOD of burnings (than background) can be attributed to the optical extinction capability of black carbon aerosol. The single scattering albedo (SSA) was insensitive to wavelength. The SSA value of dust (0.934) was higher than background (0.878), biomass burning (0.921) and firework (0.905). Additionally, the extremely large SSA of burnings here maybe was caused by the aging smoke, hygroscopic growth and so on. The peak radius of aerosol volume size distributions were 0.1-0.2 microm and 2.24 -3.85 microm in clear and polluted conditions. The value of volume concentration ratio between coarse and fine particles was in the order of clear background (1.04), biomass burning (1.10), CNY firework (1.91) and dust storm (4.96) episode.

  4. Seasonal differences in the vertical profiles of aerosol optical properties over rural Oklahoma

    Directory of Open Access Journals (Sweden)

    E. Andrews

    2011-10-01

    Full Text Available A small airplane made 597 aerosol optical property (light absorption and light scattering vertical profile measurements over a rural Oklahoma site between March 2000 and December 2007. The aerosol profiles obtained during these 8 yr of measurements suggest significant seasonal differences in aerosol loading (scattering and absorption. The highest amounts of scattering and absorbing aerosol are observed during the summer and the lowest loading occurs during the winter. The relative contribution of aerosol absorption is highest in the winter (i.e., single scattering albedo is lowest in winter, particularly aloft. Aerosol absorption generally decreased with altitude below ~1.5 km and then was relatively constant or decreased more gradually above that. Aerosol scattering decreased sharply with altitude below ~1.5 km but, unlike absorption, also decreased at higher altitudes, albeit less sharply. Scattering Ångström exponents suggest that the aerosol was dominated by sub-micron aerosol during the summer at all altitudes, but that larger particles were present, especially in the spring and winter above 1 km. The seasonal variability observed for aerosol loading is consistent with AERONET aerosol optical depth (AOD although the AOD values calculated from in situ adjusted to ambient conditions and matching wavelengths are up to a factor of two lower than AERONET AOD values depending on season. The column averaged single scattering albedo derived from in situ airplane measurements are similar in value to the AERONET single scattering albedo inversion product but the seasonal patterns are different – possibly a consequence of the strict constraints on obtaining single scattering albedo from AERONET data. A comparison of extinction Ångström exponent and asymmetry parameter from the airplane and AERONET platforms suggests similar seasonal variability with smaller particles observed in the summer and fall and larger particles observed in spring and

  5. Monitoring and tracking the trans-Pacific transport of aerosols using multi-satellite aerosol optical depth composites

    Science.gov (United States)

    Naeger, Aaron R.; Gupta, Pawan; Zavodsky, Bradley T.; McGrath, Kevin M.

    2016-06-01

    The primary goal of this study was to generate a near-real time (NRT) aerosol optical depth (AOD) product capable of providing a comprehensive understanding of the aerosol spatial distribution over the Pacific Ocean, in order to better monitor and track the trans-Pacific transport of aerosols. Therefore, we developed a NRT product that takes advantage of observations from both low-earth orbiting and geostationary satellites. In particular, we utilize AOD products from the Moderate Resolution Imaging Spectroradiometer (MODIS) and Suomi National Polar-orbiting Partnership (NPP) Visible Infrared Imaging Radiometer Suite (VIIRS) satellites. Then, we combine these AOD products with our own retrieval algorithms developed for the NOAA Geostationary Operational Environmental Satellite (GOES-15) and Japan Meteorological Agency (JMA) Multi-functional Transport Satellite (MTSAT-2) to generate a NRT daily AOD composite product. We present examples of the daily AOD composite product for a case study of trans-Pacific transport of Asian pollution and dust aerosols in mid-March 2014. Overall, the new product successfully tracks this aerosol plume during its trans-Pacific transport to the west coast of North America as the frequent geostationary observations lead to a greater coverage of cloud-free AOD retrievals equatorward of about 35° N, while the polar-orbiting satellites provide a greater coverage of AOD poleward of 35° N. However, we note several areas across the domain of interest from Asia to North America where the GOES-15 and MTSAT-2 retrieval algorithms can introduce significant uncertainties into the new product.

  6. Variations in optical properties of aerosols on monsoon seasonal change and estimation of aerosol optical depth using ground-based meteorological and air quality data

    Directory of Open Access Journals (Sweden)

    F. Tan

    2014-07-01

    Full Text Available In this study, the optical properties of aerosols in Penang, Malaysia were analyzed for four monsoonal seasons (northeast monsoon, pre-monsoon, southwest monsoon, and post-monsoon based on data from the AErosol RObotic NETwork (AERONET from February 2012 to November 2013. The aerosol distribution patterns in Penang for each monsoonal period were quantitatively identified according to the scattering plots of the aerosol optical depth (AOD against the Angstrom exponent. A modified algorithm based on the prototype model of Tan et al. (2014a was proposed to predict the AOD data. Ground-based measurements (i.e., visibility and air pollutant index were used in the model as predictor data to retrieve the missing AOD data from AERONET because of frequent cloud formation in the equatorial region. The model coefficients were determined through multiple regression analysis using selected data set from in situ data. The predicted AOD of the model was generated based on the coefficients and compared against the measured data through standard statistical tests. The predicted AOD in the proposed model yielded a coefficient of determination R2 of 0.68. The corresponding percent mean relative error was less than 0.33% compared with the real data. The results revealed that the proposed model efficiently predicted the AOD data. Validation tests were performed on the model against selected LIDAR data and yielded good correspondence. The predicted AOD can beneficially monitor short- and long-term AOD and provide supplementary information in atmospheric corrections.

  7. Variations in optical properties of aerosols on monsoon seasonal change and estimation of aerosol optical depth using ground-based meteorological and air quality data

    Science.gov (United States)

    Tan, F.; Lim, H. S.; Abdullah, K.; Yoon, T. L.; Holben, B.

    2014-07-01

    In this study, the optical properties of aerosols in Penang, Malaysia were analyzed for four monsoonal seasons (northeast monsoon, pre-monsoon, southwest monsoon, and post-monsoon) based on data from the AErosol RObotic NETwork (AERONET) from February 2012 to November 2013. The aerosol distribution patterns in Penang for each monsoonal period were quantitatively identified according to the scattering plots of the aerosol optical depth (AOD) against the Angstrom exponent. A modified algorithm based on the prototype model of Tan et al. (2014a) was proposed to predict the AOD data. Ground-based measurements (i.e., visibility and air pollutant index) were used in the model as predictor data to retrieve the missing AOD data from AERONET because of frequent cloud formation in the equatorial region. The model coefficients were determined through multiple regression analysis using selected data set from in situ data. The predicted AOD of the model was generated based on the coefficients and compared against the measured data through standard statistical tests. The predicted AOD in the proposed model yielded a coefficient of determination R2 of 0.68. The corresponding percent mean relative error was less than 0.33% compared with the real data. The results revealed that the proposed model efficiently predicted the AOD data. Validation tests were performed on the model against selected LIDAR data and yielded good correspondence. The predicted AOD can beneficially monitor short- and long-term AOD and provide supplementary information in atmospheric corrections.

  8. Modelling the optical properties of aerosols in a chemical transport model

    Science.gov (United States)

    Andersson, E.; Kahnert, M.

    2015-12-01

    According to the IPCC fifth assessment report (2013), clouds and aerosols still contribute to the largest uncertainty when estimating and interpreting changes to the Earth's energy budget. Therefore, understanding the interaction between radiation and aerosols is both crucial for remote sensing observations and modelling the climate forcing arising from aerosols. Carbon particles are the largest contributor to the aerosol absorption of solar radiation, thereby enhancing the warming of the planet. Modelling the radiative properties of carbon particles is a hard task and involves many uncertainties arising from the difficulties of accounting for the morphologies and heterogeneous chemical composition of the particles. This study aims to compare two ways of modelling the optical properties of aerosols simulated by a chemical transport model. The first method models particle optical properties as homogeneous spheres and are externally mixed. This is a simple model that is particularly easy to use in data assimilation methods, since the optics model is linear. The second method involves a core-shell internal mixture of soot, where sulphate, nitrate, ammonia, organic carbon, sea salt, and water are contained in the shell. However, by contrast to previously used core-shell models, only part of the carbon is concentrated in the core, while the remaining part is homogeneously mixed with the shell. The chemical transport model (CTM) simulations are done regionally over Europe with the Multiple-scale Atmospheric Transport and CHemistry (MATCH) model, developed by the Swedish Meteorological and Hydrological Institute (SMHI). The MATCH model was run with both an aerosol dynamics module, called SALSA, and with a regular "bulk" approach, i.e., a mass transport model without aerosol dynamics. Two events from 2007 are used in the analysis, one with high (22/12-2007) and one with low (22/6-2007) levels of elemental carbon (EC) over Europe. The results of the study help to assess the

  9. Uncertainties in Carbonaceous Aerosol Emissions, Scavenging Parameterizations, and Optical Properties

    Science.gov (United States)

    Koch, D.; Bond, T.; Kinne, S.; Klimont, Z.; Sun, H.; van Aardenne, J.; van der Werf, G.

    2006-12-01

    Estimates of human influence on climate are especially hindered by poor constraint on the amount of anthropogenic carbonaceous aerosol absorption in the atmosphere. Coordination of observation and model analyses attempt to constrain particle absorption amount, however these are limited by uncertainties in aerosol emission estimates, model scavenging parameterization, aerosol size assumption, contributions from organic aerosol absorption, air concentration observational techniques and by sparsity of data coverage. We perform multiple simulations using GISS modelE and six present-day emission estimates for black carbon (BC) and organic carbon (OC) (Bond et al 2004 middle and upper estimates, IIASA, EDGAR, GFED v1 and v2); for one of these emissions we apply 4 different BC/OC scavenging parameterizations. The resulting concentrations will be compared with a new compilation of observed BC/OC concentrations. We then use these model concentrations, together with effective radius assumptions and estimates of OC absorption to calculate a range of carbonaceous aerosol absorption. We constrain the wavelength-dependent model τ- absorption with AERONET sun-photometer observations. We will discuss regions, seasons and emission sectors with greatest uncertainty, including those where observational constraint is lacking. We calculate the range of model radiative forcing from our simulations and discuss the degree to which it is constrained by observations.

  10. Optical properties of urban aerosols in the region Bratislava-Vienna—II: Comparisons and results

    Science.gov (United States)

    Kocifaj, M.; Horvath, H.; Hrvoľ, J.

    The optical and microphysical properties of aerosols in highly urbanized region Bratislava-Vienna were determined by means of ground-based optical methods during campaign in August and September 2004. Although both cities are close to each other forming a common metropolitan region, the features of their aerosol systems are distinct. While urban and suburban zones around Vienna have mostly a clean air without major influences of emissions from industry, Bratislava itself need to be classified as polluted area—the optical data collected in the measuring site are influenced mainly by Technické Sklo factory (NW positioned), Matador (SSE), Istrochem (ENE) and Slovnaft (ESE). In contrary to an observed smooth evolution of the aerosol system in Vienna, the aerosol environment is quite unstable in Bratislava and usually follows the day changes of the wind directions (as they correspond to the position of individual sources of pollution). The particle sizes in Bratislava are predominately larger compared to Vienna. A subsidiary mode within surface size distribution frequently occurs at radius about 0.7 μm in Bratislava but not in Vienna. The size distribution of airborne particles in Vienna is more dependent on relative humidity than in Bratislava. It suggests the particles in Bratislava are larger whenever, or non-deliquescent to a great extent. The spectral attenuation of solar radiation by aerosol particles shows a typical mode at λ≈0.4μm in Bratislava, which is not observed in the spectral aerosol extinction coefficient in Vienna. In Bratislava, the average aerosol optical thickness grows from morning hours to the evening, while an opposite effect can be observed in Vienna in the same time.

  11. Investigation the optical and radiative properties of aerosol vertical profile of boundary layer by lidar and ground based measurements

    Science.gov (United States)

    Chen, W.; Chou, C.; Lin, P.; Wang, S.

    2011-12-01

    The planetary boundary layer is the air layer near the ground directly affected by diurnal heat, moisture, aerosol, and cloud transfer to or from the surface. In the daytime solar radiation heats the surface, initiating thermal instability or convection. Whereas, the scattering and absorption of aerosols or clouds might decrease the surface radiation or heat atmosphere which induce feedbacks such as the enhanced stratification and change in relative humidity in the boundary layer. This study is aimed to understand the possible radiative effect of aerosols basing on ground based aerosol measurements and lidar installed in National Taiwan University in Taipei. The optical and radiative properties of aerosols are dominated by aerosol composition, particle size, hygroscopicity property, and shape. In this study, aerosol instruments including integrating nephelometer, open air nephelometer, aethalometer are applied to investigate the relationship between aerosol hygroscopicity properties and aerosol types. The aerosol hygroscopicity properties are further applied to investigate the effect of relative humidity on aerosol vertical profiles measured by a dual-wavelength and depolarization lidar. The possible radiative effect of aerosols are approached by vertical atmospheric extinction profiles measured by lidar. Calculated atmospheric and aerosol heating effects was compared with vertical meteorological parameters measured by radiosonde. The result shows light-absorbing aerosol has the potential to affect the stability of planetary boundary layer.

  12. A closure study of aerosol optical properties at a regional background mountainous site in Eastern China

    Energy Technology Data Exchange (ETDEWEB)

    Yuan, Liang [Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters, Nanjing University of Information Science & Technology, Nanjing 210044 (China); Key Laboratory for Aerosol–Cloud–Precipitation of China Meteorological Administration, School of Atmospheric Physics, Nanjing University of Information Science and Technology, Nanjing 210044 (China); Yin, Yan, E-mail: yinyan@nuist.edu.cn [Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters, Nanjing University of Information Science & Technology, Nanjing 210044 (China); Key Laboratory for Aerosol–Cloud–Precipitation of China Meteorological Administration, School of Atmospheric Physics, Nanjing University of Information Science and Technology, Nanjing 210044 (China); Xiao, Hui [Key Laboratory for Aerosol–Cloud–Precipitation of China Meteorological Administration, School of Atmospheric Physics, Nanjing University of Information Science and Technology, Nanjing 210044 (China); Yu, Xingna [Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters, Nanjing University of Information Science & Technology, Nanjing 210044 (China); Key Laboratory for Aerosol–Cloud–Precipitation of China Meteorological Administration, School of Atmospheric Physics, Nanjing University of Information Science and Technology, Nanjing 210044 (China); Hao, Jian; Chen, Kui [Key Laboratory for Aerosol–Cloud–Precipitation of China Meteorological Administration, School of Atmospheric Physics, Nanjing University of Information Science and Technology, Nanjing 210044 (China); and others

    2016-04-15

    There is a large uncertainty in evaluating the radiative forcing from aerosol–radiation and aerosol–cloud interactions due to the limited knowledge on aerosol properties. In-situ measurements of aerosol physical and chemical properties were carried out in 2012 at Mt. Huang (the Yellow Mountain), a continental background mountainous site in eastern China. An aerosol optical closure study was performed to verify the model outputs by using the measured aerosol optical properties, in which a spherical Mie model with assumptions of external and core–shell mixtures on the basis of a two-component optical aerosol model and high size-segregated element carbon (EC) ratio was applied. Although the spherical Mie model would underestimate the real scattering with increasing particle diameters, excellent agreement between the calculated and measured values was achieved with correlation coefficients above 0.98. Sensitivity experiments showed that the EC ratio had a negligible effect on the calculated scattering coefficient, but largely influenced the calculated absorption coefficient. The high size-segregated EC ratio averaged over the study period in the closure was enough to reconstruct the aerosol absorption coefficient in the Mie model, indicating EC size resolution was more important than time resolution in retrieving the absorption coefficient in the model. The uncertainties of calculated scattering and absorption coefficients due to the uncertainties of measurements and model assumptions yielded by a Monte Carlo simulation were ± 6% and ± 14% for external mixture and ± 9% and ± 31% for core–shell mixture, respectively. This study provided an insight into the inherent relationship between aerosol optical properties and physicochemical characteristics in eastern China, which could supplement the database of aerosol optical properties for background sites in eastern China and provide a method for regions with similar climate. - Highlights: • A spherical Mie

  13. Development of 2-D-MAX-DOAS and retrievals of trace gases and aerosols optical properties

    Science.gov (United States)

    Ortega, Ivan

    Air pollution is a major problem worldwide that adversely a_ects human health, impacts ecosystems and climate. In the atmosphere, there are hundreds of important compounds participating in complex atmospheric reactions linked to air quality and climate. Aerosols are relevant because they modify the radiation balance, a_ect clouds, and thus Earth albedo. The amount of aerosol is often characterized by the vertical integral through the entire height of the atmosphere of the logarithm fraction of incident light that is extinguished called Aerosol Optical Depth (AOD). The AOD at 550 nm (AOD550) over land is 0.19 (multi annual global mean), and that over oceans is 0.13. About 43 % of the Earth surface shows AOD550 smaller than 0.1. There is a need for measurement techniques that are optimized to measure aerosol optical properties under low AOD conditions, sample spatial scales that resemble satellite ground-pixels and atmospheric models, and help integrate remote sensing and in-situ observations to obtain optical closure on the effects of aerosols and trace gases in our changing environment. In this work, I present the recent development of the University of Colorado two dimensional (2-D) Multi-AXis Differential Optical Absorption Spectroscopy (2-D-MAX-DOAS) instrument to measure the azimuth and altitude distribution of trace gases and aerosol optical properties simultaneously with a single instrument. The instrument measures solar scattered light from any direction in the sky, including direct sun light in the hyperspectral domain. In Chapter 2, I describe the capabilities of 2-D measurements in the context of retrievals of azimuth distributions of nitrogen dioxide (NO2), formaldehyde (HCHO), and glyoxal (CHOCHO), which are precursors for tropospheric O3 and aerosols. The measurements were carried out during the Multi-Axis DOAS Comparison campaign for Aerosols and Trace gases (MAD-CAT) campaign in Mainz, Germany and show the ability to bridge spatial scales to

  14. CALIOP and AERONET Aerosol Optical Depth Comparisons: One Size Fits None

    Science.gov (United States)

    Omar, A. H.; Winker, D. M.; Tackett, J. L.; Giles, D. M.; Kar, J.; Liu, Z.; Vaughan, M. A.; Powell, K. A.; Trepte, C. R.

    2013-01-01

    We compare the aerosol optical depths (AOD) retrieved from backscatter measurements of the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) aboard the Cloud Aerosol Lidar Infrared Pathfinder Satellite Observations (CALIPSO) satellite with coincident Aerosol Robotic Network (AERONET) measurements. Overpass coincidence criteria of +/- 2 h and within a 40 km radius are satisfied at least once at 149 globally distributed AERONET sites from 2006 to 2010. Most data pairs (>80%) use AERONET measurements acquired +/- 30 min of the overpass. We examine the differences in AOD estimates between CALIOP and AERONET for various aerosol, environmental, and geographic conditions. Results show CALIOP AOD are lower than AERONET AOD especially at low optical depths as measured by AERONET (500 nm AOD0.1. Differences in AOD between CALIOP and AERONET are possibly due to cloud contamination, scene inhomogeneity, instrument view angle differences, CALIOP retrieval errors, and detection limits. Comparison of daytime to nighttime number of 5 km 60m (60m in the vertical) features detected by CALIOP show that there are 20% more aerosol features at night. We find that CALIPSO and AERONET do not agree on the cloudiness of scenes. Of the scenes that meet the above coincidence criteria, CALIPSO finds clouds in more than 45% of the coincident atmospheric columns AERONET classifies as clear.

  15. Investigation of aerosol distribution patterns and its optical properties at different time scale by using LIDAR system and AERONET

    Science.gov (United States)

    Tan, Fuyi; Khor, Wei Ying; Hee, Wan Shen; Choon, Yeap Eng; San, Lim Hwee; Abdullah, Khiruddin

    2015-04-01

    Atmospheric aerosol is a major health-impairment issue in Malaysia especially during southeast monsoon period (June-September) due to the active open burning activities. However, hazy days were an issue in Penang, Malaysia during March, 2014. Haze intruded Penang during March and lasted for a month except for the few days after rain. Rain water had washed out the aerosols from the atmosphere. Therefore, this study intends to analyse the aerosol profile and the optical properties of aerosol during this haze event and after rain. Meanwhile, several days after the haze event (during April, 2014) were also analyzed for comparison purposes. Additionally, the dominant aerosol type (i.e., dust, biomass burning, industrial and urban, marine, and mixed aerosol) during the study period was identified according to the scattering plots of the aerosol optical depth (AOD) against the Angstrom exponent.

  16. In-canopy gradients, composition, and sources of optically active aerosols over the Amazon forest

    Science.gov (United States)

    Guyon, P.; Graham, B.; Roberts, G. C.; Mayol-Bracero, O. L.; Andreae, M. O.; Artaxo, P.; Maenhaut, W.

    2003-04-01

    As part of the European contribution to the Large-Scale Biosphere-Atmosphere Experiment in Amazonia (LBA-EUSTACH), size-fractionated aerosol samples were collected at a primary rainforest site in the Brazilian Amazon during the wet and dry seasons. Daytime-nighttime segregated sampling was carried out at three different heights (above, within and below canopy level) on a 54 m meteorological tower. The samples were analyzed for up to 19 trace elements, equivalent black carbon (BCe) and mass concentrations. Additionally, measurements of scattering and absorption coefficients were performed. Absolute principal component analysis revealed that the wet and dry season aerosols contained the same three main aerosol components, namely a natural biogenic, a pyrogenic, and a soil dust component, but that these were present in different (absolute and relative) amounts. The elements related to biomass burning and soil dust generally exhibited highest concentrations above the canopy and during daytime, whilst forest-derived aerosol was more concentrated underneath the canopy and during nighttime. These variations can be largely attributed to daytime convective mixing and the formation of a shallow nocturnal boundary layer, along with the possibility of enhanced nighttime release of biogenic aerosol particles. All three components contributed significantly to light extinction, suggesting that, in addition to pyrogenic particles, biogenic and soil dust aerosols must be taken into account when modeling the physical and optical properties of aerosols in forested regions such the Amazon Basin.

  17. The Deconvolution of Aerosol Backscattered Optical Pulses to Obtain System-Independent Aerosol Signatures.

    Science.gov (United States)

    1981-06-01

    S. CONTRACT OR GRANT NUMBERI.) Dennis Mc~uire Michael/~Conner 2. PERFOMN ORGANIZATION NAME AND AOORESS I0. PROGRAM ELEMENT. PROJECT. TASKC Harry...tech- niques has shown that exellent results can be obtained in simple cases (where the aerosol is known to be uniformly distributed and to completely

  18. Physical and optical properties of aerosols over an urban location in Spain: seasonal and diurnal variability

    Directory of Open Access Journals (Sweden)

    H. Lyamani

    2010-01-01

    Full Text Available Measurements of aerosol optical properties and aerosol number size distribution obtained during the period from December 2005 to November 2007 at Granada, an urban site in south-eastern Spain, are analyzed. Large variations of the measured variables have been found, and related to variations in emissions sources and meteorological conditions. High values of aerosol absorption and scattering coefficients are obtained during winter and low values are measured during summer. This seasonal pattern in the surface aerosol optical properties is opposite to the seasonal cycle showed by columnar aerosol optical depth. The differences in the seasonal features of the surface and column-integrated data are related to seasonal variations in the aerosol vertical distribution, aerosol sources and boundary layer height. In winter the number density of "fine" particles (0.5s, presents an evident seasonal cycle with values of 1.8±0.2, 1.6±0.3, 1.3±0.3 and 1.4±0.3 in winter, spring, summer and autumn, respectively. This suggests the presence of a large fraction of submicron particles at the site, especially during winter. The aerosols measured in this study contain a large fraction of absorbing material as indicated by the average single-scattering albedo that has values of 0.65±0.07, 0.66±0.06, 0.70±0.06 and 0.73±0.06 in autumn, winter, spring and summer, respectively. The aerosol scattering albedo obtained in the surface boundary layer of Granada is below the critical value of 0.86 that determines the shift from cooling to warming. These results put in evidence the need of efforts to reduce absorbing particles (black carbon emissions to avoid the possible warming that would result from the

  19. Physical and optical properties of aerosols over an urban location in Spain: seasonal and diurnal variability

    Directory of Open Access Journals (Sweden)

    H. Lyamani

    2009-09-01

    Full Text Available Measurements of aerosol optical properties and aerosol number size distribution obtained during the period from December 2005 to November 2007 at Granada, an urban site in south-eastern Spain, are analyzed. Large variations of the measured variables have been found, and related to variations in emissions sources and meteorological conditions. High values of aerosol absorption and scattering coefficients are obtained during winter and low values are measured during summer. This seasonal pattern in the surface aerosol optical properties is opposite to the seasonal cycle showed by columnar aerosol optical depth. The differences in the seasonal features of the surface and column-integrated data are related to seasonal variations in the aerosol vertical distribution, aerosol sources and boundary layer height. In winter the number density of fine particles (0.5s, presents an evident seasonal cycle with values of 1.8±0.2, 1.6±0.3, 1.3±0.3 and 1.4±0.3 in winter, spring, summer and autumn, respectively. This suggests the presence of a large fraction of submicron particles at the site, especially during winter. Urban aerosols in Granada contain a large fraction of absorbing material as indicated by the average single-scattering albedo that has values of 0.65±0.07, 0.66±0.06, 0.70±0.06 and 0.73±0.06 in autumn, winter, spring and summer, respectively. The aerosol scattering albedo obtained in the surface boundary layer of Granada is below the critical value of 0.86 that determines the shift from cooling to warming. These results put in evidence the need of efforts to reduce absorbing particles (black carbon emissions to avoid the possible warming that would result from the reductions of

  20. Empirical estimates of CCN from aerosol optical properties at four remote sites

    Directory of Open Access Journals (Sweden)

    A. Jefferson

    2010-07-01

    Full Text Available This study presents an empirical method to estimate the CCN concentration as a function of percent supersaturation. The aerosol optical properties, backscatter fraction and single scatter albedo, function as proxies for the aerosol size and composition in a power law relationship to CCN. This method is tested at four sites with aged aerosol: SGP (Oklahoma, USA, FKB (Black Forest, Germany, HFE (Hefei, China and GRW (Graciosa, Azores. Each site represents a different aerosol type and thus demonstrates the method robustness and limitations. Good agreement was found between the calculated and measured CCN with slopes between 0.81 and 1.03 and correlation coefficients (r2 values between 0.59 and 0.67. The fit quality declined at low CCN concentrations.

  1. Aerosol characterizaton in El Paso-Juarez airshed using optical methods

    Science.gov (United States)

    Esparza, Angel Eduardo

    2011-12-01

    The assessment and characterization of atmospheric aerosols and their optical properties are of great significance for several applications such as air pollution studies, atmospheric visibility, remote sensing of the atmosphere, and impacts on climate change. Decades ago, the interest in atmospheric aerosols was primarily for visibility impairment problems; however, recently interest has intensified with efforts to quantify the optical properties of aerosols, especially because of the uncertainties surrounding the role of aerosols in climate change. The main objective of the optical characterization of aerosols is to understand their properties. These properties are determined by the aerosols' chemical composition, size, shape and concentration. The general purpose of this research was to contribute to a better characterization of the aerosols present in the Paso del Norte Basin. This study permits an alternative approach in the understanding of air pollution for this zone by analyzing the predominant components and their contributions to the local environment. This dissertation work had three primary objectives, in which all three are intertwined by the general purpose of the aerosol characterization in the Paso del Norte region. The first objective was to retrieve the columnar aerosol size distribution for two different cases (clean and polluted scenarios) at each season (spring, summer, fall and winter) of the year 2009. In this project, instruments placed in buildings within the University of Texas at El Paso (UTEP) as well as a monitoring site (CAMS 12) from the Texas Commission on Environmental Quality (TCEQ) provided the measurements that delimited the aerosol size distribution calculated by our model, the Environmental Physics Inverse Reconstruction (EPIRM) model. The purpose of this objective was to provide an alternate method of quantifying and size-allocating aerosols in situ, by using the optical properties of the aerosols and inversely reconstruct and

  2. Spatial Variability of AERONET Aerosol Optical Properties and Satellite Data in South Korea during NASA DRAGON-Asia Campaign.

    Science.gov (United States)

    Lee, Hyung Joo; Son, Youn-Suk

    2016-04-05

    We investigated spatial variability in aerosol optical properties, including aerosol optical depth (AOD), fine-mode fraction (FMF), and single scattering albedo (SSA), observed at 21 Aerosol Robotic Network (AERONET) sites and satellite remote sensing data in South Korea during the spring of 2012. These dense AERONET networks established in a National Aeronautics and Space Administration (NASA) field campaign enabled us to examine the spatially detailed aerosol size distribution and composition as well as aerosol levels. The springtime particle air quality was characterized by high background aerosol levels and high contributions of coarse-mode aerosols to total aerosols. We found that between-site correlations and coefficient of divergence for AOD and FMF strongly relied on the distance between sites, particularly in the south-north direction. Higher AOD was related to higher population density and lower distance from highways, and the aerosol size distribution and composition reflected source-specific characteristics. The ratios of satellite NO2 to AOD, which indicate the relative contributions of local combustion sources to aerosol levels, represented higher local contributions in metropolitan Seoul and Pusan. Our study demonstrates that the aerosol levels were determined by both local and regional pollution and that the relative contributions of these pollutions to aerosols generated spatial heterogeneity in the particle air quality.

  3. Measurements and estimation of the columnar optical depth of tropospheric aerosols in the UV spectral region

    Directory of Open Access Journals (Sweden)

    V. E. Cachorro

    Full Text Available We report values of the columnar tropospheric aerosol optical depth at UV wavelengths based on experimental measurements of the direct spectral irradiances carried out by a commercial spectroradiometer (Li1800 of Licor company covering the range from 300–1100 nm at two stations with different climate characteristics in Spain. The first station is located in a rural site in north central Spain with continental climate. The data extend from March to the end of October of 1995. The other station is a coastal site in the Gulf of Cádiz (southwest Spain of maritime climate type. This study is mainly focused on the capability of estimating aerosol optical depth values in the UV region based on the extracted information in the visible and near infrared ranges. A first method has been used based on the Ångström turbidity parameters. However, since this method requires detailed spectral information, a second method has also been used, based on the correlation between wavelengths. A correlation has been established between the experimental aerosol optical depth values at 350 nm and 500 nm wavelengths. Although the type of aerosol seems to be the key factor that determines the quality of these estimations, the evaluation of the associated error is necessary to know the behaviour of these estimations in each area of study.

    Key words. Atmospheric composition and structure (aerosols and particles; transmission and scattering of radiation; troposphere – composition and chemistry

  4. Microphysical properties of transported biomass burning aerosols in coastal regions, and application to improving retrievals of aerosol optical depth from SeaWiFS data

    Science.gov (United States)

    Sayer, A. M.; Hsu, N. C.; Bettenhausen, C.

    2013-05-01

    Due to the limited measurement capabilities of heritage and current spaceborne passive imaging radiometers, algorithms for the retrieval of aerosol optical depth (AOD) and related quantities must make assumptions relating to aerosol microphysical properties and surface reflectance. Over the ocean, surface reflectance can be relatively well-modelled, but knowledge of aerosol properties can remain elusive. Several field campaigns and many studies have examined the microphysical properties of biomass burning (smoke) aerosol. However, these largely focus on properties over land and near to the source regions. In coastal and open-ocean regions the properties of transported smoke may differ, due to factors such as aerosol aging, wet/dry deposition, and mixture with other aerosol sources (e.g. influence of maritime, pollution, or mineral dust aerosols). Hence, models based on near-source aerosol observations may be less representative of such transported smoke aerosols, introducing additional uncertainty into satellite retrievals of aerosol properties. This study examines case studies of transported smoke from select globally-distributed coastal and island Aerosol Robotic Network (AERONET) sites. These are used to inform improved models for over-ocean transported smoke aerosol for AOD retrievals from the Sea-viewing Wide Field-of-view Sensor (SeaWiFS). These models are used in an updated version of the SeaWiFS Ocean Aerosol Retrieval (SOAR) algorithm, which has been combined with the Deep Blue algorithm over land to create a 13-year (1997-2010) high-quality record of AOD over land and ocean. Applying these algorithms to other sensors will enable the creation of a long-term global climate data record of spectral AOD.

  5. Aerosol optical properties determined from sky-radiometer over Loess Plateau of Northwest China

    Directory of Open Access Journals (Sweden)

    Y. Liu

    2011-08-01

    Full Text Available The aerosol optical properties and their associated radiative forcing are retrieved from sky-radiometer and surface solar radiation data collected over the Semi-Arid Climate and Environment Observatory of Lanzhou University (SACOL for the period of March to May (MAM 2009. The result shows that the seasonal mean aerosol optical depth (AOD at 500 nm in MAM is 0.4. The single scattering albedo (SSA at 500 nm in MAM at SACOL fluctuates significantly ranging from 0.82 to 0.97. The averaged value of SSA there for background aerosol is 0.92 in MAM, while it is smaller (0.89 during the dust event outbreak period. The smaller SSA can be interpreted as the result of larger particles during dust events. The averaged asymmetry factor (ASY at 500 nm during dust event period is 0.81, which is much larger than 0.68 of background aerosols. The averaged shortwave radiative effect of the aerosols during dust event period in MAM is −6.25, −86.33 and 80.08 wm−2, respectively, at the top of the atmosphere (TOA, surface and in the atmosphere. The aerosols heat the atmosphere during dust event period by up to 2 K day−1 (daily averaged, which is 67 % larger than the heating (1.2 K day−1 of background aerosols. The significant heating effect in the atmosphere of the aerosols during dust event is determined by larger AOD and smaller SSA.

  6. Monsoonal variations in aerosol optical properties and estimation of aerosol optical depth using ground-based meteorological and air quality data in Peninsular Malaysia

    Science.gov (United States)

    Tan, F.; Lim, H. S.; Abdullah, K.; Yoon, T. L.; Holben, B.

    2015-04-01

    Obtaining continuous aerosol-optical-depth (AOD) measurements is a difficult task due to the cloud-cover problem. With the main motivation of overcoming this problem, an AOD-predicting model is proposed. In this study, the optical properties of aerosols in Penang, Malaysia were analyzed for four monsoonal seasons (northeast monsoon, pre-monsoon, southwest monsoon, and post-monsoon) based on data from the AErosol RObotic NETwork (AERONET) from February 2012 to November 2013. The aerosol distribution patterns in Penang for each monsoonal period were quantitatively identified according to the scattering plots of the Ångström exponent against the AOD. A new empirical algorithm was proposed to predict the AOD data. Ground-based measurements (i.e., visibility and air pollutant index) were used in the model as predictor data to retrieve the missing AOD data from AERONET due to frequent cloud formation in the equatorial region. The model coefficients were determined through multiple regression analysis using selected data set from in situ data. The calibrated model coefficients have a coefficient of determination, R2, of 0.72. The predicted AOD of the model was generated based on these calibrated coefficients and compared against the measured data through standard statistical tests, yielding a R2 of 0.68 as validation accuracy. The error in weighted mean absolute percentage error (wMAPE) was less than 0.40% compared with the real data. The results revealed that the proposed model efficiently predicted the AOD data. Performance of our model was compared against selected LIDAR data to yield good correspondence. The predicted AOD can enhance measured short- and long-term AOD and provide supplementary information for climatological studies and monitoring aerosol variation.

  7. Effects of data assimilation on the global aerosol key optical properties simulations

    Science.gov (United States)

    Yin, Xiaomei; Dai, Tie; Schutgens, Nick A. J.; Goto, Daisuke; Nakajima, Teruyuki; Shi, Guangyu

    2016-09-01

    We present the one month results of global aerosol optical properties for April 2006, using the Spectral Radiation Transport Model for Aerosol Species (SPRINTARS) coupled with the Non-hydrostatic ICosahedral Atmospheric Model (NICAM), by assimilating Moderate Resolution Imaging Spectroradiometer (MODIS) aerosol optical depth (AOD) with Local Ensemble Transform Kalman Filter (LETKF). The simulated AOD, Ångström Exponent (AE) and single scattering albedo (SSA) are validated by independent Aerosol Robotic Network (AERONET) observations over the global sites. The data assimilation has the strongest positive effect on the AOD simulation and slight positive influences on the AE and SSA simulations. For the time-averaged globally spatial distribution, the data assimilation increases the model skill score (S) of AOD, AE, and SSA from 0.55, 0.92, and 0.75 to 0.79, 0.94, and 0.80, respectively. Over the North Africa (NAF) and Middle East region where the aerosol composition is simple (mainly dust), the simulated AODs are best improved by the data assimilation, indicating the assimilation correctly modifies the wrong dust burdens caused by the uncertainties of the dust emission parameterization. Assimilation also improves the simulation of the temporal variations of the aerosol optical properties over the AERONET sites, with improved S at 60 (62%), 45 (55%) and 11 (50%) of 97, 82 and 22 sites for AOD, AE and SSA. By analyzing AOD and AE at five selected sites with best S improvement, this study further indicates that the assimilation can reproduce short duration events and ratios between fine and coarse aerosols more accurately.

  8. Optical properties of urban aerosols in the region Bratislava-Vienna I. Methods and tests

    Science.gov (United States)

    Kocifaj, M.; Horvath, H.; Jovanović, O.; Gangl, M.

    Aerosol optical data obtained by means of ground-based methods are applied to determine microphysical properties of aerosols in the atmosphere of Vienna-city. The measured aerosol extinction coefficient σA serves as a source of information on the ambient aerosols. A large database of extinction efficiency factors for a set of irregularly shaped as well as the spherical particles of various sizes is pre-calculated and employed in the inversion procedure. The assumed particle models differ in chemical composition and are representative for most typical aerosol systems in the urban atmospheres. All database records are taken into a regularization scheme to solve the inverse problem for aerosol size distribution using measured extinction data. In addition, subsidiary data on spectral sky radiance are successfully incorporated into the mathematical model to retrieve the information on aerosol effective refractive index in the visible. As for Vienna, the aerosol extinction is a decreasing function of wavelength in visible spectrum—it indicates the predominance of sub-micrometer-sized particles in the atmosphere. The surface distribution function s( r)=d S/d r of aerosol particles customarily peaks at radii r≈0.2-0.3 μm, while the volume distribution function v( r)=d V/d r˜ rs( r) has a mode at radii about 0.3-0.4 μm. Analysing size distributions d V/d log( r) for irregularly shaped particles it is shown that the daily profile of this function is smoothly evolving and almost typically accounts for a first mode at radii between 0.8 and 0.9 μm.

  9. Observations of rapid aerosol optical depth enhancements in the vicinity of polluted cumulus clouds

    Science.gov (United States)

    Eck, T. F.; Holben, B. N.; Reid, J. S.; Arola, A.; Ferrare, R. A.; Hostetler, C. A.; Crumeyrolle, S. N.; Berkoff, T. A.; Welton, E. J.; Lolli, S.; Lyapustin, A.; Wang, Y.; Schafer, J. S.; Giles, D. M.; Anderson, B. E.; Thornhill, K. L.; Minnis, P.; Pickering, K. E.; Loughner, C. P.; Smirnov, A.; Sinyuk, A.

    2014-11-01

    During the July 2011 Deriving Information on Surface conditions from Column and Vertically Resolved Observations Relevant to Air Quality (DISCOVER-AQ) field experiment in Maryland, significant enhancements in Aerosol Robotic Network (AERONET) sun-sky radiometer measured aerosol optical depth (AOD) were observed in the immediate vicinity of non-precipitating cumulus clouds on some days. Both measured Ångström exponents and aerosol size distribution retrievals made before, during and after cumulus development often suggest little change in fine mode particle size; therefore, implying possible new particle formation in addition to cloud processing and humidification of existing particles. In addition to sun-sky radiometer measurements of large enhancements of fine mode AOD, lidar measurements made from both ground-based and aircraft-based instruments during the experiment also measured large increases in aerosol signal at altitudes associated with the presence of fair weather cumulus clouds. These data show modifications of the aerosol vertical profile as a result of the aerosol enhancements at and below cloud altitudes. The airborne lidar data were utilized to estimate the spatial extent of these aerosol enhancements, finding increased AOD, backscatter and extinction out to 2.5 km distance from the cloud edge. Furthermore, in situ measurements made from aircraft vertical profiles over an AERONET site during the experiment also showed large increases in aerosol scattering and aerosol volume after cloud formation as compared to before. The 15-year AERONET database of AOD measurements at the Goddard Space Flight Center (GSFC), Maryland site, was investigated in order to obtain a climatological perspective of this phenomenon of AOD enhancement. Analysis of the diurnal cycle of AOD in summer showed significant increases in AOD from morning to late afternoon, corresponding to the diurnal cycle of cumulus development.

  10. Spatio-temporal variability of satellite derived aerosol optical thickness and ground measurements over East China

    Science.gov (United States)

    Meng, Fei; Shi, Tongguang

    2016-04-01

    Two-year records of Visible Infrared Imaging Radiometer Suite (VIIRS) Intermediate Product (IP) data on the aerosol optical thickness (AOT) at 550 nm were evaluated by comparing them with sun-sky radiometer measurements from the Chinese sun hazemeter network (CSHNET) and the aerosol robotic network (AERONET). The monthly and seasonal variations in the aerosol optical properties over eastern China were then investigated using collocated VIIRS IP data and CSHNET and AERONET measurements.Results show that the performances of the current VIIRS IP AOT retrievals at the provisional stage were consistent with ground measurements. Similar characteristics of seasonal and monthly variations were found among the measurements, though the observational methodologies were different, showing maxima in the summer and spring and minima in the winter and autumn.

  11. Intercomparison of aerosol optical parameters from WALI and R-MAN510 aerosol Raman lidars in the framework of HyMeX campaign

    Science.gov (United States)

    Boytard, Mai-Lan; Royer, Philippe; Chazette, Patrick; Shang, Xiaoxia; Marnas, Fabien; Totems, Julien; Bizard, Anthony; Bennai, Baya; Sauvage, Laurent

    2013-04-01

    The HyMeX program (Hydrological cycle in Mediterranean eXperiment) aims at improving our understanding of hydrological cycle in the Mediterranen and at a better quantification and forecast of high-impact weather events in numerical weather prediction models. The first Special Observation Period (SOP1) took place in September/October 2012. During this period two aerosol Raman lidars have been deployed at Menorca Island (Spain) : one Water-vapor and Aerosol Raman LIdar (WALI) operated by LSCE/CEA (Laboratoire des Sciences du Climat et de l'Environnement/Commissariat à l'Energie Atomique) and one aerosol Raman and dual-polarization lidar (R-Man510) developed and commercialized by LEOSPHERE company. Both lidars have been continuously running during the campaign and have provided information on aerosol and cloud optical properties under various atmospheric conditions (maritime background aerosols, dust events, cirrus clouds...). We will present here the results of intercomparisons between R-Man510, and WALI aerosol lidar systems and collocated sunphotometer measurements. Limitations and uncertainties on the retrieval of extinction coefficients, depolarization ratio, aerosol optical depths and detection of atmospheric structures (planetary boundary layer height, aerosol/cloud layers) will be discussed according atmospheric conditions. The results will also be compared with theoretical uncertainty assessed with direct/inverse model of lidar profiles.

  12. An operational retrieval algorithm for determining aerosol optical properties in the ultraviolet

    Science.gov (United States)

    Taylor, Thomas E.; L'Ecuyer, Tristan S.; Slusser, James R.; Stephens, Graeme L.; Goering, Christian D.

    2008-02-01

    This paper describes a number of practical considerations concerning the optimization and operational implementation of an algorithm used to characterize the optical properties of aerosols across part of the ultraviolet (UV) spectrum. The algorithm estimates values of aerosol optical depth (AOD) and aerosol single scattering albedo (SSA) at seven wavelengths in the UV, as well as total column ozone (TOC) and wavelength-independent asymmetry factor (g) using direct and diffuse irradiances measured with a UV multifilter rotating shadowband radiometer (UV-MFRSR). A novel method for cloud screening the irradiance data set is introduced, as well as several improvements and optimizations to the retrieval scheme which yield a more realistic physical model for the inversion and increase the efficiency of the algorithm. Introduction of a wavelength-dependent retrieval error budget generated from rigorous forward model analysis as well as broadened covariances on the a priori values of AOD, SSA and g and tightened covariances of TOC allows sufficient retrieval sensitivity and resolution to obtain unique solutions of aerosol optical properties as demonstrated by synthetic retrievals. Analysis of a cloud screened data set (May 2003) from Panther Junction, Texas, demonstrates that the algorithm produces realistic values of the optical properties that compare favorably with pseudo-independent methods for AOD, TOC and calculated Ångstrom exponents. Retrieval errors of all parameters (except TOC) are shown to be negatively correlated to AOD, while the Shannon information content is positively correlated, indicating that retrieval skill improves with increasing atmospheric turbidity. When implemented operationally on more than thirty instruments in the Ultraviolet Monitoring and Research Program's (UVMRP) network, this retrieval algorithm will provide a comprehensive and internally consistent climatology of ground-based aerosol properties in the UV spectral range that can be used

  13. Atmospheric aerosol optical parameters, deep convective clouds and hail occurence - a correlation study

    Science.gov (United States)

    Talianu, Camelia; Andrei, Simona; Toanca, Florica; Stefan, Sabina

    2016-04-01

    Among the severe weather phenomena, whose frequency has increased during the past two decades, hail represents a major threat not only for agriculture but also for other economical fields. Generally, hail are produced in deep convective clouds, developed in an unstable environment. Recent studies have emphasized that besides the state of the atmosphere, the atmospheric composition is also very important. The presence of fine aerosols in atmosphere could have a high impact on nucleation processes, initiating the occurrence of cloud droplets, ice crystals and possibly the occurrence of graupel and/or hail. The presence of aerosols in the atmosphere, correlated with specific atmospheric conditions, could be predictors of the occurrence of hail events. The atmospheric investigation using multiwavelength Lidar systems can offer relevant information regarding the presence of aerosols, identified using their optical properties, and can distinguish between spherical and non-spherical shape, and liquid and solid phase of these aerosols. The aim of this study is to analyse the correlations between the presence and the properties of aerosols in atmosphere, and the production of hail events in a convective environment, using extensive and intensive optical parameters computed from lidar and ceilometer aerosols measurements. From these correlations, we try to evaluate if these aerosols can be taken into consideration as predictors for hail formation. The study has been carried out in Magurele - Romania (44.35N, 26.03E, 93m ASL) using two collocated remote sensing systems: a Raman Lidar (RALI) placed at the Romanian Atmospheric 3D Observatory and a ceilometer CL31 placed at the nearby Faculty of Physics, University of Bucharest. To evaluate the atmospheric conditions, radio sounding and satellite images were used. The period analysed was May 1st - July 15th, 2015, as the May - July period is climatologically favorable for deep convection events. Two hail events have been

  14. Investigating relationships between aerosol optical depth and cloud fraction using satellite, aerosol reanalysis and general circulation model data

    Directory of Open Access Journals (Sweden)

    B. S. Grandey

    2013-03-01

    Full Text Available Strong positive relationships between cloud fraction (fc and aerosol optical depth (τ have been reported. Data retrieved from the MODerate resolution Imaging Spectroradiometer (MODIS instrument show positive fc–τ relationships across most of the globe. A global mean fc increase of approximately 0.2 between low and high τ conditions is found for both ocean and land. However, these relationships are not necessarily due to cloud–aerosol interactions. Using state-of-the-art Monitoring Atmospheric Composition and Climate (MACC reanalysis-forecast τ data, which should be less affected by retrieval artefacts, it is demonstrated that a large part of the observed fc–τ signal may be due to cloud contamination of satellite-retrieved τ. For longer MACC forecast time steps of 24 h, which likely contain less cloud contamination, some negative fc–τ relationships are found. The global mean fc increase between low and high τ conditions is reduced to 0.1, suggesting that cloud contamination may account for approximately one half of the satellite-retrieved increase in fc. ECHAM5-HAM general circulation model (GCM simulations further demonstrate that positive fc–τ relationships may arise due to covariation with relative humidity. Widespread negative simulated fc–τ relationships in the tropics are shown to arise due to scavenging of aerosol by convective precipitation. Wet scavenging events are likely poorly sampled in satellite-retrieved data, because the properties of aerosol below clouds cannot be retrieved. Quantifying the role of wet scavenging, and assessing GCM representations of this important process, remains a challenge for future observational studies of aerosol–cloud–precipitation interactions.

  15. Optical closure for an aerosol column: Method, accuracy, and inferable properties applied to a biomass-burning aerosol and its radiative forcing

    Science.gov (United States)

    Fiebig, Markus; Petzold, Andreas; Wandinger, Ulla; Wendisch, Manfred; Kiemle, Christoph; Stifter, Armin; Ebert, Martin; Rother, Tom; Leiterer, Ulrich

    2002-11-01

    During the Lindenberg Aerosol Characterization Experiment (LACE 98), airborne measurements of aerosol size distribution, fine-particle concentration, particle absorption coefficient, backscatter coefficient, depolarization, and chemical composition as well as ground-based measurements of spectral particle optical depth and of spectral backscatter and extinction coefficients were performed in the aerosol column above Lindenberg, Germany. We compare the measured optical parameters with calculations from the size distributions, which assume the aerosol to consist of sulfuric acid near the tropopause and mixtures of ammonium sulfate and soot in the remaining column. We obtain closure to within 25% for the optical depth of a column, which includes a biomass-burning aerosol of North American origin, and infer a soot volume fraction of 35% for this aerosol. Assuming spheroidal particles of prolate shape and the average aspect ratio of the particles to be 1.3 in the biomass-burning aerosol layer, the calculated depolarization agrees with the lidar measurement, whereas comparing the spectral backscatter coefficient shows the soot to be externally mixed with the nonabsorbing particles. With the two-stream approximation, we estimate the local, instantaneous, cloud-free radiative forcing of the biomass-burning aerosol at the tropopause to -5.8 W/m2 with a corresponding optical depth of 0.09 at 710 nm wavelength and solar zenith angle of 56°. The radiative forcing for the biomass-burning aerosol is as sensitive to a change in state of mixture, either external or internal, as to a change in surface albedo, ocean to coniferous forest.

  16. Evaluation of methods to determine the spectral variations of aerosol optical thickness

    Digital Repository Service at National Institute of Oceanography (India)

    Suresh, T.; Talaulikar, M.; Rodrigues, A.; Desa, E.; Chauhan, P.

    The methods used to derive spectral variations of aerosol optical thickness, AOT are evaluated. For our analysis we have used the AOT measured using a hand held sunphotometer at the coastal station on the west coast of India, Dona-Paula, Goa...

  17. LIDAR Measurements of the Vertical Distribution of Aerosol Optical and Physical Properties over Central Asia

    Science.gov (United States)

    The vertical structure of aerosol optical and physical properties was measured by Lidar in Eastern Kyrgyzstan, Central Asia, from June 2008 to May 2009. Lidar measurements were supplemented with surface-based measurements of PM2.5 and PM10 mass and chemical ...

  18. Comparisons of LASE, aircraft, and satellite measurements of aerosol optical properties and water vapor during TARFOX

    NARCIS (Netherlands)

    Ferrare, R.; Ismail, S.; Browell, E.; Brackett, V.; Kooi, S.; Clayton, M.; Hobbs, P.V.; Hartley, S.; Veefkind, J.P.; Russell, P.; Livingston, J.; Tanré, D.; Hignett, P.

    2000-01-01

    We examine aerosol extinction and optical thickness from the Lidar Atmospheric Sensing Experiment (LASE), the in situ nephelometer and absorption photometer on the University of Washington C-131A aircraft, and the NASA Ames Airborne Tracking Sun Photometer (AATS-6) on the C-131A measured during the

  19. Retrieval of aerosol optical properties from OMI radiances using a multiwavelength algorithm : Application to Western Europe

    NARCIS (Netherlands)

    Curier, R.L.; Veefkind, J.P.; Braak, R.; Veihelmann, B.; Torres, O.; Leeuw, G. de

    2008-01-01

    The Ozone Monitoring Instrument (OMI) multiwavelength algorithm has been developed to retrieve aerosol optical depth using OMI-measured reflectance at the top of the atmosphere. This algorithm was further developed by using surface reflectance data from a field campaign in Cabauw (The Netherlands),

  20. LIDAR Measurements of the Vertical Distribution of Aerosol Optical and Physical Properties over Central Asia

    Science.gov (United States)

    The vertical structure of aerosol optical and physical properties was measured by Lidar in Eastern Kyrgyzstan, Central Asia, from June 2008 to May 2009. Lidar measurements were supplemented with surface-based measurements of PM2.5 and PM10 mass and chemical ...

  1. Latitudinal variations of aerosol optical parameters over South Africa based on MISR satellite data

    CSIR Research Space (South Africa)

    Tesfaye M

    2010-09-01

    Full Text Available The latitudunal variation of the relative weight size distribution and optical properties of aerosols over South Africa is presented here. The study uses 10-years of Multi-angle Imaging SpectroRadiometer (MISR) satellite data, collected over South...

  2. Aerosol optical thickness retrieval over land and water using SCIAMACHY/GOME data

    NARCIS (Netherlands)

    Kusmierczyk-Michulec, J.; Leeuw, G. de

    2005-01-01

    An algorithm for the retrieval of the aerosol optical thickness over land and over water from SCIAMACHY (SCanning Imaging Absorption SpectroMeter for Atmospheric ChartographY) is presented. Because calibrated data are not yet available for the SCIAMACHY channels used by the algorithm, the concepts w

  3. Comparisons of LASE, aircraft, and satellite measurements of aerosol optical properties and water vapor during TARFOX

    NARCIS (Netherlands)

    Ferrare, R.; Ismail, S.; Browell, E.; Brackett, V.; Kooi, S.; Clayton, M.; Hobbs, P.V.; Hartley, S.; Veefkind, J.P.; Russell, P.; Livingston, J.; Tanré, D.; Hignett, P.

    2000-01-01

    We examine aerosol extinction and optical thickness from the Lidar Atmospheric Sensing Experiment (LASE), the in situ nephelometer and absorption photometer on the University of Washington C-131A aircraft, and the NASA Ames Airborne Tracking Sun Photometer (AATS-6) on the C-131A measured during the

  4. Optical characteristics of biomass burning aerosols over Southeastern Europe determined from UV-Raman lidar measurements

    Directory of Open Access Journals (Sweden)

    V. Amiridis

    2008-10-01

    Full Text Available The influence of smoke on the aerosol loading in the free troposphere over Thessaloniki, Greece is examined in this paper. Ten cases during 2001–2005 were identified when very high aerosol optical depth values in the free troposphere were observed with a UV-Raman lidar. Particle dispersion modeling (FLEXPART and satellite hot spot fire detection (ATSR showed that these high free tropospheric aerosol optical depths are mainly attributed to the advection of smoke plumes from biomass burning regions over Thessaloniki. The biomass burning regions were found to extend across Russia in the latitudinal belt between 45° N–55° N, as well as in Eastern Europe (Baltic countries, Western Russia, Belarus, and the Ukraine. The highest frequency of agricultural fires occurred during the summer season (mainly in August. The data collected allowed the optical characterization of the smoke aerosols that arrived over Greece, where limited information has so far been available. Two-wavelength backscatter lidar measurements showed that the backscatter-related Ångström exponent ranged between 0.5 and 2.4 indicating a variety of particle sizes. UV-Raman lidar measurements showed that for smoke particles the extinction to backscatter ratios varied between 40 sr for small particles to 100 sr for large particles. Dispersion model estimations of the carbon monoxide tracer concentration profiles for smoke particles indicate that the variability of the optical parameters is a function of the age of the smoke plumes.

  5. Empirical Relationship between particulate matter and Aerosol Optical Depth over Northern Tien-Shan, Central Asia

    Science.gov (United States)

    Measurements were obtained at two sites in northern Tien-Shan in Central Asia during a 1-year period beginning July 2008 to examine the statistical relationship between aerosol optical depth (AOD) and of fine [PM2.5, particles less than 2.5 μm aerodynamic diameter (AD)] and coars...

  6. Characterizing Aerosol Distributions and Optical Properties Using the NASA Langley High Spectral Resolution Lidar

    Energy Technology Data Exchange (ETDEWEB)

    Hostetler, Chris; Ferrare, Richard

    2013-02-14

    The objective of this project was to provide vertically and horizontally resolved data on aerosol optical properties to assess and ultimately improve how models represent these aerosol properties and their impacts on atmospheric radiation. The approach was to deploy the NASA Langley Airborne High Spectral Resolution Lidar (HSRL) and other synergistic remote sensors on DOE Atmospheric Science Research (ASR) sponsored airborne field campaigns and synergistic field campaigns sponsored by other agencies to remotely measure aerosol backscattering, extinction, and optical thickness profiles. Synergistic sensors included a nadir-viewing digital camera for context imagery, and, later in the project, the NASA Goddard Institute for Space Studies (GISS) Research Scanning Polarimeter (RSP). The information from the remote sensing instruments was used to map the horizontal and vertical distribution of aerosol properties and type. The retrieved lidar parameters include profiles of aerosol extinction, backscatter, depolarization, and optical depth. Products produced in subsequent analyses included aerosol mixed layer height, aerosol type, and the partition of aerosol optical depth by type. The lidar products provided vertical context for in situ and remote sensing measurements from other airborne and ground-based platforms employed in the field campaigns and was used to assess the predictions of transport models. Also, the measurements provide a data base for future evaluation of techniques to combine active (lidar) and passive (polarimeter) measurements in advanced retrieval schemes to remotely characterize aerosol microphysical properties. The project was initiated as a 3-year project starting 1 January 2005. It was later awarded continuation funding for another 3 years (i.e., through 31 December 2010) followed by a 1-year no-cost extension (through 31 December 2011). This project supported logistical and flight costs of the NASA sensors on a dedicated aircraft, the subsequent

  7. Optical characteristics of aerosol trioxide dialuminum at the IR wavelength range

    Science.gov (United States)

    Voitsekhovskaya, O. K.; Shefer, O. V.; Kashirskii, D. E.

    2015-11-01

    In this work, a numerical study of the transmission function, extinction coefficient, scattering coefficient, and absorption coefficient of the aerosol generated by the jet engine emissions was performed. Analyzing the calculation results of the IR optical characteristics of anthropogenic emissions containing the dialuminum trioxide was carried out. The spectral features of the optical characteristics of the medium caused by the average size, concentration and complex refractive index of the particles were illustrated.

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

    Directory of Open Access Journals (Sweden)

    E. Giannakaki

    2010-05-01

    Full Text Available 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.

  9. Four dimensional variational data assimilation of species-resolved satellite-retrieved aerosol optical thickness

    Science.gov (United States)

    Nieradzik, Lars Peter; Elbern, Hendrik

    2010-05-01

    Aerosols play an increasingly important role in atmospheric modelling. They have a strong influence on the radiative transfer balance and a significant impact on human health. Their origin is various and so are its effects. Most of the measurement sites in Europe only account for an integrated aerosol load PMx (Particulate Matter of less than x μm in diameter) which does not give any qualitative information on the composition of the aerosol. Since very different constituents like mineral dust derived from desert storms and sea salt contribute to PMx it is necessary to make aerosol forcasts not only of load, but also type resolved. The source of information chosen for this study is the aerosol retrieval system SYNAER (SYNergetic AErosol Retrieval) from DLR-DFD that retrieves BLAOT (Boundary Layer Aerosol Optical Thickness) making use of both AATSR/SCIAMACHY and AVHRR/GOME-2 data respectively. Its strengths are a large spatial coverage, near real-time availability, and the classification of five intrinsic aerosol species, namely water-solubles, water-insolubles, soot, sea salt, and mineral dust which are furthermore size resolved in terms of modes. A widely known technique to enhance forecast skills of CTMs (Chemistry-Transport-Models) by ingesting in-situ and, especially, remote-sensing measurements is the method of four dimensional variational data assimilation (4Dvar). The EURAD-IM (EURopean Air pollution Dispersion - Inverse Model), containing a full adjoint gas-phase model, has been expanded with an adjoint of the MADE (Modal Aerosol Dynamics model for Europe) to optimise initial and boundary values for aerosols using 4Dvar. A forward and an adjoint radiative transfer model is driven by the EURAD-IM as mapping between BLAOT and internal aerosol species. Furthermore, its condensation scheme has been bypassed by an HDMR (High-Dimensional-Model-Representation) to ensure differentiability, and a time saving online NMC-module for the generation of the background

  10. Partitioning aerosol optical depth between the boundary layer and the free troposphere

    Science.gov (United States)

    Bourgeois, Quentin; Ekman, Annica; Krejci, Radovan; Devasthale, Abhay; Renard, Jean-Baptiste

    2017-04-01

    Aerosols are short-lived (about a week) compounds in the atmosphere due to the efficient removal by dry and wet deposition in the boundary layer (BL) where a majority of the emission sources are located. As a consequence, most of the aerosol mass should be found in the BL and the aerosol optical depth (AOD) integrated over the atmospheric column should be dominated by the BL contribution. As a consequence, BL aerosols would most likely have the largest climate effect. However, aerosols advected to the free troposphere (FT) have a much longer residence time (typically a few weeks) than those in the BL, potentially inducing a more long-term effect on climate. Light-absorbing aerosols may in addition have an enhanced absorption, and thereby climate warming effect, if they are located above low-level reflective clouds. Light-absorbing aerosols above clouds may also modify below cloud formation and transformation. In this study, the global AOD has been retrieved using satellite observations from CALIOP (Cloud-Aerosol Lidar with Orthogonal Polarization) over a nine-year period (2007-2015) and partitioned between the BL and FT using BL heights obtained from the ERA-Interim re-analysis data. The results show that the vertical distribution of AOD does not follow the diurnal cycle of the BL but remains similar between day and night highlighting the role of a residual layer during night. The BL and FT contribute 71% and 29%, respectively, to the global AOD during daytime. The FT AOD contribution is larger in the tropics than at mid-latitudes which indicates that convective transport largely controls the vertical profile of aerosols, and the FT AOD contribution over oceans is governed by neighboring continents. According to the CALIOP aerosol classification, dust and smoke particles are the main aerosol types transported into the FT. Overall, the study shows that the fraction of AOD in the FT - and thus potentially located above low-level clouds - is substantial and should

  11. Optical properties and cross-sections of biological aerosols

    Science.gov (United States)

    Thrush, E.; Brown, D. M.; Salciccioli, N.; Gomes, J.; Brown, A.; Siegrist, K.; Thomas, M. E.; Boggs, N. T.; Carter, C. C.

    2010-04-01

    There is an urgent need to develop standoff sensing of biological agents in aerosolized clouds. In support of the Joint Biological Standoff Detection System (JBSDS) program, lidar systems have been a dominant technology and have shown significant capability in field tests conducted in the Joint Ambient Breeze Tunnel (JABT) at Dugway Proving Ground (DPG). The release of biological agents in the open air is forbidden. Therefore, indirect methods must be developed to determine agent cross-sections in order to validate sensor against biological agents. A method has been developed that begins with laboratory measurements of thin films and liquid suspensions of biological material to obtain the complex index of refraction from the ultraviolet (UV) to the long wave infrared (LWIR). Using that result and the aerosols' particle size distribution as inputs to Mie calculations yields the backscatter and extinction cross-sections as a function of wavelength. Recent efforts to model field measurements from the UV to the IR have been successful. Measurements with aerodynamic and geometric particle sizers show evidence of particle clustering. Backscatter simulations of these aerosols show these clustered particles dominate the aerosol backscatter and depolarization signals. In addition, these large particles create spectral signatures in the backscatter signal due to material absorption. Spectral signatures from the UV to the IR have been observed in simulations of field releases. This method has been demonstrated for a variety of biological simulant materials such as Ovalbumin (OV), Erwinia (EH), Bacillus atrophaeus (BG) and male specific bacteriophage (MS2). These spectral signatures may offer new methods for biological discrimination for both stand-off sensing and point detection systems.

  12. AERONET-based models of smoke-dominated aerosol near source regions and transported over oceans, and implications for satellite retrievals of aerosol optical depth

    Science.gov (United States)

    Sayer, A. M.; Hsu, N. C.; Eck, T. F.; Smirnov, A.; Holben, B. N.

    2014-10-01

    Smoke aerosols from biomass burning are an important component of the global aerosol system. Analysis of Aerosol Robotic Network (AERONET) retrievals of aerosol microphysical/optical parameters at 10 sites reveals variety between biomass burning aerosols in different global source regions, in terms of aerosol particle size and single scatter albedo (SSA). Case studies of smoke observed at coastal/island AERONET sites also mostly lie within the range of variability at the near-source sites. Differences between sites tend to be larger than variability at an individual site, although optical properties for some sites in different regions can be quite similar. Across the sites, typical midvisible SSA ranges from ~ 0.95-0.97 (sites dominated by boreal forest or peat burning, typically with larger fine-mode particle radius and spread) to ~ 0.88-0.9 (sites most influenced by grass, shrub, or crop burning, typically smaller fine-mode particle radius and spread). The tropical forest site Alta Floresta (Brazil) is closer to this second category, although with intermediate SSA ~ 0.92. The strongest absorption is seen in southern African savannah at Mongu (Zambia), with average midvisible SSA ~ 0.85. Sites with stronger absorption also tend to have stronger spectral gradients in SSA, becoming more absorbing at longer wavelengths. Microphysical/optical models are presented in detail so as to facilitate their use in radiative transfer calculations, including extension to UV (ultraviolet) wavelengths, and lidar ratios. One intended application is to serve as candidate optical models for use in satellite aerosol optical depth (AOD) retrieval algorithms. The models presently adopted by these algorithms over ocean often have insufficient absorption (i.e. too high SSA) to represent these biomass burning aerosols. The underestimates in satellite-retrieved AOD in smoke outflow regions, which have important consequences for applications of these satellite data sets, are consistent with

  13. Aerosols optical properties in Titan's Detached Haze Layer

    Science.gov (United States)

    Seignovert, Benoit; Rannou, Pascal; Lavvas, Panayotis; West, Robert

    2016-10-01

    Titan's Detached Haze Layer (DHL) was first observed in 1983 by Rages and Pollack during the Voyager 2 is a consistent spherical haze feature surrounding Titan's upper atmosphere and detached from the main haze. Since 2005, the Imaging Science Subsystem (ISS) instrument on board the Cassini mission performs a continuous survey of the Titan's atmosphere and confirmed its persistence at 500 km up to the equinox (2009) before its drop and disappearance in 2012 (West et al. 2011). Previous analyses showed, that this layer corresponds to the transition area between small spherical aerosols and large fractal aggregates and play a key role in the aerosols formation in Titan's atmosphere (Rannou et al. 2000, Lavvas et al. 2009, Cours et al. 2011).In this talk we will present the UV photometric analyses based on radiative transfer inversion to retrieve aerosols particles properties in the DHL (bulk and monomer radius and local density) performed on ISS observations taken from 2005 to 2007.References:- Rages and Pollach, Icarus 55 (1983)- West, et al., Icarus 38 (2011)- Rannou, et al., Icarus 147 (2000)- Lavvas, et al., Icarus 201 (2009)- Cours, et al., ApJ Lett. 741 (2015)

  14. Comparison between CARIBIC aerosol samples analysed by accelerator-based methods and optical particle counter measurements

    Directory of Open Access Journals (Sweden)

    B. G. Martinsson

    2014-04-01

    Full Text Available Inter-comparison of results from two kinds of aerosol systems in the CARIBIC (Civil Aircraft for the Regular Investigation of the atmosphere Based on an Instrument Container passenger aircraft based observatory, operating during intercontinental flights at 9–12 km altitude, is presented. Aerosol from the lowermost stratosphere (LMS, the extra-tropical upper troposphere (UT and the tropical mid troposphere (MT were investigated. Aerosol particle volume concentration measured with an optical particle counter (OPC is compared with analytical results of the sum of masses of all major and several minor constituents from aerosol samples collected with an impactor. Analyses were undertaken with accelerator-based methods particle-induced X-ray emission (PIXE and particle elastic scattering analysis (PESA. Data from 48 flights during one year are used, leading to a total of 106 individual comparisons. The ratios of the particle volume from the OPC and the total mass from the analyses were in 84% within a relatively narrow interval. Data points outside this interval are connected with inlet-related effects in clouds, large variability in aerosol composition, particle size distribution effects and some cases of non-ideal sampling. Overall, the comparison of these two CARIBIC measurements based on vastly different methods show good agreement, implying that the chemical and size information can be combined in studies of the MT/UT/LMS aerosol.

  15. Aerosol Characteristics at a High Altitude Location in Central Himalayas: Optical Properties and Radiative Forcing

    CERN Document Server

    Pant, P; Dumka, U C; Sagar, R; Satheesh, S K; Moorthy, K K; Sagar, Ram

    2006-01-01

    Collocated measurements of the mass concentrations of aerosol black carbon (BC) and composite aerosols near the surface were carried out along with spectral aerosol optical depths (AODs) from a high altitude station, Manora Peak in Central Himalayas, during a comprehensive aerosol field campaign in December 2004. Despite being a pristine location in the Shivalik Ranges of Central Himalayas, and having a monthly mean AOD (at 500 nm) of 0.059 $\\pm$ 0.033 (typical to this site), total suspended particulate (TSP) concentration was in the range 15 - 40 micro g m^(-3) (mean value 27.1 $\\pm$ 8.3 micro g m^(-3)). Interestingly, aerosol BC had a mean concentration of 1.36 $\\pm$ 0.99 micro g m^(-3), contributed to ~5.0 $\\pm$ 1.3 % to the composite aerosol mass. This large abundance of BC is found to have linkages to the human activities in the adjoining valley and to the boundary layer dynamics. Consequently, the inferred single scattering albedo lies in the range of 0.87 to 0.94 (mean value 0.90 $\\pm$ 0.03), indicatin...

  16. Long-term observations of aerosol optical properties at Wuhan, an urban site in Central China

    Science.gov (United States)

    Wang, Lunche; Gong, Wei; Xia, Xiangao; Zhu, Jun; Li, Jun; Zhu, Zhongmin

    2015-01-01

    Aerosol optical properties including aerosol optical depth (AOD), Ångström exponent (α), single scattering albedo (SSA), aerosol size distribution and refractive index at urban Wuhan in Central China are investigated based on the measurements from a CIMEL sun-photometer during 2007-2013. AOD500 nm is found to be relatively high all year round and the highest value 1.52 occurs in June 2012 and the lowest (0.57) in November 2012. α shows a significant monthly variation, with the highest value in June 2010 (1.71) and the lowest value (0.78) in April 2012. Analysis of AOD and α frequencies indicate that this region is populated with fine-mode particles. Monthly variations of SSA for total, fine and coarse-mode particles are closely related to the aerosol hygroscopic growth, fossil fuel and biomass burning. The aerosol volume size distributions (bi-modal pattern) show distinct differences in particle radius for different seasons, the radius for fine-mode particles generally increase from spring to summer month, for example, the highest peak is around radius 0.15 μm in March, while the peak radius is around 0.25 μm in June. Finally, monthly statistics of real and imaginary parts of the complex refractive index are analyzed, the highest averages of real (1.50) and imaginary parts (0.0395) are found in spring and autumn, respectively at wavelength 440-1020 nm.

  17. The aerosol optical properties measurement by ground remote sensing in Zhejiang, China

    Science.gov (United States)

    Wang, Bin; Jiang, Hong; Chen, Jian; Jiang, Zishan; Yu, Shuquan; Ma, Yuandan

    2009-10-01

    The aerosol optical depth was affected by the chemical composition, the particle size and the shape of aerosol as well as the water vapor in the atmosphere; it is an important indicator for air pollution. The special and temporal characteristics of aerosol optical depth (AOD) was measured by CE318 sun-photometer, Angstrom wavelength exponent (Alpha) and the aerosol turbidity coefficient (β) were calculated in Ningbo, Lin'an and Qiandaohu of Zhejiang province from 2007 to 2008. We also analyzed the relationship between AOD and Angstrom wavelength exponent (Alpha) in these stations. The results show that there are different pattern of AOD in this gradient of urban and suburban region. Lin'an station had two peaks of AOD, but Ningbo and Qiandaohu stations had single peak of AOD in measurement year. The difference of AOD seasonal pattern exists in three sites. The Angstrom wavelength exponent (Alpha) analysis suggests that the aerosol sizes in three stations various from fine particle in autumn to coarse particle in spring. The seasonal patterns show that spring air pollution is serious, summer is relatively clean, and autumn and winter are relative serious in three stations.

  18. The regional distribution characteristics of aerosol optical depth over the Tibetan Plateau

    Science.gov (United States)

    Xu, Chao; Ma, Yaoming; You, Chao; Zhu, Zhikun

    2016-04-01

    The Tibetan Plateau (TP) is representative of typical clean atmospheric conditions. Aerosol optical depth (AOD) retrieved by Multi-angle Imaging SpectroRadiometer (MISR) is higher over Qaidam Basin than the rest of the TP all the year. Different monthly variation patterns of AOD are observed over the southern and northern TP, whereby the aerosol load is usually higher in the northern TP than in the southern part. The aerosol load over the northern part increases from April to June, peaking in May. The maximum concentration of aerosols over the southern TP occurs in July. Aerosols appear to be more easily transported to the main body of the TP across the northern edge rather than the southern edge. This is may be partly because the altitude is lower at the northern edge than that of the Himalayas located along the southern edge of the TP. Three-dimensional distributions of dust, polluted dust, polluted continental and smoke are also investigated based on Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) data. Dust is found to be the most prominent aerosol type on the TP, and other types of aerosols affect the atmospheric environment slightly. A dividing line of higher dust occurrence in the northern TP and lower dust occurrence in the southern TP can be observed clearly at altitude of 6-8 km above sea level, especially in spring and summer. This demarcation appears around 33-35°N in the middle of the plateau, and it is possibly associated with the high altitude terrain in the same geographic location. Comparisons of CALIPSO and MISR data show that the vertical dust occurrences are consistent with the spatial patterns of AOD. The different seasonal variation patterns between the northern and southern TP are primarily driven by atmospheric circulation, and are also related to the emission characteristics over the surrounding regions.

  19. Optical, physical and chemical characteristics of Australian Desert dust aerosols: results from a field experiment

    Directory of Open Access Journals (Sweden)

    M. D. Keywood

    2009-11-01

    Full Text Available Mineral dust is one of the major components of the world's aerosol mix, having a number of impacts within the Earth system. However, the climate forcing impact of mineral dust is currently poorly constrained, with even its sign uncertain. As Australian deserts are more reddish than those in the northern hemisphere, it is important to better understand the physical, chemical and optical properties of this important aerosol. We have investigated the properties of Australian desert dust at a site in SW Queensland, which is strongly influenced by both dust and biomass burning aerosol. Three years of ground-based monitoring of spectral optical thickness has provided a statistical picture of gross aerosol properties. In November 2006 we undertook a field campaign which collected 4 sets of size-resolved aerosol samples for laboratory analysis – both ion beam analysis and ion chromatography.

    The aerosol optical depth data showed a weak seasonal cycle with an annual mean of 0.06±0.03. The Angstrom coefficient showed a stronger cycle, indicating the influence of the winter-spring burning season in Australia's north. Size distribution inversions showed a bimodal character, with the coarse mode assumed to be mineral dust, and the fine mode a mixture of biomass burning and marine biogenic material. Ion Beam Analysis was used to determine the elemental composition of all filter samples, although elemental ratios were considered the most reliable output. Scatter plots showed that Fe, Al and Ti were well correlated with Si, and Co reasonably well correlated, with the Fe/Si ratio higher than the crustal average, as expected. Scatter plots for Ca, Mn and K against Si showed clear evidence of a second population, which in some cases could be identified with a particular sample day or size fraction. Ion Chromatography was used to quantify water soluble ions for 2 of our sample sets, showing the importance of marine influences on both fine (biogenic and

  20. Aerosol climatology over the Mexico City basin: Characterization of optical properties

    Science.gov (United States)

    Carabali, Giovanni; Estévez, Héctor Raúl; Valdés-Barrón, Mauro; Bonifaz-Alfonzo, Roberto; Riveros-Rosas, David; Velasco-Herrera, Víctor Manuel; Vázquez-Gálvez, Felipe Adrián

    2017-09-01

    Climatology of Aerosol Optical Depth (AOD), Single Scattering Albedo (SSA), and aerosol particle-size distribution were analyzed using a 15-year (1999-2014) dataset from AErosol RObotic NETwork (AERONET) observations over the Mexico City (MC) basin. The atmosphere over this site is dominated by two main aerosol types, represented by urban/industrial pollution and biomass-burning particles. Due to the specific meteorological conditions within the basin, seasons are usually classified into three as follows: Dry Winter (DW) (November-February); Dry Spring (DS) (March-April), and the RAiny season (RA) (May-October), which are mentioned throughout this article. Using a CIMEL sun photometer, we conducted continuous observations over the MC urban area from January 1999 to December 2014. Aerosol Optical Depth (AOD), Ångström exponent (α440-870), Single Scattering Albedo (SSA), and aerosol particle-size distribution were derived from the observational data. The overall mean AOD500 during the 1999-2014 period was 0.34 ± 0.07. The monthly mean AOD reached a maximal value of 0.49 in May and a minimal value of 0.27 in February and March. The average α440-870 value for the period studied was 1.50 ± 0.16. The monthly average of α440-870 reached a minimal value of 1.32 in August and a maximal value of 1.61 in May. Average SSA at 440 nm was 0.89 throughout the observation period, indicating that aerosols over Mexico City are composed mainly of absorptive particles. Concentrations of fine- and coarse-mode aerosols over MC were highest in DS season compared with other seasons, especially for particles with radii measuring between 0.1 and 0.2 μm. Results from the Spectral De-convolution Algorithm (SDA) show that fine-mode aerosols dominated AOD variability in MC. In the final part of this article, we present a classification of aerosols in MC by using the graphical method proposed by Gobbi et al. (2007), which is based on the combined analysis of α and its spectral curvature

  1. Aerosol optical and physical properties during winter monsoon pollution transport in an urban environment.

    Science.gov (United States)

    Verma, S; Bhanja, S N; Pani, S K; Misra, A

    2014-04-01

    We analysed aerosol optical and physical properties in an urban environment (Kolkata) during winter monsoon pollution transport from nearby and far-off regions. Prevailing meteorological conditions, viz. low temperature and wind speed, and a strong downdraft of air mass, indicated weak dispersion and inhibition of vertical mixing of aerosols. Spectral features of WinMon aerosol optical depth (AOD) showed larger variability (0.68-1.13) in monthly mean AOD at short-wavelength (SW) channels (0.34-0.5 μm) compared to that (0.28-0.37) at long-wavelength (LW) channels (0.87-1.02 μm), thereby indicating sensitivity of WinMon AOD to fine aerosol constituents and the predominant contribution from fine aerosol constituents to WinMon AOD. WinMon AOD at 0.5 μm (AOD 0. 5) and Angstrom parameter ( α) were 0.68-0.82 and 1.14-1.32, respectively, with their highest value in December. Consistent with inference from spectral features of AOD, surface aerosol loading was primarily constituted of fine aerosols (size 0.23-3 μm) which was 60-70 % of aerosol 10- μm (size 0.23-10 μm) concentration. Three distinct modes of aerosol distribution were obtained, with the highest WinMon concentration at a mass median diameter (MMD) of 0.3 μm during December, thereby indicating characteristics of primary contribution related to anthropogenic pollutants that were inferred to be mostly due to contribution from air mass originating in nearby region having predominant emissions from biofuel and fossil fuel combustion. A relatively higher contribution from aerosols in the upper atmospheric layers than at the surface to WinMon AOD was inferred during February compared to other months and was attributed to predominant contribution from open burning emissions arising from nearby and far-off regions. A comparison of ground-based measurements with Moderate Resolution Imaging Spectroradiometer (MODIS) data showed an underestimation of MODIS AOD and α values for most of the days. Discrepancy in

  2. Long term measurements of aerosol optical properties at a primary forest site in Amazonia

    Directory of Open Access Journals (Sweden)

    L. V. Rizzo

    2013-03-01

    Full Text Available A long term experiment was conducted in a primary forest area in Amazonia, with continuous in-situ measurements of aerosol optical properties between February 2008 and April 2011, comprising, to our knowledge, the longest database ever in the Amazon Basin. Two major classes of aerosol particles, with significantly different optical properties were identified: coarse mode predominant biogenic aerosols in the wet season (January–June, naturally released by the forest metabolism, and fine mode dominated biomass burning aerosols in the dry season (July–December, transported from regional fires. Dry particle median scattering coefficients at the wavelength of 550 nm increased from 6.3 Mm−1 to 22 Mm−1, whereas absorption at 637 nm increased from 0.5 Mm−1 to 2.8 Mm−1 from wet to dry season. Most of the scattering in the dry season was attributed to the predominance of fine mode (PM2 particles (40–80% of PM10 mass, while the enhanced absorption coefficients are attributed to the presence of light absorbing aerosols from biomass burning. As both scattering and absorption increased in the dry season, the single scattering albedo (SSA did not show a significant seasonal variability, in average 0.86 ± 0.08 at 637 nm for dry aerosols. Measured particle optical properties were used to estimate the aerosol forcing efficiency at the top of the atmosphere. Results indicate that in this primary forest site the radiative balance was dominated by the cloud cover, particularly in the wet season. Due to the high cloud fractions, the aerosol forcing efficiency absolute values were below −3.5 W m−2 in 70% of the wet season days and in 46% of the dry season days. Besides the seasonal variation, the influence of out-of-Basin aerosol sources was observed occasionally. Periods of influence of the Manaus urban plume were detected, characterized by a consistent increase on particle scattering (factor 2.5 and absorption coefficients (factor 5. Episodes of

  3. Measurements and estimation of the columnar optical depth of tropospheric aerosols in the UV spectral region

    Energy Technology Data Exchange (ETDEWEB)

    Cachorro, V.E.; Vergaz, R.; Martin, M.J.; Frutos, A.M. de [Grupo de Optica Atmosferica, Univ. de Valladolid (GOA-UVA), Valladolid (Spain); Vilaplana, J.M.; Morena, B. de la [Estacion de Sondeos Atmosfericos ESAT ' ' El Arenosillo' ' , INTA, Huelva (Spain)

    2002-04-01

    We report values of the columnar tropospheric aerosol optical depth at UV wavelengths based on experimental measurements of the direct spectral irradiances carried out by a commercial spectroradiometer (Li1800 of Licor company) covering the range from 300-1100 nm at two stations with different climate characteristics in Spain. The first station is located in a rural site in north central Spain with continental climate. The data extend from March to the end of October of 1995. The other station is a coastal site in the Gulf of Cadiz (southwest Spain) of maritime climate type. This study is mainly focused on the capability of estimating aerosol optical depth values in the UV region based on the extracted information in the visible and near infrared ranges. A first method has been used based on the Aangstroem turbidity parameters. However, since this method requires detailed spectral information, a second method has also been used, based on the correlation between wavelengths. A correlation has been established between the experimental aerosol optical depth values at 350 nm and 500 nm wavelengths. Although the type of aerosol seems to be the key factor that determines the quality of these estimations, the evaluation of the associated error is necessary to know the behavior of these estimations in each area of study. (orig.)

  4. Development and experimental evaluation of an optical sensor for aerosol particle characterization

    Energy Technology Data Exchange (ETDEWEB)

    Somesfalean, G.

    1998-03-01

    A sensor for individual aerosol particle characterization, based on a single-mode semiconductor laser coupled to an external cavity is presented. The light emitting semiconductor laser acts as a sensitive optical detector itself, and the whole system has the advantage of using conventional optical components and providing a compact set-up. Aerosol particles moving through the sensing volume, which is located in the external cavity of a semiconductor laser, scatter and absorb light. Thereby they act as small disturbances on the electromagnetic field inside the dynamic multi-cavity laser system. From the temporal variation of the output light intensity, information about the number, velocity, size, and refractive index of the aerosol particles can be derived. The diffracted light in the near-forward scattering direction is collected and Fourier-transformed by a lens, and subsequently imaged on a CCD camera. The recorded Fraunhofer diffraction pattern provides information about the projected area of the scattering particle, and can thus be used to determine the size and the shape of aerosol particles. The sensor has been tested on fibers which are of interest in the field of working environment monitoring. The recorded output intensity variation has been analysed, and the relationship between the shape and the size of each fibre, and the resulting scattering profiles has been investigated. A simple one-dimensional model for the optical feedback variation due to the light-particle interaction in the external cavity is also discussed 34 refs, 26 figs, 6 tabs

  5. Smartphone-Based Android app for Determining UVA Aerosol Optical Depth and Direct Solar Irradiances.

    Science.gov (United States)

    Igoe, Damien P; Parisi, Alfio; Carter, Brad

    2014-01-01

    This research describes the development and evaluation of the accuracy and precision of an Android app specifically designed, written and installed on a smartphone for detecting and quantifying incident solar UVA radiation and subsequently, aerosol optical depth at 340 and 380 nm. Earlier studies demonstrated that a smartphone image sensor can detect UVA radiation and the responsivity can be calibrated to measured direct solar irradiance. This current research provides the data collection, calibration, processing, calculations and display all on a smartphone. A very strong coefficient of determination of 0.98 was achieved when the digital response was recalibrated and compared to the Microtops sun photometer direct UVA irradiance observations. The mean percentage discrepancy for derived direct solar irradiance was only 4% and 6% for observations at 380 and 340 nm, respectively, lessening with decreasing solar zenith angle. An 8% mean percent difference discrepancy was observed when comparing aerosol optical depth, also decreasing as solar zenith angle decreases. The results indicate that a specifically designed Android app linking and using a smartphone image sensor, calendar and clock, with additional external narrow bandpass and neutral density filters can be used as a field sensor to evaluate both direct solar UVA irradiance and low aerosol optical depths for areas with low aerosol loads. © 2013 The American Society of Photobiology.

  6. Aerosol optical and microphysical retrievals from a hybrid multiwavelength lidar dataset – DISCOVER-AQ 2011

    Directory of Open Access Journals (Sweden)

    P. Sawamura

    2014-03-01

    Full Text Available Retrievals of aerosol microphysical properties (e.g. effective radius, volume and surface-area concentrations and aerosol optical properties (e.g. complex index of refraction and single scattering albedo were obtained from a hybrid multiwavelength lidar dataset for the first time. In July of 2011, in the Baltimore-Washington DC region, synergistic profiling of optical and microphysical properties of aerosols with both airborne in-situ and ground-based remote sensing systems was performed during the first deployment of DISCOVER-AQ. The hybrid multiwavelength lidar dataset combines elastic ground-based measurements at 355 nm with airborne High Spectral Resolution Lidar (HSRL measurements at 532 nm and elastic measurements at 1064 nm that were obtained less than 5 km apart of each other. This was the first study in which optical and microphysical retrievals from lidar were obtained during the day and directly compared to AERONET and in-situ measurements for 11 cases. Good agreement was observed between lidar and AERONET retrievals. Larger discrepancies were observed between lidar retrievals and in-situ measurements obtained by the aircraft and aerosol hygroscopic effects are believed to be the main factor of such discrepancies.

  7. Evaluation and application of passive and active optical remote sensing methods for the measurement of atmospheric aerosol properties

    Energy Technology Data Exchange (ETDEWEB)

    Mielonen, T.

    2010-07-01

    Atmospheric aerosol particles affect the atmosphere's radiation balance by scattering and absorbing sunlight. Moreover, the particles act as condensation nuclei for clouds and affect their reflectivity. In addition, aerosols have negative health effects and they reduce visibility. Aerosols are emitted into the atmosphere from both natural and anthropogenic sources. Different types of aerosols have different effects on the radiation balance, thus global monitoring and typing of aerosols is of vital importance. In this thesis, several remote sensing methods used in the measurement of atmospheric aerosols are evaluated. Remote sensing of aerosols can be done with active and passive instruments. Passive instruments measure radiation emitted by the sun and the Earth while active instruments have their own radiation source, for example a black body radiator or laser. The instruments utilized in these studies were sun photometers (PFR, Cimel), lidars (POLLYXT, CALIOP), transmissiometer (OLAF) and a spectroradiometer (MODIS). Retrieval results from spaceborne instruments (MODIS, CALIOP) were evaluated with ground based measurements (PFR, Cimel). In addition, effects of indicative aerosol model assumptions on the calculated radiative transfer were studied. Finally, aerosol particle mass at the ground level was approximated from satellite measurements and vertical profiles of aerosols measured with a lidar were analyzed. For the evaluation part, these studies show that the calculation of aerosol induced attenuation of radiation based on aerosol size distribution measurements is not a trivial task. In addition to dry aerosol size distribution, the effect of ambient relative humidity on the size distribution and the optical properties of the aerosols need to be known in order to achieve correct results from the calculations. Furthermore, the results suggest that aerosol size parameters retrieved from passive spaceborne measurements depend heavily on surgace reflectance

  8. Developing and diagnosing climate change indictors of regional aerosol optical properties

    Science.gov (United States)

    Sullivan, Ryan C.; Levy, Robert C.; da Silva, Arlindo M.; Pryor, Sara C.

    2017-04-01

    The US Global Change Research Program has developed climate indicators (CIs) to track changes in the physical, chemical, biological, and societal components of the climate system. Given the importance of atmospheric aerosol particles to clouds and radiative forcing, human mortality and morbidity, and biogeochemical cycles, we propose new aerosol particle CIs applicable to the US National Climate Assessment (NCA). Here we define these aerosol CIs and use them to quantify temporal trends in each NCA region. Furthermore, we use a synoptic classification (e.g., meteorological variables), and gas and particle emissions inventories to diagnose and attribute causes of observed changes. Our CIs are derived using output from the satellite-constrained Modern-Era Retrospective Analysis for Research and Application, Version 2 (MERRA-2) reanalysis. MERRA-2 provides estimates of column-integrated aerosol optical properties at 0.625° by 0.5° resolution, including aerosol optical depth (AOD), Ångström exponent (AE), and single scattering albedo (SSA), which are related to aerosol loading, relative particle size, and chemical composition, respectively. For each NCA region, and for each aerosol variable, we derive statistics that describe mean and extreme values, as well as two metrics (spatial autocorrelation and coherence) that describe the spatial scales of aerosol variability. Consistent with previous analyses of aerosol precursor emissions and near-surface fine aerosol mass concentrations in the US, analyses of our aerosol CIs show that since 2000, both mean and extreme AOD have decreased over most NCA regions. There are significant (α = 0.05, using the non-parametric Kendall's tau) decreases in AOD for the Northeast (NE), Southeast (SE), Midwest (MW), and lower Great Plains (GPl) regions, and notable but not significant decreases in the Southwest (SW). AOD has increased for the Northwest (NW; significant) and upper Great Plains (GPu; not significant). Over all regions

  9. Continuous measurements of Arctic boundary layer aerosol physical and optical properties

    Science.gov (United States)

    Asmi, E.; Kondratyev, V.; Brus, D.; Lihavainen, H.; Laurila, T. J.; Aurela, M.; Hatakka, J.; Viisanen, Y.; Reshetnikov, A.; Ivakhov, V.; Uttal, T.; Makshtas, A. P.

    2013-12-01

    The Arctic and northern boreal regions of Eurasia are experiencing rapid environmental changes due to pressures by human activities. The largest anthropogenic climate forcings are due to aerosol particles and greenhouse gases (GHGs). The Arctic environment is highly sensitive to changes in aerosol concentrations or composition, largely due to the high surface reflectance for the most part of the year. Concentrations of aerosols in winter and spring Arctic are affected by 'Arctic Haze', a phenomenon suggested to arise from the transport of pollutants from lower latitudes and further strengthened by the strong stratification of the Arctic wintertime atmosphere. Sources and transport patterns of aerosols into the Arctic are, however, not fully understood. In order to monitor the changes within the Arctic region, as well as to understand the sources and feedback mechanisms, direct measurements of aerosols within the Arctic are needed. So far, direct year-round observations have been inadequate especially within the Russian side of the Arctic. This is the reason why a new climate observatory was founded on the shore of the Arctic Ocean, in Tiksi, Russia. Tiksi meteorological observatory in northern Siberia (71_360N; 128_530E) has been operating since 1930s. Recently, it was upgraded and joint in the network of the IASOA, in the framework of the International Polar Year Activity project. The project is run in collaboration between National Oceanic and Atmospheric Administration (NOAA) with the support of the National Science Foundation (NSF), Roshydromet (AARI and MGO units), government of the Republic of Sakha (Yakutia) and the Finnish Meteorological Institute (FMI). The research activities of FMI in Tiksi include e.g. continuous long-term measurements of aerosol particle physical and optical properties. Measurements were initiated in summer 2010 and further extended in summer 2013. Together with the FMI measurements in Pallas GAW station in northern Finland since 1999

  10. MODIS Aerosol Optical Depth Bias Adjustment Using Machine Learning Algorithms

    Science.gov (United States)

    Albayrak, Arif; Wei, Jennifer; Petrenko, Maksym; Lary, David; Leptoukh, Gregory

    2011-01-01

    To monitor the earth atmosphere and its surface changes, satellite based instruments collect continuous data. While some of the data is directly used, some others such as aerosol properties are indirectly retrieved from the observation data. While retrieved variables (RV) form very powerful products, they don't come without obstacles. Different satellite viewing geometries, calibration issues, dynamically changing atmospheric and earth surface conditions, together with complex interactions between observed entities and their environment affect them greatly. This results in random and systematic errors in the final products.

  11. Comparing multiple model-derived aerosol optical properties to spatially collocated ground-based and satellite measurements

    Science.gov (United States)

    Ocko, Ilissa B.; Ginoux, Paul A.

    2017-04-01

    Anthropogenic aerosols are a key factor governing Earth's climate and play a central role in human-caused climate change. However, because of aerosols' complex physical, optical, and dynamical properties, aerosols are one of the most uncertain aspects of climate modeling. Fortunately, aerosol measurement networks over the past few decades have led to the establishment of long-term observations for numerous locations worldwide. Further, the availability of datasets from several different measurement techniques (such as ground-based and satellite instruments) can help scientists increasingly improve modeling efforts. This study explores the value of evaluating several model-simulated aerosol properties with data from spatially collocated instruments. We compare aerosol optical depth (AOD; total, scattering, and absorption), single-scattering albedo (SSA), Ångström exponent (α), and extinction vertical profiles in two prominent global climate models (Geophysical Fluid Dynamics Laboratory, GFDL, CM2.1 and CM3) to seasonal observations from collocated instruments (AErosol RObotic NETwork, AERONET, and Cloud-Aerosol Lidar with Orthogonal Polarization, CALIOP) at seven polluted and biomass burning regions worldwide. We find that a multi-parameter evaluation provides key insights on model biases, data from collocated instruments can reveal underlying aerosol-governing physics, column properties wash out important vertical distinctions, and improved models does not mean all aspects are improved. We conclude that it is important to make use of all available data (parameters and instruments) when evaluating aerosol properties derived by models.

  12. Characteristics of solid aerosols produced by optical catapulting studied by laser-induced breakdown spectroscopy

    Science.gov (United States)

    Fortes, F. J.; Laserna, J. J.

    2010-08-01

    Optical catapulting (OC) constitutes an effective method to transport small amounts of different materials in the form of a solid aerosol. In this report, laser-induced breakdown spectroscopy (LIBS) is used for the analysis of those aerosols produced by OC. For this purpose, materials were catapulted using a Q-switch Nd:YAG laser. A second Q-switch Nd:YAG laser was used for LIBS analysis of the ejected particles. Data processing of aerosols was conducted using conditional data analysis. Also, the standard deviation method was used for the qualitative identification of the ejected particles. Two modes of interaction in OC (OC with focused or defocused pulses) have been evaluated and discussed. LIBS demonstrates that the distribution (spreading) of the ejected particles along the propagation axis increased as a function of the interpulse delay time. The mass density and the thickness of the target also play an important role in OC-LIBS.

  13. Reconstruction of long-term aerosol optical depth series with sunshine duration records

    Science.gov (United States)

    Sanchez-Romero, A.; Sanchez-Lorenzo, A.; González, J. A.; Calbó, J.

    2016-02-01

    We report the suitability of sunshine duration (SD) records as a proxy for the reconstruction of atmospheric aerosol content, for which little information exists, especially prior to the 1980s. Specifically, we have treated cloudless summer days in 16 stations throughout Spain. For almost all sites we find statistically significant relationships between aerosol optical depth (AOD) and daily SD. The correlation coefficient presents a mean value of -0.72, and slope values of the linear regressions are within the range [-0.11, -0.36]. The relationships are used to generate AOD series back to the 1960s (to the 1920s for Madrid). These reconstructed series show an increase in AOD from the mid-1960s to the 1980s, followed by a decrease until the present, in agreement with changes in anthropogenic aerosol emissions and with opposite trends of solar irradiance. The method can be used to reconstruct AOD from the late nineteenth century at many stations worldwide.

  14. Preliminary investigations toward nighttime aerosol optical depth retrievals from the VIIRS day/night band

    Directory of Open Access Journals (Sweden)

    R. S. Johnson

    2013-01-01

    Full Text Available A great need exists for reliable nighttime aerosol products at high spatial and temporal resolution. In this concept demonstration study, using Visible/Infrared Imager/Radiometer Suite (VIIRS Day/Night Band (DNB observations on the Suomi National Polar-orbiting Partnership (NPP satellite, a new method is proposed for retrieving nighttime aerosol optical depth (τ using the contrast between regions with and without artificial surface lights. Evaluation of the retrieved τ values against daytime AERONET data from before and after the overpass of the VIIRS satellite over the Cape Verde, Grand Forks, and Alta Floresta AERONET stations yields a coefficient of determination (r2 of 0.71. This study suggests that the VIIRS DNB has the potential to provide useful nighttime aerosol detection and property retrievals.

  15. Automated Solar Tracking Spectrophotometer for Remote Sensing of Column Aerosol Optical Depth

    Science.gov (United States)

    Rainwater, B.; Arnott, W. P.; Moosmuller, H.; Karr, D.

    2012-12-01

    Aerosols in the atmosphere are poorly understood in terms of how they affect weather and climate. In an effort to advance this knowledge, an automated solar tracking spectrophotometer has been constructed to measure direct solar radiation from the ultraviolet to infrared. This instrument facilitates determination of solar irradiance, precipitable water, aerosol optical depth (AOD), and the Ångström turbidity exponent related to aerosol size distribution. Measurements with a CIMEL CE-318 sun photometer (part of the global NASA AERONET network) and a manual solar spectrophotometer are being used to evaluate the accuracy of our instrument. Upon successful evaluation, this instrument will provide a basis for research into spectral information that will supplement CIMEL measurements. Presented is the design of this instrument and measurement comparisons with the aforementioned instruments for the air above Reno, Nevada, USA.

  16. Implications of Satellite Swath Width on Global Aerosol Optical Thickness Statistics

    Science.gov (United States)

    Colarco, Peter; Kahn, Ralph; Remer, Lorraine; Levy, Robert; Welton, Ellsworth

    2012-01-01

    We assess the impact of swath width on the statistics of aerosol optical thickness (AOT) retrieved by satellite as inferred from observations made by the Moderate Resolution Imaging Spectroradiometer (MODIS). We sub-sample the year 2009 MODIS data from both the Terra and Aqua spacecraft along several candidate swaths of various widths. We find that due to spatial sampling there is an uncertainty of approximately 0.01 in the global, annual mean AOT. The sub-sampled monthly mean gridded AOT are within +/- 0.01 of the full swath AOT about 20% of the time for the narrow swath sub-samples, about 30% of the time for the moderate width sub-samples, and about 45% of the time for the widest swath considered. These results suggest that future aerosol satellite missions with only a narrow swath view may not sample the true AOT distribution sufficiently to reduce significantly the uncertainty in aerosol direct forcing of climate.

  17. Comparison of aerosol optical thickness retrieval from spectroradiometer measurements and from two radiative transfer models

    Energy Technology Data Exchange (ETDEWEB)

    Utrillas, M.P.; Martinez-Lozano, J.A.; Tena, F. [Universitat de Valencia, Dept. de Termodinamica, Valencia (Spain); Cachorro, V.E. [Universidad de Valladolid, Dept. de Fisica Aplicada 1, Valladolid (Spain); Hernandez, S. [Universidad de Valladolid, Dept. de Ingenieria Agricola y Forestal, Valladolid (Spain)

    2000-07-01

    The spectral values of the aerosol optical thickness {tau}{sub a{lambda}} in the 400-670 nm band have been determined from 500 solar direct irradiance spectra at normal incidence registered at Valencia (Spain) in the period from July 1993 to March 1997. The {tau}{sub a{lambda}} values obtained from experimental measurements have been compared with the boundary layer aerosol models implemented in the radiative transfer codes ZD-LOA and LOWTRAN 7. For the ZD-LOA code, the continental and maritime models have been considered and for the LOWTRAN 7 code the rural, maritime, urban and tropospheric models have been used. The obtained results show that the aerosol model that best represents the average turbidity of the boundary layer for the urban area of Valencia (Spain) is the continental model when the ZD-LOA code is used and the urban model when the LOWTRAN 7 code is used. (Author)

  18. Observations of Aerosol Optical Properties over 15 AERONET Sites in Southeast Asia

    Science.gov (United States)

    Chan, J. D.; Lagrosas, N.; Uy, S. N.; Holben, B. N.; Dorado, S.; Tobias, V., Jr.; Anh, N. X.; Po-Hsiung, L.; Janjai, S.; Salinas Cortijo, S. V.; Liew, S. C.; Lim, H. S.; Lestari, P.

    2014-12-01

    Mean column-integrated optical properties from ground sun photometers of the Aerosol Robotic Network (AERONET) are studied to provide an overview of the characteristics of aerosols over the region as part of the 7 Southeast Asian Studies (7-SEAS) mission. The 15 AERONET sites with the most available level 2 data products are selected from Thailand (Chiang Mai, Mukdahan, Songkhla and Silpakorn University), Malaysia (University Sains Malaysia), Laos (Vientiane), Vietnam (Bac Giang, Bac Lieu and Nha Trang), Taiwan (National Cheng Kung University and Central Weather Bureau Taipei), Singapore, Indonesia (Bandung) and the Philippines (Manila Observatory and Notre Dame of Marbel University). For all 15 sites, high angstrom exponent values (α>1) have been observed. Chiang Mai and USM have the highest mean Angstrom exponent indicating the dominance of fine particles that can be ascribed to biomass burning and urbanization. Sites with the lowest Angstrom exponent values include Bac Lieu (α=1.047) and Manila Observatory (α=1.021). From the average lognormal size distribution curves, Songkhla and NDMU show the smallest annual variation in the fine mode region, indicating the observed fine aerosols are local to the sites. The rest of the sites show high variation which could be due to large scale forcings (e.g., monsoons and biomass burnings) that affect aerosol properties in these sites. Both high and low single scattering albedo at 440 nm (ω0440) values are found in sites located in major urban areas. Silpakorn University, Manila Observatory and Vientiane have all mean ω0440 0.94. The discrepancy in ω0 suggests different types of major emission sources present in urban areas. The absorptivity of urban aerosols can vary depending on the strength of traffic emissions, types of fuel combusted and automobile engines used, and the effect of biomass burning aerosols during the dry season. High aerosol optical depth values (τa550 > 0.4) are mainly found over inland sites

  19. Optical and radiative properties of aerosols over Abu Dhabi in the United Arab Emirates

    Science.gov (United States)

    Beegum, S. Naseema; Romdhane, Haifa Ben; Ali, Mohammed Tauha; Armstrong, Peter; Ghedira, Hosni

    2016-12-01

    The present study is on the aerosol optical and radiative properties in the short-wave radiation and its climate implications at the arid city of Abu Dhabi (24.42 ∘N, 54.61 ∘E, 4.5 m MSL), in the United Arab Emirates. The direct aerosol radiative forcings (ARF) in the short-wave region at the top (TOA) and bottom of the atmosphere (BOA) are estimated using a hybrid approach, making use of discrete ordinate radiative transfer method in conjunction with the short-wave flux and spectral aerosol optical depth (AOD) measurements, over a period of 3 years (June 2012-July 2015), at Abu Dhabi located at the south-west coast of the Arabian Gulf. The inferred microphysical properties of aerosols at the measurement site indicate strong seasonal variations from the dominance of coarse mode mineral dust aerosols during spring (March-May) and summer (June-September), to the abundance of fine/accumulation mode aerosols mainly from combustion of fossil-fuel and bio-fuel during autumn (October-November) and winter (December-February) seasons. The monthly mean diurnally averaged ARF at the BOA (TOA) varies from -13.2 Wm-2 (˜-0.96 Wm-2) in November to -39.4 Wm-2 (-11.4 Wm-2) in August with higher magnitudes of the forcing values during spring/summer seasons and lower values during autumn/winter seasons. The atmospheric aerosol forcing varies from + 12.2 Wm-2 (November) to 28.2 Wm-2 (June) with higher values throughout the spring and summer seasons, suggesting the importance of mineral dust aerosols towards the solar dimming. Seasonally, highest values of the forcing efficiency at the surface are observed in spring (-85.0 ± 4.1 W m-2 τ -1) followed closely by winter (-79.2 ± 7.1 W m-2 τ -1) and the lowest values during autumn season (-54 ± 4.3 W m-2 τ -1). The study concludes with the variations of the atmospheric heating rates induced by the forcing. Highest heating rate is observed in June (0.39 K day -1) and the lowest in November (0.17 K day -1) and the temporal

  20. Analysis of marine aerosol optical depth retrieved from IRS-P4 OCM sensor and comparison with the aerosol derived from SeaWiFS and MODIS sensor

    Indian Academy of Sciences (India)

    A K Mishra; V K Dadhwal; C B S Dutt

    2008-07-01

    Aerosol optical depth is regularly derived from SeaWiFS and MODIS sensor and used by the scientific community in various climatic studies. In the present study an attempt has been made to retrieve the aerosol optical depth using the IRS-P4 OCM sensor data and a comparison has been carried out using few representative datasets. The results show that the IRS-P4 OCM retrieved aerosol optical depth is in good agreement with the aerosols retrieved from SeaWiFS as well as MODIS. The RMSE are found to be ± 0.0522 between OCM and SeaWIFS and ± 0.0638 between OCM and MODIS respectively. However, IRS-P4 OCM sensor retrieved aerosol optical depth is closer to SeaWiFS (correlation = 0.88, slope = 0.96 and intercept = −0.013) compared to MODIS (correlation = 0.75, slope = 0.91 and intercept = 0.0198). The mean percentage difference indicates that OCM retrieved AOD is +12% higher compared to SeaWiFS and +8% higher compared to MODIS. The mean absolute percentage between OCM derived AOD and SeaWiFS is found to be less (16%) compared to OCM and MODIS (20%).

  1. Study of aerosol optical properties at Kunming in southwest China and long-range transport of biomass burning aerosols from North Burma

    Science.gov (United States)

    Zhu, J.; Xia, X.; Che, H.; Wang, J.; Zhang, J.; Duan, Y.

    2016-03-01

    Seasonal variation of aerosol optical properties and dominant aerosol types at Kunming (KM), an urban site in southwest China, is characterized. Substantial influences of the hygroscopic growth and long-range transport of biomass burning (BB) aerosols on aerosol optical properties at KM are revealed. These results are derived from a detailed analysis of (a) aerosol optical properties (e.g. aerosol optical depth (AOD), columnar water vapor (CWV), single scattering albedo (SSA) and size distribution) retrieved from sunphotometer measurements during March 2012-August 2013, (b) satellite AOD and active fire products, (c) the attenuated backscatter profiles from the space-born lidar, and (d) the back-trajectories. The mean AOD440nm and extinction Angstrom exponent (EAE440 - 870) at KM are 0.42 ± 0.32 and 1.25 ± 0.35, respectively. Seasonally, high AOD440nm (0.51 ± 0.34), low EAE440 - 870 (1.06 ± 0.34) and high CWV (4.25 ± 0.97 cm) during the wet season (May - October) contrast with their counterparts 0.17 ± 0.11, 1.40 ± 0.31 and 1.91 ± 0.37 cm during the major dry season (November-February) and 0.53 ± 0.29, 1.39 ± 0.19, and 2.66 ± 0.44 cm in the late dry season (March-April). These contrasts between wet and major dry season, together with the finding that the fine mode radius increases significantly with AOD during the wet season, suggest the importance of the aerosol hygroscopic growth in regulating the seasonal variation of aerosol properties. BB and Urban/Industrial (UI) aerosols are two major aerosol types. Back trajectory analysis shows that airflows on clean days during the major dry season are often from west of KM where the AOD is low. In contrast, air masses on polluted days are from west (in late dry season) and east (in wet season) of KM where the AOD is often large. BB air mass is found mostly originated from North Burma where BB aerosols are lifted upward to 5 km and then subsequently transported to southwest China via prevailing westerly winds.

  2. Measurement of aerosol optical depth and sub-visual cloud detection using the optical depth sensor (ODS

    Directory of Open Access Journals (Sweden)

    D. Toledo

    2015-09-01

    Full Text Available A small and sophisticated optical depth sensor (ODS has been designed to work in the atmosphere of Earth and Mars. The instrument measures alternatively the diffuse radiation from the sky and the attenuated direct radiation from the sun on the surface. The principal goals of ODS are to retrieve the daily mean aerosol optical depth (AOD and to detect very high and optically thin clouds, crucial parameters in understanding the Martian and Earth meteorology and climatology. The detection of clouds is undertaken at twilight, allowing the detection and characterization of clouds with opacities below 0.03 (sub-visual clouds. In addition, ODS is capable to retrieve the aerosol optical depth during night-time from moonlight measurements. In order to study the performance of ODS under Mars-like conditions as well as to evaluate the retrieval algorithms for terrestrial measurements, ODS was deployed in Ouagadougou (Africa between November 2004 and October 2005, a sahelian region characterized by its high dust aerosol load and the frequent occurrence of Saharan dust storms. The daily average AOD values retrieved by ODS were compared with those provided by a CIMEL Sun-photometer of the AERONET (Aerosol Robotic NETwork network localized at the same location. Results represent a good agreement between both ground-based instruments, with a correlation coefficient of 0.79 for the whole data set and 0.96 considering only the cloud-free days. From the whole dataset, a total of 71 sub-visual cirrus (SVC were detected at twilight with opacities as thin as 1.10−3 and with a maximum of occurrence at altitudes between 14 and 20 km. Although further analysis and comparisons are required, results indicate the potential of ODS measurements to detect sub-visual clouds.

  3. Measurement of aerosol optical depth and sub-visual cloud detection using the optical depth sensor (ODS)

    Science.gov (United States)

    Toledo, D.; Rannou, P.; Pommereau, J.-P.; Sarkissian, A.; Foujols, T.

    2016-02-01

    A small and sophisticated optical depth sensor (ODS) has been designed to work in the atmosphere of Mars. The instrument measures alternatively the diffuse radiation from the sky and the attenuated direct radiation from the Sun on the surface. The principal goals of ODS are to retrieve the daily mean aerosol optical depth (AOD) and to detect very high and optically thin clouds, crucial parameters in understanding the Martian meteorology and climatology. The detection of clouds is undertaken at twilight, allowing the detection and characterization of clouds with opacities below 0.03 (sub-visual clouds). In addition, ODS is capable to retrieve the aerosol optical depth during nighttime from moonlight measurements. Recently, ODS has been selected at the METEO meteorological station on board the ExoMars 2018 Lander. In order to study the performance of ODS under Mars-like conditions as well as to evaluate the retrieval algorithms for terrestrial measurements, ODS was deployed in Ouagadougou (Africa) between November 2004 and October 2005, a Sahelian region characterized by its high dust aerosol load and the frequent occurrence of Saharan dust storms. The daily average AOD values retrieved by ODS were compared with those provided by a CIMEL sunphotometer of the AERONET (Aerosol Robotic NETwork) network localized at the same location. Results represent a good agreement between both ground-based instruments, with a correlation coefficient of 0.77 for the whole data set and 0.94 considering only the cloud-free days. From the whole data set, a total of 71 sub-visual cirrus (SVC) were detected at twilight with opacities as thin as 1.10-3 and with a maximum of occurrence at altitudes between 14 and 20 km. Although further optimizations and comparisons of ODS terrestrial measurements are required, results indicate the potential of these measurements to retrieve the AOD and detect sub-visual clouds.

  4. Aerosol optical properties and mixing state of black carbon in the Pearl River Delta, China

    Science.gov (United States)

    Tan, Haobo; Liu, Li; Fan, Shaojia; Li, Fei; Yin, Yan; Cai, Mingfu; Chan, P. W.

    2016-04-01

    Aerosols contribute the largest uncertainty to the total radiative forcing estimate, and black carbon (BC) that absorbs solar radiation plays an important role in the Earth's energy budget. This study analysed the aerosol optical properties from 22 February to 18 March 2014 at the China Meteorological Administration Atmospheric Watch Network (CAWNET) station in the Pearl River Delta (PRD), China. The representative values of dry-state particle scattering coefficient (σsp), hemispheric backscattering coefficient (σhbsp), absorption coefficient (σabsp), extinction coefficient (σep), hemispheric backscattering fraction (HBF), single scattering albedo (SSA), as well as scattering Ångström exponent (α) were presented. A comparison between a polluted day and a clean day shows that the aerosol optical properties depend on particle number size distribution, weather conditions and evolution of the mixing layer. To investigate the mixing state of BC at the surface, an optical closure study of HBF between measurements and calculations based on a modified Mie model was employed for dry particles. The result shows that the mixing state of BC might be between the external mixture and the core-shell mixture. The average retrieved ratio of the externally mixed BC to the total BC mass concentration (rext-BC) was 0.58 ± 0.12, and the diurnal pattern of rext-BC can be found. Furthermore, considering that non-light-absorbing particles measured by a Volatility-Tandem Differential Mobility Analyser (V-TDMA) exist independently with core-shell and homogenously internally mixed BC particles, the calculated optical properties were just slightly different from those based on the assumption that BC exist in each particle. This would help understand the influence of the BC mixing state on aerosol optical properties and radiation budget in the PRD.

  5. Production of aerosols by optical catapulting: Imaging, performance parameters and laser-induced plasma sampling rate

    Science.gov (United States)

    Abdelhamid, M.; Fortes, F. J.; Fernández-Bravo, A.; Harith, M. A.; Laserna, J. J.

    2013-11-01

    Optical catapulting (OC) is a sampling and manipulation method that has been extensively studied in applications ranging from single cells in heterogeneous tissue samples to analysis of explosive residues in human fingerprints. Specifically, analysis of the catapulted material by means of laser-induced breakdown spectroscopy (LIBS) offers a promising approach for the inspection of solid particulate matter. In this work, we focus our attention in the experimental parameters to be optimized for a proper aerosol generation while increasing the particle density in the focal region sampled by LIBS. For this purpose we use shadowgraphy visualization as a diagnostic tool. Shadowgraphic images were acquired for studying the evolution and dynamics of solid aerosols produced by OC. Aluminum silicate particles (0.2-8 μm) were ejected from the substrate using a Q-switched Nd:YAG laser at 1064 nm, while time-resolved images recorded the propagation of the generated aerosol. For LIBS analysis and shadowgraphy visualization, a Q-switched Nd:YAG laser at 1064 nm and 532 nm was employed, respectively. Several parameters such as the time delay between pulses and the effect of laser fluence on the aerosol production have been also investigated. After optimization, the particle density in the sampling focal volume increases while improving the aerosol sampling rate till ca. 90%.

  6. Estimation of Aerosol Optical Depth at Different Wavelengths by Multiple Regression Method

    Science.gov (United States)

    Tan, Fuyi; Lim, Hwee San; Abdullah, Khiruddin; Holben, Brent

    2015-01-01

    This study aims to investigate and establish a suitable model that can help to estimate aerosol optical depth (AOD) in order to monitor aerosol variations especially during non-retrieval time. The relationship between actual ground measurements (such as air pollution index, visibility, relative humidity, temperature, and pressure) and AOD obtained with a CIMEL sun photometer was determined through a series of statistical procedures to produce an AOD prediction model with reasonable accuracy. The AOD prediction model calibrated for each wavelength has a set of coefficients. The model was validated using a set of statistical tests. The validated model was then employed to calculate AOD at different wavelengths. The results show that the proposed model successfully predicted AOD at each studied wavelength ranging from 340 nm to 1020 nm. To illustrate the application of the model, the aerosol size determined using measure AOD data for Penang was compared with that determined using the model. This was done by examining the curvature in the ln [AOD]-ln [wavelength] plot. Consistency was obtained when it was concluded that Penang was dominated by fine mode aerosol in 2012 and 2013 using both measured and predicted AOD data. These results indicate that the proposed AOD prediction model using routine measurements as input is a promising tool for the regular monitoring of aerosol variation during non-retrieval time.

  7. Wave like signatures in aerosol optical depth and associated radiative impacts over the central Himalayan region

    Energy Technology Data Exchange (ETDEWEB)

    Shukla, K. K.; Phanikumar, D. V.; Kumar, K.  Niranjan; Reddy, Kishore; Kotamarthi, V. R.; Newsom, Rob K.; Ouarda, Taha B. M. J.

    2015-10-01

    In this study, we present a case study on 16 October 2011 to show the first observational evidence of the influence of short period gravity waves in aerosol transport during daytime over the central Himalayan region. The Doppler lidar data has been utilized to address the daytime boundary layer evolution and related aerosol dynamics over the site. Mixing layer height is estimated by wavelet covariance transform method and found to be ~ 0.7 km, AGL. Aerosol optical depth observations during daytime revealed an asymmetry showing clear enhancement during afternoon hours as compared to forenoon. Interestingly, Fourier and wavelet analysis of vertical velocity and attenuated backscatter showed similar 50-90 min short period gravity wave signatures during afternoon hours. Moreover, our observations showed that gravity waves are dominant within the boundary layer implying that the daytime boundary layer dynamics is playing a vital role in transporting the aerosols from surface to the top of the boundary layer. Similar modulations are also evident in surface parameters like temperature, relative humidity and wind speed indicating these waves are associated with the dynamical aspects over Himalayan region. Finally, time evolution of range-23 height indicator snapshots during daytime showed strong upward velocities especially during afternoon hours implying that convective processes through short period gravity waves plays a significant role in transporting aerosols from the nearby valley region to boundary layer top over the site. These observations also establish the importance of wave induced daytime convective boundary layer dynamics in the lower Himalayan region.

  8. Total Volcanic Stratospheric Aerosol Optical Depths and Implications for Global Climate Change

    Science.gov (United States)

    Ridley, D. A.; Solomon, S.; Barnes, J. E.; Burlakov, V. D.; Deshler, T.; Dolgii, S. I.; Herber, A. B.; Nagai, T.; Neely, R. R., III; Nevzorov, A. V.; Ritter, C.; Sakai, T.; Santer, B. D.; Sato, M.; Schmidt, A.; Uchino, O.; Vernier, J. P.

    2014-01-01

    Understanding the cooling effect of recent volcanoes is of particular interest in the context of the post-2000 slowing of the rate of global warming. Satellite observations of aerosol optical depth above 15 km have demonstrated that small-magnitude volcanic eruptions substantially perturb incoming solar radiation. Here we use lidar, Aerosol Robotic Network, and balloon-borne observations to provide evidence that currently available satellite databases neglect substantial amounts of volcanic aerosol between the tropopause and 15 km at middle to high latitudes and therefore underestimate total radiative forcing resulting from the recent eruptions. Incorporating these estimates into a simple climate model, we determine the global volcanic aerosol forcing since 2000 to be 0.19 +/- 0.09W/sq m. This translates into an estimated global cooling of 0.05 to 0.12 C. We conclude that recent volcanic events are responsible for more post-2000 cooling than is implied by satellite databases that neglect volcanic aerosol effects below 15 km.

  9. Reducing multisensor monthly mean aerosol optical depth uncertainty: 2. Optimal locations for potential ground observation deployments

    Science.gov (United States)

    Li, Jing; Li, Xichen; Carlson, Barbara E.; Kahn, Ralph A.; Lacis, Andrew A.; Dubovik, Oleg; Nakajima, Teruyuki

    2017-04-01

    Surface remote sensing of aerosol properties provides "ground truth" for satellite and model validation and is an important component of aerosol observation system. Due to the different characteristics of background aerosol variability, information obtained at different locations usually has different spatial representativeness, implying that the location should be carefully chosen so that its measurement could be extended to a greater area. In this study, we present an objective observation array design technique that automatically determines the optimal locations with the highest spatial representativeness based on the Ensemble Kalman Filter (EnKF) theory. The ensemble is constructed using aerosol optical depth (AOD) products from five satellite sensors. The optimal locations are solved sequentially by minimizing the total analysis error variance, which means that observations at these locations will reduce the background error variance to the largest extent. The location determined by the algorithm is further verified to have larger spatial representativeness than some other arbitrary location. In addition to the existing active Aerosol Robotic Network (AERONET) sites, the 40 selected optimal locations are mostly concentrated on regions with both high AOD inhomogeneity and its spatial representativeness, namely, the Sahel, South Africa, East Asia, and North Pacific Islands. These places should be the focuses of establishing future AERONET sites in order to further reduce the uncertainty in the monthly mean AOD. Observations at these locations contribute to approximately 50% of the total background uncertainty reduction.

  10. Comparison of PMCAMx aerosol optical depth predictions over Europe with AERONET and MODIS measurements

    Science.gov (United States)

    Panagiotopoulou, Antigoni; Charalampidis, Panagiotis; Fountoukis, Christos; Pilinis, Christodoulos; Pandis, Spyros N.

    2016-11-01

    The ability of chemical transport model (CTM) PMCAMx to reproduce aerosol optical depth (AOD) measurements by the Aerosol Robotic Network (AERONET) and the Moderate Resolution Imaging Spectroradiometer (MODIS) over Europe during the photochemically active period of May 2008 (EUCAARI campaign) is evaluated. Periods with high dust or sea-salt levels are excluded, so the analysis focuses on the ability of the model to simulate the mostly secondary aerosol and its interactions with water. PMCAMx reproduces the monthly mean MODIS and AERONET AOD values over the Iberian Peninsula, the British Isles, central Europe, and Russia with a fractional bias of less than 15 % and a fractional error of less than 30 %. However, the model overestimates the AOD over northern Europe, most probably due to an overestimation of organic aerosol and sulfates. At the other end, PMCAMx underestimates the monthly mean MODIS AOD over the Balkans, the Mediterranean, and the South Atlantic. These errors appear to be related to an underestimation of sulfates. Sensitivity tests indicate that the evaluation results of the monthly mean AODs are quite sensitive to the relative humidity (RH) fields used by PMCAMx, but are not sensitive to the simulated size distribution and the black carbon mixing state. The screening of the satellite retrievals for periods with high dust (or coarse particles in general) concentrations as well as the combination of the MODIS and AERONET datasets lead to more robust conclusions about the ability of the model to simulate the secondary aerosol components that dominate the AOD during this period.

  11. Long term measurements of the elemental composition and optical properties of aerosols in Amazonia

    Directory of Open Access Journals (Sweden)

    Arana A. A.

    2013-04-01

    Full Text Available Aerosols are being collected and analyzed for trace elements in two sites in Amazonia since January 2008. On eof the site, Manaus is located in a very pristine area in Central Amazonia. The site is nt affected directly by any urban plume for thousands of kilometers. A second site is located in Porto Velho, in a region with heavy land use change and deforestation. Optical properties (light scattering ad absorption are also being measured in order to study the climatic impact of aerosols. It was observed a clear seasonal pattern for both sites, with higher concentrations in the dry season. But the difference in seasonal concentrations observed for Porto Velho is much larger due to stronger anthropogenic influences. In Manaus during the wet season, very low concentrations of heavy metals, maybe the smallest measured in continental regions are reported. Positive Matrix Factorization (PMF was used to separate the different aerosol components. In general, for fine and coarse mode and wet and dry season, 3 aerosol components could be observed: 1 Natural biogenic aerosol; 2 biomass burning component; 3 Soil dust both locally and long range transported Sahara dust

  12. Estimation of aerosol optical depth at different wavelengths by multiple regression method.

    Science.gov (United States)

    Tan, Fuyi; Lim, Hwee San; Abdullah, Khiruddin; Holben, Brent

    2016-02-01

    This study aims to investigate and establish a suitable model that can help to estimate aerosol optical depth (AOD) in order to monitor aerosol variations especially during non-retrieval time. The relationship between actual ground measurements (such as air pollution index, visibility, relative humidity, temperature, and pressure) and AOD obtained with a CIMEL sun photometer was determined through a series of statistical procedures to produce an AOD prediction model with reasonable accuracy. The AOD prediction model calibrated for each wavelength has a set of coefficients. The model was validated using a set of statistical tests. The validated model was then employed to calculate AOD at different wavelengths. The results show that the proposed model successfully predicted AOD at each studied wavelength ranging from 340 nm to 1020 nm. To illustrate the application of the model, the aerosol size determined using measure AOD data for Penang was compared with that determined using the model. This was done by examining the curvature in the ln [AOD]-ln [wavelength] plot. Consistency was obtained when it was concluded that Penang was dominated by fine mode aerosol in 2012 and 2013 using both measured and predicted AOD data. These results indicate that the proposed AOD prediction model using routine measurements as input is a promising tool for the regular monitoring of aerosol variation during non-retrieval time.

  13. Detection of a gas flaring signature in the AERONET optical properties of aerosols at a tropical station in West Africa

    Science.gov (United States)

    Fawole, Olusegun G.; Cai, Xiaoming; Levine, James G.; Pinker, Rachel T.; MacKenzie, A. R.

    2016-12-01

    The West African region, with its peculiar climate and atmospheric dynamics, is a prominent source of aerosols. Reliable and long-term in situ measurements of aerosol properties are not readily available across the region. In this study, Version 2 Level 1.5 Aerosol Robotic Network (AERONET) data were used to study the absorption and size distribution properties of aerosols from dominant sources identified by trajectory analysis. The trajectory analysis was used to define four sources of aerosols over a 10 year period. Sorting the AERONET aerosol retrievals by these putative sources, the hypothesis that there exists an optically distinct gas flaring signal was tested. Dominance of each source cluster varies with season: desert-dust (DD) and biomass burning (BB) aerosols are dominant in months prior to the West African Monsoon (WAM); urban (UB) and gas flaring (GF) aerosol are dominant during the WAM months. BB aerosol, with single scattering albedo (SSA) at 675 nm value of 0.86 ± 0.03 and GF aerosol with SSA (675 nm) value of 0.9 ± 0.07, is the most absorbing of the aerosol categories. The range of Absorption Angstr&öm Exponent (AAE) for DD, BB, UB and GF classes are 1.99 ± 0.35, 1.45 ± 0.26, 1.21 ± 0.38 and 0.98 ± 0.25, respectively, indicating different aerosol composition for each source. The AAE (440-870 nm) and Angstr&öm Exponent (AE) (440-870 nm) relationships further show the spread and overlap of the variation of these optical and microphysical properties, presumably due in part to similarity in the sources of aerosols and in part, due to mixing of air parcels from different sources en route to the measurement site.

  14. Aerosol Optical Thickness Derived From Atmospheric Transmittance Using Spectroradiometer Measurements

    Science.gov (United States)

    Hwee San, Hslim; Matjafri, M. Z.; Abdullah, Abdul K.; Chow Jeng, C. J.

    section The objective of this study was to test the feasibility of hand held spectroradiometer measurements for the retrieval AOT values Twenty-six stations were chosen randomly around Penang Island and the atmospheric transmittance measurements were collected using a handheld spectroradiometer The corresponding PM10 concentrations were measured using a portable DustTrak Aerosol Monitor 8520 simultaneously with the measurements of the transmittance data The AOT values were calculated using the Beer-Lambert-Bouguer law Linear relationship was found between AOT and PM10 values in this study Finally a PM10 map was created using Kriging interpolation technique The result of the study showed the potential of a spectroradiometer data for the retrieval of AOT and PM10 to provide the air pollution information

  15. Aerosol optical properties under the condition of heavy haze over an urban site of Beijing, China.

    Science.gov (United States)

    Che, Huizheng; Xia, Xiangao; Zhu, Jun; Wang, Hong; Wang, Yaqiang; Sun, Junying; Zhang, Xiaoye; Shi, Guangyu

    2015-01-01

    In January 2013, several serious haze pollution events happened in North China. Cimel sunphotometer measurements at an urban site of Beijing (Chinese Academy of Meteorological Sciences-CAMS) from 1 to 30 January 2013 were used to investigate the detailed variation of aerosol optical properties. It was found that Angstrom exponents were mostly larger than 0.80 when aerosol optical depth values are higher than 0.60 at the urban region of Beijing during January 2013. The aerosol optical depth (AOD) at the urban region of Beijing can remain steady at approximately 0.40 before haze happening and then increased sharply to more than 1.50 at 500 nm with the onset of haze, which suggests that the fine-mode AOD is a factor of 20 of the coarse-mode AOD during a serious haze pollution event. The single scattering albedo was approximately 0.90 ± 0.03 at 440, 675, 870 and 1,020 nm during the haze pollution period. The single scattering albedo at 440 nm as a function of the fine-mode fraction was relatively consistent, but it was highly variable at 675, 870 and 1,020 nm. Except on January 12 and 18, all the fine-mode particle volumes were larger than those of coarse particles, which suggests that fine particles from anthropogenic activities made up most of the haze. Aerosol type classification analysis showed that the dominant aerosol types can be classified as both "mixed" and "urban/industrial (U/I) and biomass burning (BB)" categories during the heavy haze period of Beijing in January of 2013. The mixed category occurrence was about 31 %, while the U/I and BB was about 69 %.

  16. Direct effect of aerosol optical properties on global dimming and brightening

    Science.gov (United States)

    Kudo, R.; Uchiyama, A.

    2011-12-01

    Surface solar radiation observed at numerous locations has decreased from the 1960s to the 1980s (Global dimming), thereafter increased (Global brightening). The dimming and brightening is considered to be due to the changes in both clouds and aerosols. Aerosols have a direct impact on the surface solar radiation by scattering and absorption. The impact is determined by three parameters: optical depth (AOD), single scattering albedo (SSA), and asymmetry factor, but the effect of asymmetry factor is rather smaller than the others. Therefore, the long-term changes in AOD and SSA are necessary to evaluate the aerosol impact on the global dimming and brightening. We have developed the method to estimate AOD and SSA from the hourly accumulated direct and diffuse irradiances measured by the ground-based broadband radiometers. In the estimation, the real part of the refractive index is fixed, and the size distribution is defined by the Junge distribution with a fixed shaping constant. Using the developed method, the measurements from 1975 to 2008 at 14 sites in Japan were analyzed. Consequently, a decrease of AOD by 0.02 and an increase of SSA by 0.2 during the period were seen. The surface solar radiation under the clear sky conditions, which was calculated from the estimated aerosol optical properties, was increased by 5% due to the changes in AOD and SSA; the influence of SSA was dominant. We also investigate the cloud impact on the surface solar radiation which was simply defined as the difference between the surface solar radiation under the cloudy sky conditions and under the clear sky conditions; the cloud impact had no statistically significant trends. The brightening in Japan may be due to the changes in aerosol optical properties, especially SSA. Our developed method can be applied to measurements at other sites around the world and would be helpful to understand the causes of the global dimming and brightening.

  17. Lidar Measurements of the Vertical Distribution of Aerosol Optical and Physical Properties over Central Asia

    Directory of Open Access Journals (Sweden)

    Boris B. Chen

    2013-01-01

    Full Text Available The vertical structure of aerosol optical and physical properties was measured by Lidar in Eastern Kyrgyzstan, Central Asia, from June 2008 to May 2009. Lidar measurements were supplemented with surface-based measurements of PM2.5 and PM10 mass and chemical composition in both size fractions. Dust transported into the region is common, being detected 33% of the time. The maximum frequency occurred in the spring of 2009. Dust transported to Central Asia comes from regional sources, for example, Taklimakan desert and Aral Sea basin, and from long-range transport, for example, deserts of Arabia, Northeast Africa, Iran, and Pakistan. Regional sources are characterized by pollution transport with maximum values of coarse particles within the planetary boundary layer, aerosol optical thickness, extinction coefficient, integral coefficient of aerosol backscatter, and minimum values of the Ångström exponent. Pollution associated with air masses transported over long distances has different characteristics during autumn, winter, and spring. During winter, dust emissions were low resulting in high values of the Ångström exponent (about 0.51 and the fine particle mass fraction (64%. Dust storms were more frequent during spring with an increase in coarse dust particles in comparison to winter. The aerosol vertical profiles can be used to lower uncertainty in estimating radiative forcing.

  18. Aerosol optical properties in the southeastern United States in summer – Part 1: Hygroscopic growth

    Directory of Open Access Journals (Sweden)

    C. A. Brock

    2015-09-01

    Full Text Available Aircraft observations of meteorological, trace gas, and aerosol properties were made during May–September 2013 in the southeastern United States (US under fair-weather, afternoon conditions with well-defined planetary boundary layer structure. Optical extinction at 532 nm was directly measured at three relative humidities and compared with extinction calculated from measurements of aerosol composition and size distribution using the κ-Köhler approximation for hygroscopic growth. Using this approach, the hygroscopicity parameter κ for the organic fraction of the aerosol must have been We present a new parameterization of the change in aerosol extinction as a function of relative humidity that better describes the observations than does the widely used power-law (gamma, γ parameterization. This new single-parameter κext formulation is based upon κ-Köhler and Mie theories and relies upon the well-known approximately linear relationship between particle volume (or mass and optical extinction (Charlson et al., 1967. The fitted parameter, κext, is nonlinearly related to the chemically derived κ parameter used in κ-Köhler theory. The values of κext we determined from airborne measurements are consistent with independent observations at a nearby ground site.

  19. Studies of seasonal variations of aerosol optical properties with use of remote techniques

    Science.gov (United States)

    Strzalkowska, Agata; Zielinski, Tymon; Petelski, Tomasz; Pakszys, Paulina; Markuszewski, Piotr; Makuch, Przemyslaw

    2014-05-01

    According to the IPCC report, atmospheric aerosols due to their properties -extinction of Sun and Earth radiation and participation in processes of creation of clouds, are among basic "unknowns" in climate studies. Aerosols have large effect on the radiation balance of the Earth which has a significant impact on climate changes. They are also a key issue in the case of remote sensing measurements. The optical properties of atmospheric aerosols depend not only on their type but also on physical parameters such as pressure, humidity, wind speed and direction. The wide range of properties in which atmospheric aerosols affect Earth's climate is the reason of high unrelenting interest of scientists from different disciplines such as physics, chemistry and biology. Numerous studies have dealt with aerosol optical properties, e.g. Dubovik et al. (2002), but only in a few have regarded the influence of meteorological parameters on the optical properties of aerosols in the Baltic Sea area. Studies of aerosol properties over the Baltic were conducted already in the last forty years, e.g. Zielinski T. et. al. (1999) or Zielinski T. & A. Zielinski (2002). The experiments carried out at that time involved only one measuring instrument -e.g. LIDAR (range of 1 km) measurements and they were conducted only in selected areas of the Polish coastal zone. Moreover in those publications authors did not use measurements performed on board of research vessel (R/V Oceania), which belongs to Institute of Oceanology Polish Academy of Science (IO PAN) or data received from satellite measurements. In 2011 Zdun and Rozwadowska performed an analysis of all data derived from the AERONET station on the Gotland Island. The data were divided into seasons and supplemented by meteorological factors. However, so far no comprehensive study has been carried out for the entire Baltic Sea area. This was the reason to conduct further research of SEasonal Variations of Aerosol optical depth over the Baltic

  20. Improvement of Aerosol Optical Depth Retrieval over Hong Kong from a Geostationary Meteorological Satellite Using Critical Reflectance with Background Optical Depth Correction

    Science.gov (United States)

    Kim, Mijin; Kim, Jhoon; Wong, Man Sing; Yoon, Jongmin; Lee, Jaehwa; Wu, Dong L.; Chan, P.W.; Nichol, Janet E.; Chung, Chu-Yong; Ou, Mi-Lim

    2014-01-01

    Despite continuous efforts to retrieve aerosol optical depth (AOD) using a conventional 5-channelmeteorological imager in geostationary orbit, the accuracy in urban areas has been poorer than other areas primarily due to complex urban surface properties and mixed aerosol types from different emission sources. The two largest error sources in aerosol retrieval have been aerosol type selection and surface reflectance. In selecting the aerosol type from a single visible channel, the season-dependent aerosol optical properties were adopted from longterm measurements of Aerosol Robotic Network (AERONET) sun-photometers. With the aerosol optical properties obtained fromthe AERONET inversion data, look-up tableswere calculated by using a radiative transfer code: the Second Simulation of the Satellite Signal in the Solar Spectrum (6S). Surface reflectance was estimated using the clear sky composite method, awidely used technique for geostationary retrievals. Over East Asia, the AOD retrieved from the Meteorological Imager showed good agreement, although the values were affected by cloud contamination errors. However, the conventional retrieval of the AOD over Hong Kong was largely underestimated due to the lack of information on the aerosol type and surface properties. To detect spatial and temporal variation of aerosol type over the area, the critical reflectance method, a technique to retrieve single scattering albedo (SSA), was applied. Additionally, the background aerosol effect was corrected to improve the accuracy of the surface reflectance over Hong Kong. The AOD retrieved froma modified algorithmwas compared to the collocated data measured by AERONET in Hong Kong. The comparison showed that the new aerosol type selection using the critical reflectance and the corrected surface reflectance significantly improved the accuracy of AODs in Hong Kong areas,with a correlation coefficient increase from0.65 to 0.76 and a regression line change from tMI [basic algorithm] = 0

  1. Gradient Correlation Method for the Stabilization of Inversion Results of Aerosol Microphysical Properties Retrieved from Profiles of Optical Data

    Directory of Open Access Journals (Sweden)

    Kolgotin Alexei

    2016-01-01

    Full Text Available Correlation relationships between aerosol microphysical parameters and optical data are investigated. The results show that surface-area concentrations and extinction coefficients are linearly correlated with a correlation coefficient above 0.99 for arbitrary particle size distribution. The correlation relationships that we obtained can be used as constraints in our inversion of optical lidar data. Simulation studies demonstrate a significant stabilization of aerosol microphysical data products if we apply the gradient correlation method in our traditional regularization technique.

  2. Fog-induced variations in aerosol optical and physical properties over the Indo-Gangetic Basin and impact to aerosol radiative forcing

    Science.gov (United States)

    Das, S. K.; Jayaraman, A.; Misra, A.

    2008-06-01

    A detailed study on the changes in aerosol physical and optical properties during fog events were made in December 2004 at Hissar (29.13° N, 75.70° E), a city located in the Indo-Gangetic basin. The visible aerosol optical depth was relatively low (0.3) during the initial days, which, however, increased (0.86) as the month progressed. The increasing aerosol amount, the decreasing surface temperature and a higher relative humidity condition were found favoring the formation of fog. The fog event is also found to alter the aerosol size distribution. An increase in the number concentration of the nucleation mode (radiuscompute the aerosol radiative forcing. The top of the atmosphere forcing is found to increase during foggy days due to large backscattering of radiation back to space. It is also shown that during foggy days, as the day progresses the RH value decreases, which reduces the forcing value while the increasing solar elevation increases the forcing value. Thus the fog event which prolongs longer into the daytime has a stronger effect on the diurnally averaged aerosol radiative forcing than those events which are confined only to the early morning hours.

  3. Rigorous bounds on aerosol optical properties from measurement and/or model constraints

    Science.gov (United States)

    McGraw, Robert; Fierce, Laura

    2016-04-01

    Sparse-particle aerosol models are an attractive alternative to sectional and modal methods for representation of complex, generally mixed particle populations. In the quadrature method of moments (QMOM) a small set of abscissas and weights, determined from distributional moments, provides the sparse set. Linear programming (LP) yields a generalization of the QMOM that is especially convenient for sparse particle selection. In this paper we use LP to obtain rigorous, nested upper and lower bounds to aerosol optical properties in terms of a prescribed Bayesian-like sequence of model or simulated measurement constraints. Examples of such constraints include remotely-sensed light extinction at different wavelengths, modeled particulate mass, etc. Successive reduction in bound separation with each added constraint provides a quantitative measure of its contextual information content. The present study is focused on univariate populations as a first step towards development of new simulation algorithms for tracking the physical and optical properties of multivariate particle populations.

  4. Optical properties in the UV and visible spectral region of organic acids relevant to tropospheric aerosols

    Directory of Open Access Journals (Sweden)

    C. E. Lund Myhre

    2004-06-01

    Full Text Available Refractive and absorption indices in the UV and visible region of selected aqueous organic acids relevant to tropospheric aerosols are reported. The acids investigated are the aliphatic dicarboxylic acids oxalic, malonic, tartronic, succinic and glutaric acid. In addition we report data for pyruvic, pinonic, benzoic and phthalic acid. To cover a wide range of conditions we have investigated the aqueous organic acids at different concentrations spanning from highly diluted samples to concentrations close to saturation. The density of the investigated samples is reported and a parameterisation of the absorption and refractive index that allows the calculation of the optical constants of mixed aqueous organic acids at different concentrations is presented. The single scattering albedo is calculated for two size distributions using measured and a synthetic set of optical constants. The results show that tropospheric aerosols consisting of only these organic acids and water have a pure scattering effect.

  5. Optical properties in the UV and visible spectral region of organic acids relevant to tropospheric aerosols

    Directory of Open Access Journals (Sweden)

    C. E. Lund Myhre

    2004-01-01

    Full Text Available Refractive and absorption indices in the UV and visible region of selected aqueous organic acids relevant to tropospheric aerosols are reported. The acids investigated are the aliphatic dicarboxylic acids oxalic, malonic, tartronic, succinic and glutaric acid. In addition we report data for pyruvic, pinonic, benzoic and phthalic acid. To cover a wide range of conditions we have investigated the aqueous organic acids at different concentrations spanning from highly diluted samples to concentrations close to saturation. The density of the investigated samples is reported and a parameterisation of the absorption and refractive index that allows the calculation of the optical constants of mixed aqueous organic acids at different concentrations is presented. The single scattering albedo is calculated for two size distributions using measured and a synthetic set of optical constants. The results show that tropospheric aerosols consisting of only these organic acids and water have a pure scattering effect.

  6. Optical and radiative properties of aerosols over Abu Dhabi in the United Arab Emirates

    Indian Academy of Sciences (India)

    S Naseema Beegum; Haifa Ben Romdhane; Mohammed Tauha Ali; Peter Armstrong; Hosni Ghedira

    2016-12-01

    The present study is on the aerosol optical and radiative properties in the short-wave radiation and its climate implications at the arid city of Abu Dhabi (24.42°N, 54.61°E, 4.5 m MSL), in the United Arab Emirates. The direct aerosol radiative forcings (ARF) in the short-wave region at the top (TOA) and bottom of the atmosphere (BOA) are estimated using a hybrid approach, making use of discrete ordinate radiative transfer method in conjunction with the short-wave flux and spectral aerosol optical depth (AOD) measurements, over a period of 3 years (June 2012–July 2015), at Abu Dhabi located at the southwest coast of the Arabian Gulf. The inferred microphysical properties of aerosols at the measurementsite indicate strong seasonal variations from the dominance of coarse mode mineral dust aerosols during spring (March–May) and summer (June–September), to the abundance of fine/accumulation modeaerosols mainly from combustion of fossil-fuel and bio-fuel during autumn (October–November) and winter(December–February) seasons. The monthly mean diurnally averaged ARF at the BOA (TOA) varies from −13.2Wm⁻² (∼ −0.96 Wm⁻²) in November to −39.4 Wm⁻² (−11.4 Wm⁻²) in August with higher magnitudes of the forcing values during spring/summer seasons and lower values during autumn/winter seasons. The atmospheric aerosol forcing varies from +12.2 Wm⁻² (November) to 28.2 Wm⁻² (June) with higher values throughout the spring and summer seasons, suggesting the importance of mineral dust aerosols towards the solar dimming. Seasonally, highest values of the forcing efficiency at the surfaceare observed in spring (−85.0± 4.1Wm⁻²τ⁻¹) followed closely by winter (−79.2±7.1 W m⁻²τ⁻¹) and the lowest values during autumn season (−54±4.3W m⁻²τ⁻¹). The study concludes with the variations of the atmospheric heating rates induced by the forcing. Highest heating rate is observed in June (0.39 K day⁻¹) and the lowest in November

  7. Annual cycle of global distributions of aerosol optical depth from integration of MODIS retrievals and GOCART model simulations

    Science.gov (United States)

    Yu, Hongbin; Dickinson, R. E.; Chin, M.; Kaufman, Y. J.; Holben, B. N.; Geogdzhayev, I. V.; Mishchenko, M. I.

    2003-02-01

    The Moderate-Resolution Imaging Spectroradiometer (MODIS) instrument onboard the Earth Observing System (EOS) satellites provides an unprecedented opportunity to study aerosols from space with high accuracy and on a nearly global scale. However, difficulty with highly reflective arid and snow-covered lands introduces significant gaps in global or regional coverage that must be filled by some other means. This study provides a complete global coverage of an annual cycle of aerosol optical depth by combining the MODIS retrievals and Georgia Tech/Goddard Global Ozone Chemistry Aerosol Radiation and Transport (GOCART) simulations weighted with the uncertainties in each product. The assimilated aerosol optical depths over land are better correlated with the ground-based Aerosol Robotic Network (AERONET) measurements than are either the MODIS retrievals or the GOCART simulations alone. The gaps in the MODIS retrievals are filled with values that are generally consistent with the AERONET aerosol climatology. The assimilated aerosol optical depths are in good agreement with the Advanced Very High Resolution Radiometer (AVHRR) aerosol climatology over the Atlantic and North Indian Oceans. In spring, large discrepancies between the MODIS retrievals in 2001 and the AVHRR climatology over the North Pacific are likely a result of extremely active transcontinental transport of Asian dust/pollutants to North America in the year 2001. Large model-satellite differences in the South Pacific and South Indian Oceans may be attributable to missing or underestimated sources in the model and/or cloud, whitecap, and glint contamination in satellite retrievals.

  8. Aerosol optical properties in pristine and biomass burning areas in the Amazon Basin

    Science.gov (United States)

    Artaxo, P.; Rizzo, L.; Lucca, S.; Paixao, M.; Sena, E. T.; Cirino, G.; Arana, A.

    2011-12-01

    Aerosol physical and chemical properties were measured in two sites in Amazonia. The clean site is at Central Amazonia, close to Manaus. A second sampling site is located in Porto Velho, Rondonia, an area strongly affected by biomass burning emissions. Long term measurements, from February 2008 are being carried out in these two sites. In the pristine central Amazonia, measurements were taken at the Cuieiras forest site, tower TT34, 55 Km North of Manaus under dry conditions (RHMAAP 5012 absorption photometer in series with a nephelometer (TSI 3563) was used to measure aerosol absorption and scattering, respectively. Aerosol size distributions were measure using a TSI SMPS system. Aerosol composition, and several trace gases that helps to characterize aerosol sources were also measured. In Rondonia, a sampling station was installed close to the city of Porto Velho. Similar instrumentation as in Manaus was used in Rondonia. In the pristine Amazonian atmosphere, aerosol scattering coefficients ranged between 1 and 200 Mm-1 at 450 nm, while absorption ranged between 1 and 20 Mm-1 at 637 nm. A strong seasonal behavior was observed, with greater aerosol loadings during the dry season (Jul-Nov) as compared to the wet season (Dec-Jun). During the wet season in Manaus, aerosol scattering (450 nm) and absorption (637 nm) coefficients averaged, respectively, 14±22 and 0.9±0.8 Mm-1. Both optical coefficients were greatly increased during the dry season, averaging 58±35 Mm-1 and 4.1±3.8 Mm-1, correspondingly. Angstrom exponents for scattering were lower during the wet season (1.6±0.4) in comparison to the dry season (1.9±0.2), which is consistent with the shift from biomass burning aerosols. Single scattering albedo, calculated at 637 nm, did not show a significant seasonal variation, averaging 0.86 ± 0.06 and 0.86 ± 0.04, respectively for wet and dry season. In Rondonia, even in the wet season it was possible to observe a strong impact from anthropogenic sources

  9. Optical Properties of Boreal Region Biomass Burning Aerosols in Central Alaska and Seasonal Variation of Aerosol Optical Depth at an Arctic Coastal Site

    Science.gov (United States)

    Eck, T. F.; Holben, B. N.; Reid, J. S.; Sinyuk, A.; Hyer, E. J.; O'Neill, N. T.; Shaw, G. E.; VandeCastle, J. R.; Chapin, F. S.; Dubovik, O.; hide

    2010-01-01

    Long-term monitoring of aerosol optical properties at a boreal forest AERONET site in interior Alaska was performed from 1994 through 2008 (excluding winter). Large interannual variability was observed, with some years showing near background aerosol optical depth (AOD) levels (burning regions. Single scattering albedo (omega (sub 0); 440 nm) at the boreal forest site ranged from approximately 0.91 to 0.99 with an average of approximately 0.96 for observations in 2004 and 2005. This suggests a significant amount of smoldering combustion of woody fuels and peat/soil layers that would result in relatively low black carbon mass fractions for smoke particles. The fine mode particle volume median radius during the heavy burning years was quite large, averaging approximately 0.17 micron at AOD(440 nm) = 0.1 and increasing to approximately 0.25 micron at AOD(440 nm) = 3.0. This large particle size for biomass burning aerosols results in a greater relative scattering component of extinction and, therefore, also contributes to higher omega (sub 0). Additionally, monitoring at an Arctic Ocean coastal site (Barrow, Alaska) suggested transport of smoke to the Arctic in summer resulting in individual events with much higher AOD than that occurring during typical spring Arctic haze. However, the springtime mean AOD(500 nm) is higher during late March through late May (approximately 0.150) than during summer months (approximately 0.085) at Barrow partly due to very few days with low background AOD levels in spring compared with many days with clean background conditions in summer.

  10. Analysis of aerosol optical depth evaluation in polar regions and associated uncertainties

    Directory of Open Access Journals (Sweden)

    P. Ortiz de Galisteo

    2008-04-01

    Full Text Available Some available processing algorithms used to calculate the aerosol optical depth from radiometric measurements were tested. The aim was to evaluate the associated uncertainties in polar regions due to the data processing, in order to adjust the methodology of the calculation and illustrate the importance of these error sources. The measurements were obtained during a sun photometer campaign in Ny-Ålesund within the framework of the POLAR-AOD project.

  11. Physical and chemical study of single aerosol particles using optical trapping cavity ringdown spectroscopy

    Science.gov (United States)

    2016-08-30

    benefits from the stable ringdown baseline stability of this pulsed UV -CRDS system that offers a laser beam in a wide wavelength range from visible to...measure wavelength-dependent single particle extinction for different types of particles and in different wavelength regions ( Visible - UV ). We found: (1...SECURITY CLASSIFICATION OF: We report a new single-aerosol particle scope using an optical trapping-cavity ringdown spectroscopy (OT-CRDS) technique

  12. Size stabilization of surface-supported liquid aerosols using tapered optical fiber coupling

    OpenAIRE

    Karadağ, Yasin; Jonas, Alexandr; Küçükkara, İbrahim; Kiraz, Alper

    2013-01-01

    We demonstrate long-term size stabilization of surface-supported liquid aerosols of salt-water. Single tapered optical fibers were used to couple the light from independent heating and probe lasers into individual microdroplets that were kept on a superhydrophobic surface in a high-humidity chamber. Size stabilization of microdroplets resulted from competition between resonant absorption of the infrared heating laser by a microdroplet whispering gallery mode and water condensation in the samp...

  13. Mixing State and Optical Properties of Biomass Burning Aerosol during the SAMBBA 2012 Campaign

    Science.gov (United States)

    Brooke, Jennifer; Brooks, Barbara; McQuaid, Jim; Osborne, Simon

    2013-04-01

    Emissions of black carbon are a global phenomenon associated with combustion activities with an estimated 40 % of global emissions from biomass burning. These emissions are typically dominated in regional hotspots, such as along the edges of the Amazon Basin, and contribute to the regional air quality and have associated health impacts as well as the global climatic impacts of this major source of black carbon as well as other radiatively active species. New airborne measurements will be presented of biomass burning emissions across the Amazon region from the South AMerican Biomass Burning Analysis (SAMBBA) campaign based at Porto Vehlo, Rondônia, Brazil in September 2012. This airborne campaign aboard the FAAM BAe-146 coincided with the seasonal peak in South American biomass burning emissions, which make up the most dominant source of atmospheric pollutants in the region at this time. SAMBBA included dedicated flights involving in-situ measurements and remote sensing of single plume studies through to multi-plume sampling of smouldering and flaming vegetation fires, regional haze sampling, and measurements of biogenic aerosol and gases across Amazonas. This presentation summarises early findings from the SAMBBA aircraft observations focusing on the relationship between biomass burning aerosol properties; size distributions, aerosol mixing state and optical properties from a suite of instruments onboard the FAAM BAe-146. The interplay of these properties influences the regional radiative balance impacting on weather and climate. The Leeds airborne VACC (Volatile Aerosol Concentration and Composition) instrument is designed to investigate the volatility properties of different aerosol species in order to determine aerosol composition; furthermore it can be used to infer the mixing state of the aerosol. Size distributions measured with the volatility system will be compared with ambient size distribution measurements this allows information on organic coating

  14. Absorbing aerosols at high relative humidity: linking hygroscopic growth to optical properties

    Directory of Open Access Journals (Sweden)

    J. Michel Flores

    2012-06-01

    Full Text Available One of the major uncertainties in the understanding of Earth's climate system is the interaction between solar radiation and aerosols in the atmosphere. Aerosols exposed to high humidity will change their chemical, physical, and optical properties due to their increased water content. To model hydrated aerosols, atmospheric chemistry and climate models often use the volume weighted mixing rule to predict the complex refractive index (RI of aerosols when they interact with high relative humidity, and, in general, assume homogeneous mixing. This study explores the validity of these assumptions. A humidified cavity ring down aerosol spectrometer (CRD-AS and a tandem hygroscopic DMA (differential mobility analyzer are used to measure the extinction coefficient and hygroscopic growth factors of humidified aerosols, respectively. The measurements are performed at 80% and 90%RH at wavelengths of 532 nm and 355 nm using size-selected aerosols with different degrees of absorption; from purely scattering to highly absorbing particles. The ratio of the humidified to the dry extinction coefficients (fRHext(%RH, Dry is measured and compared to theoretical calculations based on Mie theory. Using the measured hygroscopic growth factors and assuming homogeneous mixing, the expected RIs using the volume weighted mixing rule are compared to the RIs derived from the extinction measurements.

    We found a weak linear dependence or no dependence of fRH(%RH, Dry with size for hydrated absorbing aerosols in contrast to the non-monotonically decreasing behavior with size for purely scattering aerosols. No discernible difference could be made between the two wavelengths used. Less than 7% differences were found between the real parts of the complex refractive indices derived and those calculated using the volume weighted mixing rule, and the imaginary parts had up to a 20% difference. However, for substances with growth factor less than 1

  15. Aerosol optical properties in the North China Plain during HaChi campaign: an in-situ optical closure study

    Directory of Open Access Journals (Sweden)

    N. Ma

    2011-03-01

    Full Text Available The largest uncertainty in the estimation of radiative forcings on climate stems from atmospheric aerosols. In winter and summer of 2009, two periods of in-situ measurements on aerosol physical and chemical properties were conducted within the HaChi project at Wuqing, a town between Beijing and Tianjin in the North China Plain (NCP. Aerosol optical properties including scattering coefficient (σsp, hemispheric back scattering coefficient (σbsp, absorption coefficient (σap, as well as single scattering albedo (ω are presented. The characteristics of diurnal and seasonal variations are analyzed together with the meteorological and satellite data. The mean values of σsp, 550 nm of the dry aerosol in winter and summer are 280 ± 253 and 379 ± 251 Mm−1, respectively. The average σap for the two periods are respectively 47 ± 38 and 43 ± 27 Mm−1. The mean values of ω are 0.83 ± 0.05 and 0.87 ± 0.05 for winter and summer, respectively. The relative high levels of σsp and σbsp are representative of the regional polluted aerosol of the North China Plain. Pronounced diurnal cycle of σsp, σap and ω are found, mainly influenced by the evolution of boundary layer and accumulation of local emissions during night-time. Regional transport of pollutants from southwest in the NCP is significant both in winter and summer, while high values of σsp and σap correlate with calm winds in winter, which indicating the significant contribution of local emissions. An optical closure experiment is conducted to better understand uncertainties of the measurements. Good correlations (R>0.98 are found between values measured by nephelometer and values calculated with a modified Mie model. Monte Carlo simulations show an uncertainty of about 30% for the calculations. Considering all possible uncertainties of

  16. Aerosol optical properties in the North China Plain during HaChi campaign: an in-situ optical closure study

    Directory of Open Access Journals (Sweden)

    N. Ma

    2011-06-01

    Full Text Available The largest uncertainty in the estimation of climate forcing stems from atmospheric aerosols. In early spring and summer of 2009, two periods of in-situ measurements on aerosol physical and chemical properties were conducted within the HaChi (Haze in China project at Wuqing, a town between Beijing and Tianjin in the North China Plain (NCP. Aerosol optical properties, including the scattering coefficient (σsp, the hemispheric back scattering coefficient (σbsp, the absorption coefficient (σap, as well as the single scattering albedo (ω, are presented. The diurnal and seasonal variations are analyzed together with meteorology and satellite data. The mean values of σsp, 550 nm of the dry aerosol in spring and summer are 280±253 and 379±251 Mm−1, respectively. The average σap for the two periods is respectively 47±38 and 43±27 Mm−1. The mean values of ω at the wavelength of 637 nm are 0.82±0.05 and 0.86±0.05 for spring and summer, respectively. The relative high levels of σsp and σbsp are representative of the regional aerosol pollution in the NCP. Pronounced diurnal cycle of $σsp, σap and ω are found, mainly influenced by the evolution of boundary layer and the accumulation of local emissions during nighttime. The pollutants transported from the southwest of the NCP are more significant than that from the two megacities, Beijing and Tianjin, in both spring and summer. An optical closure experiment is conducted to better understand the uncertainties of the measurements. Good correlations (R>0.98 are found between the values measured by the nephelometer and the values calculated with a modified Mie model. The Monte Carlo simulation shows an uncertainty of about 30 % for the calculations. Considering all possible uncertainties of measurements, calculated σsp and σbsp agree well

  17. Retrieval of aerosol microphysical and optical properties above liquid clouds from POLDER/PARASOL polarization measurements

    Directory of Open Access Journals (Sweden)

    F. Waquet

    2013-04-01

    Full Text Available Most of the current aerosol retrievals from passive sensors are restricted to cloud-free scenes, which strongly reduces our ability to monitor the aerosol properties at a global scale and to estimate their radiative forcing. The presence of aerosol above clouds (AAC affects the polarized light reflected by the cloud layer, as shown by the spaceborne measurements provided by the POlarization and Directionality of Earth Reflectances (POLDER instrument on the PARASOL satellite. In a previous work, a first retrieval method was developed for AAC scenes and evaluated for biomass-burning aerosols transported over stratocumulus clouds. The method was restricted to the use of observations acquired at forward scattering angles (90–120° where polarized measurements are highly sensitive to fine-mode particle scattering. Non-spherical particles in the coarse mode, such as mineral dust particles, do not much polarize light and cannot be handled with this method. In this paper, we present new developments that allow retrieving also the properties of mineral dust particles above clouds. These particles do not much polarize light but strongly reduce the polarized cloud bow generated by the liquid cloud layer beneath and observed for scattering angles around 140°. The spectral attenuation can be used to qualitatively identify the nature of the particles (i.e. accumulation mode versus coarse mode, i.e. mineral dust particles versus biomass-burning aerosols, whereas the magnitude of the attenuation is related to the optical thickness of the aerosol layer. We also use the polarized measurements acquired in the cloud bow to improve the retrieval of both the biomass-burning aerosol properties and the cloud microphysical properties. We provide accurate polarized radiance calculations for AAC scenes and evaluate the contribution of the POLDER polarization measurements for the simultaneous retrieval of the aerosol and cloud properties. We investigate various scenes

  18. Interaction of aerosol particles with a standing wave optical field

    Science.gov (United States)

    Curry, John J.

    2016-09-01

    Trajectories of spherical dielectric particles carried across an optical standing wave by a flowing medium are investigated. Trajectories are determined by a three-dimensional Monte Carlo calculation that includes drag forces, Brownian motion, and optical gradient forces. We analyze the case of polystyrene particles with radii of order 100 nm carried across a Gaussian-mode standing wave by slowly flowing air. Particles are injected into the flowing air from a small source area such as the end of a capillary tube. Different sizes are dispersed continuously in space on the opposite side of the standing wave, demonstrating a practical way to sort particles. Certain discrete values of particle size show no interaction with the optical field, independent of intensity. These particles can be sorted with exceptionally high resolution. For example, particles with radii of 275 nm can be sorted with 1 nm resolution. This sorting scheme has the advantages of accommodating a high throughput, producing a continuous stream of continuously dispersed particles, and exhibiting excellent size resolution. The Monte Carlo results are in agreement with those obtained by a much simpler, and faster, fluid calculation based on effective velocities and effective diffusion coefficients, both obtained by averaging trajectories over multiple fringes of the optical field.

  19. Measurement of aerosol optical properties by cw cavity enhanced spectroscopy

    Science.gov (United States)

    Jie, Guo; Ye, Shan-Shan; Yang, Xiao; Han, Ye-Xing; Tang, Huai-Wu; Yu, Zhi-Wei

    2016-10-01

    The CAPS (Cavity Attenuated Phase shift Spectroscopy) system, which detects the extinction coefficients within a 10 nm bandpass centered at 532 nm, comprises a green LED with center wavelength in 532nm, a resonant optical cavity (36 cm length), a Photo Multiplier Tube detector, and a lock in amplifier. The square wave modulated light from the LED passes through the optical cavity and is detected as a distorted waveform which is characterized by a phase shift with respect to the initial modulation. Extinction coefficients are determined from changes in the phase shift of the distorted waveform of the square wave modulated LED light that is transmitted through the optical cavity. The performance of the CAPS system was evaluated by using measurements of the stability and response of the system. The minima ( 0.1 Mm-1) in the Allan plots show the optimum average time ( 100s) for optimum detection performance of the CAPS system. In the paper, it illustrates that extinction coefficient was correlated with PM2.5 mass (0.91). These figures indicate that this method has the potential to become one of the most sensitive on-line analytical techniques for extinction coefficient detection. This work aims to provide an initial validation of the CAPS extinction monitor in laboratory and field environments. Our initial results presented in this paper show that the CAPS extinction monitor is capable of providing state-of-the-art performance while dramatically reducing the complexity of optical instrumentation for directly measuring the extinction coefficients.

  20. Identification of aerosol types over Indo-Gangetic Basin: implications to optical properties and associated radiative forcing.

    Science.gov (United States)

    Tiwari, S; Srivastava, A K; Singh, A K; Singh, Sachchidanand

    2015-08-01

    The aerosols in the Indo-Gangetic Basin (IGB) are a mixture of sulfate, dust, black carbon, and other soluble and insoluble components. It is a challenge not only to identify these various aerosol types, but also to assess the optical and radiative implications of these components. In the present study, appropriate thresholds for fine-mode fraction and single-scattering albedo have been used to first identify the aerosol types over IGB. Four major aerosol types may be identified as polluted dust (PD), polluted continental (PC), black carbon-enriched (BCE), and organic carbon-enriched (OCE). Further, the implications of these different types of aerosols on optical properties and radiative forcing have been studied. The aerosol products derived from CIMEL sun/sky radiometer measurements, deployed under Aerosol Robotic Network program of NASA, USA were used from four different sites Karachi, Lahore, Jaipur, and Kanpur, spread over Pakistan and Northern India. PD is the most dominant aerosol type at Karachi and Jaipur, contributing more than 50% of all the aerosol types. OCE, on the other hand, contributes only about 12-15% at all the stations except at Kanpur where its contribution is ∼38%. The spectral dependence of AOD was relatively low for PD aerosol type, with the lowest AE values (1.0). SSA was found to be the highest for OCE (>0.9) and the lowest for BCE (<0.9) type aerosols, with drastically different spectral variability. The direct aerosol radiative forcing at the surface and in the atmosphere was found to be the maximum at Lahore among all the four stations in the IGB.

  1. Diurnal variations of aerosol optical properties in the North China Plain and their influences on the estimates of direct aerosol radiative effect

    Science.gov (United States)

    Kuang, Ye; Zhao, Chunsheng

    2016-04-01

    In this paper, the diurnal variations of aerosol optical properties and their influences on the estimation of daily average direct aerosol radiative effect (DARE) in the North China Plain (NCP) are investigated based on in situ measurements from Haze in China campaign. For ambient aerosol, the diurnal patterns of single scattering albedo (SSA) and asymmetry factor (g) in the NCP are both highest at dawn and lowest in the late afternoon, and quite different from those of dry-state aerosol. The relative humidity is the dominant factor which determines the diurnal patterns of SSA and g for ambient aerosol. Basing on the calculated SSA and g, several cases are designed to investigate the impacts of the diurnal changes of aerosol optical properties on DARE. The results demonstrate that the diurnal changes of SSA and g in the NCP have significant influences on the estimation of DARE at the top of the atmosphere (TOA). If the full temporal coverage of aerosol optical depth (AOD), SSA and g are available, an accurate estimation of daily average DARE can be achieved by using the daily averages of AOD, SSA and g. However, due to the lack of full temporal coverage datasets of SSA and g, their daily averages are usually not available. Basing on the results of designed cases, if the RH plays a dominant role in the diurnal variations of SSA and g, we suggest that using both SSA and g averaged over early morning and late afternoon as inputs for radiative transfer model to improve the accurate estimation of DARE. If the temporal samplings of SSA or g are too few to adopt this method, either averaged over early morning or late afternoon of both SSA and g can be used to improve the estimation of DARF at TOA.

  2. Aerosol decadal trends – Part 1: In-situ optical measurements at GAW and IMPROVE stations

    Directory of Open Access Journals (Sweden)

    B. A. Schichtel

    2012-08-01

    Full Text Available Currently many ground-based atmospheric stations include in-situ measurements of aerosol physical and optical properties, resulting in more than 20 long-term (>10 yr aerosol measurement sites in the Northern Hemisphere and Antarctica. Most of these sites are located at remote locations and monitor the aerosol particle number concentration, wavelength-dependent light scattering, backscattering, and absorption coefficients. The existence of these multi-year datasets enables the analysis of long-term trends of these aerosol parameters of the derived light scattering Ångström exponent and backscatter fraction. Since the aerosol variables are not normally distributed, three different methods (the seasonal Mann-Kendall test associated with the Sen's slope, the generalized least squares fit associated with an autoregressive bootstrap algorithm for confidence intervals, and the least-mean square fit applied to logarithms of the data were applied to detect the long-term trends and their magnitudes for each month. To allow a comparison among measurement sites with varying length of data records, trends on the most recent 10 and 15 yr periods were calculated. No significant trends were found for the three continental European sites. Statistically significant trends were found for the two European marine sites but the signs of the trends varied with aerosol property and location. Statistically significant decreasing trends for both scattering and absorption coefficient were found for most North American stations, although positive trends were found for a few desert and high-altitude sites. No significant trends in scattering coefficient were found for the Arctic or Antarctic stations, whereas the Arctic station had a negative trend in absorption coefficient.

  3. Climatology of aerosol optical depth in north-central Oklahoma: 1992–2008

    Energy Technology Data Exchange (ETDEWEB)

    Michalsky, Joseph; Denn, Frederick; Flynn, Connor; Hodges, Gary; Kiedron, Piotr; Koontz, Annette; Schlemmer, James; Schwartz, Stephen E.

    2010-04-13

    Aerosol optical depth (AOD) has been measured at the Atmospheric Radiation Measurement Program central facility near Lamont, Oklahoma, since the fall of 1992. Most of the data presented are from the multifilter rotating shadowband radiometer, a narrow-band, interference-filter Sun radiometer with five aerosol bands in the visible and near infrared; however, AOD measurements have been made simultaneously and routinely at the site by as many as three different types of instruments, including two pointing Sun radiometers. Scatterplots indicate high correlations and small biases consistent with earlier comparisons. The early part of this 16 year record had a disturbed stratosphere with residual Mt. Pinatubo aerosols, followed by the cleanest stratosphere in decades. As such, the last 13 years of the record reflect changes that have occurred predominantly in the troposphere. The field calibration technique is briefly described and compared to Langley calibrations from Mauna Loa Observatory. A modified cloudscreening technique is introduced that increases the number of daily averaged AODs retrieved annually to about 250 days compared with 175 days when a more conservative method was employed in earlier studies. AODs are calculated when the air mass is less than six; that is, when the Sun’s elevation is greater than 9.25°. The more inclusive cloud screen and the use of most of the daylight hours yield a data set that can be used to more faithfully represent the true aerosol climate for this site. The diurnal aerosol cycle is examined month-by-month to assess the effects of an aerosol climatology on the basis of infrequent sampling such as that from satellites.

  4. Climatology of aerosol optical depth in North-Central Oklahoma: 1992-2008

    Energy Technology Data Exchange (ETDEWEB)

    Michalsky, J.; Schwartz, S.; Denn, F.; Flynn, C.; Hodges, G.; Kiedron, P.; Koontz, A.; Schlemmer, J., and Schwartz, S. E

    2010-04-01

    Aerosol optical depth (AOD) has been measured at the Atmospheric Radiation Measurement Program central facility near Lamont, Oklahoma, since the fall of 1992. Most of the data presented are from the multifilter rotating shadowband radiometer, a narrow-band, interference-filter Sun radiometer with five aerosol bands in the visible and near infrared; however, AOD measurements have been made simultaneously and routinely at the site by as many as three different types of instruments, including two pointing Sun radiometers. Scatterplots indicate high correlations and small biases consistent with earlier comparisons. The early part of this 16 year record had a disturbed stratosphere with residual Mt. Pinatubo aerosols, followed by the cleanest stratosphere in decades. As such, the last 13 years of the record reflect changes that have occurred predominantly in the troposphere. The field calibration technique is briefly described and compared to Langley calibrations from Mauna Loa Observatory. A modified cloud-screening technique is introduced that increases the number of daily averaged AODs retrieved annually to about 250 days compared with 175 days when a more conservative method was employed in earlier studies. AODs are calculated when the air mass is less than six; that is, when the Sun's elevation is greater than 9.25{sup o}. The more inclusive cloud screen and the use of most of the daylight hours yield a data set that can be used to more faithfully represent the true aerosol climate for this site. The diurnal aerosol cycle is examined month-by-month to assess the effects of an aerosol climatology on the basis of infrequent sampling such as that from satellites.

  5. Assimilation of Polder aerosol optical thickness into LMD2-Inca model in order to study aerosol-climate interactions; Etude des interactions entre aerosols et climat: assimilation des observations spatiales de Polder dans LMDz-Inca

    Energy Technology Data Exchange (ETDEWEB)

    Generoso, S.

    2004-12-15

    Aerosols influence the Earth radiative budget both through their direct (scattering and absorption of solar radiation) and indirect (impacts on cloud microphysics) effects. The anthropogenic perturbation due to aerosol emissions is of the same order of magnitude than the one due to greenhouse gases, but less well known. To improve our knowledge, we need to better know aerosol spatial and temporal distributions. Indeed, aerosol modeling still suffers from large uncertainties in sources and transport, while satellite observations are incomplete (no detection in the presence of clouds, no information on the vertical distribution or on the chemical nature). Moreover, field campaigns are localized in space and time. This study aims to reduce uncertainties in aerosol distributions, developing assimilation of satellite data into a chemical transport model. The basic idea is to combine information obtained from spatial observation (optical thickness) and modeling studies (aerosol types, vertical distribution). In this study, we assimilate data from the POLDER space-borne instrument into the LMDz-INCA model. The results show the advantage of merging information from different sources. In many regions, the method reduces uncertainties on aerosol distribution (reduction of RMS error). An application of the method to the study of aerosol impact on cloud microphysics is shown. (author)

  6. The Impacts of Optical Properties on Radiative Forcing Due to Dust Aerosol

    Institute of Scientific and Technical Information of China (English)

    WANG Hong; SHI Guangyu; LI Shuyan; LI Wei; WANG Biao; HUANG Yanbin

    2006-01-01

    There are large uncertainties in the quantitative assessment of radiative effects due to atmospheric dust aerosol. The optical properties contribute much to those uncertainties. The authors perform several sensitivity experiments to estimate the impacts of optical characteristics on regional radiative forcing in this paper. The experiments involve in refractive indices, single scattering albedo, asymmetry factor and optical depth. An updated dataset of refractive indices representing East Asian dust and the one recommended by the World Meteorology Organization (WMO) are contrastively analyzed and used. A radiative transfer code for solar and thermal infrared radiation with detailed aerosol parameterization is employed. The strongest emphasis is on the refractive indices since other optical parameters strongly depend on it, and the authors found a strong sensitivity of radiative forcing on refractive indices. Studies show stronger scattering, weaker absorption and forward scattering of the East Asian dust particles at solar wavelengths, which leads to higher negative forcing, lower positive forcing and bigger net forcing at the top of the atmosphere (TOA) than that of the WMO dust model. It is also found that the TOA forcings resulting from these two dust models have opposite signs in certain regions, which implies the importance of accurate measurements of optical properties in the quantitative estimation of radiative forcing.

  7. Aerosol decadal trends – Part 1: In-situ optical measurements at GAW and IMPROVE stations

    Directory of Open Access Journals (Sweden)

    M. Collaud Coen

    2013-01-01

    Full Text Available Currently many ground-based atmospheric stations include in-situ measurements of aerosol physical and optical properties, resulting in more than 20 long-term (> 10 yr aerosol measurement sites in the Northern Hemisphere and Antarctica. Most of these sites are located at remote locations and monitor the aerosol particle number concentration, wavelength-dependent light scattering, backscattering, and absorption coefficients. The existence of these multi-year datasets enables the analysis of long-term trends of these aerosol parameters, and of the derived light scattering Ångström exponent and backscatter fraction. Since the aerosol variables are not normally distributed, three different methods (the seasonal Mann-Kendall test associated with the Sen's slope, the generalized least squares fit associated with an autoregressive bootstrap algorithm for confidence intervals, and the least-mean square fit applied to logarithms of the data were applied to detect the long-term trends and their magnitudes. To allow a comparison among measurement sites, trends on the most recent 10 and 15 yr periods were calculated. No significant trends were found for the three continental European sites. Statistically significant trends were found for the two European marine sites but the signs of the trends varied with aerosol property and location. Statistically significant decreasing trends for both scattering and absorption coefficients (mean slope of −2.0% yr−1 were found for most North American stations, although positive trends were found for a few desert and high-altitude sites. The difference in the timing of emission reduction policy for the Europe and US continents is a likely explanation for the decreasing trends in aerosol optical parameters found for most American sites compared to the lack of trends observed in Europe. No significant trends in scattering coefficient were found for the Arctic or Antarctic stations, whereas the Arctic station

  8. The optical constants of several atmospheric aerosol species - Ammonium sulfate, aluminum oxide, and sodium chloride

    Science.gov (United States)

    Toon, O. B.; Pollack, J. B.; Khare, B. N.

    1976-01-01

    An investigation is conducted of problems which are related to a use of measured optical constants in the simulation of the optical constants of real atmospheric aerosols. The techniques of measuring optical constants are discussed, taking into account transmission measurements through homogeneous and inhomogeneous materials, the immersion of a material in a liquid of a known refractive index, the consideration of the minimum deviation angle of prism measurement, the interference of multiply reflected light, reflectivity measurements, and aspects of mathematical analysis. Graphs show the real and the imaginary part of the refractive index as a function of wavelength for aluminum oxide, NaCl, and ammonium sulfate. Tables are provided for the dispersion parameters and the optical constants.

  9. Large differences in aerosol optical properties over the north-west Atlantic Ocean during the TCAP field campaign

    Science.gov (United States)

    Chand, D.; Berg, L. K.; Comstock, J. M.; Fast, J. D.; Flynn, C. J.; Hubbe, J. M.; Kassianov, E.; Mei, F.; Pekour, M. S.; Schmid, B.; Sedlacek, A. J., III; Tomlinson, J. M.; Shilling, J. E.; Wilson, J. M.; Zelenyuk, A.; Berkowitz, C. M.

    2014-12-01

    Aerosol radiative forcing is an important parameter in the Earth's radiation budget and can be an important driver of atmospheric circulation and the hydrological cycle. Accurate estimation of aerosol radiative forcing requires measurement of both the extensive and intensive optical properties of aerosols. While the intensive optical properties are independent of aerosol mass or number, they are critical inputs when calculating radiative forcing with applications to climate research, satellite remote sensing and model validations. The key aerosol intensive properties that need to be evaluated include single scattering albedo (SSA), the angstrom exponent, the asymmetry parameter, the radiative forcing efficiency, and the hygroscopic scattering factor. We report here on values of these variables over the Cape Cod and nearby northwest Atlantic Ocean during the Two Column Aerosol Project (TCAP). The average SSA shows a distinct profile having higher SSA values below the top of well-mixed residual layer (RL) and lower SSA above it. Aerosol in the free troposphere (FT) were found to have less spectral dependence in their optical properties, lower back scatter fraction and higher hygroscopic growth relative to aerosols found in the RL. Analysis of individual particle composition suggests that that ratio of aged to fresh aerosol numbers in the FT is 70% higher compared to aerosols measured in the RL, and that smoke from biomass burning contributed ~10% to this number. Single particle analysis also reveals that the fraction and variability of coated black carbon (BC) aerosol is higher in the FT relative to that measured in the residual layer. The daily radiative forcing efficiency of these aerosols in the FT is factor 2 higher than below RL. Seven years (2007-2013) of CALIPSO satellite observations show that the mean altitude of the top of smoke layers (~3.3 km) consistent with these in situ observations from TCAP. Overall, the long term CALIPSO observations characterizes

  10. Spatio-temporal variability of aerosols over East China inferred by merged visibility-GEOS-Chem aerosol optical depth

    Science.gov (United States)

    Lin, Jintai; Li, Jing

    2016-05-01

    Long-term visibility measurements offer useful information for aerosol and climate change studies. Recently, a new technique to converting visibility measurements to aerosol optical depth (AOD) has been developed on a station-to-station basis (Lin et al., 2014). However, factors such as human observation differences and local meteorological conditions often impair the spatial consistency of the visibility converted AOD dataset. Here we further adopt AOD spatial information from a chemical transport model GEOS-Chem, and merge visibility inferred and modeled early-afternoon AOD over East China on a 0.667° long. × 0.5° lat. grid for 2005-2012. Comparisons with MODIS/Aqua retrieved AOD and subsequent spectral decomposition analyses show that the merged dataset successfully corrects the low bias in the model while preserving its spatial pattern, resulting in very good agreement with MODIS in both magnitude and spatio-temporal variability. The low bias is reduced from 0.10 in GEOS-Chem AOD to 0.04 in the merged data averaged over East China, and the correlation in the seasonal and interannual variability between MODIS and merged AOD is well above 0.75 for most regions. Comparisons between the merged and AERONET data also show an overall small bias and high correlation. The merged dataset reveals four major pollution hot spots in China, including the North China Plain, the Yangtze River Delta, the Pearl River Delta and the Sichuan Basin, consistent with previous works. AOD peaks in spring-summer over the North China Plain and Yangtze River Delta and in spring over the Pearl River Delta, with no distinct seasonal cycle over the Sichuan Basin. The merged AOD has the largest difference from MODIS over the Sichuan Basin. We also discuss possible benefits of visibility based AOD data that correct the sampling bias in MODIS retrievals related to cloud-free sampling and misclassified heavy haze conditions.

  11. Aerosol optical properties in ultraviolet ranges and respiratory diseases in Thailand

    Science.gov (United States)

    Kumharn, Wilawan; Hanprasert, Kasarin

    2016-10-01

    This study investigated the values of Angstrom parameters (α,β) in ultraviolet (UV) ranges by using AERONET Aerosol Optical Depth (AOD) data. A second-order polynomial was applied to the AERONET data in order to extrapolate to 320 nm from 2003 to 2013 at seven sites in Thailand. The α,β were derived by applying the Volz Method (VM) and Linear Method (LM) at 320-380 nm at seven monitoring sites in Thailand. Aerosol particles were categorized in both coarse and fine modes, depending on regions. Aerosol loadings were related to dry weather, forest fires, sea salt and most importantly, biomass burning in the North, and South of Thailand. Aerosol particles in the Central region contain coarse and fine modes, mainly emitted from vehicles. The β values obtained were associated with turbid and very turbid skies in Northern and Central regions except Bangkok, while β results are associated with clean skies in South. Higher values of the β at all sites were found in the winter and summer compared with the rainy season, in contrast to South where the highest AOD was observed in June. The β values were likely to increase during 2003-2013. These values correlate with worsening health situations as evident from increasing respiratory diseases reported.

  12. Improving Calculation Accuracies of Accumulation-Mode Fractions Based on Spectral of Aerosol Optical Depths

    Science.gov (United States)

    Ying, Zhang; Zhengqiang, Li; Yan, Wang

    2014-03-01

    Anthropogenic aerosols are released into the atmosphere, which cause scattering and absorption of incoming solar radiation, thus exerting a direct radiative forcing on the climate system. Anthropogenic Aerosol Optical Depth (AOD) calculations are important in the research of climate changes. Accumulation-Mode Fractions (AMFs) as an anthropogenic aerosol parameter, which are the fractions of AODs between the particulates with diameters smaller than 1μm and total particulates, could be calculated by AOD spectral deconvolution algorithm, and then the anthropogenic AODs are obtained using AMFs. In this study, we present a parameterization method coupled with an AOD spectral deconvolution algorithm to calculate AMFs in Beijing over 2011. All of data are derived from AErosol RObotic NETwork (AERONET) website. The parameterization method is used to improve the accuracies of AMFs compared with constant truncation radius method. We find a good correlation using parameterization method with the square relation coefficient of 0.96, and mean deviation of AMFs is 0.028. The parameterization method could also effectively solve AMF underestimate in winter. It is suggested that the variations of Angstrom indexes in coarse mode have significant impacts on AMF inversions.

  13. Impact of wild forest fires in Eastern Europe on aerosol composition and particle optical properties

    Directory of Open Access Journals (Sweden)

    Tymon Zielinski

    2016-01-01

    Full Text Available In this paper the authors discuss the changes of aerosol optical depth (AOD in the region of eastern Europe and the Baltic Sea due to wild fire episodes which occurred in the area of Belarus and Ukraine in 2002. The authors discuss how the biomass burning aerosols were advected over the Baltic area and changed the composition of aerosol ensemble for a period of several summer weeks. The air pressure situation and slow wind speeds also facilitated the development of such conditions. As a consequence very high AOD levels were recorded, by an order of 3–4 higher versus normal conditions and they significantly increased the annual averages. On particular days of August 2002 the AOD values reached a level of over 0.7. On these days fine particles fully dominated the entire ensemble of aerosol particles. They were either sulfates or smoke particles. Such situation was unique over a period of many years and it had its serious consequences for the region and especially for the Baltic Sea.

  14. Aerosol optical depth under "clear" sky conditions derived from sea surface reflection of lidar signals.

    Science.gov (United States)

    He, Min; Hu, Yongxiang; Huang, Jian Ping; Stamnes, Knut

    2016-12-26

    There are considerable demands for accurate atmospheric correction of satellite observations of the sea surface or subsurface signal. Surface and sub-surface reflection under "clear" atmospheric conditions can be used to study atmospheric correction for the simplest possible situation. Here "clear" sky means a cloud-free atmosphere with sufficiently small aerosol particles. The "clear" aerosol concept is defined according to the spectral dependence of the scattering cross section on particle size. A 5-year combined CALIPSO and AMSR-E data set was used to derive the aerosol optical depth (AOD) from the lidar signal reflected from the sea surface. Compared with the traditional lidar-retrieved AOD, which relies on lidar backscattering measurements and an assumed lidar ratio, the AOD retrieved through the surface reflectance method depends on both scattering and absorption because it is based on two-way attenuation of the lidar signal transmitted to and then reflected from the surface. The results show that the clear sky AOD derived from the surface signal agrees with the clear sky AOD available in the CALIPSO level 2 database in the westerly wind belt located in the southern hemisphere, but yields significantly higher aerosol loadings in the tropics and in the northern hemisphere.

  15. Where does the optically detectable aerosol in the European Arctic come from?

    Directory of Open Access Journals (Sweden)

    Maria Stock

    2014-03-01

    Full Text Available In this paper, we pose the question where the source regions of the aerosol, which occurs in the European Arctic, are located. Long-term aerosol optical depth (AOD data from Ny-Ålesund and Sodankylä as well as short-term data from a campaign on a Russian drifting station were analysed by air backtrajectories, analysis of the general circulation pattern and a correlation to chemical composition from in-situ measurements. Surprisingly, our data clearly shows that direct transport of pollutants from Europe does not play an important role. Instead, Arctic haze in Ny-Ålesund has been found for air masses from the Eastern Arctic, while events with increased AOD but chemically more diverse composition have been found for air from Siberia or the central Arctic. Moreover, the AOD in Ny-Ålesund does not depend on the North Atlantic Oscillation (NAO. Hence, either the pollution pathways of aerosol are more complex or aerosol is significantly altered by clouds.

  16. Multiple regression method to determine aerosol optical depth in atmospheric column in Penang, Malaysia

    Science.gov (United States)

    Tan, F.; Lim, H. S.; Abdullah, K.; Yoon, T. L.; Zubir Matjafri, M.; Holben, B.

    2014-02-01

    Aerosol optical depth (AOD) from AERONET data has a very fine resolution but air pollution index (API), visibility and relative humidity from the ground truth measurements are coarse. To obtain the local AOD in the atmosphere, the relationship between these three parameters was determined using multiple regression analysis. The data of southwest monsoon period (August to September, 2012) taken in Penang, Malaysia, was used to establish a quantitative relationship in which the AOD is modeled as a function of API, relative humidity, and visibility. The highest correlated model was used to predict AOD values during southwest monsoon period. When aerosol is not uniformly distributed in the atmosphere then the predicted AOD can be highly deviated from the measured values. Therefore these deviated data can be removed by comparing between the predicted AOD values and the actual AERONET data which help to investigate whether the non uniform source of the aerosol is from the ground surface or from higher altitude level. This model can accurately predict AOD if only the aerosol is uniformly distributed in the atmosphere. However, further study is needed to determine this model is suitable to use for AOD predicting not only in Penang, but also other state in Malaysia or even global.

  17. Retrieval of aerosol optical depth for Chongqing using the HJ-1 satellite data

    Science.gov (United States)

    Wang, Zengwu; Yang, Shiqi; Zeng, Qiaolin; Wang, Yongqian

    2017-06-01

    Aerosol optical depth (AOD) is a common indicator applied in monitoring aerosols in the atmosphere. The hilly landscape and rapid economic growth of the megacity Chongqing have facilitated increased aerosol concentration, and it is meaningful to accurately retrieve AOD over Chongqing. The HJ-1A/B satellite of China carries a sensor/camera called the Charge Coupled Device (CCD), the spatial resolution of which meets the requirement for retrieving high resolution AOD. In this paper, analysis of the AOD retrievals from different methods using the HJ-1 satellite data revealed the most suitable algorithm. Through comparison with the AOD product of Moderate Resolution Imaging Spectroradiometer (MODIS), the AOD retrieval results using enhanced vegetation index (EVI) to estimate dark pixels showed the highest correlation. The continental aerosol model was used to build a lookup table that was able to facilitate a good AOD retrieval for both city and rural areas. Finally, the algorithm that combined dark pixels, buffer areas, and the deep blue algorithm was found to be most suitable for AOD retrieval. The AOD retrieval results based on the HJ-1 data were consistent with MODIS products, and our algorithm yields reasonable results in most cases. The results were also compared with ground-based PM10 measurements synchronized with the overpass time of the HJ-1 satellite, and high correlation was found. The findings are relevant to other Chinese satellite data used for retrieving AOD on the same channels.

  18. Review on optical constants of Titan aerosols: Experimental results and modeling/observational data

    Science.gov (United States)

    Brassé, Coralie; Muñoz, Olga; Coll, Patrice; Raulin, François

    2014-05-01

    During the last years many studies have been performed to improve the experimental database of optical constants of Titan aerosols. Indeed, the determination of the optical constants of these particles is essential to quantify their capacity to absorb and to scatter solar radiation, and thus to evaluate their role on Titan's radiative balance and climate. The study of optical properties is also crucial to analyze and to better interpret many of Titan's observational data, in particular those acquired during the Cassini-Huygens mission. One way to determine Titan aerosols optical constant is to measure the optical constants of analogues of Titan complex organic material synthesized in the laboratory, usually named Titan's tholins (Sagan and Khare, 1979). But the optical constants depend on the chemical composition, the size and the shape of particles (Raulin et al., 2012). Those three parameters result from the experimental conditions such as energy source, gas mixing ratio, gas pressure, flow rate and irradiation time (Cable et al., 2012). Besides the determination of the refractive index in the laboratory, there are others methods using theoretical models or observational data. Nevertheless, theoretical models are based on laboratory data or/and observational data. The visible - near infrared spectral region of optical constants has been widely studied with laboratory analogues. Comparison of the obtained results suggest that tholins synthesized by Tran et al. (2003) and Majhoub et al. (2012) are the best representative of Titan aerosols with regards to their refractive indexes in this spectral region. The mid-infrared spectral range has been studied only by Imanaka et al. (2012) and slightly by Tran et al. (2003). In that spectral range, Titan tholins do not exhibit the features displayed by Kim and Courtin (2013) from Titan's observations. For spectral region of wavelengths smaller than 0.20µm or higher than 25µm, only the data from Khare et al. (1984) are

  19. Modeling South America regional smoke plume: aerosol optical depth variability and shortwave surface forcing

    Science.gov (United States)

    Rosário, N. E.; Longo, K. M.; Freitas, S. R.; Yamasoe, M. A.; Fonseca, R. M.

    2012-07-01

    Intra-seasonal variability of smoke aerosol optical depth (AOD) and downwelling solar irradiance at the surface during the 2002 biomass burning season in South America was modeled using the Coupled Chemistry-Aerosol-Tracer Transport model to the Brazilian developments on the Regional Atmospheric Modeling System (CCATT-BRAMS). Measurements of AOD from the AErosol RObotic NETwork (AERONET) and solar irradiance at the surface from the Solar Radiation Network (SolRad-NET) were used to evaluate model results. In general, the major features associated with AOD evolution over the southern part of the Amazon Basin and cerrado ecosystem are captured by the model. The main discrepancies were found for high aerosol loading events. In the northeastern portion of the Amazon Basin the model systematically underestimated AOD. This is likely due to the cloudy nature of the region, preventing accurate detection of the fire spots used in the emission model. Moreover, measured AOD were very often close to background conditions and emissions other than smoke were not considered in the simulation. Therefore, under the background scenario, one would expect the model to underestimate AOD. The issue of high aerosol loading events in the southern part of the Amazon and cerrado is also discussed in the context of emission shortcomings. The Cuiabá cerrado site was the only one where the highest quality AERONET data were unavailable. Thus, lower quality data were used. Root-mean-square-error (RMSE) between the model and observations decreased from 0.48 to 0.17 when extreme AOD events (AOD550 nm ≥ 1.0) and Cuiabá were excluded from analysis. Downward surface solar irradiance comparisons also followed similar trends when extremes AOD were excluded. This highlights the need to improve the modelling of the regional smoke plume in order to enhance the accuracy of the radiative energy budget. Aerosol optical model based on the mean intensive properties of smoke from the southern part of the

  20. Aerosol optical depth in a western Mediterranean site: An assessment of different methods

    Science.gov (United States)

    Sanchez-Romero, A.; González, J. A.; Calbó, J.; Sanchez-Lorenzo, A.; Michalsky, J.

    2016-06-01

    Column aerosol optical properties were derived from multifilter rotating shadowing radiometer (MFRSR) observations carried out at Girona (northeast Spain) from June 2012 to June 2014. We used a technique that allows estimating simultaneously aerosol optical depth (AOD) and Ångström exponent (AE) at high time-resolution. For the period studied, mean AOD at 500 nm was 0.14, with a noticeable seasonal pattern, i.e. maximum in summer and minimum in winter. Mean AE from 500 to 870 nm was 1.2 with a strong day-to-day variation and slightly higher values in summer. So, the summer increase in AOD seems to be linked with an enhancement in the number of fine particles. A radiative closure experiment, using the SMARTS2 model, was performed to confirm that the MFRSR-retrieved aerosol optical properties appropriately represent the continuously varying atmospheric conditions in Girona. Thus, the calculated broadband values of the direct flux show a mean absolute difference of less than 5.9 W m- 2 (0.77%) and R = 0.99 when compared to the observed fluxes. The sensitivity of the achieved closure to uncertainties in AOD and AE was also examined. We use this MFRSR-based dataset as a reference for other ground-based and satellite measurements that might be used to assess the aerosol properties at this site. First, we used observations obtained from a 100 km away AERONET station; despite a general similar behavior when compared with the in-situ MFRSR observations, certain discrepancies for AOD estimates in the different channels (R < 0.84 and slope < 1) appear. Second, AOD products from MISR and MODIS satellite observations were compared with our ground-based retrievals. Reasonable agreements are found for the MISR product (R = 0.92), with somewhat poorer agreement for the MODIS product (R = 0.70). Finally, we apply all these methods to study in detail the aerosol properties during two singular aerosol events related to a forest fire and a desert dust intrusion.

  1. Aerosol optical properties over the Svalbard region of Arctic: ground-based measurements and satellite remote sensing

    Science.gov (United States)

    Gogoi, Mukunda M.; Babu, S. Suresh

    2016-05-01

    In view of the increasing anthropogenic presence and influence of aerosols in the northern polar regions, long-term continuous measurements of aerosol optical parameters have been investigated over the Svalbard region of Norwegian Arctic (Ny-Ålesund, 79°N, 12°E, 8 m ASL). This study has shown a consistent enhancement in the aerosol scattering and absorption coefficients during spring. The relative dominance of absorbing aerosols is more near the surface (lower single scattering albedo), compared to that at the higher altitude. This is indicative of the presence of local anthropogenic activities. In addition, long-range transported biomass burning aerosols (inferred from the spectral variation of absorption coefficient) also contribute significantly to the higher aerosol absorption in the Arctic spring. Aerosol optical depth (AOD) estimates from ground based Microtop sun-photometer measurements reveals that the columnar abundance of aerosols reaches the peak during spring season. Comparison of AODs between ground based and satellite remote sensing indicates that deep blue algorithm of Moderate Resolution Imaging Spectroradiometer (MODIS) retrievals over Arctic snow surfaces overestimate the columnar AOD.

  2. Airborne measurements of aerosol optical properties related to early spring transport of mid-latitude sources into the Arctic

    Directory of Open Access Journals (Sweden)

    R. Adam de Villiers

    2009-12-01

    Full Text Available Airborne lidar and in-situ measurements of the aerosol properties were conducted between Svalbard Island and Scandinavia in April 2008. Evidence of aerosol transport from Europe and Asia is given. The analysis of the aerosol optical properties based on a multiwavelength lidar (355, 532, 1064 nm including depolarization at 355 nm aims at distinguishing the role of the different aerosol sources (Siberian wild fires, Eastern Asia and European anthropogenic emissions. Combining, first aircraft measurements, second FLEXPART simulations with a calculation of the PBL air fraction originating from the three different mid-latitude source regions, and third level-2 CALIPSO data products (i.e. backscatter coefficient, depolarisation and color ratio in aerosol layers along the transport pathways, appears a valuable approach to identify the role of the different aerosol sources even after a transport time larger than 4 days. Above Asia, CALIPSO data indicate more depolarisation (up to 15% and largest color ratio (>0.5 for the northeastern Asia emissions (i.e. an expected mixture of Asian pollution and dust, while low depolarisation together with smaller and quasi constant color ratio (≈0.3 are observed for the Siberian biomass burning emissions. A similar difference is visible between two layers observed by the aircraft above Scandinavia. The analysis of the time evolution of the aerosol optical properties revealed by CALIPSO between Asia and Scandinavia shows a gradual decrease of the aerosol backscatter, depolarisation ratio and color ratio which suggests the removal of the largest particles in the accumulation mode. A similar study conducted for a European plume has shown aerosol optical properties intermediate between the two Asian sources with color ratio never exceeding 0.4 and moderate depolarisation ratio being always less than 8%, i.e. less aerosol from the accumulation mode.

  3. Optical properties of mixed aerosol layers over Japan derived with multi-wavelength Mie-Raman lidar system

    Science.gov (United States)

    Hara, Yukari; Nishizawa, Tomoaki; Sugimoto, Nobuo; Matsui, Ichiro; Pan, Xiaole; Kobayashi, Hiroshi; Osada, Kazuo; Uno, Itsushi

    2017-02-01

    Mixing state of aerosols and optical properties including lidar ratio, particle depolarization ratio, and Ångström exponent were investigated at Fukuoka in western Japan using a multi-wavelength Mie-Raman lidar (MMRL), various aerosol mass-concentration measurements, and a polarization optical particle counter during Winter-Spring 2015. Aerosol extinction coefficient, backscatter coefficient, and depolarization at 355 and 532 nm and attenuated backscatter coefficient at 1064 nm are obtained from the MMRL measurements. Ten aerosol episodes were classified into three categories (air pollution, mineral dust, and marine aerosol) based on aerosol mass-concentration measurements in the fine-mode (particle diameter Dplidar ratio for air pollution was 57±4 sr at 355 nm and 53±8 sr at 532 nm with Ångström exponent of 1.4±0.5. For mineral dust, a slightly high averaged lidar ratio (50±7 sr at 355 nm and 54±9 sr at 532 nm) was obtained with relatively high Ångström exponent of 0.8±0.3 owing to contributions from fine-mode particles (PMf). The mean particle depolarization ratios of 13±8% at 355 nm and 16±6% at 532 nm also suggest mixing of mineral dust and anthropogenic fine-mode aerosols. The lowest lidar ratio was obtained for marine case. Classification of aerosol types using the lidar ratio and particle depolarization ratio was conducted based on the results obtained in this study. The classified aerosol types almost corresponded to aerosol category obtained by previous studies. We found no remarkable correlation between the fraction of black carbon and the lidar ratio: this might be due to the complexity of the mixing state among various aerosols. The obtained lidar ratio was rather correlated with the ratio of PMf to PM10, representing the mixing state of fine- and coarse-mode particles.

  4. Optical and microphysical properties of column-integrated aerosols at a SKYNET site downwind of Seoul, Korea

    Science.gov (United States)

    Choi, Y.; Park, J. S.; Ghim, Y. S.

    2014-12-01

    A skyradiometer (POM-02, Prede Co. Ltd.) has been operated to investigate aerosol properties at a SKYNET (SKYradiometer NETwork) site, YGN (Yongin) for six years starting from November 2008. The site is at the rooftop of a five-story building on the hill, about 35 km southeast of downtown Seoul (37.34 °N, 127.27 °E and 167 m above sea level). POM-02 measures the diffuse radiation at six minute intervals at 11 wavelengths. Using version 5 of the skyrad.pack, aerosol optical (aerosol optical depth and single scattering albedo) and microphysical (volume size distribution) properties were retrieved from the measurements at five wavelengths such as 400, 500, 675, 870 and 1020 nm. In comparison with CIMEL sun photometers used in AERONET (AErosol RObotic NETwork), another worldwide ground-based network, skyradiometers have an advantage that they can provide larger number of aerosol property data at shorter time intervals. However, standard procedures for instrument operation and data retrieval have not been established. In this study, we first showed how we calibrated the instrument and how we obtained cloud screened and quality assured data. Next, we presented variations in aerosol optical and microphysical properties, depending on air masses and/or meteorological conditions, and examined the characteristic of high aerosol loading episodes including Asian dust storm and smog.

  5. Evaluation of aerosol optical properties of GEOS-Chem over East Asia during the DRAGON-Asia 2012 campaign

    Science.gov (United States)

    Jo, D. S.; Park, R.; Kim, J.

    2015-12-01

    A nested version of 3-D chemical transport model (GEOS-Chem v9-01-02) is evaluated over East Asia during the Distributed Regional Aerosol Gridded Observation Networks (DRAGON)-Asia 2012 campaign period, focusing on fine-mode aerosol optical depth (fAOD) and single scattering albedo (SSA). Both are important to assess the effect of anthropogenic aerosols on climate. We compare the daily mean simulated optical properties of aerosols with the observations from DRAGON-Asia campaign for March-May, 2012 (provided in level 2.0: cloud screened and quality assured). We find that the model reproduces the observed daily variability of fAOD (R=0.67), but overestimates the magnitude by 30%, which is in general consistent with other global model comparisons from ACCMIP. However, a significant high bias in the model is found compared to the observed SSA at 440 nm, which is important for determining the sign of aerosol radiative forcing. In order to understand causes for this gap we conduct several sensitivity tests by changing source magnitudes and input parameters of aerosols, affecting the aerosol optical properties under various atmospheric conditions, which allows us to reduce the gap and to find the optimal values in the model.

  6. Compositional and Optical Properties of Titan Haze Analogs Using Aerosol Mass Spectrometry, Photoacoustic Spectroscopy and Cavity Ring-Down Spectroscopy

    Science.gov (United States)

    Ugelow, M.; Zarzana, K. J.; Tolbert, M. A.

    2015-12-01

    The organic haze that surrounds Saturn's moon Titan is formed through the photolysis and electron initiated dissociation of methane and nitrogen. The chemical pathways leading to haze formation and the resulting haze optical properties are still highly uncertain. Here we examine the compositional and optical properties of Titan haze aerosol analogs. By studying these properties together, the impact of haze on Titan's radiative balance can be better understood. The aerosol analogs studied are produced from different initial methane concentrations (0.1, 2 and 10% CH4) using spark discharge excitation. To determine the complex refractive index of the aerosol, we combine two spectroscopic techniques, one that measures absorption and one that measures extinction: photoacoustic spectroscopy coupled with cavity ring-down spectroscopy (PASCaRD). This technique provides the benefit of a high precision determination of the imaginary component of the refractive index (k), along with the highly sensitive determination of the real component of the refractive index (n). The refractive indices are retrieved at two wavelengths, 405 and 532 nm, using the PASCaRD system. To yield aerosol composition, quadrupole aerosol mass spectrometry is used. Compositional information is obtained from a technique that uses isotopically labeled and unlabeled methane gas. I will present preliminary data on the complex refractive indices of Titan aerosol analogs at both wavelengths, in conjunction with the aerosol composition as a percent by weight of carbon, nitrogen and hydrogen. The correlation of optical and chemical properties should be useful for remote sensing instruments probing Titan haze.

  7. A new operational EUMETSAT product for the retrieval of aerosol optical properties over land (PMAp v2)

    Science.gov (United States)

    Grzegorski, Michael; Munro, Rosemary; Poli, Gabriele; Holdak, Andriy; Lang, Ruediger

    2016-04-01

    The retrieval of aerosol optical properties is an important task to provide data for industry and climate forecasting. An ideal instrument should include observations with moderate spectral and high spatial resolution for a wide range of wavelengths (from the UV to the TIR), measurements of the polarization state at different wavelengths and measurements of the same scene for different observation geometries. As such an ideal instrument is currently unavailable the usage of different instruments on one satellite platform is an alternative choice. Since February 2014, the Polar Multi sensor Aerosol product (PMAp) has been delivered as an operational GOME product to our customers. The algorithm retrieves aerosol optical properties over ocean (AOD, volcanic ash, aerosol type) using a multi-sensor approach (GOME, AVHRR, IASI). The product is now extended to pixels over land using a new release of the operational PMAp processor (PMAp v2). The pre-operational data dissemination of the new PMAp v2 data to our users is scheduled for March 2016. This presentation gives an overview on the new operational product PMAp v2 with a focus on the validation of the PMAp aerosol optical depth over land. The impact of different error sources on the results (e.g. surface contribution to the TOA reflectance) is discussed. We also show first results of upcoming extensions of our PMAp processor, in particular the improvement of the cloud/aerosol discrimination of thick aerosol events (e.g. volcanic ash plumes, desert dust outbreaks).

  8. Online Simulations of Global Aerosol Distributions in the NASA GEOS-4 Model and Comparisons to Satellite and Ground-Based Aerosol Optical Depth

    Science.gov (United States)

    Colarco, Peter; daSilva, Arlindo; Chin, Mian; Diehl, Thomas

    2010-01-01

    We have implemented a module for tropospheric aerosols (GO CART) online in the NASA Goddard Earth Observing System version 4 model and simulated global aerosol distributions for the period 2000-2006. The new online system offers several advantages over the previous offline version, providing a platform for aerosol data assimilation, aerosol-chemistry-climate interaction studies, and short-range chemical weather forecasting and climate prediction. We introduce as well a methodology for sampling model output consistently with satellite aerosol optical thickness (AOT) retrievals to facilitate model-satellite comparison. Our results are similar to the offline GOCART model and to the models participating in the AeroCom intercomparison. The simulated AOT has similar seasonal and regional variability and magnitude to Aerosol Robotic Network (AERONET), Moderate Resolution Imaging Spectroradiometer, and Multiangle Imaging Spectroradiometer observations. The model AOT and Angstrom parameter are consistently low relative to AERONET in biomass-burning-dominated regions, where emissions appear to be underestimated, consistent with the results of the offline GOCART model. In contrast, the model AOT is biased high in sulfate-dominated regions of North America and Europe. Our model-satellite comparison methodology shows that diurnal variability in aerosol loading is unimportant compared to sampling the model where the satellite has cloud-free observations, particularly in sulfate-dominated regions. Simulated sea salt burden and optical thickness are high by a factor of 2-3 relative to other models, and agreement between model and satellite over-ocean AOT is improved by reducing the model sea salt burden by a factor of 2. The best agreement in both AOT magnitude and variability occurs immediately downwind of the Saharan dust plume.

  9. Single Particle Extinction and Scattering allows novel optical characterization of aerosols

    Science.gov (United States)

    Mariani, Federico; Bernardoni, Vera; Riccobono, Francesco; Vecchi, Roberta; Valli, Gianluigi; Sanvito, Tiziano; Paroli, Bruno; Pullia, Alberto; Potenza, Marco A. C.

    2017-08-01

    We apply to aerosols the optical method of Single Particle Extinction and Scattering recently proposed for characterizing liquid suspensions and specifically adapted to the aim. It provides simultaneous measurements of the real and imaginary parts of the field scattered in the forward direction by single airborne particles passing through a tightly focused laser beam. The intensity of transmitted light is collected in the forward direction, thus realizing a self-reference interferometric scheme relying on the fundamentals of the optical theorem. A high frequency (20 MS/s), extended dynamics (12 bits) sampling is performed by a cheap segmented photodiode, and a specific pulse shape analysis is exploited to validate the signals against a precise mathematical model. We show that accessing two independent physical quantities allows to exploit physical models to recover the aerosol size distribution from the measurement of the refractive index, either real or even complex. Laboratory measurements have been performed with polydisperse aerosols made of water droplets and NaCl in the submicron range, and the system has been accurately characterized. Examples of measurements of graphite nanoparticles and Pyrethrum smoke are shown. Limitations are discussed.

  10. Estimation of Optical Properties for HULIS Aerosols at Anmyeon Island, Korea

    Directory of Open Access Journals (Sweden)

    Ji Yi Lee

    2017-07-01

    Full Text Available In this study, the sensitivity of the optical properties of carbonaceous aerosols, especially humic-like substances (HULIS, are investigated based on a one-year measurement of ambient fine atmospheric particulate matter (PM2.5 at a Global Atmospheric Watch (GAW station in South Korea. The extinction, absorption coefficient, and radiative forcing (RF are calculated from the analysis data of water soluble (WSOC and insoluble (WISOC organic aerosols, elemental carbon (EC, and HULIS. The sensitivity of the optical properties on the variations of refractive index, hygroscopicity, and light absorption properties of HULIS as well as the polydispersity of organic aerosols are studied. The results showed that the seasonal absorption coefficient of HULIS varied from 0.09 to 11.64 Mm−1 and EC varied from 0.11 to 3.04 Mm−1 if the geometric mean diameter varied from 0.1 to 1.0 µm and the geometric standard deviation varied from 1.1 to 2.0, with the imaginary refractive index (IRI of HULIS varying from 0.006 to 0.3. Subsequently, this study shows that the RF of HULIS was larger than other constituents, which suggested that HULIS contributed significantly to radiative forcing.

  11. Intercomparison between CMIP5 model and MODIS satellite-retrieved data of aerosol optical depth, cloud fraction, and cloud-aerosol interactions

    Science.gov (United States)

    Sockol, Alyssa; Small Griswold, Jennifer D.

    2017-08-01

    Aerosols are a critical component of the Earth's atmosphere and can affect the climate of the Earth through their interactions with solar radiation and clouds. Cloud fraction (CF) and aerosol optical depth (AOD) at 550 nm from the Moderate Resolution Imaging Spectroradiometer (MODIS) are used with analogous cloud and aerosol properties from Historical Phase 5 of the Coupled Model Intercomparison Project (CMIP5) model runs that explicitly include anthropogenic aerosols and parameterized cloud-aerosol interactions. The models underestimate AOD by approximately 15% and underestimate CF by approximately 10% overall on a global scale. A regional analysis is then used to evaluate model performance in two regions with known biomass burning activity and absorbing aerosol (South America (SAM) and South Africa (SAF)). In SAM, the models overestimate AOD by 4.8% and underestimate CF by 14%. In SAF, the models underestimate AOD by 35% and overestimate CF by 13.4%. Average annual cycles show that the monthly timing of AOD peaks closely match satellite data in both SAM and SAF for all except the Community Atmosphere Model 5 and Geophysical Fluid Dynamics Laboratory (GFDL) models. Monthly timing of CF peaks closely match for all models (except GFDL) for SAM and SAF. Sorting monthly averaged 2° × 2.5° model or MODIS CF as a function of AOD does not result in the previously observed "boomerang"-shaped CF versus AOD relationship characteristic of regions with absorbing aerosols from biomass burning. Cloud-aerosol interactions, as observed using daily (or higher) temporal resolution data, are not reproducible at the spatial or temporal resolution provided by the CMIP5 models.

  12. Combining data from lidar and in situ instruments to characterize the vertical structure of aerosol optical properties

    Science.gov (United States)

    Redemann, J.; Turco, R. P.; Pueschel, R. F.; Browell, E. V.; Grant, W. B.

    1998-01-01

    Over the last decade, the quantification of tropospheric aerosol abundance, composition and radiative impacts has become an important research endeavor. For the most part, the interest in tropospheric aerosols is derived from questions related to the global and local (instantaneous) radiative forcing of climate due to these aerosols. One approach is to study local forcing under well-defined conditions, and to extrapolate such results to global scales. To estimate local aerosol forcing, appropriate radiative transfer models can be employed (e.g., the Fu-Liou radiative transfer code, [Fu and Liou, 1993]). In general, such models require information on derived aerosol properties [Toon, 1994]; namely the aerosol optical depth, single-scattering albedo, and asymmetry factor (phase function), all of which appear in the equations of radiative transfer. In this paper, we report on a method that utilizes lidar data and in situ aerosol size distribution measurements to deduce the vertical structure of the aerosol complex index of refraction in the near IR, thus identifying the aerosol type. Together with aerosol size distributions obtained in situ, the aerosol refractive index can be used to calculate the necessary derived aerosol properties. The data analyzed here were collected during NASA's PEM West-B (Pacific Exploratory Mission) experiment, which took place in February/March 1994. The platform for the measurements was the NASA DC-8 aircraft. The primary goal of the PEM West missions [Browell et al., 1996] was the assessment of potential anthropogenic perturbations of the chemistry in the Pacific Basin troposphere. For this purpose the timing of PEM West-B corresponded to the seasonal peak in transport from the Asian continent into the Pacific basin [Merrill et al., in press]. This period normally occurs during Northern Hemisphere spring, when the Japan jet is well developed.

  13. Synergistic analyses of optical and microphysical properties of agricultural crop residue burning aerosols over the Indo-Gangetic Basin (IGB)

    Science.gov (United States)

    Mishra, Amit Kumar; Shibata, Takashi

    2012-09-01

    Agriculture crop residue burning is one of the important sources of trace gas emissions and aerosol loading over the Indo-Gangetic Basin (IGB). The present study deals with the spatial variability including the vertical structure of optical and microphysical properties of aerosols, during the crop residue burning season (October and November) of 2009 over the IGB. Increased number of fire counts observed by MODIS (MODerate resolution Imaging Spectroradiometer) that is associated with high aerosol optical depth (MODIS-AOD > 0.7) and enhanced tropospheric columnar NO2 concentrations observed by OMI (Ozone Monitoring Instrument), suggests agriculture crop residue burning as a main source of aerosol loading over the IGB during October and November. PARASOL (Polarization and Anisotropy of Reflectances for Atmospheric Science coupled with Observations from a Lidar) observations show an increase in fine mode AOD (at 865 nm) from October (0.1-0.2) to November (0.2-0.3) over the IGB, which is well corroborated with MODIS observations. CALIOP (Cloud-Aerosol Lidar with Orthogonal Polarization) data shows the elevated aerosol plume (4.0-4.5 km) over the north-west IGB (associated with burning activities) that could have been caused by positive buoyancy through pyro-convection. However, large concentrations of aerosol were found below 1.0 km altitude. The averaged vertical structure of crop residue burning aerosols shows an exponential decrease with altitude (mean scale height ˜1.44 ± 0.20 km). Aerosol optical and microphysical properties coupled with backward air trajectories analyses at Kanpur indicated regional transport of biomass burning aerosols in a downwind direction from north-west IGB to south-east IGB. Aerosol classification, using AERONET (AErosol RObotic NETwork)-derived absorption properties coupled with size parameter (2006-2010) showed clear seasonal dependency of aerosol types which revealed the presence of biomass burning aerosols only during the crop

  14. Contribution of long-range transported aerosols to aerosol optical and physical properties: 3-year measurements at Gosan, Korea

    Science.gov (United States)

    Heo, J.; Kim, S. W.; Kim, J. H.; Ogren, J. A.; Yoon, S. C.

    2015-12-01

    Recently, more attentions have been paid to air quality in East Asia due to the enhanced loading of atmospheric pollutants related to rapid industrialization. Gosan Climate Observatory (GCO), Korea is regarded as an ideal site to study the transport of atmospheric pollutants because it is frequently influenced by various airmasses from China, Korea, Japan and Pacific Ocean. In order to understand aerosol optical and physical properties according to airmass transport routes, three-year (2012-2014) continuous measurements of aerosol scattering/absorption coefficient and number size distribution were analyzed, together with 48-hour backward trajectory calculations. The averaged aerosol absorption (σa) and scattering coefficient (σs) for airmasses transported from North China (NC; 36% of all trajectories) were 6.65 Mm-1 and 94.72 Mm-1 at 550 nm wavelength, respectively, which were similar to those for stagnant airmasses (ST; 22% of all trajectories; σa: 6.26 Mm-1, σs: 93.99 Mm-1). The highest values of σa (7.03 Mm-1) and σs (108.34 Mm-1) were observed when airmasses were traveled from South China (SC; 11% of all trajectories). σa and σs for airmasses from Korean Peninsula (KP; 7% of all trajectories) and Pacific Ocean (PO; 14% of all trajectories; in parenthesis) were 5.63 (2.76) Mm-1 and 73.63 (50.93) Mm-1, respectively. Compared to other airmasses, the higher values of Scattering Angstrom Exponent (SAE) for ST (1.65) is thought to be the build-up of anthropogenic fine particulate pollutants. The Absorption Angstrom Exponent (AAE) was estimated to be 1.32 for NC airmass and 1.02 for SC airmass. Over the study period, 130 days of total 557 days were identified as new particle formation and growth event (NPF) from Scanning Mobility Particle Sizer (SMPS) measurements by Cyclostationary Empirical Orthogonal Function (CSEOF) approach. Especially, 55.4% (72 days) of total 130 NPF days were found when a cold and dry airmass comes from NC after passing the frontal

  15. Identification of columnar aerosol types under high aerosol optical depth conditions for a single AERONET site in Korea

    Science.gov (United States)

    Choi, Yongjoo; Ghim, Young Sung; Holben, B. N.

    2016-02-01

    Dominant aerosol types were classified using level 2 inversion products for the Anmyon Aerosol Robotic Network (AERONET) site in Korea for the period 1999-2007. The aerosol types were mineral dust (MD), MD mixed with carbon, and black carbon mixed coarse particles (BCCP) for coarse mode aerosols, black carbon (BC), organic carbon (OC), and secondary inorganic ions (SII) for fine mode aerosols, and mixed particles between. The classification was carried out using a clustering method based on parameters, including single scattering albedo (SSA), absorption Angstrom exponent (AAE), and fine mode volume fraction (FMVF). Among the seven aerosol types, MD was distinct, with the highest AAE and a very low FMVF and SII with the highest SSA and FMVF. BCCP was introduced to designate coarse particles mixed with BC, of which the AAE was lower than 1, despite a low FMVF. In addition to a large difference in AAE between BC and OC, the SSA of OC was larger than that of BC, indicating the effects of the white smoke produced from the smoldering phase of biomass burning. Monthly variations of the aerosol types were well interpreted by meteorology and emissions and coincided with those in the previous studies. Applying our results to well-characterized global AERONET sites, we confirmed that the aerosol types at Anmyon were valid at other sites. However, the results also showed that the mean properties for aerosol types were influenced by the specific aerosols prevalent at the study sites.

  16. Comparing mesoscale chemistry-transport model and remote-sensed Aerosol Optical Depth

    CERN Document Server

    Carnevale, C; Pisoni, E; Volta, M

    2010-01-01

    A comparison of modeled and observed Aerosol Optical Depth (AOD) is presented. 3D Eulerian multiphase chemistry-transport model TCAM is employed for simulating AOD at mesoscale. MODIS satellite sensor and AERONET photometer AOD are used for comparing spatial patterns and temporal timeseries. TCAM simulations for year 2004 over a domain containing Po-Valley and nearly whole Northern Italy are employed. For the computation of AOD, a configuration of external mixing of the chemical species is considered. Furthermore, a parametrization of the effect of moisture affecting both aerosol size and composition is used. An analysis of the contributions of the granulometric classes to the extinction coefficient reveals the dominant role of the inorganic compounds of submicron size. For the analysis of spatial patterns, summer and winter case study are considered. TCAM AOD reproduces spatial patterns similar to those retrieved from space, but AOD values are generally smaller by an order of magnitude. However, accounting a...

  17. Significant overestimation of global aerosol optical thickness by MODIS over land

    Institute of Scientific and Technical Information of China (English)

    XIA Xiang'ao

    2006-01-01

    Global aerosol optical thickness (AOT)data over land obtained from the Moderate Resolution Imaging Spectroradiometer (MODIS) are evaluated through comparisons with AOT data retrieved by Aerosol Robotic Network (AERONET). In general,MODIS overestimates AOT except at a few AERONET sites in Africa and eastern Asia. MODIS/AOTs are, on average, larger than AERONET/AOTs by 0.041 and 0.090 at 470 nm and 660 nm, respectively. The AOT bias at 660 nm is significantly correlated to the surface reflectance at 2130 nm. Both facts suggest that the underestimation of the surface reflectance is the principal reason for this bias at 660 nm. To use the MODIS/AOT at 470 nm is strongly recommended because it is much more reliable than the AOT at 660 nm.

  18. Retrieval of the aerosol optical thickness from UV global irradiance measurements

    Science.gov (United States)

    Costa, M. J.; Salgueiro, V.; Bortoli, D.; Obregón, M. A.; Antón, M.; Silva, A. M.

    2015-12-01

    The UV irradiance is measured at Évora since several years, where a CIMEL sunphotometer integrated in AERONET is also installed. In the present work, measurements of UVA (315 - 400 nm) irradiances taken with Kipp&Zonen radiometers, as well as satellite data of ozone total column values, are used in combination with radiative transfer calculations, to estimate the aerosol optical thickness (AOT) in the UV. The retrieved UV AOT in Évora is compared with AERONET AOT (at 340 and 380 nm) and a fairly good agreement is found with a root mean square error of 0.05 (normalized root mean square error of 8.3%) and a mean absolute error of 0.04 (mean percentage error of 2.9%). The methodology is then used to estimate the UV AOT in Sines, an industrialized site on the Atlantic western coast, where the UV irradiance is monitored since 2013 but no aerosol information is available.

  19. Impact of wet scavenging of natural and anthropogenic aerosol components on the columnar aerosol optical depth over a tropical rural atmosphere

    Science.gov (United States)

    Chatterjee, Abhijit; Jayaraman, Achuthan

    A typical feature of Indian monsoon is that, several dry days are observed even between the rain events. Atmospheric aerosol shows significant variations in their concentration between "before" and "after" the rain because of their efficient scavenging during the rain. The below cloud scavenging of several aerosol components during the rain has a direct impact on the columnar aerosol optical depth (AOD) between "before" and "after" the rain. In order to investigate the impact of the scavenging of several natural and anthropogenic aerosol components on spectral properties of aerosol, simultaneous studies on the characterization of aerosol, rainwater and AOD were done during July-December 2009 over a tropical rural atmosphere at Gadanki (13.5 0N, 79.2 0E) in southern peninsular India. Aerosols were collected and analyzed before, during and after the rain along with the collection and analysis of rainwater in several rain events during the entire study period. AOD data (at wavelengths of 400, 500, 675, 870, 1020 nm) was retrieved by processing the data obtained from an automatic sunphotomer (PREDE, PM 01) using the standard SKYRAD pack. Aerosols and rainwater samples were analyzed for water soluble ionic species using an Ion Chromatograph (Metrohm, 861). We observed that aerosols were highly loaded in the atmosphere just before the rain, efficiently scavenged during the rain and built-up slowly after the rain. Interestingly, the loading of sulphate aerosol after the rain was remarkably high whereas that of calcium and magnesium were remarkably low. The poor resuspension of soil dust from the wet soils after the rain could not allow calcium and magnesium to be loaded in the atmosphere whereas the high relative humidity favored the gas-to-particle conversion of SO2 to SO42-which allowed the high loading of sulphate aerosol in the atmosphere. Significant reductions in AOD both at lower (400 nm) and higher wavelength (1020 nm) were observed after the rain events. Two

  20. Remote Marine Aerosol: A Characterization of Physical, Chemical and Optical Properties and their Relation to Radiative Transfer in the Troposphere

    Science.gov (United States)

    Clarke, Antony D.; Porter, John N.

    1997-01-01

    Our research effort is focused on improving our understanding of aerosol properties needed for optical models for remote marine regions. This includes in-situ and vertical column optical closure and involves a redundancy of approaches to measure and model optical properties that must be self consistent. The model is based upon measured in-situ aerosol properties and will be tested and constrained by the vertically measured spectral differential optical depth of the marine boundary layer, MBL. Both measured and modeled column optical properties for the boundary layer, when added to the free-troposphere and stratospheric optical depth, will be used to establish spectral optical depth over the entire atmospheric column for comparison to and validation of satellite derived radiances (AVHRR).

  1. Long-term Observation of Aerosol Optical Properties at the SORPES station in Nanjing, China

    Science.gov (United States)

    Shen, Yicheng; Ding, Aijun; Virkkula, Aki; Wang, Jiaping; Chi, Xuguang; Qi, Ximeng; Liu, Qiang; Zheng, Longfei; Xie, Yuning

    2016-04-01

    Atmospheric aerosols influence the earth's radiation budget by scattering and absorbing solar radiation and contribute substantial uncertainty in the estimation of climate forcing. Thorough and comprehensive measurements on different parameters including absorption and scattering coefficient, wavelength dependence and angular dependence along with their daily and seasonal variation help to understand the influence of aerosol on radiation. 2-years continuous measurement of aerosol optical properties has been conducted from June 2013 to May 2015 at the Station for Observing Regional Process of Earth System (SORPES) station, which is a regional background station located in downwind direction of Yangtze River Delta (YRD) urban agglomeration in China. A 7-wavelenths aethalometer and a 3-wavelenths nephelometer were used to measure absorption and scattering coefficient, and also other parameters like single scattering albedo (SSA), absorption angstrom Exponent (AAE), scattering angstrom exponent (SAE) and back-scattering refraction. In addtion, simultaneous measurements on chemical composition and particle size distribution were performed so as to investigate the dependencies of aerosol optical properties on chemical composition and size distribution. To get further insight on the influencing factors, Lagrangian particle dispersion modeling (LPDM) was employed for source identification in this study. The averages of absorption coefficient, scattering coefficient and SSA are 26.0±18.7 Mm-1, 426±327 Mm-1 , 0.936±0.3 at 520nm respectively for whole period. SAE between 450 and 635nm is 1.299±0.34 and have strong negative correlation with particle Surface Mean Diameter (SMD). AAE between 370 and 950nm is 1.043±0.15 for whole period but growth to more than 1.6 in all identified Biomass Burning (BB) events.

  2. Observations of aerosol optical properties at a coastal site in Hong Kong, South China

    Science.gov (United States)

    Wang, Jiaping; Virkkula, Aki; Gao, Yuan; Lee, Shuncheng; Shen, Yicheng; Chi, Xuguang; Nie, Wei; Liu, Qiang; Xu, Zheng; Huang, Xin; Wang, Tao; Cui, Long; Ding, Aijun

    2017-02-01

    Temporal variations in aerosol optical properties were investigated at a coastal station in Hong Kong based on the field observation from February 2012 to February 2015. At 550 nm, the average light-scattering (151 ± 100 Mm-1) and absorption coefficients (8.3 ± 6.1 Mm-1) were lower than most of other rural sites in eastern China, while the single-scattering albedo (SSA = 0.93 ± 0.05) was relatively higher compared with other rural sites in the Pearl River Delta (PRD) region. Correlation analysis confirmed that the darkest aerosols were smaller in particle size and showed strong scattering wavelength dependencies, indicating possible sources from fresh emissions close to the measurement site. Particles with Dp of 200-800 nm were less in number, yet contributed the most to the light-scattering coefficients among submicron particles. In summer, both ΔBC / ΔCO and SO2 / BC peaked, indicating the impact of nearby combustion sources on this site. Multi-year backward Lagrangian particle dispersion modeling (LPDM) and potential source contribution (PSC) analysis revealed that these particles were mainly from the air masses that moved southward over Shenzhen and urban Hong Kong and the polluted marine air containing ship exhausts. These fresh emission sources led to low SSA during summer months. For winter and autumn months, contrarily, ΔBC / ΔCO and SO2 / BC were relatively low, showing that the site was more under influence of well-mixed air masses from long-range transport including from South China, East China coastal regions, and aged aerosol transported over the Pacific Ocean and Taiwan, causing stronger abilities of light extinction and larger variability of aerosol optical properties. Our results showed that ship emissions in the vicinity of Hong Kong could have visible impact on the light-scattering and absorption abilities as well as SSA at Hok Tsui.

  3. Optical properties of aerosol mixtures derived from sun-sky radiometry during SAMUM-2

    Energy Technology Data Exchange (ETDEWEB)

    Toledano, C. (Meteorological Institute, Ludwig-Maximilians-Universitaet, Munich (Germany); Group of Atmospheric Optics, Valladolid Univ., Valladolid (Spain)), e-mail: toledano@goa.uva.es; Wiegner, M.; Gross, S. (Meteorological Institute, Ludwig-Maximilians-Universitaet, Munich (Germany)) (and others)

    2011-09-15

    The SAMUM-2 experiment took place in the Cape Verde islands in January-February 2008. The colocated ground-based and airborne instruments allow the study of desert dust optical and microphysical properties in a closure experiment. The Meteorological Institute of the Univ. of Munich deployed one sun-sky photometer and two tropospheric lidar systems. A travelling AERONET-Cimel sun-sky radiometer was also deployed. During the measurement period the aerosol scenario over Cape Verde mostly consisted of a dust layer below 2 km and a smoke-dust layer above 2-4 km a.s.l. The Saharan dust arrived at the site from the NE, whereas the smoke originated in the African equatorial region. This paper describes the main results of the Sun photometer observations, supported by lidar information. An analysis of the variations in the aerosol optical depth (AOD) in the range 340-1550 nm, the Aangstroem exponent, volume size distributions and single scattering albedo is presented. The aerosol mixtures are analysed by means of the fine mode fraction of the AOD provided by the sun-sky inversion data and the Spectral Deconvolution Algorithm. The mean AOD (500 nm) was 0.31, with associated low Aangstroem exponent of 0.46. Several types of events were detected within the data set, with prevalence of dust or mixtures as characterized by the Aangstroem exponents of extinction and absorption and the fine mode fraction. Aerosol properties derived from sunphotometry were compared to in situ measurements of size distribution, effective radius and single scattering albedo

  4. Carbonaceous aerosols in megacity Xi'an, China: Implications of thermal/optical protocols comparison

    Science.gov (United States)

    Han, Y. M.; Chen, L.-W. A.; Huang, R.-J.; Chow, J. C.; Watson, J. G.; Ni, H. Y.; Liu, S. X.; Fung, K. K.; Shen, Z. X.; Wei, C.; Wang, Q. Y.; Tian, J.; Zhao, Z. Z.; Prévôt, André S. H.; Cao, J. J.

    2016-05-01

    Carbonaceous aerosol is an important component that influences the environment, climate, and human health. Organic and elemental carbon (OC and EC) are the two main constituents of carbonaceous aerosols that have opposite, i.e., cooling versus warming, effects on the Earth's radiation balance. Knowledge on the variability of OC/EC splits measured by different thermal/optical protocols is useful for understanding the uncertainty in the climate models. This study shows good correlations within OC or EC (r2 > 0.83, P burning samples. However, EC concentrations differ by more than two folds, and OC/EC ratios differ up to a factor of 2.7. The discrepancies were attributed to the selection between the reflectance and transmittance corrections and the different peak inert-atmosphere temperature. The IMPROVE and IMPROVE_A protocols also quantified different char and soot concentrations, two subtypes of EC with distinct chemical and optical properties. Char, but not soot, was found to correlate with the humic-like substances (HULIS) content in the samples, suggesting that both char and HULIS originate mainly from biomass burning. A one-year (2012-2013) ambient aerosol monitoring in Xi'an, China, shows that OC, EC, and char displayed winter highs and summer lows, while soot had no seasonal trend. The char/soot ratios showed a "single peak" in winter, while OC/EC ratios exhibited "dual peak" feature due to the influence of secondary organic aerosol formation. In addition to commonly measured OC and EC, we recommend both char and soot from a common reference method to be considered in the chemical transport and climate models.

  5. Reducing multisensor satellite monthly mean aerosol optical depth uncertainty: 1. Objective assessment of current AERONET locations

    Science.gov (United States)

    Li, Jing; Li, Xichen; Carlson, Barbara E.; Kahn, Ralph A.; Lacis, Andrew A.; Dubovik, Oleg; Nakajima, Teruyuki

    2016-11-01

    Various space-based sensors have been designed and corresponding algorithms developed to retrieve aerosol optical depth (AOD), the very basic aerosol optical property, yet considerable disagreement still exists across these different satellite data sets. Surface-based observations aim to provide ground truth for validating satellite data; hence, their deployment locations should preferably contain as much spatial information as possible, i.e., high spatial representativeness. Using a novel Ensemble Kalman Filter (EnKF)-based approach, we objectively evaluate the spatial representativeness of current Aerosol Robotic Network (AERONET) sites. Multisensor monthly mean AOD data sets from Moderate Resolution Imaging Spectroradiometer, Multiangle Imaging Spectroradiometer, Sea-viewing Wide Field-of-view Sensor, Ozone Monitoring Instrument, and Polarization and Anisotropy of Reflectances for Atmospheric Sciences coupled with Observations from a Lidar are combined into a 605-member ensemble, and AERONET data are considered as the observations to be assimilated into this ensemble using the EnKF. The assessment is made by comparing the analysis error variance (that has been constrained by ground-based measurements), with the background error variance (based on satellite data alone). Results show that the total uncertainty is reduced by 27% on average and could reach above 50% over certain places. The uncertainty reduction pattern also has distinct seasonal patterns, corresponding to the spatial distribution of seasonally varying aerosol types, such as dust in the spring for Northern Hemisphere and biomass burning in the fall for Southern Hemisphere. Dust and biomass burning sites have the highest spatial representativeness, rural and oceanic sites can also represent moderate spatial information, whereas the representativeness of urban sites is relatively localized. A spatial score ranging from 1 to 3 is assigned to each AERONET site based on the uncertainty reduction

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

    Science.gov (United States)

    Yu, Xingna; Lü, Rui; Liu, Chao; Yuan, Liang; Shao, Yixing; Zhu, Bin; Lei, Lu

    2017-10-01

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

  7. Use of Lidar Derived Optical Extinction and Backscattering Coefficients Near Cloud Base to Explore Aerosol-Cloud Interactions

    Science.gov (United States)

    Han, Zaw; Wu, Yonhgua; Gross, Barry; Moshary, Fred

    2016-06-01

    Combination of microwave radiometer (MWR) and mutlifilter rotating shadowband radiometer (MFRSR) measurement data together with SBDART radiative transfer model to compute cloud optical depth (COD) and cloud droplet effective radius (Reff). Quantify the first aerosol indirect effect using calculated Reff and aerosol extinction from Raman lidar measurement in urban coastal region. Illustrate comparison between ground-based and satellite retrievals. Demonstrate relationship between surface aerosol (PM2.5) loading and Reff. We also explain the sensitivity of aerosol-cloud-index (ACI) depend on the aerosol layer from cloud base height. Potential used of less noisy elastic backscattering to calculate the ACI instead of using Raman extinction. We also present comparison of elastic backscattering and Raman extinction correlation to Reff.

  8. MODIS Aerosol Optical Depth retrieval over land considering surface BRDF effects

    Science.gov (United States)

    Wu, Yerong; de Graaf, Martin; Menenti, Massimo

    2016-04-01

    Aerosols in the atmosphere play an important role in the climate system and human health. Retrieval from satellite data, Aerosol Optical Depth (AOD), one of most important indices of aerosol optical properties, has been extensively investigated. Benefiting from the high resolution at spatial and temporal and the maturity of the aerosol retrieval algorithm, MOderate Resolution Imaging Spectroradiometer (MODIS) Dark Target AOD product has been extensively applied in other scientific research such as climate change and air pollution. The latest product - MODIS Collection 6 Dark Target AOD (C6_DT) has been released. However, the accuracy of C6_DT AOD (global mean ±0.03) over land is still too low for the constraint on radiative forcing in the climate system, where the uncertainty should be reduced to ±0.02. The major uncertainty mainly lies on the underestimation/overestimation of the surface contribution to the Top Of Atmosphere (TOA) radiance since a lambertian surface is assumed in the C6_DT land algorithm. In the real world, it requires considering the heterogeneity of the surface reflection in the radiative transfer process. Based on this, we developed a new algorithm to retrieve AOD by considering surface Bidirectional Reflectance Distribution Function (BRDF) effects. The surface BRDF is much more complicated than isotropic reflection, described as 4 elements: directional-directional, directional-hemispherical, hemispherical-directional and hemispherical-hemispherical reflectance, and coupled into radiative transfer equation to generate an accurate top of atmosphere reflectance. The limited MODIS measurements (three channels available) allow us to retrieve only three parameters, which including AOD, the surface directional-directional reflectance and fine aerosol ratio η. The other three elements of the surface reflectance are expected to be constrained by ancillary data and assumptions or "a priori" information since there are more unknowns than MODIS

  9. Temporal and spatial variability of aerosol optical depth in the Sahel region in relation to vegetation remote sensing

    Science.gov (United States)

    Holben, B. N.; Fraser, R. S.; Eck, T. F.

    1991-01-01

    In order to monitor the aerosol characteristics needed for atmospheric correction of remotely sensed data, a network of sun photometers was established in the Sahel region of Senegal, Mali, and Niger. Data analysis suggests that there is a high spatial variability of the aerosol optical thickness tau(a) in the western Sahel region. At a 67 percent confidence level the instantaneous values of tau(a) can be extrapolated approximately 270-400 km with an error tolerance of 50 percent. Spatial variability in the dry season is found to be of a similar magnitude. The ranges of variations in the NDVI in the Sahel region are shown to be approximately 0.02 and 0.01, respectively, due to commonly observed fluctuations in the aerosol optical thickness and aerosol size distribution.

  10. Fast and low noise optical receiver using Si APD for cloud-aerosol LIDAR

    Science.gov (United States)

    Gasmi, Khaled

    2016-04-01

    A Fast and Low-noise Optical Receiver using a Silicon Avalanche Photodiode with an internal gain of 100 connected to a Broadband Preamplifier Circuit was developed. The optical receiver and the receiving optics form the detection channel of a Cloud-Aerosol Lidar Remote Sensing System used to measure profiles of aerosol and cloud backscatter at the near-infrared wavelength of 1064 nm. While a 10 Hz repetition rate solid state pulsed Nd:YAG laser emitting at 1.06 μm and the emission optics form the transmission channel. The preamplifier circuit with a 300 MHz bandwidth and a gain of 10 is capable of accommodating laser pulses of 10 ns full width at half maximum. The preamplifier matches 50 Ω impedances at the input and the output sides. The input matching is used to reduce the Johnson noise and hence a much better sensitivity was achieved. The output matching was useful when this preamplifier is to be connected to other instrumentation requiring 50 Ω impedance matching or to be interfaced in cascade to increase the overall gain of the detection chain. These 50 Ω impedances at the input and output sides, also allows using the preamplifier coupled with a photodiode at the input in the detection of fast signals without distortion or integration. A low noise level at the preamplifier circuit input of only 1.6 nV/Hz1/2 and a very good linearity from 1 KHz to 280 MHz were achieved, allowing the transmission of the backscattered signal to the acquisition system without distortion. In addition, the experimental characterization of the optical receiver coupled with the receiving optics showed good detection performance of the lidar detection channel: A low Noise Equivalent Power of 50 pW/Hz1/2 and a high Signal-to- Noise Ratio of 2 were achieved. Furthermore, the maximal range of the lidar remote sensing system was estimated.

  11. Similarities and differences of aerosol optical properties between southern and northern slopes of the Himalayas

    Directory of Open Access Journals (Sweden)

    C. Xu

    2013-08-01

    Full Text Available The Himalayas is located at the southern edge of the Tibetan Plateau, and it acts as a natural barrier for the transport of atmospheric aerosols, e.g. from the polluted regions of South Asia to the main body of the Tibetan Plateau. In this study, we investigate the seasonal and diurnal variations of aerosol optical properties measured at the three Aerosol Robotic Network (AERONET sites over the southern (Pokhara station and EVK2-CNR station in Nepal and northern (Qomolangma (Mt. Everest station for Atmospheric and Environmental Observation and Research, Chinese Academy of Sciences (QOMS_CAS in Tibet, China slopes of the Himalayas. While observations at QOMS_CAS and EVK2-CNR can generally be representative of a remote background atmosphere, Pokhara is an urban site with much higher aerosol load due to the influence of local anthropogenic activities. The annual mean of aerosol optical depth (AOD during the investigated period was 0.06 at QOMS_CAS, 0.04 at EVK2-CNR and 0.51 at Pokhara, respectively. Seasonal variations of aerosols are profoundly affected by large scale atmospheric circulation. Vegetation fires, peaking during April in the Himalayan region and northern India, contribute to a growing fine mode AOD at 500 nm at the three stations. Dust transported to these sites results in an increase of coarse mode AOD during the monsoon season at the three sites. Meanwhile, coarse mode AOD at EVK2-CNR is higher than QOMS_CAS from July to September, indicating the Himalayas blocks the coarse particles carried by the southwest winds. The precipitation scavenging effect is obvious at Pokhara, which can significantly reduce the aerosol load during the monsoon season. Unlike the seasonal variations, diurnal variations are mainly influenced by meso-scale systems and local topography. In general, precipitation can lead to a decrease of the aerosol load and the average particle size at each station. AOD changes in a short time with the emission rate near

  12. Modeling the South American regional smoke plume: aerosol optical depth variability and surface shortwave flux perturbation

    Directory of Open Access Journals (Sweden)

    N. E. Rosário

    2013-03-01

    Full Text Available Intra-seasonal variability of smoke aerosol optical depth (AOD and downwelling solar irradiance at the surface during the 2002 biomass burning season in South America was modeled using the Coupled Chemistry-Aerosol-Tracers Transport model with the Brazilian developments on the Regional Atmospheric Modeling System (CCATT-BRAMS. Measurements of total and fine mode fraction (FMF AOD from the AErosol RObotic NETwork (AERONET and solar irradiance at the surface from the Solar Radiation Network (SolRad-NET were used to evaluate model results. In general, the major features associated with AOD evolution over the southern part of the Amazon basin and cerrado ecosystem are captured by the model. The main discrepancies were found for high aerosol loading events. In the northeastern portion of the Amazon basin the model systematically underestimated total AOD, as expected, since smoke contribution is not dominant as it is in the southern portion and emissions other than smoke were not considered in the simulation. Better agreement was obtained comparing the model results with observed FMF AOD, which pointed out the relevance of coarse mode aerosol emission in that region. Likewise, major discrepancies over cerrado during high AOD events were found to be associated with coarse mode aerosol omission in our model. The issue of high aerosol loading events in the southern part of the Amazon was related to difficulties in predicting the smoke AOD field, which was discussed in the context of emissions shortcomings. The Cuiabá cerrado site was the only one where the highest quality AERONET data were unavailable for both total and FMF AOD. Thus, lower quality data were used. Root-mean-square error (RMSE between the model and observed FMF AOD decreased from 0.34 to 0.19 when extreme AOD events (FMF AOD550 nm ≥ 1.0 and Cuiabá were excluded from the analysis. Downward surface solar irradiance comparisons also followed similar trends when extreme AOD were excluded

  13. Airborne measurements of aerosol optical properties related to early spring transport of mid-latitude sources into the Arctic

    Directory of Open Access Journals (Sweden)

    R. A. de Villiers

    2010-06-01

    Full Text Available Airborne lidar and in-situ measurements of the aerosol properties were conducted between Svalbard Island and Scandinavia in April 2008. Evidence of aerosol transport from Europe and Asia is given. The analysis of the aerosol optical properties based on a multiwavelength lidar (355, 532, 1064 nm including volume depolarization at 355 nm aims at distinguishing the role of the different aerosol sources (Siberian wild fires, Eastern Asia and European anthropogenic emissions. Combining, first aircraft measurements, second FLEXPART simulations with a calculation of the PBL air fraction originating from the three different mid-latitude source regions, and third level-2 CALIPSO data products (i.e. backscatter coefficient 532 nm,volume depolarization and color ratio between 1064 and 532 nm in aerosol layers along the transport pathways, appears a valuable approach to identify the role of the different aerosol sources even after a transport time larger than 4 days. Optical depth of the aerosol layers are always rather small (<4% while transported over the Arctic and ratio of the total attenuated backscatter (i.e. including molecular contribution provide more stable result than conventional aerosol backscatter ratio. Above Asia, CALIPSO data indicate more depolarization (up to 15% and largest color ratio (>0.5 for the northeastern Asia emissions (i.e. an expected mixture of Asian pollution and dust, while low depolarization together with smaller and quasi constant color ratio (≈0.3 are observed for the Siberian biomass burning emissions. A similar difference is visible between two layers observed by the aircraft above Scandinavia. The analysis of the time evolution of the aerosol optical properties revealed by CALIPSO between Asia and Scandinavia shows a gradual decrease of the aerosol backscatter, depolarization ratio and color ratio which suggests the removal of the largest particles in the accumulation mode. A similar study conducted for a European

  14. An 11-year global gridded aerosol optical thickness reanalysis (v1.0) for atmospheric and climate sciences

    Science.gov (United States)

    Lynch, Peng; Reid, Jeffrey S.; Westphal, Douglas L.; Zhang, Jianglong; Hogan, Timothy F.; Hyer, Edward J.; Curtis, Cynthia A.; Hegg, Dean A.; Shi, Yingxi; Campbell, James R.; Rubin, Juli I.; Sessions, Walter R.; Turk, F. Joseph; Walker, Annette L.

    2016-04-01

    While stand alone satellite and model aerosol products see wide utilization, there is a significant need in numerous atmospheric and climate applications for a fused product on a regular grid. Aerosol data assimilation is an operational reality at numerous centers, and like meteorological reanalyses, aerosol reanalyses will see significant use in the near future. Here we present a standardized 2003-2013 global 1 × 1° and 6-hourly modal aerosol optical thickness (AOT) reanalysis product. This data set can be applied to basic and applied Earth system science studies of significant aerosol events, aerosol impacts on numerical weather prediction, and electro-optical propagation and sensor performance, among other uses. This paper describes the science of how to develop and score an aerosol reanalysis product. This reanalysis utilizes a modified Navy Aerosol Analysis and Prediction System (NAAPS) at its core and assimilates quality controlled retrievals of AOT from the Moderate Resolution Imaging Spectroradiometer (MODIS) on Terra and Aqua and the Multi-angle Imaging SpectroRadiometer (MISR) on Terra. The aerosol source functions, including dust and smoke, were regionally tuned to obtain the best match between the model fine- and coarse-mode AOTs and the Aerosol Robotic Network (AERONET) AOTs. Other model processes, including deposition, were tuned to minimize the AOT difference between the model and satellite AOT. Aerosol wet deposition in the tropics is driven with satellite-retrieved precipitation, rather than the model field. The final reanalyzed fine- and coarse-mode AOT at 550 nm is shown to have good agreement with AERONET observations, with global mean root mean square error around 0.1 for both fine- and coarse-mode AOTs. This paper includes a discussion of issues particular to aerosol reanalyses that make them distinct from standard meteorological reanalyses, considerations for extending such a reanalysis outside of the NASA A-Train era, and examples of how

  15. Development studies towards an 11-year global gridded aerosol optical thickness reanalysis for climate and applied applications

    Science.gov (United States)

    Lynch, P.; Reid, J. S.; Westphal, D. L.; Zhang, J.; Hogan, T. F.; Hyer, E. J.; Curtis, C. A.; Hegg, D. A.; Shi, Y.; Campbell, J. R.; Rubin, J. I.; Sessions, W. R.; Turk, F. J.; Walker, A. L.

    2015-12-01

    While standalone satellite and model aerosol products see wide utilization, there is a significant need in numerous climate and applied applications for a fused product on a regular grid. Aerosol data assimilation is an operational reality at numerous centers, and like meteorological reanalyses, aerosol reanalyses will see significant use in the near future. Here we present a standardized 2003-2013 global 1° × 1° and 6 hourly modal aerosol optical thickness (AOT) reanalysis product. This dataset can be applied to basic and applied earth system science studies of significant aerosol events, aerosol impacts on numerical weather prediction, and electro-optical propagation and sensor performance, among other uses. This paper describes the science of how to develop and score an aerosol reanalysis product. This reanalysis utilizes a modified Navy Aerosol Analysis and Prediction System (NAAPS) at its core and assimilates quality controlled retrievals of AOT from the Moderate Resolution Imaging Spectroradiometer (MODIS) on Terra and Aqua and the Multi-angle Imaging SpectroRadiometer (MISR) on Terra. The aerosol source functions, including dust and smoke, were regionally tuned to obtain the best match between the model fine and coarse mode AOTs and the Aerosol Robotic Network (AERONET) AOTs. Other model processes, including deposition, were tuned to minimize the AOT difference between the model and satellite AOT. Aerosol wet deposition in the tropics is driven with satellite retrieved precipitation, rather than the model field. The final reanalyzed fine and coarse mode AOT at 550 nm is shown to have good agreement with AERONET observations, with global mean root mean square error around 0.1 for both fine and coarse mode AOTs. This paper includes a discussion of issues particular to aerosol reanalyses that make them distinct from standard meteorological reanalyses, considerations for extending such a reanalysis outside of the NASA A-Train era, and examples of how the

  16. Comparison of aerosol optical properties above clouds between POLDER and AeroCom models over the South East Atlantic Ocean during the fire season

    OpenAIRE

    F. Peers; Bellouin, Nicolas; F. Waquet; F. Ducos; P. Goloub; Mollard, J.; Myhre, G; R. B. Skeie; T. Takemura; Tanré, D.; F. Thieuleux; Zhang, K

    2016-01-01

    Aerosol properties above clouds have been retrieved over the South East Atlantic Ocean during the fire season 2006 using satellite observations from POLDER (Polarization and Directionality of Earth Reflectances). From June to October, POLDER has observed a mean Above-Cloud Aerosol Optical Thickness (ACAOT) of 0.28 and a mean Above-Clouds Single Scattering Albedo (ACSSA) of 0.87 at 550nm. These results have been used to evaluate the simulation of aerosols above clouds in five Aerosol Compariso...

  17. A revisit to decadal change of aerosol optical depth and its impact on global radiation over China

    Science.gov (United States)

    Tang, Wenjun; Yang, Kun; Qin, Jun; Niu, Xiaolei; Lin, Changgui; Jing, Xianwen

    2017-02-01

    Global radiation over China decreased between the 1960s and 1990, since when it has remained stable. As the total cloud cover has continued to decrease since the 1960s, variations in aerosols were suggested in previous studies to be the primary cause for variations in global radiation over China. However, the effect of aerosols on global radiation on a decadal scale has not been physically quantified over China. In this study, aerosol optical depth (AOD) data since 1980 are estimated by combining horizontal visibility data at stations in China and AOD observed by the moderate resolution imaging spectroradiometer (MODIS). It is found that the AOD exhibits decadal changes, with two decreasing periods (before the end of 1980s and after 2006) and one increasing period (from 1990 to 2006). With the derived AOD, a clear-sky model is then applied to quantify the role of aerosols in the variations in global radiation over China. The results show that aerosol direct effect cannot fully explain the decadal variations in the global radiation over China between 1980 and 2010, though it has a considerable effect on global radiation climatology. There are significant differences between the trends of clear-sky global radiation impacted by aerosols and those of all-sky global radiation impacted by aerosols and clouds, and the correlation coefficient for the comparison is very low. Therefore, the variations in all-sky global radiation over China are likely to be due to changes in cloud properties and to interactions between clouds and aerosols.

  18. Intercomparison of Aerosol Optical Properties Derived from PREDE Skyradiometer and CIMEL Sunphotometer Measurements for the DRAGON-Korea Campaign

    Science.gov (United States)

    Choi, Y.; Ghim, Y.; Holben, B. N.

    2012-12-01

    The Distributed Regional Aerosol Gridded Observation Networks (DRAGON) campaign for validation of satellite aerosol products and comparison/validation of ground-based aerosol retrievals has been launched in Asia. It was conducted in Korea (DRAGON-Korea) between March and May 2012, with CIMEL sunphotometers being operated at around 20 sites throughout the country. The Hankuk University of Foreign Studies site (Hankuk_UFS, 37.02oN, 127.16oE, 167 m above sea level) is located about 35 km southeast of downtown Seoul. A PREDE skyradiometer (POM-02) is operated along with CIMEL sunphotometer (CE 318-1) to compare the aerosol optical properties derived from the two instruments. The operation for intercomparison study started with the DRAGON-Korea campaign and will continue for a year. POM-02 and CE 318-1 measure diffuse radiation at 6-minute intervals and 11 wavelengths and at 1-hour intervals and 4 wavelengths, respectively. Aerosol optical depths from these two instruments are compared at 440, 675, 870, and 1020 nm when the measurement time coincides within 3 minutes. Other aerosol optical properties such as Angstrom exponent and single scattering albedo (SSA) from the two instruments are also compared in a similar way. It is reported that SSA from the skyradiometer tends to be larger than that from sunphotometer. Factors causing the difference are closely examined.

  19. Ground-based aerosol optical depth inter-comparison campaigns at European EUSAAR super-sites

    Science.gov (United States)

    Nyeki, S.; Gröbner, J.; Wehrli, C.

    2013-05-01

    This work summarizes eight aerosol optical depth (AOD) inter-comparison campaigns conducted during the 2008-2011 period. A PFR (precision filter radiometer) travelling standard from the GAW-PFR network (based at PMOD/WRC, Switzerland) was run alongside existing CIMEL sun-photometers from the PHOTONS/AERONET network located at European stations. Basic statistical analysis of coincident measurements at λ = 500 and 862 nm illustrated good agreement. However, when WMO criteria for traceability were applied only one wavelength at three stations was traceable. Other stations were close to being traceable but had slight issues with window cleanliness and calibration.

  20. Intercomparison of aerosol optical depth from Brewer ozone spectrophotometers and CIMEL sunphotometers measurements

    Directory of Open Access Journals (Sweden)

    A. Cheymol

    2008-06-01

    Full Text Available The Langley plot method applied on the Brewer Ozone measurements can provide accurate Aerosol Optical Depth (AOD in the UV-B. We present seven intercomparisons between AOD retrieved from Brewer Ozone measurements and AOD measured by CIMEL sunphotometer, which are stored in the international AERONET database. Only the intercomparisons between co-located instruments can be used to validate the Langley Plot method applied to the Brewer measurements: in this case, all the correlation coefficient are above 0.83. If the instruments are not at the same site, the correlation between the AOD retrieved by both instruments is much lower.

  1. Ship-borne rotating shadowband radiometer observations for determination of components of spectral irradiance and aerosol optical properties

    Science.gov (United States)

    Walther, Jonas; Deneke, Hartwig; Macke, Andreas; Bernhard, Germar

    2015-04-01

    The Maritime Aerosol Network (MAN) has been established as a sub-project of AERONET and a long-term program to collect ship-borne aerosol optical depth measurements over ocean. Its purpose is to serve as reliable reference database for the evaluation of models and satellite products. Data are currently collected by handheld Microtops II photometers, as the automated acquisition of data from sun photometers on stabilized platforms is so far too expensive for wide-spread use. A promising alternative to the sun photometer is the rotating shadowband radiometer, whose principle of operation allows the determination of the direct-beam component of solar radiation without stabilizing the instrument, if the orientation of the detector horizontal is known. OCEANET, a project to investigate the exchange fluxes of energy and matter between the atmosphere and ocean, has contributed aerosol observations to MAN on several of its cruises on RV Polarstern during the transit between the hemispheres. On the recent cruise (PS 83) from Cape Town to Bremerhaven, TROPOS has operated for the first time a 19 channel rotating shadowband radiometer (GUVis-3511) built by the company Biospherical, as a possible means to provide automated irradiance and aerosol optical depth measurements. Calibration and processing of the raw data will be described, and an initial evaluation of the instrumental performance will be given. Aerosol optical depths derived from Microtops II measurements and the rotating shadowband radiometer will be compared. We show that the standard deviation of Aerosol optical depths observed with Microtops II and the shadowband radiometer is about 0.02 for matching channels, and an aerosol type classification based on Angstrom exponent shows good agreement. Also the influence of ship smoke and ocean swell is studied. The suitability of the instrument to automate MAN observations is discussed, and an outlook to the use of the instrument to also derive cloud optical properties is

  2. In situ aerosol optics in Reno, NV, USA during and after the summer 2008 California wildfires and the influence of aerosol coatings

    Directory of Open Access Journals (Sweden)

    M. Gyawali

    2009-06-01

    Full Text Available Hundreds of wildfires in Northern California were sparked by lightning during the summer of 2008, resulting in downwind smoke for the months of June and July. Comparisons are reported for aerosol optics measurements in Reno Nevada made during the very smoky summer month of July and the relatively clean month of August. Photoacoustic instruments equipped with integrating nephelometers were used to measure aerosol light scattering and absorption at wavelengths of 405 nm and 870 nm, revealing a strong variation of the aerosol light absorption with wavelength. Coated sphere calculations were used to show that Ångström exponents of absorption (AEA as large as 1.6 are possible even with non-absorbing organic coatings on black carbon cores, suggesting care be exercised when diagnosing AEA. Insight on fuels burned is gleaned from comparison of AEA versus single scattering albedo (SSA of the ambient measurements with laboratory biomass smoke measurements for many fuels. Measurements during the month of August, which were largely unaffected by fire smoke, exhibit surprisingly low AEA for aerosol light absorption when the SSA is highest, again likely as a consequence of the underappreciated wavelength dependence of aerosol light absorption by particles coated with non absorbing organic and inorganic matter.

  3. Trends in aerosol optical depth in northern China retrieved from sunshine duration data

    Science.gov (United States)

    Li, Jun; Liu, Run; Liu, Shaw Chen; Shiu, Chein-Jung; Wang, Jingli; Zhang, Yuanhang

    2016-01-01

    A new method has been developed to retrieve aerosol optical depth (AOD) from sunshine duration (SSD). Retrieved AODs from SSD at the six stations in northern China in 2003-2005 agree reasonably well with AODs retrieved from Moderate Resolution Imaging Spectroradiometer observations near the six stations. Values and trends in AOD retrieved from SSD in Beijing and Tianjin in the period 1961-2005 also agree with those retrieved from solar radiation and visibility. These agreements allow the retrieval of credible upper and lower limits for anthropogenic AODs from SSD at the six stations during 1961-2005. The trends in anthropogenic AODs are approximately a factor of 3 to 5 lower than the trends in emissions of gas-phase precursors of aerosols in 1973-2005, implying a significant sublinear relationship between the level of aerosols and emissions of their gas phase precursors. This finding has important implications for formulating a control strategy for PM2.5 or haze pollution in northern China.

  4. Ground truth methods for optical cross-section modeling of biological aerosols

    Science.gov (United States)

    Kalter, J.; Thrush, E.; Santarpia, J.; Chaudhry, Z.; Gilberry, J.; Brown, D. M.; Brown, A.; Carter, C. C.

    2011-05-01

    Light detection and ranging (LIDAR) systems have demonstrated some capability to meet the needs of a fastresponse standoff biological detection method for simulants in open air conditions. These systems are designed to exploit various cloud signatures, such as differential elastic backscatter, fluorescence, and depolarization in order to detect biological warfare agents (BWAs). However, because the release of BWAs in open air is forbidden, methods must be developed to predict candidate system performance against real agents. In support of such efforts, the Johns Hopkins University Applied Physics Lab (JHU/APL) has developed a modeling approach to predict the optical properties of agent materials from relatively simple, Biosafety Level 3-compatible bench top measurements. JHU/APL has fielded new ground truth instruments (in addition to standard particle sizers, such as the Aerodynamic particle sizer (APS) or GRIMM aerosol monitor (GRIMM)) to more thoroughly characterize the simulant aerosols released in recent field tests at Dugway Proving Ground (DPG). These instruments include the Scanning Mobility Particle Sizer (SMPS), the Ultraviolet Aerodynamic Particle Sizer (UVAPS), and the Aspect Aerosol Size and Shape Analyser (Aspect). The SMPS was employed as a means of measuring smallparticle concentrations for more accurate Mie scattering simulations; the UVAPS, which measures size-resolved fluorescence intensity, was employed as a path toward fluorescence cross section modeling; and the Aspect, which measures particle shape, was employed as a path towards depolarization modeling.

  5. Lidar-based Studies of Aerosol Optical Properties Over Coastal Areas

    Directory of Open Access Journals (Sweden)

    Bringfried Pflug

    2007-12-01

    Full Text Available Aerosol size distribution and concentration strongly depend on wind speed,direction, and measuring point location in the marine boundary layer over coastal areas.The marine aerosol particles which are found over the sea waves in high wind conditionsaffect visible and near infrared propagation for paths that pass very close to the surface aswell as the remote sensing measurements of the sea surface. These particles are producedby various air sea interactions. This paper presents the results of measurements taken atnumerous coastal stations between 1992 and 2006 using an FLS-12 lidar system togetherwith other supporting instrumentation. The investigations demonstrated that near-waterlayers in coastal areas differ significantly from those over open seas both in terms ofstructure and physical properties. Taking into consideration the above mentioned factors,aerosol concentrations and optical properties were determined in the marine boundary layeras a function of offshore distance and altitude at various coastal sites in two seasons. Thelidar results show that the remote sensing algorithms used currently in coastal areas needverification and are not fully reliable.

  6. Lidar-based Studies of Aerosol Optical Properties Over Coastal Areas.

    Science.gov (United States)

    Zielinski, Tymon; Pflug, Bringfried

    2007-12-19

    Aerosol size distribution and concentration strongly depend on wind speed,direction, and measuring point location in the marine boundary layer over coastal areas.The marine aerosol particles which are found over the sea waves in high wind conditionsaffect visible and near infrared propagation for paths that pass very close to the surface aswell as the remote sensing measurements of the sea surface. These particles are producedby various air sea interactions. This paper presents the results of measurements taken atnumerous coastal stations between 1992 and 2006 using an FLS-12 lidar system togetherwith other supporting instrumentation. The investigations demonstrated that near-waterlayers in coastal areas differ significantly from those over open seas both in terms ofstructure and physical properties. Taking into consideration the above mentioned factors,aerosol concentrations and optical properties were determined in the marine boundary layeras a function of offshore distance and altitude at various coastal sites in two seasons. Thelidar results show that the remote sensing algorithms used currently in coastal areas needverification and are not fully reliable.

  7. Organic component vapor pressures and hygroscopicities of aqueous aerosol measured by optical tweezers.

    Science.gov (United States)

    Cai, Chen; Stewart, David J; Reid, Jonathan P; Zhang, Yun-hong; Ohm, Peter; Dutcher, Cari S; Clegg, Simon L

    2015-01-29

    Measurements of the hygroscopic response of aerosol and the particle-to-gas partitioning of semivolatile organic compounds are crucial for providing more accurate descriptions of the compositional and size distributions of atmospheric aerosol. Concurrent measurements of particle size and composition (inferred from refractive index) are reported here using optical tweezers to isolate and probe individual aerosol droplets over extended timeframes. The measurements are shown to allow accurate retrievals of component vapor pressures and hygroscopic response through examining correlated variations in size and composition for binary droplets containing water and a single organic component. Measurements are reported for a homologous series of dicarboxylic acids, maleic acid, citric acid, glycerol, or 1,2,6-hexanetriol. An assessment of the inherent uncertainties in such measurements when measuring only particle size is provided to confirm the value of such a correlational approach. We also show that the method of molar refraction provides an accurate characterization of the compositional dependence of the refractive index of the solutions. In this method, the density of the pure liquid solute is the largest uncertainty and must be either known or inferred from subsaturated measurements with an error of <±2.5% to discriminate between different thermodynamic treatments.

  8. Retrieval and Validation of Aerosol Optical Depth by using the GF-1 Remote Sensing Data

    Science.gov (United States)

    Zhang, L.; Xu, S.; Wang, L.; Cai, K.; Ge, Q.

    2017-05-01

    Based on the characteristics of GF-1 remote sensing data, the method and data processing procedure to retrieve the Aerosol Optical Depth (AOD) are developed in this study. The surface contribution over dense vegetation and urban bright target areas are respectively removed by using the dark target and deep blue algorithms. Our method is applied for the three serious polluted Beijing-Tianjin-Hebei (BTH), Yangtze River Delta (YRD) and Pearl River Delta (PRD) regions. The retrieved AOD are validated by ground-based AERONET data from Beijing, Hangzhou, Hong Kong sites. Our results show that, 1) the heavy aerosol loadings are usually distributed in high industrial emission and dense populated cities, with the AOD value near 1. 2) There is a good agreement between satellite-retrievals and in-site observations, with the coefficient factors of 0.71 (BTH), 0.55 (YRD) and 0.54(PRD). 3) The GF-1 retrieval uncertainties are mainly from the impact of cloud contamination, high surface reflectance and assumed aerosol model.

  9. Probing the micro-rheological properties of aerosol particles using optical tweezers.

    Science.gov (United States)

    Power, Rory M; Reid, Jonathan P

    2014-07-01

    The use of optical trapping techniques to manipulate probe particles for performing micro-rheological measurements on a surrounding fluid is well-established. Here, we review recent advances made in the use of optical trapping to probe the rheological properties of trapped particles themselves. In particular, we review observations of the continuous transition from liquid to solid-like viscosity of sub-picolitre supersaturated solution aerosol droplets using optical trapping techniques. Direct measurements of the viscosity of the particle bulk are derived from the damped oscillations in shape following coalescence of two particles, a consequence of the interplay between viscous and surface forces and the capillary driven relaxation of the approximately spheroidal composite particle. Holographic optical tweezers provide a facile method for the manipulation of arrays of particles allowing coalescence to be controllably induced between two micron-sized aerosol particles. The optical forces, while sufficiently strong to confine the composite particle, are several orders of magnitude weaker than the capillary forces driving relaxation. Light, elastically back-scattered by the particle, is recorded with sub-100 ns resolution allowing measurements of fast relaxation (low viscosity) dynamics, while the brightfield image can be used to monitor the shape relaxation extending to times in excess of 1000 s. For the slowest relaxation dynamics studied (particles with the highest viscosity) the presence and line shape of whispering gallery modes in the cavity enhanced Raman spectrum can be used to infer the relaxation time while serving the dual purpose of allowing the droplet size and refractive index to be measured with accuracies of ±0.025% and ±0.1%, respectively. The time constant for the damped relaxation can be used to infer the bulk viscosity, spanning from the dilute solution limit to a value approaching that of a glass, typically considered to be >10(12)

  10. Spectral aerosol optical depths over Bay of Bengal and Chennai: I—measurements

    Science.gov (United States)

    Ramachandran, S.; Jayaraman, A.

    A cruise experiment to study the aerosol optical characteristics was conducted in February-March 2001 over the Bay of Bengal, a data void region. An analysis of aerosol optical depths (AODs) measured onboard Sagar Kanya shows that the AODs are higher when compared to those measured over the west coast of India and the Arabian Sea. The mean AODs at 0.5 μm over the Bay of Bengal are in the range of 0.2-0.7, and are found to show a variation of about 40-50% in the wavelength region of 0.4- 0.85 μm. The mean wavelength exponent α over the Bay of Bengal is found to be 1.80, higher than the Arabian Sea value of 1.46, indicating a relatively higher concentration of submicron size particles. The mean Ångström coefficient β, which represents the columnar aerosol loading, over the Bay of Bengal is found to be 0.10. Measurements of AODs, made before and after the cruise in Chennai, an urban station located on the eastern coast of India, show higher values compared to the Bay of Bengal data. The mean α for Chennai is found to be 1.53, which is lower than the Bay of Bengal value while the mean β is higher at 0.18. While a higher α value indicates the dominance of smaller size particles over Bay of Bengal, a higher β and a higher AOD at all wavelengths indicate the dominance of both bigger and smaller particles over Chennai. A comparison of AODs obtained over a coastal station Trivandrum, located on the southwest coast of India, during March 2001 showed that in the smaller wavelength range the Chennai AODs are higher while above 0.6 μm the AODs are comparable. The day-to-day variations of AODs measured at Chennai are less significant when compared to Bay of Bengal and are below 10%. As Chennai is an urban, industrial and a well-populated city, and is a constant source of aerosol particles, there are lesser day-to-day variations in the AOD, while over the Bay of Bengal the air masses come from different source regions carrying aerosols of different chemical and

  11. Size distribution and optical properties of mineral dust aerosols transported in the western Mediterranean

    Directory of Open Access Journals (Sweden)

    C. Denjean

    2015-08-01

    Full Text Available This study presents in situ aircraft measurements of Saharan mineral dust transported over the western Mediterranean basin in June–July 2013 during the ChArMEx/ADRIMED (the Chemistry-Aerosol Mediterranean Experiment/Aerosol Direct Radiative Impact on the regional climate in the MEDiterranean region airborne campaign. Dust events differing in terms of source region (Algeria, Tunisia and Morocco, time of tranport (1–5 days and height of transport were sampled. Mineral dust were transported above the marine boundary layer, which conversely was dominated by pollution and marine aerosols. The dust vertical structure was extremely variable and characterized by either a single layer or a more complex and stratified structure with layers originating from different source regions. Mixing of mineral dust with pollution particles was observed depending on the height of transport of the dust layers. Dust layers carried higher concentration of pollution particles at intermediate altitude (1–3 km than at elevated altitude (> 3 km, resulting in scattering Angstrom exponent up to 2.2 within the intermediate altitude. However, the optical properties of the dust plumes remained practically unchanged with respect to values previously measured over source regions, regardless of the altitude. Moderate light absorption of the dust plumes was observed with values of aerosol single scattering albedo at 530 nm ranging from 0.90 to 1.00 ± 0.04. Concurrent calculations from the aerosol chemical composition revealed a negligible contribution of pollution particles to the absorption properties of the dust plumes that was due to a low contribution of refractory black carbon in regards to the fraction of dust and sulfate particles. This suggests that, even in the presence of moderate pollution, likely a persistent feature in the Mediterranean, the optical properties of the dust plumes could be assimilated to those of native dust in radiative transfer simulations

  12. Size distribution and optical properties of mineral dust aerosols transported in the western Mediterranean

    Science.gov (United States)

    Denjean, C.; Cassola, F.; Mazzino, A.; Triquet, S.; Chevaillier, S.; Grand, N.; Bourrianne, T.; Momboisse, G.; Sellegri, K.; Schwarzenbock, A.; Freney, E.; Mallet, M.; Formenti, P.

    2016-02-01

    This study presents in situ aircraft measurements of Saharan mineral dust transported over the western Mediterranean basin in June-July 2013 during the ChArMEx/ADRIMED (the Chemistry-Aerosol Mediterranean Experiment/Aerosol Direct Radiative Impact on the regional climate in the MEDiterranean region) airborne campaign. Dust events differing in terms of source region (Algeria, Tunisia and Morocco), time of transport (1-5 days) and height of transport were sampled. Mineral dust were transported above the marine boundary layer, which conversely was dominated by pollution and marine aerosols. The dust vertical structure was extremely variable and characterized by either a single layer or a more complex and stratified structure with layers originating from different source regions. Mixing of mineral dust with pollution particles was observed depending on the height of transport of the dust layers. Dust layers carried a higher concentration of pollution particles below 3 km above sea level (a.s.l.) than above 3 km a.s.l., resulting in a scattering Ångström exponent up to 2.2 below 3 km a.s.l. However, the optical properties of the dust plumes remained practically unchanged with respect to values previously measured over source regions, regardless of the altitude. Moderate absorption of light by the dust plumes was observed with values of aerosol single scattering albedo at 530 nm ranging from 0.90 to 1.00. Concurrent calculations from the aerosol chemical composition revealed a negligible contribution of pollution particles to the absorption properties of the dust plumes that was due to a low contribution of refractory black carbon in regards to the fraction of dust and sulfate particles. This suggests that, even in the presence of moderate pollution, likely a persistent feature in the Mediterranean, the optical properties of the dust plumes could be assumed similar to those of native dust in radiative transfer simulations, modelling studies and satellite retrievals

  13. Characterization of aerosol optical properties, chemical composition and mixing states in the winter season in Shanghai, China

    Institute of Scientific and Technical Information of China (English)

    Yong Tang; Yuanlong Huang; Ling Li; Hong Chen; Jianmin Chen; Xin Yang; Song Gao

    2014-01-01

    Physical and chemical properdes of ambient aerosols at the single particle level were studied in Shanghai from December 22 to 28,2009.A Cavity-Ring-Down Aerosol Extinction Spectrometer (CRD-AES) and a nephelometer were deployed to measure aerosol light extinction and scattering properties,respectively.An Aerosol Time-of-Flight Mass Spectrometer (ATOFMS)was used to detect single particle sizes and chemical composition.Seven particle types were detected.Air parcels arrived at the sampling site from the vicinity of Shanghai until mid-day of December 25,when they started to originate from North China.The aerosol extinction,scattering,and absorption coefficients all dropped sharply when this cold,clean air arrived.Aerosol particles changed from a highly aged type before this meteorological shift to a relatively fresh type afterwards.The aerosol optical properties were dependent on the wind direction.Aerosols with high extinction coefficient and scattering Angstr(o)m exponent (SAE) were observed when the wind blew from the west and northwest,indicating that they were predominantly fine particles.Nitrate and ammonium correlated most strongly with the change in aerosol optical properties.In the elemental carbon/organic carbon (ECOC) particle type,the diurnal trends of single scattering albedo (SSA) and elemental carbon (EC) signal intensity had a negative correlation.We also found a negative correlation (r =-0.87) between high mass-OC particle number fraction and the SSA in a relatively clean period,suggesting that particulate aromatic components might play an important role in light absorption in urban areas.

  14. Joint elastic side-scattering LIDAR and Raman LIDAR measurements of aerosol optical properties in south east Colorado

    Science.gov (United States)

    Wiencke, L.; Rizi, V.; Will, M.; Allen, C.; Botts, A.; Calhoun, M.; Carande, B.; Claus, J.; Coco, M.; Emmert, L.; Esquibel, S.; Grillo, A. F.; Hamilton, L.; Heid, T. J.; Iarlori, M.; Klages, H.-O.; Kleifges, M.; Knoll, B.; Koop, J.; Mathes, H.-J.; Menshikov, A.; Morgan, S.; Patterson, L.; Petrera, S.; Robinson, S.; Runyan, C.; Sherman, J.; Starbuck, D.; Wakin, M.; Wolf, O.

    2017-03-01

    We describe an experiment, located in south-east Colorado, U.S.A., that measured aerosol optical depth profiles using two LIDAR techniques. Two independent detectors measured scattered light from a vertical UV laser beam. One detector, located at the laser site, measured light via the inelastic Raman backscattering process. This is a common method used in atmospheric science for measuring aerosol optical depth profiles. The other detector, located approximately 40 km distant, viewed the laser beam from the side. This detector featured a 3.5 m2 mirror and measured elastically scattered light in a bistatic LIDAR configuration following the method used at the Pierre Auger cosmic ray observatory. The goal of this experiment was to assess and improve methods to measure atmospheric clarity, specifically aerosol optical depth profiles, for cosmic ray UV fluorescence detectors that use the atmosphere as a giant calorimeter. The experiment collected data from September 2010 to July 2011 under varying conditions of aerosol loading. We describe the instruments and techniques and compare the aerosol optical depth profiles measured by the Raman and bistatic LIDAR detectors.

  15. MODIS 3 km and 10 km aerosol optical depth for China: Evaluation and comparison

    Science.gov (United States)

    He, Qingqing; Zhang, Ming; Huang, Bo; Tong, Xuelian

    2017-03-01

    The recently released Moderate Resolution Imaging Spectrometer (MODIS) Collection 6 introduced a fine scale aerosol optical depth (AOD) distribution, the 3 km product, which is expected to perform well in analyzing aerosols and identifying local air pollution, especially in the severely polluted atmosphere of China. However, few detailed evaluations of regional variations have been conducted. In this paper, we evaluate MODIS 3 km and 10 km AOD products for China against ground-based measurements and compare their performance with respect to spatial and temporal variations. The ground validations indicate that the two products are generally correlated well to ground-based observations. Spatially, the 3 km product slightly outperform the 10 km product in well-developed areas of southern China. Temporally, both products perform worse during spring and summer. Atmospheric clouds and underlying surface are two key factors that influence the accuracy and number of retrievals for both products. The comparison analysis reveals the newly introduced AOD product clearly shows good relationships with the coarse resolution retrievals in spatial and temporal variation but significant differences regarding details. The 3 km AOD product provides better aerosol gradients, more retrievals in bare areas of western China and some spikes of diurnal variation in cloudy days. Seasonal comparisons show the 3 km AOD product is higher than the 10 km product in all seasons, especially during spring and summer. Although the 3 km product for China generally performs slightly worse than the 10 km product, the added information of the MODIS 3 km AOD product shows potential for studying local aerosol characterization, and may facilitate studies of air pollution.

  16. Optical properties of humic-like substances (HULIS in biomass-burning aerosols

    Directory of Open Access Journals (Sweden)

    A. Hoffer

    2006-01-01

    Full Text Available We present here the optical properties of humic-like substances (HULIS isolated from the fine fraction of biomass-burning aerosol collected in the Amazon basin during the LBA-SMOCC (Large scale Biosphere atmosphere experiment in Amazonia – SMOke aerosols, Clouds, rainfall and Climate experiment in September 2002. From the isolated HULIS, aerosol particles were generated and their scattering and absorption coefficients measured. The size distribution and mass of the particles were also recorded. The value of the index of refraction was derived from "closure" calculations based on particle size, scattering and absorption measurements. On average, the complex index of refraction at 532 nm of HULIS collected during day and nighttime was 1.65–0.0019i and 1.69–0.0016i, respectively. In addition, the imaginary part of the complex index of refraction was calculated using the measured absorption coefficient of the bulk HULIS. The mass absorption coefficient of the HULIS at 532 nm was found to be quite low (0.031 and 0.029 m2 g−1 for the day and night samples, respectively. However, due to the high absorption Ångström exponent (6–7 of HULIS, the specific absorption increases substantially towards shorter wavelengths (~2–3 m2 g−1 at 300 nm, causing a relatively high (up to 50% contribution to the light absorption of our Amazonian aerosol at 300 nm. For the relative contribution of HULIS to light absorption in the entire solar spectrum, lower values (6.4–8.6% are obtained, but those are still not negligible.

  17. A consistent aerosol optical depth (AOD) dataset over mainland China by integration of several AOD products

    Science.gov (United States)

    Xu, H.; Guang, J.; Xue, Y.; de Leeuw, Gerrit; Che, Y. H.; Guo, Jianping; He, X. W.; Wang, T. K.

    2015-08-01

    The Moderate Resolution Imaging Spectroradiometer (MODIS), the Multiangle Imaging Spectroradiometer (MISR) and the Sea-viewing Wide Field-of-view Sensor (SeaWiFS) provide validated aerosol optical depth (AOD) products over both land and ocean. However, the values of the AOD provided by each of these satellites may show spatial and temporal differences due to the instrument characteristics and aerosol retrieval algorithms used for each instrument. In this article we present a method to produce an AOD data set over Asia for the year 2007 based on fusion of the data provided by different instruments and/or algorithms. First, the bias of each satellite-derived AOD product was calculated by comparison with ground-based AOD data derived from the AErosol RObotic NETwork (AERONET) and the China Aerosol Remote Sensing NETwork (CARSNET) for different values of the surface albedo and the AOD. Then, these multiple AOD products were combined using the maximum likelihood estimate (MLE) method using weights derived from the root mean square error (RMSE) associated with the accuracies of the original AOD products. The original and merged AOD dataset has been validated by comparison with AOD data from the CARSNET. Results show that the mean bias error (MBE) and mean absolute error (MAE) of the merged AOD dataset are not larger than that of any of the original AOD products. In addition, for the merged AOD dataset the fraction of pixels with no data is significantly smaller than that of any of the original products, thus increasing the spatial coverage. The fraction of retrievable area is about 50% for the merged AOD dataset and between 5% and 20% for the MISR, SeaWiFS, MODIS-DT and MODIS-DB algorithms.

  18. Some implications of sampling choices on comparisons between satellite and model aerosol optical depth fields

    Directory of Open Access Journals (Sweden)

    A. M. Sayer

    2010-11-01

    Full Text Available The comparison of satellite and model aerosol optical depth (AOD fields provides useful information on the strengths and weaknesses of both. However, the sampling of satellite and models is very different and some subjective decisions about data selection and aggregation must be made in order to perform such comparisons. This work examines some implications of these decisions, using GlobAerosol AOD retrievals at 550 nm from Advanced Along-Track Scanning Radiometer (AATSR measurements, and aerosol fields from the GEOS-Chem chemistry transport model. It is recommended to sample the model only where the satellite flies over on a particular day; neglecting this can cause regional differences in model AOD of up to 0.1 on monthly and annual timescales. The comparison is observed to depend strongly upon thresholds for sparsity of satellite retrievals in the model grid cells. Requiring at least 25% coverage of the model grid cell by satellite data decreases the observed difference between the two by approximately half over land. The impact over ocean is smaller. In both model and satellite datasets, there is an anticorrelation between the proportion p of a model grid cell covered by satellite retrievals and the AOD. This is attributed to small p typically occuring due to high cloud cover and lower AODs being found in large clear-sky regions. Daily median AATSR AODs were found to be closer to GEOS-Chem AODs than daily means (with the root mean squared difference being approximately 0.05 smaller. This is due to the decreased sensitivity of medians to outliers such as cloud-contaminated retrievals, or aerosol point sources not included in the model.

  19. Infrared spectroscopic methods for the study of aerosol particles using White cell optics: Development and characterization of a new aerosol flow tube

    Science.gov (United States)

    Nájera, Juan J.; Fochesatto, Javier G.; Last, Deborah J.; Percival, Carl J.; Horn, Andrew B.

    2008-12-01

    A description of a new aerosol flow tube apparatus for measurements in situ under atmospherically relevant conditions is presented here. The system consists of a laboratory-made nebulizer generation system and a flow tube with a White cell-based Fourier transform IR for the detection system. An assessment of the White cell coupled to the flow tube was carried out by an extensive set of experiments to ensure the alignment of the infrared beam and optimize the performance of this system. The detection limit for CO was established as (1.0±0.3) ppm and 16 passes was chosen as the optimum number of passes to be used in flow tube experiments. Infrared spectroscopy was used to characterize dry aerosol particles in the flow tube. Pure particles composed of ammonium sulfate or sodium chloride ranging between 0.8 and 2.1 μm for size diameter and (0.8-4.9)×106 particles/cm3 for density number were generated by nebulization of aqueous solutions. Direct measurements of the aerosol particle size agree with size spectra retrieved from inversion of the extinction measurements using Mie calculations, where the difference residual value is in the order of 0.2%. The infrared detection limit for ammonium sulfate aerosol particles was determined as dp=0.9 μm and N =5×103 particles/cm3 with σ =1.1 by Mie calculation. Alternatively, Mie calculations were performed to determine the flexibility in varying the optical length when aerosol particles are sent by the injector. The very good agreement between the values retrieved for aerosol particles injected through the flow tube or through the injector clearly validates the estimation of the effective optical path length for the injector. To determine the flexibility in varying the reaction zone length, analysis of the extinction spectra as function of the position of the injector was carried out by monitoring the integrated area of different absorption modes of the ammonium sulfate. We conclude that the aerosol loss in the flow tube

  20. Inter-comparison of model-simulated and satellite-retrieved componential aerosol optical depths in China

    Science.gov (United States)

    Li, Shenshen; Yu, Chao; Chen, Liangfu; Tao, Jinhua; Letu, Husi; Ge, Wei; Si, Yidan; Liu, Yang

    2016-09-01

    China's large aerosol emissions have major impacts on global climate change as well as regional air pollution and its associated disease burdens. A detailed understanding of the spatiotemporal patterns of aerosol components is necessary for the calculation of aerosol radiative forcing and the development of effective emission control policy. Model-simulated and satellite-retrieved aerosol components can support climate change research, PM2.5 source appointment and epidemiological studies. This study evaluated the total and componential aerosol optical depth (AOD) from the GEOS-Chem model (GC) and the Global Ozone Chemistry Aerosol Radiation and Transport model (GOCART), and the Multiangle Imaging Spectroradiometer (MISR) from 2006 to 2009 in China. Linear regression analysis between the GC and AErosol RObotic NETwork (AERONET) in China yielded similar correlation coefficients (0.6 daily, 0.71 monthly) but lower slopes (0.41 daily, 0.58 monthly) compared with those in the U.S. This difference was attributed to GC's underestimation of water-soluble AOD (WAOD) west of the Heihe-Tengchong Line, the dust AOD (DAOD) in the fall and winter, and the soot AOD (SAOD) throughout the year and throughout the country. GOCART exhibits the strongest dust estimation capability among all datasets. However, the GOCART soot distribution in the Northeast and Southeast has significant errors, and its WAOD in the polluted North China Plain (NCP) and the South is underestimated. MISR significantly overestimates the water-soluble aerosol levels in the West, and does not capture the high dust loadings in all seasons and regions, and the SAOD in the NCP. These discrepancies can mainly be attributed to the uncertainties in the emission inventories of both models, the poor performance of GC under China's high aerosol loading conditions, the omission of certain aerosol tracers in GOCART, and the tendency of MISR to misidentify dust and non-dust mixtures.

  1. Long-term analysis of aerosol optical depth over Northeast Asia using a satellite-based measurement: MI Yonsei Aerosol Retrieval Algorithm (YAER)

    Science.gov (United States)

    Kim, Mijin; Kim, Jhoon; Yoon, Jongmin; Chung, Chu-Yong; Chung, Sung-Rae

    2017-04-01

    In 2010, the Korean geostationary earth orbit (GEO) satellite, the Communication, Ocean, and Meteorological Satellite (COMS), was launched including the Meteorological Imager (MI). The MI measures atmospheric condition over Northeast Asia (NEA) using a single visible channel centered at 0.675 μm and four IR channels at 3.75, 6.75, 10.8, 12.0 μm. The visible measurement can also be utilized for the retrieval of aerosol optical properties (AOPs). Since the GEO satellite measurement has an advantage for continuous monitoring of AOPs, we can analyze the spatiotemporal variation of the aerosol using the MI observations over NEA. Therefore, we developed an algorithm to retrieve aerosol optical depth (AOD) using the visible observation of MI, and named as MI Yonsei Aerosol Retrieval Algorithm (YAER). In this study, we investigated the accuracy of MI YAER AOD by comparing the values with the long-term products of AERONET sun-photometer. The result showed that the MI AODs were significantly overestimated than the AERONET values over bright surface in low AOD case. Because the MI visible channel centered at red color range, contribution of aerosol signal to the measured reflectance is relatively lower than the surface contribution. Therefore, the AOD error in low AOD case over bright surface can be a fundamental limitation of the algorithm. Meanwhile, an assumption of background aerosol optical depth (BAOD) could result in the retrieval uncertainty, also. To estimate the surface reflectance by considering polluted air condition over the NEA, we estimated the BAOD from the MODIS dark target (DT) aerosol products by pixel. The satellite-based AOD retrieval, however, largely depends on the accuracy of the surface reflectance estimation especially in low AOD case, and thus, the BAOD could include the uncertainty in surface reflectance estimation of the satellite-based retrieval. Therefore, we re-estimated the BAOD using the ground-based sun-photometer measurement, and

  2. Optical, physical and chemical properties of aerosols transported to a coastal site in the western Mediterranean: a focus on primary marine aerosols

    Science.gov (United States)

    Claeys, Marine; Roberts, Greg; Mallet, Marc; Arndt, Jovanna; Sellegri, Karine; Sciare, Jean; Wenger, John; Sauvage, Bastien

    2017-06-01

    As part of the ChArMEx-ADRIMED campaign (summer 2013), ground-based in situ observations were conducted at the Ersa site (northern tip of Corsica; 533 m a.s.l.) to characterise the optical, physical and chemical properties of aerosols. During the observation period, a major influence of primary marine aerosols was detected (22-26 June), with a mass concentration reaching up to 6.5 µg m-3 and representing more than 40 % of the total PM10 mass concentration. Its relatively low ratio of chloride to sodium (average of 0.57) indicates a fairly aged sea salt aerosol at Ersa. In this work, an original data set, obtained from online real-time instruments (ATOFMS, PILS-IC) has been used to characterise the ageing of primary marine aerosols (PMAs). During this PMA period, the mixing of fresh and aged PMAs was found to originate from both local and regional (Gulf of Lion) emissions, according to local wind measurements and FLEXPART back trajectories. Two different aerosol regimes have been identified: a dust outbreak (dust) originating from Algeria/Tunisia, and a pollution period with aerosols originating from eastern Europe, which includes anthropogenic and biomass burning sources (BBP). The optical, physical and chemical properties of the observed aerosols, as well as their local shortwave (SW) direct radiative effect (DRE) in clear-sky conditions, are compared for these three periods in order to assess the importance of the direct radiative impact of PMAs compared to other sources above the western Mediterranean Basin. As expected, AERONET retrievals indicate a relatively low local SW DRF during the PMA period with mean values of -11 ± 4 at the surface and -8 ± 3 W m-2 at the top of the atmosphere (TOA). In comparison, our results indicate that the dust outbreak observed at our site during the campaign, although of moderate intensity (AOD of 0.3-0.4 at 440 nm and column-integrated SSA of 0.90-0.95), induced a local instantaneous SW DRF that is nearly 3 times the effect

  3. Retrieval of aerosol optical depth in the visible range with a Brewer spectrophotometer in Athens

    Science.gov (United States)

    Diémoz, Henri; Eleftheratos, Kostas; Kazadzis, Stelios; Amiridis, Vassilis; Zerefos, Christos S.

    2016-04-01

    A MkIV Brewer spectrophotometer has been operating in Athens since 2004. Direct-sun measurements originally scheduled for nitrogen dioxide retrievals were reprocessed to provide aerosol optical depths (AODs) at a wavelength of about 440 nm. A novel retrieval algorithm was specifically developed and the resulting AODs were compared to those obtained from a collocated Cimel filter radiometer belonging to the Aerosol Robotic Network (AERONET). The series are perfectly correlated, with Pearson's correlation coefficients being as large as 0.996 and with 90 % of AOD deviations between the two instruments being within the World Meteorological Organisation (WMO) traceability limits. In order to reach such a high agreement, several instrumental factors impacting the quality of the Brewer retrievals must be taken into account, including sensitivity to the internal temperature, and the state of the external optics and pointing accuracy must be carefully checked. Furthermore, the long-term radiometric stability of the Brewer was investigated and the performances of in situ Langley extrapolations as a way to track the absolute calibration of the Brewer were assessed. Other sources of error, such as slight shifts of the wavelength scale, are discussed and some recommendations to Brewer operators are drawn. Although MkIV Brewers are rarely employed to retrieve AODs in the visible range, they represent a key source of information about aerosol changes in the past three decades and a potential worldwide network for present and future coordinated AOD measurements. Moreover, a better understanding of the AOD retrieval at visible wavelengths will also contribute in improving similar techniques in the more challenging UV range.

  4. Column ozone and aerosol optical properties retrieved from direct solar irradiance measurements during SOLVE II

    Directory of Open Access Journals (Sweden)

    W. H. Swartz

    2004-11-01

    Full Text Available Direct observation of the Sun at large solar zenith angles during the second SAGE III Ozone Loss and Validation Experiment (SOLVE II/Validation of International Satellites and study of Ozone Loss (VINTERSOL campaign by several instruments provided a rich dataset for the retrieval and analysis of line-of-sight column composition, intercomparison, and measurement validation. A flexible, multi-species spectral fitting technique is presented and applied to spectral solar irradiance measurements made by the NCAR Direct beam Irradiance Atmospheric Spectrometer (DIAS on-board the NASA DC-8. The approach allows for the independent retrieval of O3, O2·O2, and aerosol optical properties, by constraining Rayleigh extinction. We examine the 19 January 2003 and 6 February 2003 flights and find very good agreement of O3 and O2·O2 retrievals with forward-modeling calculations, even at large solar zenith angles, where refraction is important. Intercomparisons of retrieved ozone and aerosol optical thickness with results from the Ames Airborne Tracking Sunphotometer (AATS-14 are summarized.

  5. Detection of Biomass in New York City Aerosols: Light Scattering and Optical Fluorescence Techniques

    Science.gov (United States)

    Niebauer, M.; Alimova, A.; Katz, A.; Xu, M.; Rudolph, E.; Steiner, J.; Alfano, R. R.

    2005-12-01

    Optical spectroscopy is an ideal method for detecting bacteria and spores in real time. Optical fluorescence spectroscopy examination of New York City aerosols is used to quantify the mass of bacteria spores present in air masses collected at 14 liters/minute onto silica fiber filters, and on silica fiber ribbons using an Environmental Beta Attenuation Monitor manufactured by MetOne Instruments configured for the PM2.5 fraction. Dipicolinic acid (DPA), a molecule found primarily in bacterial spores, is the most characteristic component of spores in trial experiments on over 200 collected aerosol samples. DPA is extracted from the spores using a heat bath and chelated with Terbium. The DPA:Tb is detected by measuring its characteristic fluorescence with emission bands at 490, 545 and 585 nm for 270 nm excitation. Light scattering also measures the size distribution for a number of a variety of bacteria - Bacillus subtilis (rod shaped), Staphylococcus aureus (spherical) and Pseudomonas aeruginosa (short rods) establishing that optical techniques satisfactorily distinguish populations based on their variable morphology. Size and morphology are obtained by applying a variation of the Gaussian Ray Approximation theory of anomalous diffraction theory to an analysis of the transmission spectra in the range of 0.4 to 1.0 microns. In test experiments, the refractive index of the inner spore core of Bacillus subtilis decreases from 1.51 to 1.39 while the spore radius enlarges from 0.38 to 0.6 micrometers. Optical determinations are verified by oil-immersion techniques and by scanning electron microscope measurements. Characterization of spores, germinating spore materials, and bacteria is considered vital to tracing bacteria in the environment, for the development of life-detection systems for planetary exploration, monitoring pathogens in environmental systems, and for the preparation of anti-terrorism strategies.

  6. Profiling aerosol optical, microphysical and hygroscopic properties in ambient conditions by combining in situ and remote sensing

    Science.gov (United States)

    Tsekeri, Alexandra; Amiridis, Vassilis; Marenco, Franco; Nenes, Athanasios; Marinou, Eleni; Solomos, Stavros; Rosenberg, Phil; Trembath, Jamie; Nott, Graeme J.; Allan, James; Le Breton, Michael; Bacak, Asan; Coe, Hugh; Percival, Carl; Mihalopoulos, Nikolaos

    2017-01-01

    We present the In situ/Remote sensing aerosol Retrieval Algorithm (IRRA) that combines airborne in situ and lidar remote sensing data to retrieve vertical profiles of ambient aerosol optical, microphysical and hygroscopic properties, employing the ISORROPIA II model for acquiring the particle hygroscopic growth. Here we apply the algorithm on data collected from the Facility for Airborne Atmospheric Measurements (FAAM) BAe-146 research aircraft during the ACEMED campaign in the Eastern Mediterranean. Vertical profiles of aerosol microphysical properties have been derived successfully for an aged smoke plume near the city of Thessaloniki with aerosol optical depth of ˜ 0.4 at 532 nm, single scattering albedos of ˜ 0.9-0.95 at 550 nm and typical lidar ratios for smoke of ˜ 60-80 sr at 532 nm. IRRA retrieves highly hydrated particles above land, with 55 and 80 % water volume content for ambient relative humidity of 80 and 90 %, respectively. The proposed methodology is highly advantageous for aerosol characterization in humid conditions and can find valuable applications in aerosol-cloud interaction schemes. Moreover, it can be used for the validation of active space-borne sensors, as is demonstrated here for the case of CALIPSO.

  7. Interpreting the cloud cover – aerosol optical depth relationship found in satellite data using a general circulation model

    Directory of Open Access Journals (Sweden)

    J. Quaas

    2010-07-01

    Full Text Available Statistical analysis of satellite data shows a positive correlation between aerosol optical depth (AOD and total cloud cover (TCC. Reasons for this relationship have been disputed in recent literature. The aim of this study is to explore how different processes contribute to one model's analog of the positive correlation between aerosol optical depth and total cloud cover seen in the satellite retrievals. We compare the slope of the linear regression between the logarithm of TCC and the logarithm of AOD, or the strength of the relationship, as derived from three satellite data sets to the ones simulated by a global aerosol-climate model. We analyse model results from two different simulations with and without a parameterisation of aerosol indirect effects, and using dry compared to humidified AOD. Perhaps not surprisingly we find that no single one of the hypotheses discussed in the literature is able to uniquely explain the positive relationship. However the dominant contribution to the model's AOD-TCC relationship can be attributed to aerosol swelling in regions where humidity is high and clouds are coincidentally found. This finding leads us to hypothesise that much of the AOD-TCC relationship seen in the satellite data is also carried by such a process, rather than the direct effects of the aerosols on the cloud fields themselves.

  8. Separating Real and Apparent Effects of Cloud, Humidity, and Dynamics on Aerosol Optical Thickness near Cloud Edges

    Science.gov (United States)

    Jeong, Myeong-Jae; Li, Zhanqing

    2010-01-01

    Aerosol optical thickness (AOT) is one of aerosol parameters that can be measured on a routine basis with reasonable accuracy from Sun-photometric observations at the surface. However, AOT-derived near clouds is fraught with various real effects and artifacts, posing a big challenge for studying aerosol and cloud interactions. Recently, several studies have reported correlations between AOT and cloud cover, pointing to potential cloud contamination and the aerosol humidification effect; however, not many quantitative assessments have been made. In this study, various potential causes of apparent correlations are investigated in order to separate the real effects from the artifacts, using well-maintained observations from the Aerosol Robotic Network, Total Sky Imager, airborne nephelometer, etc., over the Southern Great Plains site operated by the U.S. Department of Energy's Atmospheric Radiation Measurement Program. It was found that aerosol humidification effects can explain about one fourth of the correlation between the cloud cover and AOT. New particle genesis, cloud-processed particles, atmospheric dynamics, and aerosol indirect effects are likely to be contributing to as much as the remaining three fourth of the relationship between cloud cover and AOT.

  9. On the correlation between aerosol optical depth and precipitation over hyperarid regions: A case study from the Arabian Peninsula

    Science.gov (United States)

    Rodrigo Vargas Godoy, Mijael; Reddy Marpu, Prashanth; Chiesa, Matteo; Molini, Annalisa

    2017-04-01

    Atmospheric turbidity plays a crucial - and controversial - role in the hydroclimatology of arid regions, with atmospheric aerosols both acting as rainfall inhibitors and enhancers. Aircraft observations and model simulations show that cloud development is strongly modulated by dust-cloud interactions at the microscales, during the drop formation process. However, the influence of aerosols and dust on precipitation remains poorly understood, mainly due to our limited knowledge of the dynamical processes that - acting over a wider range of spatial and temporal scales - drive cloud formation and trigger precipitation. The effects of dust and aerosols on precipitation mostly depend on the concentration of dust particles acting as cloud condensation nuclei (CCNs) and ice nuclei (IN), their chemical composition, size and morphology. In the recent years, the application of satellite data to characterize aerosol distribution has advanced dramatically through the systematic acquisition of aerosol optical depth (AOD) data over land from space borne sensors like MODIS onboard the EOS-Terra satellite. Although AOD is not a direct measure of the aerosol concentration in atmosphere, but rather an estimate of the atmospheric optical thickness due to scattering and absorption by aerosols, it is frequently used as a proxy of dust concentration in the atmospheric column. Many studies have analyzed the coupling between dust/aerosol abundance and precipitation through the use of remotely sensed data of AOD and precipitation. However, their focus has been mainly on the long-term influence (at monthly or annual scales) of dust/aerosols on precipitation onset, and on the influence of transport processes (through Lagrangian tracking). In this contribution, we move our attention to hyperarid regions - and in particular to a large region centered on the Arabian Peninsula, Persia and Eastern Africa - where precipitation events are highly sporadic and scattered in space. We use aerosol

  10. Spectral optical properties of long-range transport Asian dust and pollution aerosols over Northeast Asia in 2007 and 2008

    Directory of Open Access Journals (Sweden)

    J. Jung

    2010-06-01

    Full Text Available As a part of the IGAC (International Global Atmospheric Chemistry Mega-cities program, aerosol physical and optical properties were continuously measured from March 2007 to March 2008 at an urban site (37.57° N, 126.94° E in Seoul, Korea. Spectral optical properties of long-range transported Asian dust and pollution aerosols have been investigated based on the year long measurement data. Optically measured black carbon/thermally measured elemental carbon (BC/EC ratio showed clear monthly variation with high values in summer and low values in winter mainly due to the enhancement of light attenuation by the internal mixing of EC. Novel approach has been suggested to retrieve the spectral light absorption coefficient (babs from Aethalometer raw data by using BC/EC ratio. Mass absorption efficiency, σabs (=babs/EC at 550 nm was determined to be 9.0±1.3, 8.9±1.5, 9.5±2.0, and 10.3±1.7 m2 g−1 in spring, summer, fall, and winter, respectively with an annual mean of 9.4±1.8 m2 g−1. Threshold values to classify severe haze events were suggested in this study. Increasing trend of aerosol single scattering albedo (SSA with wavelength was observed during Asian dust events while little spectral dependence of SSA was observed during long-range transport pollution (LTP events. Satellite aerosol optical thickness (AOT and Hysplit air mass backward trajectory analyses as well as chemical analysis were performed to characterize the dependence of spectral optical properties on aerosol type. Results from this study can provide useful information for studies on regional air quality and aerosol's effects on climate change.

  11. Sensitivity of nitrate aerosols to ammonia emissions and to nitrate chemistry: implications for present and future nitrate optical depth

    Directory of Open Access Journals (Sweden)

    F. Paulot

    2015-09-01

    Full Text Available We update and evaluate the treatment of nitrate aerosols in the Geophysical Fluid Dynamics Laboratory (GFDL atmospheric model (AM3. Accounting for the radiative effects of nitrate aerosols generally improves the simulated aerosol optical depth, although nitrate concentrations at the surface are biased high. This bias can be reduced by increasing the deposition of nitrate to account for the near-surface volatilization of ammonium nitrate or by neglecting the heterogeneous production of nitric acid to account for the inhibition of N2O5 reactive uptake at high nitrate concentrations. Globally, uncertainties in these processes can impact the simulated nitrate optical depth by up to 25 %, much more than the impact of uncertainties in the seasonality of ammonia emissions (6 % or in the uptake of nitric acid on dust (13 %. Our best estimate for present-day fine nitrate optical depth at 550 nm is 0.006 (0.005–0.008. We only find a modest increase of nitrate optical depth (2 (−40 % and ammonia (+38 % from 2010 to 2050. Nitrate burden is projected to increase in the tropics and in the free troposphere, but to decrease at the surface in the midlatitudes because of lower nitric acid concentrations. Our results suggest that better constraints on the heterogeneous chemistry of nitric acid on dust, on tropical ammonia emissions, and on the transport of ammonia to the free troposphere are needed to improve projections of aerosol optical depth.

  12. Characteristics of Aerosol Spectral Optical Depths over Manora Peak, Nainital $-$ A High Altitude Station in the Central Himalayas

    CERN Document Server

    Sagar, R; Dumka, U C; Moorthy, K K; Pant, P

    2003-01-01

    We present for the first time spectral behaviour of aerosol optical depths (AODs) over Manora Peak, Nainital located at an altitude of ~2 km in the central Himalayas. The observations were carried out using a Multi-Wavelength Solar Radiometer during January to December 2002. The primary features of the study are (i) larger AOD during afternoon periods compared to forenoon, attributable to change in the ray path from comparatively cleaner environment in the forenoon to polluted environment in the afternoon (ii) extremely low AODs during local winter and a remarkable increase to high values in summer (iii) a distinct change in the spectral dependencies of AODs from a relatively steeper spectra during winter to a shallower one in summer representing both transparent (meteorological aerosols) and polluted summer (urban haze aerosols) skies.The mean aerosol extinction law at Nainital during 2002 is best represented by $0.10 \\lambda^{-0.61}$.

  13. Optical, physical and chemical characteristics of Australian continental aerosols: results from a field experiment

    Directory of Open Access Journals (Sweden)

    M. Radhi

    2010-07-01

    Full Text Available Mineral dust is one of the major components of the world's aerosol mix, having a number of impacts within the Earth system. However, the climate forcing impact of mineral dust is currently poorly constrained, with even its sign uncertain. As Australian deserts are more reddish than those in the Northern Hemisphere, it is important to better understand the physical, chemical and optical properties of this important aerosol. We have investigated the properties of Australian desert dust at a site in SW Queensland, which is strongly influenced by both dust and biomass burning aerosol.

    Three years of ground-based monitoring of spectral optical thickness has provided a statistical picture of gross aerosol properties. The aerosol optical depth data showed a clear though moderate seasonal cycle with an annual mean of 0.06 ± 0.03. The Angstrom coefficient showed a stronger cycle, indicating the influence of the winter-spring burning season in Australia's north. AERONET size distributions showed a generally bimodal character, with the coarse mode assumed to be mineral dust, and the fine mode a mixture of fine dust, biomass burning and marine biogenic material.

    In November 2006 we undertook a field campaign which collected 4 sets of size-resolved aerosol samples for laboratory analysis – ion beam analysis and ion chromatography. Ion beam analysis was used to determine the elemental composition of all filter samples, although elemental ratios were considered the most reliable output. Scatter plots showed that Fe, Al and Ti were well correlated with Si, and Co reasonably well correlated with Si, with the Fe/Al ratio somewhat higher than values reported from Northern Hemisphere sites (as expected. Scatter plots for Ca, Mn and K against Si showed clear evidence of a second population, which in some cases could be identified with a particular sample day or size fraction. These data may be used to attempt to build a signature of soil in this

  14. Time Series of Aerosol Column Optical Depth at the Barrow, Alaska, ARM Climate Research Facility for 2008 Fourth Quarter 2009 ARM and Climate Change Prediction Program Metric Report

    Energy Technology Data Exchange (ETDEWEB)

    C Flynn; AS Koontz; JH Mather

    2009-09-01

    The uncertainties in current estimates of anthropogenic radiative forcing are dominated by the effects of aerosols, both in relation to the direct absorption and scattering of radiation by aerosols and also with respect to aerosol-related changes in cloud formation, longevity, and microphysics (See Figure 1; Intergovernmental Panel on Climate Change, Assessment Report 4, 2008). Moreover, the Arctic region in particular is especially sensitive to changes in climate with the magnitude of temperature changes (both observed and predicted) being several times larger than global averages (Kaufman et al. 2009). Recent studies confirm that aerosol-cloud interactions in the arctic generate climatologically significant radiative effects equivalent in magnitude to that of green house gases (Lubin and Vogelmann 2006, 2007). The aerosol optical depth is the most immediate representation of the aerosol direct effect and is also important for consideration of aerosol-cloud interactions, and thus this quantity is essential for studies of aerosol radiative forcing.

  15. Retrieval of aerosol optical depth over land surfaces from AVHRR data

    Directory of Open Access Journals (Sweden)

    L. Mei

    2013-02-01

    Full Text Available The Advanced Very High Resolution Radiometer (AVHRR radiance data provide a global, long-term, consistent time series having high spectral and spatial resolution and thus being valuable for the retrieval of surface spectral reflectance, albedo and surface temperature. Long term time series of such data products are necessary for studies addressing climate change, sea ice distribution and movement, and ice sheet coastal configuration. These data have also been used to retrieve aerosol properties over ocean and land surfaces. However, the retrieval of aerosol over land and land surface albedo are challenging because of the information content of the measurement is limited and the inversion of these data products being ill defined. Solving the radiative transfer equations requires additional information and knowledge to reduce the number of unknowns. In this contribution we utilise an empirical linear relationship between the surface reflectances in the AVHRR channels at wavelengths of 3.75 μm and 2.1 μm, which has been identified in Moderate Resolution Imaging Spectroradiometer (MODIS data. Next, following the MODIS dark target approach, the surface reflectance at 0.64 μm was obtained. The comparison of the estimated surface reflectance at 0.64 μm with MODIS reflectance products (MOD09 shows a strong correlation (R = 0.7835. Once this was established, the MODIS "dark-target" aerosol retrieval method was adapted to Advanced Very High Resolution Radiometer (AVHRR data. A simplified Look-Up Table (LUT method, adopted from Bremen AErosol Retrieval (BAER algorithm, was used in the retrieval. The Aerosol Optical Depth (AOD values retrieved from AVHRR with this method compare favourably with ground-based measurements, with a correlation coefficient R = 0.861 and Root Mean Square Error (RMSE = 0.17. This method can be easily applied to other satellite instruments which do not have a 2.1 μm channel, such as those currently planned to

  16. Aerosol optical properties and radiative effect determined from sky-radiometer over Loess Plateau of Northwest China

    Directory of Open Access Journals (Sweden)

    Y. Liu

    2011-11-01

    Full Text Available The aerosol optical properties and their associated radiative effects are derived from sky-radiometer and surface solar radiation data collected over the Semi-Arid Climate and Environment Observatory of Lanzhou University (SACOL for the period of March to May (MAM 2009. The result shows that the seasonal mean aerosol optical depth (AOD at 500 nm in MAM is 0.40. The single scattering albedo (SSA at 500 nm in MAM at SACOL fluctuates significantly ranging from 0.82 to 0.98. The averaged value of SSA there for background aerosol is 0.90 in MAM, while it is smaller (0.87 during the dust event outbreak period. The smaller SSA can be interpreted as the result of larger particles during dust events. The averaged asymmetry factor (ASY at 500 nm during dust event period is 0.73, which is larger than 0.70 of background aerosols. The averaged shortwave radiative effects of the aerosols during dust event period in MAM are 0.68, −70.02 and 70.70 W m−2, respectively, at the top of the atmosphere (TOA, surface and in the atmosphere. The aerosols heat the atmosphere during dust event period by up to about 2 K day−1 (daily averaged, which is 60 % larger than the heating (1.25 K day−1 of background aerosols. The significant heating effect in the atmosphere of the aerosols during dust event is determined by larger AOD and smaller SSA.

  17. Total ozone column, aerosol optical depth and precipitable water effects on solar erythemal ultraviolet radiation recorded in Malta.

    Science.gov (United States)

    Bilbao, Julia; Román, Roberto; Yousif, Charles; Mateos, David; Miguel, Argimiro

    2013-04-01

    The Universities of Malta and Valladolid (Spain) developed a measurement campaign, which took place in the Institute for Energy Technology in Marsaxlokk (Southern Malta) between May and October 2012, and it was supported by the Spanish government through the Project titled "Measurement campaign about Solar Radiation, Ozone, and Aerosol in the Mediterranean area" (with reference CGL2010-12140-E). This campaign provided the first ground-based measurements in Malta of erythemal radiation and UV index, which indicate the effectiveness of the sun exposure to produce sunburn on human skin. A wide variety of instruments was involved in the campaign, providing a complete atmospheric characterization. Data of erythemal radiation and UV index (from UVB-1 pyranometer), total shortwave radiaton (global and diffuse components from CM-6B pyranometers), and total ozone column, aerosol optical thickness, and precitable water column (from a Microtops-II sunphotometer) were available in the campaign. Ground-based and satellite instruments were used in the analysis, and several intercomparisons were carried out to validate remote sensing data. OMI, GOME, GOME-2, and MODIS instruments, which provide data of ozone, aerosol load and optical properties, were used to this end. The effects on solar radiation, ultraviolet and total shortwave ranges, of total ozone column, aerosol optical thickness and precipitable water column were obtained using radiation measurements at different fixed solar zenith angles. The empirical results shown a determinant role of the solar position, a negligible effect of ozone on total shortwave radiation, and a stronger attenuation provided by aerosol particles in the erythemal radiation. A variety of aerosol types from different sources (desert dust, biomass burning, continental, and maritime) reach Malta, in this campaign several dust events from the Sahara desert occurred and were analyzed establishing the air mass back-trajectories ending at Malta at

  18. Optical phase curves as diagnostics for aerosol composition in exoplanetary atmospheres

    CERN Document Server

    Oreshenko, Maria; Demory, Brice-Olivier

    2016-01-01

    Optical phase curves have become one of the common probes of exoplanetary atmospheres, but the information they encode has not been fully elucidated. Building on a diverse body of work, we upgrade the Flexible Modeling System (FMS) to include scattering in the two-stream, dual-band approximation and generate plausible, three-dimensional structures of irradiated atmospheres to study the radiative effects of aerosols or condensates. In the optical, we treat the scattering of starlight using a generalisation of Beer's law that allows for a finite Bond albedo to be prescribed. In the infrared, we implement the two-stream solutions and include scattering via an infrared scattering parameter. We present a suite of four-parameter general circulation models for Kepler-7b and demonstrate that its climatology is expected to be robust to variations in optical and infrared scattering. The westward and eastward shifts of the optical and infrared phase curves, respectively, are shown to be robust outcomes of the simulation...

  19. Dynamics of submicron aerosol droplets in a robust optical trap formed by multiple Bessel beams

    Energy Technology Data Exchange (ETDEWEB)

    Thanopulos, Ioannis [Laboratory of Physical Chemistry, Vladimir-Prelog-Weg 2, ETH Zurich, CH-8093 Zurich (Switzerland); Theoretical and Physical Chemistry Institute, National Hellenic Research Foundation, Athens 11635 (Greece); Luckhaus, David; Signorell, Ruth, E-mail: rsignorell@ethz.ch [Laboratory of Physical Chemistry, Vladimir-Prelog-Weg 2, ETH Zurich, CH-8093 Zurich (Switzerland); Preston, Thomas C. [School of Chemistry, University of Bristol, Cantock' s Close, Clifton, Bristol BS8 1TS (United Kingdom)

    2014-04-21

    In this paper, we model the three-dimensional escape dynamics of single submicron-sized aerosol droplets in optical multiple Bessel beam traps. Trapping in counter-propagating Bessel beams (CPBBs) is compared with a newly proposed quadruple Bessel beam (QBB) trap, which consists of two perpendicularly arranged CPBB traps. Calculations are performed for perfectly and imperfectly aligned traps. Mie-theory and finite-difference time-domain methods are used to calculate the optical forces. The droplet escape kinetics are obtained from the solution of the Langevin equation using a Verlet algorithm. Provided the traps are perfectly aligned, the calculations indicate very long lifetimes for droplets trapped either in the CPBB or in the QBB trap. However, minor misalignments that are hard to control experimentally already severely diminish the stability of the CPBB trap. By contrast, such minor misalignments hardly affect the extended droplet lifetimes in a QBB trap. The QBB trap is found to be a stable, robust optical trap, which should enable the experimental investigation of submicron droplets with radii down to 100 nm. Optical binding between two droplets and its potential role in preventing coagulation when loading a CPBB trap is briefly addressed.

  20. Optical and microphysical properties of mineral dust and biomass burning aerosol observed over Warsaw on 10th July 2013

    Science.gov (United States)

    Janicka, Lucja; Stachlewska, Iwona; Veselovskii, Igor; Baars, Holger

    2016-04-01

    Biomass burning aerosol originating from Canadian forest fires was widely observed over Europe in July 2013. Favorable weather conditions caused long-term westward flow of smoke from Canada to Western and Central Europe. During this period, PollyXT lidar of the University of Warsaw took wavelength dependent measurements in Warsaw. On July 10th short event of simultaneous advection of Canadian smoke and Saharan dust was observed at different altitudes over Warsaw. Different origination of both air masses was indicated by backward trajectories from HYSPLIT model. Lidar measurements performed with various wavelength (1064, 532, 355 nm), using also Raman and depolarization channels for VIS and UV allowed for distinguishing physical differences of this two types of aerosols. Optical properties acted as input for retrieval of microphysical properties. Comparisons of microphysical and optical properties of biomass burning aerosols and mineral dust observed will be presented.

  1. Sensitivity of nitrate aerosols to ammonia emissions and to nitrate chemistry: implications for present and future nitrate optical depth

    Science.gov (United States)

    Paulot, F.; Ginoux, P.; Cooke, W. F.; Donner, L. J.; Fan, S.; Lin, M.-Y.; Mao, J.; Naik, V.; Horowitz, L. W.

    2016-02-01

    We update and evaluate the treatment of nitrate aerosols in the Geophysical Fluid Dynamics Laboratory (GFDL) atmospheric model (AM3). Accounting for the radiative effects of nitrate aerosols generally improves the simulated aerosol optical depth, although nitrate concentrations at the surface are biased high. This bias can be reduced by increasing the deposition of nitrate to account for the near-surface volatilization of ammonium nitrate or by neglecting the heterogeneous production of nitric acid to account for the inhibition of N2O5 reactive uptake at high nitrate concentrations. Globally, uncertainties in these processes can impact the simulated nitrate optical depth by up to 25 %, much more than the impact of uncertainties in the seasonality of ammonia emissions (6 %) or in the uptake of nitric acid on dust (13 %). Our best estimate for fine nitrate optical depth at 550 nm in 2010 is 0.006 (0.005-0.008). In wintertime, nitrate aerosols are simulated to account for over 30 % of the aerosol optical depth over western Europe and North America. Simulated nitrate optical depth increases by less than 30 % (0.0061-0.010) in response to projected changes in anthropogenic emissions from 2010 to 2050 (e.g., -40 % for SO2 and +38 % for ammonia). This increase is primarily driven by greater concentrations of nitrate in the free troposphere, while surface nitrate concentrations decrease in the midlatitudes following lower concentrations of nitric acid. With the projected increase of ammonia emissions, we show that better constraints on the vertical distribution of ammonia (e.g., convective transport and biomass burning injection) and on the sources and sinks of nitric acid (e.g., heterogeneous reaction on dust) are needed to improve estimates of future nitrate optical depth.

  2. Aerosol optical properties at a coastal site in Hong Kong, South China: temporal features, size dependencies and source analysis

    Science.gov (United States)

    Wang, Jiaping; Ding, Aijun; Virkkula, Aki; Lee, Shuncheng; Shen, Yicheng; Chi, Xuguang; Xu, Zheng

    2016-04-01

    Hong Kong is a typical coastal city adjacent to the Pearl River Delta (PRD) region in southern China, which is one of the regions suffering from severe air pollution. Atmospheric aerosols can affect the earth's radiative balance by scattering and absorbing incoming solar radiation. Black Carbon (BC) aerosol is a particularly emphasized component due to its strong light absorption. Aerosol transported from different source areas consists of distinct size distributions, leading to different optical properties. As the byproducts of the incomplete oxidation, BC and CO both have relatively long life time, their relationship is a good indicator for distinguishing different pollutant sources. In this study, temporal variations of aerosol optical properties and concentrations of BC and CO at a coastal background station in Hong Kong were investigated. Transport characteristics and origins of aerosol were elucidated by analyzing backward Lagrangian particle dispersion modeling (LPDM) results, together with related parameters including the relationships between optical properties and particle size, BC-CO correlations, ship location data and meteorological variables. From February 2012 to September 2013 and March 2014 to February 2015, continuous in-situ measurements of light scattering and absorption coefficients, particle size distribution and concentrations of BC and CO were conducted at Hok Tsui (HT), a coastal background station on the southeast tip of Hong Kong Island (22.22°N, 114.25°E, 60 m above the sea level) with few local anthropogenic activities. Affected by the Asian monsoon, this region is dominated by continental outflow in winter and by marine inflow from the South China Sea in summer, which is an ideal station for identifying the transport characteristics of aerosol and their effects on optical properties from different anthropogenic emission sources. 7-day backward Lagrangian particle dispersion modeling was performed for source identification. Three

  3. Vertical profiles of aerosol optical properties and the solar heating rate estimated by combining sky radiometer and lidar measurements

    Science.gov (United States)

    Kudo, Rei; Nishizawa, Tomoaki; Aoyagi, Toshinori

    2016-07-01

    The SKYLIDAR algorithm was developed to estimate vertical profiles of aerosol optical properties from sky radiometer (SKYNET) and lidar (AD-Net) measurements. The solar heating rate was also estimated from the SKYLIDAR retrievals. The algorithm consists of two retrieval steps: (1) columnar properties are retrieved from the sky radiometer measurements and the vertically mean depolarization ratio obtained from the lidar measurements and (2) vertical profiles are retrieved from the lidar measurements and the results of the first step. The derived parameters are the vertical profiles of the size distribution, refractive index (real and imaginary parts), extinction coefficient, single-scattering albedo, and asymmetry factor. Sensitivity tests were conducted by applying the SKYLIDAR algorithm to the simulated sky radiometer and lidar data for vertical profiles of three different aerosols, continental average, transported dust, and pollution aerosols. The vertical profiles of the size distribution, extinction coefficient, and asymmetry factor were well estimated in all cases. The vertical profiles of the refractive index and single-scattering albedo of transported dust, but not those of transported pollution aerosol, were well estimated. To demonstrate the performance and validity of the SKYLIDAR algorithm, we applied the SKYLIDAR algorithm to the actual measurements at Tsukuba, Japan. The detailed vertical structures of the aerosol optical properties and solar heating rate of transported dust and smoke were investigated. Examination of the relationship between the solar heating rate and the aerosol optical properties showed that the vertical profile of the asymmetry factor played an important role in creating vertical variation in the solar heating rate. We then compared the columnar optical properties retrieved with the SKYLIDAR algorithm to those produced with the more established scheme SKYRAD.PACK, and the surface solar irradiance calculated from the SKYLIDAR

  4. Chemical apportionment of aerosol optical properties during the Asia-Pacific Economic Cooperation summit in Beijing, China

    Science.gov (United States)

    Han, Tingting; Xu, Weiqi; Chen, Chen; Liu, Xingang; Wang, Qingqing; Li, Jie; Zhao, Xiujuan; Du, Wei; Wang, Zifa; Sun, Yele

    2015-12-01

    We have investigated the chemical and optical properties of aerosol particles during the 2014 Asia-Pacific Economic Cooperation (APEC) summit in Beijing, China, using the highly time-resolved measurements by a high-resolution aerosol mass spectrometer and a cavity attenuated phase shift extinction monitor. The average (±σ) extinction coefficient (bext) and absorption coefficient (bap) were 186.5 (±184.5) M m-1 and 23.3 (±21.9) M m-1 during APEC, which were decreased by 63% and 56%, respectively, compared to those before APEC primarily due to strict emission controls. The aerosol composition and size distributions showed substantial changes during APEC; as a response, the mass scattering efficiency (MSE) of PM1 was decreased from 4.7 m2 g-1 to 3.5 m2 g-1. Comparatively, the average single-scattering albedo (SSA) remained relatively unchanged, illustrating the synchronous reductions of bext and bap during APEC. MSE and SSA were found to increase as function of the oxidation degree of organic aerosol (OA), indicating a change of aerosol optical properties during the aging processes. The empirical relationships between chemical composition and particle extinction were established using a multiple linear regression model. Our results showed the largest contribution of ammonium nitrate to particle extinction, accounting for 35.1% and 29.3% before and during APEC, respectively. This result highlights the important role of ammonium nitrate in the formation of severe haze pollution during this study period. We also observed very different optical properties of primary and secondary aerosol. Owing to emission controls in Beijing and surrounding regions and also partly the influences of meteorological changes, the average bext of secondary aerosol during APEC was decreased by 71% from 372.3 M m-1 to 108.5 M m-1, whereas that of primary aerosol mainly from cooking, traffic, and biomass burning emissions showed a smaller reduction from 136.7 M m-1 to 71.3 M m-1. As a result

  5. Comparison of the aerosol optical properties and size distribution retrieved by sun photometer with in situ measurements at midlatitude

    Science.gov (United States)

    Chauvigné, Aurélien; Sellegri, Karine; Hervo, Maxime; Montoux, Nadège; Freville, Patrick; Goloub, Philippe

    2016-09-01

    Aerosols influence the Earth radiative budget through scattering and absorption of solar radiation. Several methods are used to investigate aerosol properties and thus quantify their direct and indirect impacts on climate. At the Puy de Dôme station, continuous high-altitude near-surface in situ measurements and low-altitude ground-based remote sensing atmospheric column measurements give the opportunity to compare the aerosol extinction measured with both methods over a 1-year period. To our knowledge, it is the first time that such a comparison is realised with continuous measurements of a high-altitude site during a long-term period. This comparison addresses to which extent near-surface in situ measurements are representative of the whole atmospheric column, the aerosol mixing layer (ML) or the free troposphere (FT). In particular, the impact of multi-aerosol layers events detected using lidar backscatter profiles is analysed. A good correlation between in situ aerosol extinction coefficient and aerosol optical depth (AOD) measured by the Aerosol Robotic Network (AERONET) sun photometer is observed with a correlation coefficient around 0.80, indicating that the in situ measurements station is representative of the overall atmospheric column. After filtering for multilayer cases and correcting for each layer optical contribution (ML and FT), the atmospheric structure seems to be the main factor influencing the comparison between the two measurement techniques. When the site lies in the ML, the in situ extinction represents 45 % of the sun photometer ML extinction while when the site lies within the FT, the in situ extinction is more than 2 times higher than the FT sun photometer extinction. Moreover, the assumption of a decreasing linear vertical aerosol profile in the whole atmosphere has been tested, significantly improving the instrumental agreement. Remote sensing retrievals of the aerosol particle size distributions (PSDs) from the sun photometer

  6. Aerosol optical depth over central north Asia based on MODIS-Aqua data

    Science.gov (United States)

    Avgousta Foutsi, Athina; Korras Carraca, Marios Bruno; Matsoukas, Christos; Biskos, George

    2016-04-01

    Atmospheric aerosols, both natural and anthropogenic, can affect the regional and global climate through their direct, indirect, and semi-direct effects on the radiative energy budget of the Earth-atmosphere system. To quantify these effects it is important to determine the aerosol load, and an effective way to do that is by measuring the aerosol optical depth (AOD). The central Asia region (mainly the Caspian and Aral sea basins), the arid and semi-arid regions of Western China as well as Siberia are of great interest due to the significant natural sources of mineral aerosols originating from local deserts and biomass burning from wildfires in boreal forests. What is of particular interest in the region is the phenomenal shrinking and desertification of the Aral Sea that drives an intense salt and dust transport from the exposed sea-bed to the surrounding regions with important implications in regional air quality. Anthropogenic particles are also observed due to fossil-fuel combustion occurring mainly at oil refineries in the Caspian Sea basin. Here we investigate the spatial and temporal variability of the AOD at 550 nm over central Asia, Siberia and western China, in the region located between 35° N - 65° N and 45° E - 110° E. For our analysis we use Level-3 daily MODIS - Aqua Dark Target - Deep Blue combined product, from the latest collection (006), available in a 1°×1° resolution (ca. 100 km × 100 km) over the period 2002-2014. Our results indicate a significant spatial variability of the aerosol load over the study region. The highest AODs are observed over the Aral Sea year-round, with extreme values reaching 2.1 during July. In the rest of our study region a clear seasonal cycle with highest AOD values (up to 1.2 over the Taklamakan Desert) during spring and summer is observed. The arid parts of central north Asia are characterized by larger aerosol loads during spring, lower but still high AOD in summer and much lower values in autumn and spring

  7. Micropulse lidar-derived aerosol optical depth climatology at ARM sites worldwide

    Science.gov (United States)

    Kafle, D. N.; Coulter, R. L.

    2013-07-01

    This paper focuses on climatology of the vertical distribution of aerosol optical depth (AOD (z)) from micropulse lidar (MPL) observations for climatically different locations worldwide. For this, a large data set obtained by MPL systems operating at 532 nm during the 4 year period 2007-2010 was used to derive vertical profiles of AOD (z) by combining the corresponding AOD data as an input from an independent measurement using nearly colocated multifilter rotating shadowband radiometer (MFRSR) systems at five different U.S. Department of Energy Atmospheric Radiation Measurement (ARM) Program sites—three permanent sites (SGP in north-central Oklahoma, at 36.6°N, 97.5°W, 320 m; TWP-Darwin in the tropical western Pacific, at 12.4°S, 130.9°E, 30 m; and NSA at Barrow on the North Slope of Alaska, at 71.3°N, 156.6°W, 8 m) and two mobile facility sites (GRW at Graciosa Island in the Azores, at 39°N, 28°W, 15 m; and FKB in the Black Forest of Germany, at 48.5°N, 8.4°E, 511 m). Therefore, amount of data used in this study is constrained by the availability of the MFRSR data. The MPL raw data were averaged for 30 s in time and 30 m in altitude. The diurnally averaged AOD (z) profiles from 4 years were combined to obtain a multiyear vertical profile of AOD (z) climatology at various ARM sites, including diurnal, day-to-day, and seasonal variabilities. Most aerosols were found to be confined to 0-2 km (approximately the planetary boundary layer region) at all sites; however, all sites exhibited measurable aerosols well above the mixed layer, with different height maxima. The entire data set demonstrates large day-to-day variability at all sites. However, there is no significant diurnal variation in AOD (z) at all sites. Significant interannual variability was observed at the SGP site. Clear seasonal variations in AOD (z) profiles exist for all five sites, but seasonal behavior was distinct. Moreover, the different seasonal variability for the lower level (0 to ~2

  8. The regime of aerosol optical depth over Central Asia based on MODIS Aqua Deep Blue data

    Science.gov (United States)

    Floutsi, Athina; KorrasCarraca, Marios; Matsoukas, Christos; Biskos, George

    2015-04-01

    Atmospheric aerosols, both natural and anthropogenic, can affect the regional and global climate through their direct, indirect, and semi-direct effects on the radiative energy budget of the Earth-atmosphere system. To quantify these effects it is therefore important to determine the aerosol load, and an effective way to do that is by measuring the aerosol optical depth (AOD). In this study we investigate the spatial and temporal variability of the AOD over the climatically sensitive region of Central Asia (36° N - 50° N, 46° E - 75° E), which has significant sources of both natural and anthropogenic particles. The primary source of anthropogenic particles is fossil fuel combustion occurring mainly at oil refineries in the Caspian Sea basin. Natural particles originate mostly from the two deserts in the region (namely Kara-Kum and Kyzyl-Kum), where persistent dust activity is observed. Another source is the Aral Sea region, which due to its phenomenal desertification also drives an intense salt and dust transport from the exposed sea-bed to the surrounding regions. This transport is of particular interest because of health-hazardous materials contained in the Aral Sea sea-bed. For our analysis we use Level-3 daily MODIS - Aqua Dark Target - Deep Blue combined product, from the latest MODIS collection (006), available in 1° x 1° resolution (about 100 km x 100 km) over the period 2002-2014.Our first results indicate a significant spatial variability of the aerosol load over the study region. The data also show a clear seasonal cycle, with large aerosol load being associated with strong dust activity during spring and summer (AOD up to 0.5), and low during autumn and winter (AOD up to 0.4). In spring and summer significant aerosol load is observed in the Garabogazköl basin, Northeast and South-southeast Caspian Sea (offshore North Iran and Azerbaijan), as well as southwest of the Aral Sea. In the later region, the high AOD values can be explained by export of

  9. Cloud and aerosol optics by polarized micro pulse Lidar and ground based measurements of zenith radiance

    Science.gov (United States)

    Delgadillo, Rodrigo

    Clouds impact Earth's climate through cloud transmission and reflection properties. Clouds reflect approximately 15 percent of the incoming solar radiation at the top of the atmosphere. A key cloud radiative variable is cloud optical depth, which gives information about how much light is transmitted through a cloud. Historically, remote measurements of cloud optical depth have been limited to uniform overcast conditions and had low temporal and spatial resolution. We present a novel method to measure cloud optical depth for coastal regions from spectral zenith radiance measurements for optically thin clouds, which removes some of these limitations. Our measurement site is part of South Florida's Cloud-Aerosol-Rain Observatory (CAROb), located on Virginia Key, FL (6 km from Miami). This work is based on Marshak et al.'s method for finding cloud optical depth from vegetative sites that provide a strong spectral contrast between red and near infrared surface albedo. However, given the unique nature of our site, which contains water, vegetation, beach, and urban surface types, we found no such spectral contrast at those wavelength pairs. We measured albedo, with hyperspectral resolution, for different surface types around our measurement site to estimate the effective spectral albedo for the area centered on the site with a 5km radius. From this analysis, we found the best possible albedo contrast (573.9 and 673.1 nm) for our site. We tested the derived cloud optical depth from zenith radiance at these two wavelengths against a concurrently running polarized micro pulse LIDAR (MPL) and found good agreement.

  10. NOAA Climate Data Record (CDR) of AVHRR Daily and Monthly Aerosol Optical Thickness over Global Oceans, Version 2.0

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This NOAA Climate Data Record (CDR) of Aerosol Optical Thickness (AOT) is derived from data taken over global oceans from the PATMOS-x AVHRR level-2b channel 1 (0.63...

  11. Shipboard Sunphotometer Measurements of Aerosol Optical Depth During ACE-2 and Comparison with Selected Ship, Aircraft and Satellite Measurements

    Science.gov (United States)

    Livingston, J. M.; Kapustin, V. N.; Schmid, B.; Russell, P. B.; Quinn, P. K.; Bates, T. S.; Durkee, P. A.; Nielsen, K.; Freudenthaler, V.; Wiegner, M.; Covert, D. S.

    2000-01-01

    We present analyses of aerosol optical depth (AOD) measurements taken with a shipboard six-channel tracking sunphotometer during ACE-2. For 10 July 1997, results are also shown for measurements acquired 70 km from the ship with a fourteen-channel airborne tracking sunphotometer.

  12. Constraining Black Carbon Aerosol over Asia using OMI Aerosol Absorption Optical Depth and the Adjoint of GEOS-Chem

    Science.gov (United States)

    Zhang, Li; Henze, David K.; Grell, Georg A.; Carmichael. Gregory R.; Bousserez, Nicolas; Zhang, Qiang; Torres, Omar; Ahn, Changwoo; Lu, Zifeng; Cao, Junji; Mao, Yuhao

    2015-01-01

    Accurate estimates of the emissions and distribution of black carbon (BC) in the region referred to here as Southeastern Asia (70degE-l50degE, 11degS-55degN) are critical to studies of the atmospheric environment and climate change. Analysis of modeled BC concentrations compared to in situ observations indicates levels are underestimated over most of Southeast Asia when using any of four different emission inventories. We thus attempt to reduce uncertainties in BC emissions and improve BC model simulations by developing top-down, spatially resolved, estimates of BC emissions through assimilation of OMI observations of aerosol absorption optical depth (AAOD) with the GEOS-Chem model and its adjoint for April and October of 2006. Overwhelming enhancements, up to 500%, in anthropogenic BC emissions are shown after optimization over broad areas of Southeast Asia in April. In October, the optimization of anthropogenic emissions yields a slight reduction (1-5%) over India and parts of southern China, while emissions increase by 10-50% over eastern China. Observational data from in situ measurements and AERONET observations are used to evaluate the BC inversions and assess the bias between OMI and AERONET AAOD. Low biases in BC concentrations are improved or corrected in most eastern and central sites over China after optimization, while the constrained model still underestimates concentrations in Indian sites in both April and October, possibly as a. consequence of low prior emissions. Model resolution errors may contribute up to a factor of 2.5 to the underestimate of surface BC concentrations over northern India. We also compare the optimized results using different anthropogenic emission inventories and discuss the sensitivity of top-down constraints on anthropogenic emissions with respect to biomass burning emissions. In addition, the impacts of brown carbon, the formulation of the observation operator, and different a priori constraints on the optimization are

  13. Characteristics of atmospheric aerosol optical depth variation in China during 1993-2012

    Science.gov (United States)

    Xu, Xiaofeng; Qiu, Jinhuan; Xia, Xiangao; Sun, Ling; Min, Min

    2015-10-01

    The long-term variations of atmospheric aerosol optical depth (AOD) over 14 first-class solar radiation stations in China during 1993-2012 are studied. The AOD at 750 nm wavelength is retrieved with the hourly accumulated direct solar radiation by using a broadband extinction method. The retrievals are validated in comparison with AERONET (Aerosol Robotic Network) and MODIS (Moderate Resolution Imaging Spectroradiometer) AOD products. For the comparison with AERONET, the correlation coefficient (R), mean bias error (MBE) and root mean square error (RMSE) of the monthly mean AODs are respectively 0.848, 0.029 and 0.101. Based on the statistical analysis, the monthly, seasonal and annual AOD variation characteristics are categorized as follow: (1) There are three major types of the seasonal AOD variations, which shows the largest seasonal averaged AOD appearing in spring, summer and winter. The smallest seasonal averaged AOD appears mostly in autumn. (2) Beijing and Guangzhou show a significant decreasing trend of the yearly AOD, while an increasing tendency appears in Zhengzhou, Shanghai, Kunming, Kashi and Wuhan. Although no significant variation trends are found, some fluctuations appear in the 20-year period in other cities. (3) The 20-year mean AOD ranges from 0.135 (Lhasa) to 0.678 (Zhengzhou). The aerosol hygroscopic growth contributes a lot to AOD in major cities in the eastern part of China, while not in most cities in the western part. A simple correction method is applied for enhancing the relationship of AOD and PM2.5 concentration.

  14. Retrieval of Aerosol Optical Depth over Arid Areas from MODIS Data

    Directory of Open Access Journals (Sweden)

    Xin-peng Tian

    2016-10-01

    Full Text Available Moderate Resolution Imaging Spectroradiometer (MODIS data have been widely applied for the remote sensing of aerosol optical depth (AOD because the MODIS sensor features a short revisit period and a moderate spatial resolution. The Dense Dark Vegetation (DDV method is the most popular retrieval method. However, the DDV method can only be used to retrieve the AOD with high precision when the surface reflectance in the visible spectrum is low, such as over dense vegetation or water. To obtain precise AOD values in areas with higher reflectance, such as arid areas, Land Surface Reflectance (LSR must be estimated accurately. This paper proposes a method of estimating LSR for AOD retrieval over arid areas from long-term series of MODIS images. According to the atmospheric parameters (AOD and water vapor, the clearest image without clouds was selected from the long-term series of continuous MODIS images. Atmospheric correction was conducted based on similar ground-measured atmospheric parameters and was used to estimate the LSR and retrieve the AOD at adjacent times. To validate this method, aerosol inversion experiments were performed in northern Xinjiang, in which the inverted AOD was compared to ground-measured AOD and MODIS aerosol products (MOD04. The AOD retrieved using the new algorithm was highly consistent with the AOD derived from ground-based measurements, with a correlation coefficient of 0.84. Additionally, 82.22% of the points fell within the expected error defined by NASA. The precision of the retrieved AOD data was better than that of MOD04 AOD products over arid areas.

  15. Aerosol optical depth thresholds as a tool to assess diffuse radiation fertilization of the land carbon uptake in China

    Science.gov (United States)

    Yue, Xu; Unger, Nadine

    2017-01-01

    China suffers from frequent haze pollution episodes that alter the surface solar radiation and influence regional carbon uptake by the land biosphere. Here, we apply combined vegetation and radiation modeling and multiple observational datasets to assess the radiative effects of aerosol pollution in China on the regional land carbon uptake for the 2009-2011 period. First, we assess the inherent sensitivity of China's land biosphere to aerosol pollution by defining and calculating two thresholds of aerosol optical depth (AOD) at 550 nm, (i) AODt1, resulting in the maximum net primary productivity (NPP), and (ii) AODt2, such that if local AOD fertilization effect (DFE) always promotes local NPP compared with aerosol-free conditions. Then, we apply the thresholds, satellite data, and interactive vegetation modeling to estimate current impacts of aerosol pollution on land ecosystems. In the northeast, observed AOD is 55 % lower than AODt1, indicating a strong aerosol DFE on local NPP. In the southeastern coastal regions, observed AOD is close to AODt1, suggesting that regional NPP is promoted by the current level of aerosol loading, but that further increases in AOD in this region will weaken the fertilization effects. The North China Plain experiences limited enhancement of NPP by aerosols because observed AOD is 77 % higher than AODt1 but 14 % lower than AODt2. Aerosols always inhibit regional NPP in the southwest because of the persistent high cloud coverage that already substantially reduces the total light availability there. Under clear-sky conditions, simulated NPP shows widespread increases of 20-60 % (35.0 ± 0.9 % on average) by aerosols. Under all-sky conditions, aerosol pollution has spatially contrasting opposite sign effects on NPP from -3 % to +6 % (1.6 ± 0.5 % on average), depending on the local AOD relative to the regional thresholds. Stringent aerosol pollution reductions motivated by public health concerns, especially in the North China Plain and

  16. Comparison of aerosol optical depth (AOD) determined from UVMRP and AERONET

    Science.gov (United States)

    Wang, Manyi; Liu, Chaoshun; Shi, Runhe; Gao, Wei

    2013-09-01

    Aerosol optical depth (AOD) is critically important for a better understanding of how Earth's climate is radiatively forced. To compensate for the conventional satellite observations, several types of ground-based radiometers are operated by AOD measurement programs. This study compares the Bratts Lake climate station's long-term AOD measurements from 1999 to 2012 which are derived from two ground-based programs with high accuracy: the United States Department of Agriculture (USDA) UV-B Monitoring and Research Program (UVMRP) and the AERONET (AErosol RObotic NETwork) program. The comparison shows that, in the 14-year period, the AOD values have an excellent agreement at six wavelengths (368, 415, 500, 610, 665, and 860 nm) with varying slopes (ranging from 0.95763 to 1.04089), intercepts (ranging from 0.0219 to 0.03945), correlation coefficients (R) (ranging from 0.82005 to 0.96155), and root mean square errors (RMSE) (ranging from 0.02639 to 0.03663). The correlations of both monthly and hourly averaged AOD measurements are highly consistent for each band. Specifically, the shorter (with larger AOD values) the wavelength is, the better the correlation is. Also, the results show that the peaks of relative errors generally occur in summer each year, and at noon each day. Our analyses suggest that AOD products derived from UVMRP are accurate and can serve as an alternative ground-based validation source for satellite AOD measurements.

  17. Retrieval of aerosol optical depth in vicinity of broken clouds from reflectance ratios: case study

    Directory of Open Access Journals (Sweden)

    E. Kassianov

    2010-10-01

    Full Text Available A recently developed reflectance ratio (RR method for the retrieval of aerosol optical depth (AOD is evaluated using extensive airborne and ground-based data sets collected during the Cloud and Land Surface Interaction Campaign (CLASIC and the Cumulus Humilis Aerosol Processing Study (CHAPS, which took place in June 2007 over the US Department of Energy (DOE Atmospheric Radiation Measurement (ARM Southern Great Plains site. A detailed case study is performed for a field of single-layer shallow cumuli observed on 12 June 2007. The RR method is applied to retrieve the spectral values of AOD from the reflectance ratios measured by the MODIS Airborne Simulator (MAS for two pairs of wavelengths (660 and 470 nm, 870 and 470 nm collected at a spatial resolution of 0.05 km. The retrieval is compared with an independent AOD estimate from three ground-based Multi-filter Rotating Shadowband Radiometers (MFRSRs. The interpolation algorithm that is used to project MFRSR point measurements onto the aircraft flight tracks is tested using AOD derived from NASA Langley High Spectral Resolution Lidar (HSRL. The RR AOD estimates are in a good agreement (within 5% with the MFRSR-derived AOD values for the 660-nm wavelength. The AODs obtained from MAS reflectance ratios overestimate those derived from MFRSR measurements by 15–30% for the 470-nm wavelength and underestimate the 870-nm AOD by the same amount.

  18. Long-term trend in aerosol optical depth from 1980 to 2001 in north China

    Institute of Scientific and Technical Information of China (English)

    Jiangxia Xie; Xiangao Xia

    2008-01-01

    Using the Total Ozone Mapping Spectrometer (TOMS) monthly aerosol optical depth (AOD) at 500 nm data from 1980 to 2001 in north China, the spatial and temporal variations of AOD were examined. Seasonal AODs in Taldimakan Desert were 0.69 and 0.44 in spring and summer,respectively, which were mainly due to frequent occurrences of dust events in this region. Dust activities in spring also led to high aerosol loading in Gobi Desert and in northeast China where spring AODs were 0.33 and 0.29, respectively. Heavily impacted by events such as volcano eruption, forest fires and extraordinary dust storms, AODs showed large inter-annual variations. A decreasing tendency in AOD was observed in north China during 1980-1991, though a reverse tendency was revealed during 1997-2001, especially for spring AOD in northeast China. Further study is required to figure out how much human activities have contributed to the AOD tendency in north China.

  19. Evaluation of BAER surface model for aerosol optical thickness retrieval over land surface

    Directory of Open Access Journals (Sweden)

    Y. S. Chiang

    2012-04-01

    Full Text Available Estimation of surface reflectance is essential for an accurate retrieval of aerosol optical thickness (AOT by satellite remote sensing approach. Due to the variability of surface reflectance over land surfaces, a surface model is required to take into account the crucial factor controlling this variability. In the present study, we attempted to simulate surface reflectance in the short-wave channels with two methods, namely the land cover type dependent method and a two-source linear model. In the two-source linear model, we assumed that the spectral property can be described by a mixture of vegetated and non-vegetated area, and both the normalized difference vegetation index (NDVI, and the vegetation continuous field (VCF was applied to summarize this surface characteristic. By comparing our estimation with surface reflectance data derived from Moderate Resolution Imaging Spectroradiometer (MODIS, it indicated that the land cover type approach did not provide a better estimation because of inhomogeneous land cover pattern and the mixing pixel properties. For the two-source linear method, the study suggested that the use of NDVI as parameterization for vegetation fraction can reflect the spectral behavior of shortwave surface reflectance, despite of some deviation due to the averaging characteristics in our linear combination process. A channel-dependent offset and scalar factor could enhance reflectance estimation and further improve AOT retrieval by the current Bremen AErosol Retrieval (BAER approach.

  20. High Resolution Aerosol Optical Depth Retrieval Using Gaofen-1 WFV Camera Data

    Directory of Open Access Journals (Sweden)

    Kun Sun

    2017-01-01

    Full Text Available Aerosol Optical Depth (AOD is crucial for urban air quality assessment. However, the frequently used moderate-resolution imaging spectroradiometer (MODIS AOD product at 10 km resolution is too coarse to be applied in a regional-scale study. Gaofen-1 (GF-1 wide-field-of-view (WFV camera data, with high spatial and temporal resolution, has great potential in estimation of AOD. Due to the lack of shortwave infrared (SWIR band and complex surface reflectivity brought from high spatial resolution, it is difficult to retrieve AOD from GF-1 WFV data with traditional methods. In this paper, we propose an improved AOD retrieval algorithm for GF-1 WFV data. The retrieved AOD has a spatial resolution of 160 m and covers all land surface types. Significant improvements in the algorithm include: (1 adopting an improved clear sky composite method by using the MODIS AOD product to identify the clearest days and correct the background atmospheric effect; and (2 obtaining local aerosol models from long-term CIMEL sun-photometer measurements. Validation against MODIS AOD and ground measurements showed that the GF-1 WFV AOD has a good relationship with MODIS AOD (R2 = 0.66; RMSE = 0.27 and ground measurements (R2 = 0.80; RMSE = 0.25. Nevertheless, the proposed algorithm was found to overestimate AOD in some cases, which will need to be improved upon in future research.

  1. Simultaneous Retrieval of Aerosol and Surface Optical Properties from Combined Airborne- and Ground-Based Direct and Diffuse Radiometric Measurements

    Science.gov (United States)

    Gatebe, C. K.; Dubovik, O.; King, M. D.; Sinyuk, A.

    2010-01-01

    This paper presents a new method for simultaneously retrieving aerosol and surface reflectance properties from combined airborne and ground-based direct and diffuse radiometric measurements. The method is based on the standard Aerosol Robotic Network (AERONET) method for retrieving aerosol size distribution, complex index of refraction, and single scattering albedo, but modified to retrieve aerosol properties in two layers, below and above the aircraft, and parameters on surface optical properties from combined datasets (Cloud Absorption Radiometer (CAR) and AERONET data). A key advantage of this method is the inversion of all available spectral and angular data at the same time, while accounting for the influence of noise in the inversion procedure using statistical optimization. The wide spectral (0.34-2.30 m) and angular range (180 ) of the CAR instrument, combined with observations from an AERONET sunphotometer, provide sufficient measurement constraints for characterizing aerosol and surface properties with minimal assumptions. The robustness of the method was tested on observations made during four different field campaigns: (a) the Southern African Regional Science Initiative 2000 over Mongu, Zambia, (b) the Intercontinental Transport Experiment-Phase B over Mexico City, Mexico (c) Cloud and Land Surface Interaction Campaign over the Atmospheric Radiation Measurement (ARM) Central Facility, Oklahoma, USA, and (d) the Arctic Research of the Composition of the Troposphere from Aircraft and Satellites (ARCTAS) over Elson Lagoon in Barrow, Alaska, USA. The four areas are dominated by different surface characteristics and aerosol types, and therefore provide good test cases for the new inversion method.

  2. Retrieval of Aerosol Optical Depth Using the Empirical Orthogonal Functions (EOFs Based on PARASOL Multi-Angle Intensity Data

    Directory of Open Access Journals (Sweden)

    Yang Zhang

    2017-06-01

    Full Text Available Aerosol optical depth (AOD is a widely used aerosol optical parameter in atmospheric physics. To obtain this parameter precisely, many institutions plan to launch satellites with multi-angle measurement sensors, but one important step in aerosol retrieval, the estimation of surface reflectance, is still a pressing issue. This paper presents an AOD retrieval method based on the multi-angle intensity data from the Polarization and Anisotropy of Reflectances for Atmospheric Science coupled with Observations from a Lidar (PARASOL platform using empirical orthogonal functions (EOFs, which can be universally applied to multi-angle observations. The function of EOFs in this study is to estimate surface intensity contributions, associated with aerosol lookup tables (LUTs, so that the retrieval of AOD can be implemented. A comparison of the retrieved AODs for the Beijing, Xianghe, Taihu, and Hongkong_PolyU sites with those from the Aerosol Robotic Network (AERONET ground-based observations produced high correlation coefficients (r of 0.892, 0.915, 0.831, and 0.897, respectively, while the corresponding root mean square errors (RMSEs are 0.095, 0.093, 0.099, and 0.076, respectively.

  3. Models for the optical simulations of fractal aggregated soot particles thinly coated with non-absorbing aerosols

    Science.gov (United States)

    Wu, Yu; Cheng, Tianhai; Zheng, Lijuan; Chen, Hao

    2016-10-01

    Light absorption enhancement of aged soot aerosols is highly sensitive to the morphologies and mixing states of soot aggregates and their non-absorbing coatings, such as organic materials. The quantification of these effects on the optical properties of thinly coated soot aerosols is simulated using an effective model with fixed volume fractions. Fractal aggregated soot was simulated using the diffusion limited aggregation (DLA) algorithm and discretized into soot dipoles. The dipoles of non-absorbing aerosols, whose number was fixed by the volume fraction, were further generated from the neighboring random edge dipoles. Their optical properties were calculated using the discrete dipole approximation (DDA) method and were compared with other commonly used models. The optical properties of thinly coated soot calculated using the fixed volume fraction model are close to (less than ~10% difference) the results of the fixed coating thickness model, except their asymmetry parameters (up to ~25% difference). In the optical simulations of thinly coated soot aerosols, this relative difference of asymmetry parameters and phase functions between these realistic models may be notable. The realizations of the fixed volume fraction model may introduce smaller variation of optical results than those of the fixed coating thickness model. Moreover, the core-shell monomers model and homogeneous aggregated spheres model with the Maxwell-Garnett (MG) theory may underestimate (up to ~20%) the cross sections of thinly coated soot aggregates. The single core-shell sphere model may largely overestimate (up to ~150%) the cross sections and single scattering albedo of thinly coated soot aggregates, and it underestimated (up to ~60%) their asymmetry parameters. It is suggested that the widely used single core-shell sphere approximation may not be suitable for the single scattering calculations of thinly coated soot aerosols.

  4. Optical-chemical relationships for carbonaceous aerosols observed at Jeju Island, Korea with a 3-laser photoacoustic spectrometer

    Directory of Open Access Journals (Sweden)

    B. A. Flowers

    2010-04-01

    Full Text Available Transport of aerosols in pollution plumes from the mainland Asian continent was observed in situ at Jeju, South Korea during the Cheju Asian Brown Cloud Plume-Asian Monsoon Experiment (CAPMEX field campaign throughout August and September 2008 using a 3-laser photoacoustic spectrometer. Transport of mixed sulfate, carbonaceous, and nitrate aerosols from various Asian pollution plumes to Jeju accounted for 76% of the deployment days, showing large variations in their measured chemical and optical properties. Our analysis of eight distinct episodes, spanning a wide range of chemical composition, optical properties, and source regions, reveals that at episodes with higher OC/SO2−4 and NO3/SO2−4 composition ratios exhibit lower single scatter albedo at shorter wavelengths (ω405; significantly lower [ω405meas = 0.79±0.06, ω405calc = 0.86±0.01] than predicted by an optical model that assumes constant complex index of refraction with wavelength (an optical model of soot. We attribute this discrepancy to enhanced absorption by organic material. Organic carbon absorption accounts for up to 50% of the measured aerosol absorption at 405 nm for the high OC/SO2−4 episode. Coatings of elemental carbon aerosol cores are hypothesized to increase absorption by factors up to 6 at visible wavelengths. Carbonaceous aerosol absorption can alter global radiative forcing estimates substantially, underscoring the need to understand and predict chemical composition effects on optical properties.

  5. A three-dimensional sectional representation of aerosol mixing state for simulating optical properties and cloud condensation nuclei

    Energy Technology Data Exchange (ETDEWEB)

    Ching, Ping Pui; Zaveri, Rahul A.; Easter, Richard C.; Riemer, Nicole; Fast, Jerome D.

    2016-05-27

    Light absorption by black carbon (BC) particles emitted from fossil fuel combustion depends on the how thickly they are coated with non-refractory species such as ammonium, sulfate, nitrate, organics, and water. The cloud condensation nuclei (CCN) activation property of a particle depends on its dry size and the hygroscopicities of all the individual species mixed together. It is therefore necessary to represent both size and mixing state of aerosols to reliably predict their climate-relevant properties in atmospheric models. Here we describe and evaluate a novel sectional framework in the Model for Simulating Aerosol Interactions and Chemistry, referred to as MOSAIC-mix, that represents the mixing state by resolving aerosol dry size (Ddry), BC dry mass fraction (wBC), and hygroscopicity (κ). Using ten idealized urban plume scenarios in which different types of aerosols evolve over 24 hours under a range of atmospherically relevant environmental conditions, we examine errors in CCN concentrations and optical properties with respect to a more explicit aerosol mixing state representation. We find that only a small number of wBC and κ bins are needed to achieve significant reductions in the errors, and propose a configuration consisting of 24 Ddry bins, 2 wBC bins, and 2 κ bins that gives 24-hour average errors of about 5% or less in CCN concentrations and optical properties, 3-4 times lower than those from size-only-resolved simulations. These results show that MOSAIC-mix is suitable for use in regional and global models to examine the effects of evolving aerosol mixing states on aerosol-radiation-cloud feedbacks.

  6. A global comparison of GEOS-Chem predicted and remotely-sensed mineral dust aerosol optical depth

    Directory of Open Access Journals (Sweden)

    Matthew S Johnson

    2012-07-01

    Full Text Available Dust aerosol optical depth (AOD and vertical distribution of aerosol extinction predicted by a global chemical transport model (GEOS-Chem are compared to space-borne data from the Moderate-resolution Imaging Spectroradiometer (MODIS, Multi-Angle Imaging SpectroRadiometer (MISR, and Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO for March 2009 to February 2010. Model-predicted and remotely-sensed AOD/aerosol extinction profiles are compared over six regions where aerosol abundances are dominated by mineral dust. Calculations indicate that over the regions examined in this study (with the exception of Middle Eastern dust sources GEOS-Chem predicts higher AOD values compared to MODIS and MISR. The positive bias is particularly pronounced over the Saharan dust source regions, where model-predicted AOD values are a factor of 2 to 3 higher. The comparison with CALIPSO-derived dust aerosol extinction profiles revealed that the model overestimations of dust abundances over the study regions primarily occur below ~4 km, suggesting excessive emissions of mineral dust and/or uncertainties in dust optical properties. The implementation of a new dust size distribution scheme into GEOS-Chem reduced the yearly-mean positive bias in model-predicted AOD values over the study regions. The results were most noticeable over the Saharan dust source regions where the differences between model-predicted and MODIS/MISR retrieved AOD values were reduced from 0.22 and 0.17 to 0.02 and -0.04, respectively. Our results suggest that positive/negative biases between satellite and model-predicted aerosol extinction values at different altitudes can sometimes even out, giving a false impression for the agreement between remotely-sensed and model-predicted column-integrated AOD data.

  7. Intercomparison of Aerosol Optical Depth from Brewer Ozone spectrophotometers and CIMEL sunphotometers measurements

    Directory of Open Access Journals (Sweden)

    A. Cheymol

    2009-01-01

    Full Text Available The Langley plot method applied on the Brewer Ozone measurements can provide accurate Aerosol Optical Depth (AOD in the UV-B. We present seven intercomparisons between AOD retrieved from Brewer Ozone measurements at 320 nm and AOD measured by CIMEL sunphotometer at 340 nm or 440 nm (shifted to 320 nm in using the Angström's law, which are stored in the international AERONET database. Only the intercomparisons between co-located instruments can be used to validate the Langley Plot Method applied to the Brewer measurements: in this case, all the correlation coefficients are above 0.82. If the instruments are not at the same site, the correlation between the AOD retrieved by both instruments is much lower. In applying the Angström's law the intercomparison is improved compared to previous study.

  8. Measurements of UV aerosol optical depth in the French Southern Alps

    Directory of Open Access Journals (Sweden)

    J. Lenoble

    2008-11-01

    Full Text Available Routine measurements of global and diffuse UV irradiances at Briançon station (1310 m a.s.l. are used to retrieve the direct solar irradiance and the aerosol optical depth (AOD, for cloudless days. Data of three years (2003, 2004, 2005 are analyzed; the results confirm those of a preliminary analysis for 2001, 2002.

    The atmosphere is very clear in winter, with AODs between 0.05 and 0.1. The turbidity increases slowly in spring, starting end of February, with AODs around 0.2–0.3 in mid summer, some values reaching 0.4. A similar behaviour is observed for all years, with somewhat higher values in late summer for the year 2003.

  9. Optical properties and aging of light-absorbing secondary organic aerosol

    Science.gov (United States)

    Liu, Jiumeng; Lin, Peng; Laskin, Alexander; Laskin, Julia; Kathmann, Shawn M.; Wise, Matthew; Caylor, Ryan; Imholt, Felisha; Selimovic, Vanessa; Shilling, John E.

    2016-10-01

    The light-absorbing organic aerosol (OA) commonly referred to as "brown carbon" (BrC) has attracted considerable attention in recent years because of its potential to affect atmospheric radiation balance, especially in the ultraviolet region and thus impact photochemical processes. A growing amount of data has indicated that BrC is prevalent in the atmosphere, which has motivated numerous laboratory and field studies; however, our understanding of the relationship between the chemical composition and optical properties of BrC remains limited. We conducted chamber experiments to investigate the effect of various volatile organic carbon (VOC) precursors, NOx concentrations, photolysis time, and relative humidity (RH) on the light absorption of selected secondary organic aerosols (SOA). Light absorption of chamber-generated SOA samples, especially aromatic SOA, was found to increase with NOx concentration, at moderate RH, and for the shortest photolysis aging times. The highest mass absorption coefficient (MAC) value is observed from toluene SOA products formed under high-NOx conditions at moderate RH, in which nitro-aromatics were previously identified as the major light-absorbing compounds. BrC light absorption is observed to decrease with photolysis time, correlated with a decline of the organic nitrate fraction of SOA. SOA formed from mixtures of aromatics and isoprene absorb less visible (Vis) and ultraviolet (UV) light than SOA formed from aromatic precursors alone on a mass basis. However, the mixed SOA absorption was underestimated when optical properties were predicted using a two-product SOA formation model, as done in many current climate models. Further investigation, including analysis on detailed mechanisms, are required to explain the discrepancy.

  10. Improvement of aerosol optical depth retrieval from MODIS spectral reflectance over the global ocean using new aerosol models archived from AERONET inversion data and tri-axial ellipsoidal dust database

    Directory of Open Access Journals (Sweden)

    J. Lee

    2012-08-01

    Full Text Available New over-ocean aerosol models are developed by integrating the inversion data from the Aerosol Robotic Network (AERONET sun/sky radiometers with a database for the optical properties of tri-axial ellipsoid particles. The new aerosol models allow more accurate retrieval of aerosol optical depth (AOD from the Moderate Resolution Imaging Spectroradiometer (MODIS in the case of high AOD (AOD > 0.3. The aerosol models are categorized by using the fine-mode fraction (FMF at 550 nm and the single-scattering albedo (SSA at 440 nm from the AERONET inversion data to include a variety of aerosol types found around the globe. For each aerosol model, the changes in the aerosol optical properties (AOPs as functions of AOD are considered to better represent aerosol characteristics. Comparisons of AODs between AERONET and MODIS for the period from 2003 to 2010 show that the use of the new aerosol models enhances the AOD accuracy with a Pearson coefficient of 0.93 and a regression slope of 0.99 compared to 0.92 and 0.85 calculated using the MODIS Collection 5 data. Moreover, the percentage of data within an expected error of ± (0.03 + 0.05 × AOD is increased from 62% to 64% for overall data and from 39% to 5% for AOD > 0.3. Errors in the retrieved AOD are further characterized with respect to the Ångström exponent (AE, scattering angle (Θ, SSA, and air mass factor (AMF. Due to more realistic AOPs assumptions, the new algorithm generally reduces systematic errors in the retrieved AODs compared with the current operational algorithm. In particular, the underestimation of fine-dominated AOD and the scattering angle dependence of dust-dominated AOD are significantly mitigated as results of the new algorithm's improved treatment of aerosol size distribution and dust particle nonsphericity.

  11. Improvement of aerosol optical depth retrieval from MODIS spectral reflectance over the global ocean using new aerosol models archived from AERONET inversion data and tri-axial ellipsoidal dust database

    Science.gov (United States)

    Lee, J.; Kim, J.; Yang, P.; Hsu, N. C.

    2012-08-01

    New over-ocean aerosol models are developed by integrating the inversion data from the Aerosol Robotic Network (AERONET) sun/sky radiometers with a database for the optical properties of tri-axial ellipsoid particles. The new aerosol models allow more accurate retrieval of aerosol optical depth (AOD) from the Moderate Resolution Imaging Spectroradiometer (MODIS) in the case of high AOD (AOD > 0.3). The aerosol models are categorized by using the fine-mode fraction (FMF) at 550 nm and the single-scattering albedo (SSA) at 440 nm from the AERONET inversion data to include a variety of aerosol types found around the globe. For each aerosol model, the changes in the aerosol optical properties (AOPs) as functions of AOD are considered to better represent aerosol characteristics. Comparisons of AODs between AERONET and MODIS for the period from 2003 to 2010 show that the use of the new aerosol models enhances the AOD accuracy with a Pearson coefficient of 0.93 and a regression slope of 0.99 compared to 0.92 and 0.85 calculated using the MODIS Collection 5 data. Moreover, the percentage of data within an expected error of ± (0.03 + 0.05 × AOD) is increased from 62% to 64% for overall data and from 39% to 5% for AOD > 0.3. Errors in the retrieved AOD are further characterized with respect to the Ångström exponent (AE), scattering angle (Θ), SSA, and air mass factor (AMF). Due to more realistic AOPs assumptions, the new algorithm generally reduces systematic errors in the retrieved AODs compared with the current operational algorithm. In particular, the underestimation of fine-dominated AOD and the scattering angle dependence of dust-dominated AOD are significantly mitigated as results of the new algorithm's improved treatment of aerosol size distribution and dust particle nonsphericity.

  12. Improvement of Aerosol Optical Depth Retrieval from MODIS Spectral Reflectance over the Global Ocean Using New Aerosol Models Archived from AERONET Inversion Data and Tri-axial Ellipsoidal Dust Database

    Science.gov (United States)

    Lee, J.; Kim, J.; Yang, P.; Hsu, N. C.

    2012-01-01

    New over-ocean aerosol models are developed by integrating the inversion data from the Aerosol Robotic Network (AERONET) sun/sky radiometers with a database for the optical properties of tri-axial ellipsoid particles. The new aerosol models allow more accurate retrieval of aerosol optical depth (AOD) from the Moderate Resolution Imaging Spectroradiometer (MODIS) in the case of high AOD (AOD greater than 0.3). The aerosol models are categorized by using the fine-mode fraction (FMF) at 550 nm and the singlescattering albedo (SSA) at 440 nm from the AERONET inversion data to include a variety of aerosol types found around the globe. For each aerosol model, the changes in the aerosol optical properties (AOPs) as functions of AOD are considered to better represent aerosol characteristics. Comparisons of AODs between AERONET and MODIS for the period from 2003 to 2010 show that the use of the new aerosol models enhances the AOD accuracy with a Pearson coefficient of 0.93 and a regression slope of 0.99 compared to 0.92 and 0.85 calculated using the MODIS Collection 5 data. Moreover, the percentage of data within an expected error of +/-(0.03 + 0.05xAOD) is increased from 62 percent to 64 percent for overall data and from 39 percent to 51 percent for AOD greater than 0.3. Errors in the retrieved AOD are further characterized with respect to the Angstrom exponent (AE), scattering angle, SSA, and air mass factor (AMF). Due to more realistic AOPs assumptions, the new algorithm generally reduces systematic errors in the retrieved AODs compared with the current operational algorithm. In particular, the underestimation of fine-dominated AOD and the scattering angle dependence of dust-dominated AOD are significantly mitigated as results of the new algorithm's improved treatment of aerosol size distribution and dust particle nonsphericity.

  13. Improvements in AOD retrieval from geostationary measurements over Asia with aerosol optical properties derived from the DRAGON-Asia campaign

    Directory of Open Access Journals (Sweden)

    M. Kim

    2015-04-01

    Full Text Available An aerosol model optimized for East Asia is improved by applying inversion data from both long-term monitoring of the Aerosol Robotic Network (AERONET sun photometer and the Distributed Regional Aerosol Gridded Observation Networks (DRAGON-Asia campaign from 2012. This model plays an important role in retrieving accurate aerosol optical depth (AOD from satellite-based measurements. In particular, the performance of a single visible channel algorithm, limited to a specific aerosol type, from real-time measurements is strongly affected by the assumed aerosol optical properties (AOPs for the measured scene. In sensitivity tests, a 4% difference in single scattering albedo (SSA between modeled and measured values can cause a retrieval error in AOD of over 20%, and the overestimation of SSA leads to an underestimation of AOD. Based on the AERONET inversion datasets obtained over East Asia before 2011, seasonally analyzed AOPs can be summarized by SSAs (measured at 675 nm of 0.92, 0.94, 0.92, and 0.91 for spring (March, April, and May, summer (June, July, and August, autumn (September, October, and November, and winter (December, January, and February, respectively. After DRAGON-Asia 2012, the SSA during spring shows a slight increase to 0.93. The large volume of data and spatially concentrated measurements from this campaign can be used to improve the representative aerosol model for East Asia. Accordingly, the AOD datasets retrieved from a single channel algorithm, which uses a pre-calculated look-up table (LUT with the new aerosol model, show an improved correlation with the measured AOD during the DRAGON-Asia campaign (March to May 2012. Compared with the correlation of the AOD retrieved using the original aerosol model, the regression slope between the new AOD and the AERONET values is reduced from 1.08 to 1.00, while the change of the y-offset of −0.08 is significant. The correlation coefficients for the comparisons are 0.87 and 0

  14. Improvements in AOD retrieval from geostationary measurements over Asia with aerosol optical properties derived from the DRAGON-Asia campaign

    Science.gov (United States)

    Kim, M.; Kim, J.; Jeong, U.; Kim, W.; Holben, B.; Eck, T. F.; Lim, J. H.; Song, C. K.; Lee, S.

    2015-04-01

    An aerosol model optimized for East Asia is improved by applying inversion data from both long-term monitoring of the Aerosol Robotic Network (AERONET) sun photometer and the Distributed Regional Aerosol Gridded Observation Networks (DRAGON)-Asia campaign from 2012. This model plays an important role in retrieving accurate aerosol optical depth (AOD) from satellite-based measurements. In particular, the performance of a single visible channel algorithm, limited to a specific aerosol type, from real-time measurements is strongly affected by the assumed aerosol optical properties (AOPs) for the measured scene. In sensitivity tests, a 4% difference in single scattering albedo (SSA) between modeled and measured values can cause a retrieval error in AOD of over 20%, and the overestimation of SSA leads to an underestimation of AOD. Based on the AERONET inversion datasets obtained over East Asia before 2011, seasonally analyzed AOPs can be summarized by SSAs (measured at 675 nm) of 0.92, 0.94, 0.92, and 0.91 for spring (March, April, and May), summer (June, July, and August), autumn (September, October, and November), and winter (December, January, and February), respectively. After DRAGON-Asia 2012, the SSA during spring shows a slight increase to 0.93. The large volume of data and spatially concentrated measurements from this campaign can be used to improve the representative aerosol model for East Asia. Accordingly, the AOD datasets retrieved from a single channel algorithm, which uses a pre-calculated look-up table (LUT) with the new aerosol model, show an improved correlation with the measured AOD during the DRAGON-Asia campaign (March to May 2012). Compared with the correlation of the AOD retrieved using the original aerosol model, the regression slope between the new AOD and the AERONET values is reduced from 1.08 to 1.00, while the change of the y-offset of -0.08 is significant. The correlation coefficients for the comparisons are 0.87 and 0.85, respectively. The

  15. MACv2-SP: a parameterization of anthropogenic aerosol optical properties and an associated Twomey effect for use in CMIP6

    Science.gov (United States)

    Stevens, Bjorn; Fiedler, Stephanie; Kinne, Stefan; Peters, Karsten; Rast, Sebastian; Müsse, Jobst; Smith, Steven J.; Mauritsen, Thorsten

    2017-02-01

    A simple plume implementation of the second version (v2) of the Max Planck Institute Aerosol Climatology, MACv2-SP, is described. MACv2-SP provides a prescription of anthropogenic aerosol optical properties and an associated Twomey effect. It was created to provide a harmonized description of post-1850 anthropogenic aerosol radiative forcing for climate modeling studies. MACv2-SP has been designed to be easy to implement, change and use, and thereby enable studies exploring the climatic effects of different patterns of aerosol radiative forcing, including a Twomey effect. MACv2-SP is formulated in terms of nine spatial plumes associated with different major anthropogenic source regions. The shape of the plumes is fit to the Max Planck Institute Aerosol Climatology, version 2, whose present-day (2005) distribution is anchored by surface-based observations. Two types of plumes are considered: one predominantly associated with biomass burning, the other with industrial emissions. These differ in the prescription of their annual cycle and in their optical properties, thereby implicitly accounting for different contributions of absorbing aerosol to the different plumes. A Twomey effect for each plume is prescribed as a change in the host model's background cloud-droplet population density using relationships derived from satellite data. Year-to-year variations in the amplitude of the plumes over the historical period (1850-2016) are derived by scaling the plumes with associated national emission sources of SO2 and NH3. Experiments using MACv2-SP are performed with the Max Planck Institute Earth System Model. The globally and annually averaged instantaneous and effective aerosol radiative forcings are estimated to be -0.6 and -0.5 W m-2, respectively. Forcing from aerosol-cloud interactions (the Twomey effect) offsets the reduction of clear-sky forcing by clouds, so that the net effect of clouds on the aerosol forcing is small; hence, the clear-sky forcing, which is more

  16. A case study of the highly time-resolved evolution of aerosol chemical and optical properties in urban Shanghai, China

    Directory of Open Access Journals (Sweden)

    Y. Huang

    2013-04-01

    Full Text Available Characteristics of the chemical and optical properties of aerosols in urban Shanghai and their relationship were studied over a three-day period in October 2011. A suite of real-time instruments, including an Aerosol Time-Of-Flight Mass Spectrometer (ATOFMS, a Monitor for AeRosols and GAses (MARGA, a Cavity Ring Down Spectrometer (CRDS, a nephelometer and a Scanning Mobility Particle Sizer (SMPS, was employed to follow the quick changes of the aerosol properties within the 72 h sampling period. The origin of the air mass arriving in Shanghai during this period shifted from the East China Sea to the northwest area of China, offering a unique opportunity to observe the evolution of aerosols influenced by regional transport from the most polluted areas in China. According to the meteorological conditions and temporal characterizations of the chemical and optical properties, the sampling period was divided into three periods. During Period 1 (00:00–23:00 LT, 13 October, the aerosols in urban Shanghai were mainly fresh and the single scattering albedo varied negatively with the emission of elemental carbon, indicating that local sources dominated. Period 2 (23:00 LT on 13 October to 10:00 LT on 15 October was impacted by regionally transported pollutants and had the highest particulate matter (PM mass loading and the lowest particle acidity, characterized by large fractions of aged particles and high secondary ion (nitrate, sulfate and ammonium mass concentrations. Comparison between ATOFMS particle acidity and quantitative particle acidity by MARGA indicated the significance of semi-quantitative calculation in ATOFMS. Two sub-periods were identified in Period 2 based on the scattering efficiency of PM1 mass. Period 3 (from 10:00 LT on 15 October to 00:00 LT on 16 October had a low PM1/PM10 ratio and a new particle formation event. The comparison of these sub-periods highlights the influence of particle mixing state on aerosol optical properties

  17. Initial investigation of the wavelength dependence of optical properties measured with a new multi-pass aerosol extinction differential optical absorption spectrometer (AE-DOAS

    Directory of Open Access Journals (Sweden)

    R. T. Chartier

    2011-10-01

    Full Text Available Atmospheric aerosols directly affect climate by scattering and absorbing radiation. The magnitude of the impact is dependent upon the wavelength of light, but is often estimated near 550 nm. When light scattering and absorption by aerosols is approximated, the wavelength dependence of the refractive index for specific components is lost. As a result, climate models would have inherent uncertainties for aerosol contributions to radiative forcing when considering the entire solar spectrum. An aerosol extinction differential optical absorption spectrometer has been developed to directly measure aerosol extinction at mid-ultraviolet to near infrared wavelengths. The instrument consists of a spectrometer coupled to a closed White-type multi-pass gas cell with an adjustable path length of up to approximately 20 m. Laboratory measurements of various gases are compared with known absorption cross sections. Additionally, the extinction of monodisperse samples of polystyrene latex spheres are measured and compared to Mie theory generated with refractive index values from the literature to validate the new instrument. The polystyrene experiments also emphasize the ability of the new instrument to retrieve the wavelength dependent refractive index, especially in the ultraviolet wavelength regions where variability is expected. The spectrometer will be a significant advancement for determining wavelength dependent complex refractive indices in future laboratory studies as well as provide the ability to monitor ambient aerosol light extinction.

  18. Initial investigation of the wavelength dependence of optical properties measured with a new multi-pass Aerosol Extinction Differential Optical Absorption Spectrometer (AE-DOAS

    Directory of Open Access Journals (Sweden)

    R. T. Chartier

    2012-04-01

    Full Text Available Atmospheric aerosols directly affect climate by scattering and absorbing radiation. The magnitude of the impact is dependent upon the wavelength of light, but is often estimated near 550 nm. When light scattering and absorption by aerosols is approximated, the wavelength dependence of the refractive index for specific components is lost. As a result, climate models would have inherent uncertainties for aerosol contributions to radiative forcing when considering the entire solar spectrum. An aerosol extinction differential optical absorption spectrometer has been developed to directly measure aerosol extinction at mid-ultraviolet to near infrared wavelengths. The instrument consists of a spectrometer coupled to a closed White-type multi-pass gas cell with an adjustable path length of up to approximately 20 m. Laboratory measurements of various gases are compared with known absorption cross sections. Additionally, the extinction of monodisperse samples of polystyrene latex spheres are measured and compared to Mie theory generated with refractive index values from the literature to validate the new instrument. The polystyrene experiments also emphasize the ability of the new instrument to retrieve the wavelength dependent refractive index, especially in the ultraviolet wavelength regions where variability is expected. The spectrometer will be a significant advancement for determining wavelength dependent complex refractive indices in future laboratory studies as well as provide the ability to monitor ambient aerosol light extinction.

  19. Retrieval of Aerosol Optical Depth over Water and over Land from Multi-Spectral Electro-Optical Sensors on Satellites

    NARCIS (Netherlands)

    Leeuw, G. de; Veefkind, J.P.

    1999-01-01

    Aerosols have been identified as an important factor in the regulation of the Earth climate. The incoming solar radiation is scattered by aerosols, which induces a negative (cooling) effect on the atmospheric radiation balance. The present contribution is focused on the detection of aerosols by usin

  20. Comparison of aerosol optical properties at the sub-arctic stations ALOMAR-Andenes, Abisko and Sodankylä in late spring and summer 2007

    Science.gov (United States)

    Rodríguez, E.; Toledano, C.; Cachorro, V.; de Leeuw, G.; De Frutos, A.; Gausa, M.; Holben, B.

    2012-04-01

    Aerosol concentration and aerosol type, retrieved from observations with CIMEL sun-photometers at three sub-arctic locations at the Scandinavian Peninsula are presented. The observations were made at ALOMAR-Andenes in Norway, Abisko in Sweden and Sodankylä in Finland. This field campaign took place in late spring and summer 2007 as part of the activities of the International Polar Year (IPY) within the POLARCAT project at ALOMAR and Abisko. Aerosol properties were characterized using the relationship between the aerosol optical depth and the Ångström Exponent. The characteristics of the predominant aerosol type and microphysics are largely determined by the location of the site (continental or coastal). During summer the fine mode particles dominate, as indicated by the fine mode volume fraction and the Ångström Exponent. The aerosol concentration was on average very low, except during an event in which long-range transported aerosols (dust and pollution) were detected.

  1. Aerosol optical depth determination in the UV using a four-channel precision filter radiometer

    Science.gov (United States)

    Carlund, Thomas; Kouremeti, Natalia; Kazadzis, Stelios; Gröbner, Julian

    2017-03-01

    The determination of aerosol properties, especially the aerosol optical depth (AOD) in the ultraviolet (UV) wavelength region, is of great importance for understanding the climatological variability of UV radiation. However, operational retrievals of AOD at the biologically most harmful wavelengths in the UVB are currently only made at very few places. This paper reports on the UVPFR (UV precision filter radiometer) sunphotometer, a stable and robust instrument that can be used for AOD retrievals at four UV wavelengths. Instrument characteristics and results of Langley calibrations at a high-altitude site were presented. It was shown that due to the relatively wide spectral response functions of the UVPFR, the calibration constants (V0) derived from Langley plot calibrations underestimate the true extraterrestrial signals. Accordingly, correction factors were introduced. In addition, the instrument's spectral response functions also result in an apparent air-mass-dependent decrease in ozone optical depth used in the AOD determinations. An adjusted formula for the calculation of AOD, with a correction term dependent on total column ozone amount and ozone air mass, was therefore introduced. Langley calibrations performed 13-14 months apart resulted in sensitivity changes of ≤ 1.1 %, indicating good instrument stability. Comparison with a high-accuracy standard precision filter radiometer, measuring AOD at 368-862 nm wavelengths, showed consistent results. Also, very good agreement was achieved by comparing the UVPFR with AOD at UVB wavelengths derived with a Brewer spectrophotometer, which was calibrated against the UVPFR at an earlier date. Mainly due to non-instrumental uncertainties connected with ozone optical depth, the total uncertainty of AOD in the UVB is higher than that reported from AOD instruments measuring in UVA and visible ranges. However, the precision can be high among instruments using harmonized algorithms for ozone and Rayleigh optical depth as

  2. Assessment of aerosol optics, microphysics, and transport process of biomass-burning haze over northern SE Asia: 7-SEAS AERONET observations

    Science.gov (United States)

    Wang, S.; Giles, D. M.; Eck, T. F.; Lin, N.; Tsay, S.; Holben, B. N.

    2013-12-01

    Initiated in 2007, the Seven South East Asian Studies (7-SEAS) is aimed to facilitate an interdisciplinary research on the aerosol environment in SE Asia (SEA) as a whole, promote international collaboration, and further enhance scientific understanding of the impact of biomass burning on clouds, atmospheric radiation, hydrological cycle, and region climates. One of the key measurements proposed in the 7-SEAS is the NASA/AERONET (AErosol RObotic NETwork) observation, which provides helpful information on columnar aerosol optical properties and allows us consistently to examine biomass-burning aerosols across northern SEA from ground-based remote-sensing point of view. In this presentation, we will focus on the two 7-SEAS field deployments, i.e. the 2012 Son La Experiment and the 2013 BASELInE (Biomass-burning Aerosols & Stratocumulus Environment: Lifecycles and Interactions Experiment). We analyze the daytime variation of aerosol by using consistent measurements from 15 of AERONET sites over Indochina, the South China Sea, and Taiwan. Spatiotemporal characteristics of aerosol optical properties (e.g., aerosol optical depth (AOD), fine/coarse mode AOD, single-scattering albedo, asymmetry factor) will be discussed. Strong diurnal variation of aerosol optical properties was observed to be attributed to planetary boundary layer (PBL) dynamics. A comparison between aerosol loading (i.e. AOD) and surface PM2.5 concentration will be presented. Our results demonstrate that smoke aerosols emitted from agriculture burning that under certain meteorological conditions can degrade regional air quality 3000 km from the source region, with additional implications for aerosol radiative forcing and regional climate change over northern SE Asia.

  3. The effect of aerosol optical depth on rainfall with reference to meteorology over metro cities in India.

    Science.gov (United States)

    Gunaseelan, Indira; Bhaskar, B Vijay; Muthuchelian, K

    2014-01-01

    Rainfall is a key link in the global water cycle and a proxy for changing climate; therefore, proper assessment of the urban environment's impact on rainfall will be increasingly important in ongoing climate diagnostics and prediction. Aerosol optical depth (AOD) measurements on the monsoon seasons of the years 2008 to 2010 were made over four metro regional hotspots in India. The highest average of AOD was in the months of June and July for the four cities during 3 years and lowest was in September. Comparing the four regions, Kolkata was in the peak of aerosol contamination and Chennai was in least. Pearson correlation was made between AOD with climatic parameters. Some changes in the parameters were found during drought year. Temperature, cloud parameters, and humidity play an important role for the drought conditions. The role of aerosols, meteorological parameters, and their impacts towards the precipitation during the monsoon was studied.

  4. Assessment of the Aerosol Optics Component of the Coupled WRF-CMAQ Model usingCARES Field Campaign data and a Single Column Model

    Science.gov (United States)

    The Carbonaceous Aerosols and Radiative Effects Study (CARES), a field campaign held in central California in June 2010, provides a unique opportunity to assess the aerosol optics modeling component of the two-way coupled Weather Research and Forecasting (WRF) – Community Multisc...

  5. Simulation of aerosol optical properties over a tropical urban site in India using a global model and its comparison with ground measurements

    Directory of Open Access Journals (Sweden)

    T. Takemura

    2011-05-01

    Full Text Available Aerosols have great impacts on atmospheric environment, human health, and earth's climate. Therefore, information on their spatial and temporal distribution is of paramount importance. Despite numerous studies have examined the variation and trends of BC and AOD over India, only very few have focused on their spatial distribution or even correlating the observations with model simulations. In the present study, a three-dimensional aerosol transport-radiation model coupled with a general circulation model. SPRINTARS, simulated atmospheric aerosol distributions including BC and aerosol optical properties, i.e., aerosol optical thickness (AOT, Ångström Exponent (AE, and single scattering albedo (SSA. The simulated results are compared with both BC measurements by aethalometer and aerosol optical properties measured by ground-based skyradiometer and by satellite sensor, MODIS/Terra over Hyderabad, which is a tropical urban area of India, for the year 2008. The simulated AOT and AE in Hyderabad are found to be comparable to ground-based measured ones. The simulated SSA tends to be higher than the ground-based measurements. Both these comparisons of aerosol optical properties between the simulations with different emission inventories and the measurements indicate that, firstly the model uncertainties derived from aerosol emission inventory cannot explain the gaps between the simulations and the measurements and secondly the vertical transport of BC and the treatment of BC-containing particles can be the main issue in the global model to solve the gap.

  6. Evolution of aerosol optical thickness over Europe during the August 2003 heat wave as seen from CHIMERE model simulations and POLDER data

    NARCIS (Netherlands)

    Hodzic, A; Vautard, R; Chepfer, H; Goloub, P; Menut, L; Chazette, P; Deuzé, J L; Apituley, A; Couvert, P

    2006-01-01

    This study describes the atmospheric aerosol load encountered during the large-scale pollution episode that occurred in August 2003, by means of the aerosol optical thicknesses (AOTs) measured at 865 nm by the Polarization and Directionality of the Earth's Reflectances (POLDER) sensor and the simula

  7. MACv2-SP: a parameterization of anthropogenic aerosol optical properties and an associated Twomey effect for use in CMIP6

    Energy Technology Data Exchange (ETDEWEB)

    Stevens, Bjorn [Max Planck Inst. for Meteorology, Hamburg (Germany); Fiedler, Stephanie [Max Planck Inst. for Meteorology, Hamburg (Germany); Kinne, Stefan [Max Planck Inst. for Meteorology, Hamburg (Germany); Peters, Karsten [Max Planck Inst. for Meteorology, Hamburg (Germany); Rast, Sebastian [Max Planck Inst. for Meteorology, Hamburg (Germany); Müsse, Jobst [Max Planck Inst. for Meteorology, Hamburg (Germany); Smith, Steven J. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States). Joint Global Change Research Inst.; Mauritsen, Thorsten [Max Planck Inst. for Meteorology, Hamburg (Germany)

    2017-02-01

    A simple plume implementation of the second version (v2) of the Max Planck Institute Aerosol Climatology, MACv2-SP, is described. MACv2-SP provides a prescription of anthropogenic aerosol optical properties and an associated Twomey effect. It was created to provide a harmonized description of post-1850 anthropogenic aerosol radiative forcing for climate modeling studies. MACv2-SP has been designed to be easy to implement, change and use, and thereby enable studies exploring the climatic effects of different patterns of aerosol radiative forcing, including a Twomey effect. MACv2-SP is formulated in terms of nine spatial plumes associated with different major anthropogenic source regions. The shape of the plumes is fit to the Max Planck Institute Aerosol Climatology, version 2, whose present-day (2005) distribution is anchored by surface-based observations. Two types of plumes are considered: one predominantly associated with biomass burning, the other with industrial emissions. These differ in the prescription of their annual cycle and in their optical properties, thereby implicitly accounting for different contributions of absorbing aerosol to the different plumes. A Twomey effect for each plume is prescribed as a change in the host model's background cloud-droplet population density using relationships derived from satellite data. Year-to-year variations in the amplitude of the plumes over the historical period (1850–2016) are derived by scaling the plumes with associated national emission sources of SO2 and NH3. Experiments using MACv2-SP are performed with the Max Planck Institute Earth System Model. The globally and annually averaged instantaneous and effective aerosol radiative forcings are estimated to be -0.6 and -0.5 W m-2, respectively. Forcing from aerosol–cloud interactions (the Twomey effect) offsets the reduction of clear-sky forcing by clouds, so that the net effect of clouds on the aerosol forcing is small

  8. Evaluation of seven European aerosol optical depth retrieval algorithms for climate analysis

    NARCIS (Netherlands)

    Leeuw, G. de; Holzer-Popp, T.; Bevan, S.; Davies, W.H.; Descloitres, J.; Grainger, R.G.; Griesfeller, J.; Heckel, A.; Kinne, S.; Klüser, L.; Kolmonen, P.; Litvinov, P.; Martynenko, D.; North, P.; Ovigneur, B.; Pascal, N.; Poulsen, C.; Ramon, D.; Schu