The Experts below are selected from a list of 5715 Experts worldwide ranked by ideXlab platform
David J. Diner - One of the best experts on this subject based on the ideXlab platform.
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Improving MISR AOD Retrievals With Low-Light-Level Corrections for Veiling Light
IEEE Transactions on Geoscience and Remote Sensing, 2018Co-Authors: Marcin L Witek, Michael J. Garay, David J. Diner, Michael A Bull, Feng Xu, Felix C. SeidelAbstract:Operational retrievals of aerosol optical depth (AOD) from Multi-angle Imaging SpectroRadiometer (MISR) data have been shown to have a high bias in pristine oceanic areas. One line of evidence involves comparison with Maritime Aerosol Network (MAN) observations, including the areas of low aerosol loading close to Antarctica. In this paper, a principal reason for the AOD overestimation is identified, which is stray light measured by the MISR cameras in dark regions of high-contrast scenes. A small fraction of the light from surrounding bright areas, such as clouds or sea ice, is redistributed to dark areas, artificially increasing their brightness. Internal reflections and light scattering from optical elements in MISR's pushbroom cameras contribute to this veiling light effect. A simple correction model is developed that relies on the average scene brightness and an empirically determined set of veiling light coefficients for each MISR camera and wavelength. Several independent methods are employed to determine these coefficients. Three sets of coefficients are further implemented and tested in prototype MISR 4.4-km AOD retrievals. The results show dramatic improvements in retrieved AODs compared against MAN observations and the currently operational V22 MISR retrievals. For the best performing set of coefficients, the bias is reduced by 51%, from 0.039 to 0.019, the RMSE is lowered by 19%, from 0.062 to 0.050, and 84% of retrievals fall within the uncertainty envelope compared with 66% of retrievals in V22. The best performing set will be implemented operationally in the next V23 MISR AOD product release.
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assessment of MISR cloud motion vectors cmvs relative to goes and modis atmospheric motion vectors amvs
Journal of Applied Meteorology and Climatology, 2017Co-Authors: Kevin J. Mueller, Janpeter Muller, Michael J. Garay, David J. Diner, Catherine Moroney, Veljko M. Jovanovic, Larry Di Girolamo, Dong L Wu, Akos Horvath, Steve WanzongAbstract:AbstractCloud motion vector (CMV) winds retrieved from the Multiangle Imaging SpectroRadiometer (MISR) instrument on the polar-orbiting Terra satellite from 2003 to 2008 are compared with collocated atmospheric motion vectors (AMVs) retrieved from Geostationary Operational Environmental Satellite (GOES) imagery over the tropics and midlatitudes and from Moderate Resolution Imaging Spectroradiometer (MODIS) imagery near the poles. MISR imagery from multiple view angles is exploited to jointly retrieve stereoscopic cloud heights and motions, showing advantages over the AMV heights assigned by radiometric means, particularly at low heights (<3 km) that account for over 95% of MISR CMV sampling. MISR–GOES wind differences exhibit a standard deviation ranging with increasing height from 3.3 to 4.5 m s−1 for a high-quality [quality indicator (QI) ≥ 80] subset where height differences are <1.5 km. Much of the observed difference can be attributed to the less accurately retrieved component of CMV motion along the...
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aerosol optical depths over oceans a view from MISR retrievals and collocated man and aeronet in situ observations
Journal of Geophysical Research, 2013Co-Authors: Marcin L Witek, Michael J. Garay, David J. Diner, A. SmirnovAbstract:[1] In this study, aerosol optical depths over oceans are analyzed from satellite and surface perspectives. Multiangle Imaging SpectroRadiometer (MISR) aerosol retrievals are investigated and validated primarily against Maritime Aerosol Network (MAN) observations. Furthermore, AErosol RObotic NETwork (AERONET) data from 19 island and coastal sites is incorporated in this study. The 270 MISR/MAN comparison points scattered across all oceans were identified. MISR on average overestimates aerosol optical depths (AODs) by 0.04 as compared to MAN; the correlation coefficient and root-mean-square error are 0.95 and 0.06, respectively. A new screening procedure based on retrieval region characterization is proposed, which is capable of substantially reducing MISR retrieval biases. Over 1000 additional MISR/AERONET comparison points are added to the analysis to confirm the validity of the method. The bias reduction is effective within all AOD ranges. Setting a clear flag fraction threshold to 0.6 reduces the bias to below 0.02, which is close to a typical ground-based measurement uncertainty. Twelve years of MISR data are analyzed with the new screening procedure. The average over ocean AOD is reduced by 0.03, from 0.15 to 0.12. The largest AOD decrease is observed in high latitudes of both hemispheres, regions with climatologically high cloud cover. It is postulated that the screening procedure eliminates spurious retrieval errors associated with cloud contamination and cloud adjacency effects. The proposed filtering method can be used for validating aerosol and chemical transport models.
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MISR Dark Water aerosol retrievals: operational algorithm sensitivity to particle non-sphericity
Atmospheric Measurement Techniques, 2013Co-Authors: Olga V. Kalashnikova, Michael J. Garay, John V Martonchik, David J. DinerAbstract:Abstract. The aim of this study is to theoretically investigate the sensitivity of the Multi-angle Imaging SpectroRadiometer (MISR) operational (version 22) Dark Water retrieval algorithm to aerosol non-sphericity over the global oceans under actual observing conditions, accounting for current algorithm assumptions. Non-spherical (dust) aerosol models, which were introduced in version 16 of the MISR aerosol product, improved the quality and coverage of retrievals in dusty regions. Due to the sensitivity of the retrieval to the presence of non-spherical aerosols, the MISR aerosol product has been successfully used to track the location and evolution of mineral dust plumes from the Sahara across the Atlantic, for example. However, the MISR global non-spherical aerosol optical depth (AOD) fraction product has been found to have several climatological artifacts superimposed on valid detections of mineral dust, including high non-spherical fraction in the Southern Ocean and seasonally variable bands of high non-sphericity. In this paper we introduce a formal approach to examine the ability of the operational MISR Dark Water algorithm to distinguish among various spherical and non-spherical particles as a function of the variable MISR viewing geometry. We demonstrate the following under the criteria currently implemented: (1) Dark Water retrieval sensitivity to particle non-sphericity decreases for AOD below about 0.1 primarily due to an unnecessarily large lower bound imposed on the uncertainty in MISR observations at low light levels, and improves when this lower bound is removed; (2) Dark Water retrievals are able to distinguish between the spherical and non-spherical particles currently used for all MISR viewing geometries when the AOD exceeds 0.1; (3) the sensitivity of the MISR retrievals to aerosol non-sphericity varies in a complex way that depends on the sampling of the scattering phase function and the contribution from multiple scattering; and (4) non-sphericity artifacts occur at those view-illumination geometries where dust aerosols are indistinguishable from certain types of cirrus particles. Based on these results, we suggest that interested parties use caution with the version 22 MISR Dark Water aerosol non-sphericity product in situations where cirrus may be present.
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MISR observations of etna volcanic plumes
Journal of Geophysical Research, 2012Co-Authors: Simona Scollo, Michael J. Garay, David J. Diner, Ralph A Kahn, David L Nelson, M Coltelli, V J RealmutoAbstract:[1] In the last twelve years, Mt. Etna, located in eastern Sicily, has produced a great number of explosive eruptions. Volcanic plumes have risen to several km above sea level and created problems for aviation and the communities living near the volcano. A reduction of hazards may be accomplished using remote sensing techniques to evaluate important features of volcanic plumes. Since 2000, the Multiangle Imaging SpectroRadiometer (MISR) on board NASA's Terra spacecraft has been extensively used to study aerosol dispersal and to extract the three-dimensional structure of plumes coming from anthropogenic or natural sources, including volcanoes. In the present work, MISR data from several explosive events occurring at Etna are analyzed using a program named MINX (MISR INteractive eXplorer). MINX uses stereo matching techniques to evaluate the height of the volcanic aerosol with a precision of a few hundred meters, and extracts aerosol properties from the MISR Standard products. We analyzed twenty volcanic plumes produced during the 2000, 2001, 2002–03, 2006 and 2008 Etna eruptions, finding that volcanic aerosol dispersal and column height obtained by this analysis is in good agreement with ground-based observations. MISR aerosol type retrievals: (1) clearly distinguish volcanic plumes that are sulphate and/or water vapor dominated from ash-dominated ones; (2) detect even low concentrations of volcanic ash in the atmosphere; (3) demonstrate that sulphate and/or water vapor dominated plumes consist of smaller-sized particles compared to ash plumes. This work highlights the potential of MISR to detect important volcanic plume characteristics that can be used to constrain the eruption source parameters in volcanic ash dispersion models. Further, the possibility of discriminating sulphate and/or water vapor dominated plumes from ash-dominated ones is important to better understand the atmospheric impact of these plumes.
John V Martonchik - One of the best experts on this subject based on the ideXlab platform.
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MISR Dark Water aerosol retrievals: operational algorithm sensitivity to particle non-sphericity
Atmospheric Measurement Techniques, 2013Co-Authors: Olga V. Kalashnikova, Michael J. Garay, John V Martonchik, David J. DinerAbstract:Abstract. The aim of this study is to theoretically investigate the sensitivity of the Multi-angle Imaging SpectroRadiometer (MISR) operational (version 22) Dark Water retrieval algorithm to aerosol non-sphericity over the global oceans under actual observing conditions, accounting for current algorithm assumptions. Non-spherical (dust) aerosol models, which were introduced in version 16 of the MISR aerosol product, improved the quality and coverage of retrievals in dusty regions. Due to the sensitivity of the retrieval to the presence of non-spherical aerosols, the MISR aerosol product has been successfully used to track the location and evolution of mineral dust plumes from the Sahara across the Atlantic, for example. However, the MISR global non-spherical aerosol optical depth (AOD) fraction product has been found to have several climatological artifacts superimposed on valid detections of mineral dust, including high non-spherical fraction in the Southern Ocean and seasonally variable bands of high non-sphericity. In this paper we introduce a formal approach to examine the ability of the operational MISR Dark Water algorithm to distinguish among various spherical and non-spherical particles as a function of the variable MISR viewing geometry. We demonstrate the following under the criteria currently implemented: (1) Dark Water retrieval sensitivity to particle non-sphericity decreases for AOD below about 0.1 primarily due to an unnecessarily large lower bound imposed on the uncertainty in MISR observations at low light levels, and improves when this lower bound is removed; (2) Dark Water retrievals are able to distinguish between the spherical and non-spherical particles currently used for all MISR viewing geometries when the AOD exceeds 0.1; (3) the sensitivity of the MISR retrievals to aerosol non-sphericity varies in a complex way that depends on the sampling of the scattering phase function and the contribution from multiple scattering; and (4) non-sphericity artifacts occur at those view-illumination geometries where dust aerosols are indistinguishable from certain types of cirrus particles. Based on these results, we suggest that interested parties use caution with the version 22 MISR Dark Water aerosol non-sphericity product in situations where cirrus may be present.
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MISR Aerosol Product Attributes and Statistical Comparisons With MODIS
IEEE Transactions on Geoscience and Remote Sensing, 2009Co-Authors: Ralph A Kahn, Michael J. Garay, David J. Diner, John V Martonchik, Michael A Bull, David L Nelson, Robert C. Levy, Susan R. Paradise, Earl G. Hansen, Lorraine A. RemerAbstract:In this paper, Multi-angle Imaging SpectroRadiometer (MISR) aerosol product attributes are described, including geometry and algorithm performance flags. Actual retrieval coverage is mapped and explained in detail using representative global monthly data. Statistical comparisons are made with coincident aerosol optical depth (AOD) and Angstrom exponent (ANG) retrieval results from the Moderate Resolution Imaging Spectroradiometer (MODIS) instrument. The relationship between these results and the ones previously obtained for MISR and MODIS individually, based on comparisons with coincident ground-truth observations, is established. For the data examined, MISR and MODIS each obtain successful aerosol retrievals about 15% of the time, and coincident MISR-MODIS aerosol retrievals are obtained for about 6%-7% of the total overlap region. Cloud avoidance, glint and oblique-Sun exclusions, and other algorithm physical limitations account for these results. For both MISR and MODIS, successful retrievals are obtained for over 75% of locations where attempts are made. Where coincident AOD retrievals are obtained over ocean, the MISR-MODIS correlation coefficient is about 0.9; over land, the correlation coefficient is about 0.7. Differences are traced to specific known algorithm issues or conditions. Over-ocean ANG comparisons yield a correlation of 0.67, showing consistency in distinguishing aerosol air masses dominated by coarse-mode versus fine-mode particles. Sampling considerations imply that care must be taken when assessing monthly global aerosol direct radiative forcing and AOD trends with these products, but they can be used directly for many other applications, such as regional AOD gradient and aerosol air mass type mapping and aerosol transport model validation. Users are urged to take seriously the published product data-quality statements.
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Validation of MISR land surface broadband albedo
Journal of remote sensing, 2008Co-Authors: Y. M. Chen, Shunlin Liang, Jinfei Wang, John V MartonchikAbstract:Land surface broadband albedo is a critical variable for many scientific applications. Due to the scarcity of spectral albedo measurements of the Earth's surface environments, it is useful to construct broadband albedo from spectral albedo data obtained by multi-angle satellite observations. The Multi-angle Imaging SpectroRadiometer (MISR) onboard NASA's Earth Observing System (EOS) Terra satellite provides land surface albedo products from multi-angular observations; however, the products have not been comprehensively validated. We convert MISR spectral albedos to total shortwave albedos and validate them using ground measurements at different validation sites. For most surface types, a published narrowband to broadband conversion formula was used, but a new conversion formula for snow and ice covered sites is developed in this study where the spectral range of the instrument is different. Several comparisons are made: (1) between MISR directional-hemispherical reflectance (DHR) or albedo and MODIS (Moderate Resolution Imaging Spectroradiometer) DHR; and (2) between MISR spectral DHR and bi-hemispherical reflectance (BHR). The results show that: (1) both the value and the temporal trends of the MISR shortwave albedo and the ground measured shortwave albedo are in good agreement, with the exception of the snow and ice sites; (2) the MISR DHR conforms well to MODIS DHR; and (3) the values of MISR DHR and BHR are nearly identical.
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Evaluation of MISR Land Surface BRF Measurements: Intercomparison with Coincident Airborne and Ground Field Measurements
2005Co-Authors: Wedad A. Abdou, M.c. Helmlinger, David J. Diner, John V Martonchik, Veljko M. Jovanovic, Charles K. Gatebe, Michael D. KingAbstract:The bidirectional reflectance factor, BRF, retrieved by the Multiangle Imaging SpectroRadiometer, MISR, is compared with those coincidently measured from aircraft, by the Cloud Absorption Radiometer, CAR, and MISR airborne simulator, AirMISR, and on the ground, by the Portable Apparatus for Rabid Acquisition of Bidirectional Observations of Land and Atmosphere, PARABOLA Ill. The intercomparisons are made for six types of surfaces: bright desert, salt pans, grassland, forests, snow and the Dismal Swamp. The results show that MISR BRF values are mostly within +/- 10% in agreement with the corresponding airborne and ground measurements, independent of the surface types This study is part of an effort to evaluate and validate MISR surface products.
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analysis of multi angle imaging spectroradiometer MISR aerosol optical depths over greater india during winter 2001 2004
Geophysical Research Letters, 2004Co-Authors: L Di Girolamo, David J. Diner, Ralph A Kahn, John V Martonchik, Tami C Bond, D Bramer, F Fettinger, M V Ramana, V Ramanathan, Philip J RaschAbstract:[1] We present the first detailed spatial analysis of a four-year, wintertime visible aerosol optical depth (AOD) climatology from the Multi-angle Imaging SpectroRadiometer (MISR) over greater India. Meteorological fields from the National Centers for Environmental Prediction (NCEP) reanalysis, topographic data, and information related to aerosol source regions are used to explain the spatial patterns in MISR AODs. High AODs are found over much of greater India. The highest AODs are over the northern Indian state of Bihar, where we show that meteorology, topography, and aerosol sources all favor development of a concentrated pool of airborne particles. MISR AODs are validated against five ground-based sites in India and Nepal, revealing similar error characteristics found in other validation studies for the MISR aerosol product.
Ralph A Kahn - One of the best experts on this subject based on the ideXlab platform.
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climatology of the aerosol optical depth by components from the multi angle imaging spectroradiometer MISR and chemistry transport models
Atmospheric Chemistry and Physics, 2016Co-Authors: Olga V. Kalashnikova, A. Braverman, Michael J. Garay, Kentaroh Suzuki, Ralph A KahnAbstract:Abstract. The Multi-angle Imaging SpectroRadiometer (MISR) Joint Aerosol (JOINT_AS) Level 3 product has provided a global, descriptive summary of MISR Level 2 aerosol optical depth (AOD) and aerosol type information for each month over 16+ years since March 2000. Using Version 1 of JOINT_AS, which is based on the operational (Version 22) MISR Level 2 aerosol product, this study analyzes, for the first time, characteristics of observed and simulated distributions of AOD for three broad classes of aerosols: spherical nonabsorbing, spherical absorbing, and nonspherical – near or downwind of their major source regions. The statistical moments (means, standard deviations, and skewnesses) and distributions of AOD by components derived from the JOINT_AS are compared with results from two chemistry transport models (CTMs), the Goddard Chemistry Aerosol Radiation and Transport (GOCART) and SPectral RadIatioN-TrAnSport (SPRINTARS). Overall, the AOD distributions retrieved from MISR and modeled by GOCART and SPRINTARS agree with each other in a qualitative sense. Marginal distributions of AOD for each aerosol type in both MISR and models show considerable high positive skewness, which indicates the importance of including extreme AOD events when comparing satellite retrievals with models. The MISR JOINT_AS product will greatly facilitate comparisons between satellite observations and model simulations of aerosols by type.
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MISR empirical stray light corrections in high-contrast scenes
Atmospheric Measurement Techniques, 2015Co-Authors: James A. Limbacher, Ralph A KahnAbstract:Abstract. We diagnose the potential causes for the Multi-angle Imaging SpectroRadiometer's (MISR) persistent high aerosol optical depth (AOD) bias at low AOD with the aid of coincident MODerate-resolution Imaging Spectroradiometer (MODIS) imagery from NASA's Terra satellite. Stray light in the MISR instrument is responsible for a large portion of the high AOD bias in high-contrast scenes, such as broken-cloud scenes that are quite common over ocean. Discrepancies among MODIS and MISR nadir-viewing blue, green, red, and near-infrared images are used to optimize seven parameters individually for each wavelength, along with a background reflectance modulation term that is modeled separately, to represent the observed features. Independent surface-based AOD measurements from the AErosol RObotic NETwork (AERONET) and the Marine Aerosol Network (MAN) are compared with MISR research aerosol retrieval algorithm (RA) AOD retrievals for 1118 coincidences to validate the corrections when applied to the nadir and off-nadir cameras. With these corrections, plus the baseline RA corrections and enhanced cloud screening applied, the median AOD bias for all data in the mid-visible (green, 558 nm) band decreases from 0.006 (0.020 for the MISR standard algorithm (SA)) to 0.000, and the RMSE decreases by 5 % (27 % compared to the SA). For AOD558 nm
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MISR observations of etna volcanic plumes
Journal of Geophysical Research, 2012Co-Authors: Simona Scollo, Michael J. Garay, David J. Diner, Ralph A Kahn, David L Nelson, M Coltelli, V J RealmutoAbstract:[1] In the last twelve years, Mt. Etna, located in eastern Sicily, has produced a great number of explosive eruptions. Volcanic plumes have risen to several km above sea level and created problems for aviation and the communities living near the volcano. A reduction of hazards may be accomplished using remote sensing techniques to evaluate important features of volcanic plumes. Since 2000, the Multiangle Imaging SpectroRadiometer (MISR) on board NASA's Terra spacecraft has been extensively used to study aerosol dispersal and to extract the three-dimensional structure of plumes coming from anthropogenic or natural sources, including volcanoes. In the present work, MISR data from several explosive events occurring at Etna are analyzed using a program named MINX (MISR INteractive eXplorer). MINX uses stereo matching techniques to evaluate the height of the volcanic aerosol with a precision of a few hundred meters, and extracts aerosol properties from the MISR Standard products. We analyzed twenty volcanic plumes produced during the 2000, 2001, 2002–03, 2006 and 2008 Etna eruptions, finding that volcanic aerosol dispersal and column height obtained by this analysis is in good agreement with ground-based observations. MISR aerosol type retrievals: (1) clearly distinguish volcanic plumes that are sulphate and/or water vapor dominated from ash-dominated ones; (2) detect even low concentrations of volcanic ash in the atmosphere; (3) demonstrate that sulphate and/or water vapor dominated plumes consist of smaller-sized particles compared to ash plumes. This work highlights the potential of MISR to detect important volcanic plume characteristics that can be used to constrain the eruption source parameters in volcanic ash dispersion models. Further, the possibility of discriminating sulphate and/or water vapor dominated plumes from ash-dominated ones is important to better understand the atmospheric impact of these plumes.
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Capabilities and Limitations of MISR Aerosol Products in Dust-Laden Regions
Remote Sensing of Clouds and the Atmosphere XVI, 2011Co-Authors: Olga V. Kalashnikova, Michael J. Garay, David J. Diner, Ralph A Kahn, Irina N. Sokolik, John V. Martonchcik, Omar Torres, Weidong Yang, Alexander MarshakAbstract:Atmospheric mineral dust particles have significant effects on climate and the environment, and despite notable advances in modeling and satellite and ground-based measurements, remain one of the major factors contributing to large uncertainty in aerosol radiative forcing. We examine the Multi-angle Imaging SpectroRadiometer (MISR) 11+ year aerosol data record to demonstrate MISR's unique strengths and assess potential biases of MISR products for dust study applications. In particular, we examine MISR's unique capabilities to 1) distinguish dust aerosol from spherical aerosol types, 2) provide aerosol optical depths over bright desert source regions, and 3) provide high-resolution retrievals of dust plume heights and associated winds. We show examples of regional and global MISR data products in dusty regions together with quantitative evaluations of product accuracies through comparisons with independent data sources, and demonstrate applications of MISR data to dust regional and climatological studies, such as dust property evolution during transport, dust source climatology in relation to climatic factors, and dust source dynamics. The potential use of MISR radiance data to study dust properties is also discussed.
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MISR Aerosol Product Attributes and Statistical Comparisons With MODIS
IEEE Transactions on Geoscience and Remote Sensing, 2009Co-Authors: Ralph A Kahn, Michael J. Garay, David J. Diner, John V Martonchik, Michael A Bull, David L Nelson, Robert C. Levy, Susan R. Paradise, Earl G. Hansen, Lorraine A. RemerAbstract:In this paper, Multi-angle Imaging SpectroRadiometer (MISR) aerosol product attributes are described, including geometry and algorithm performance flags. Actual retrieval coverage is mapped and explained in detail using representative global monthly data. Statistical comparisons are made with coincident aerosol optical depth (AOD) and Angstrom exponent (ANG) retrieval results from the Moderate Resolution Imaging Spectroradiometer (MODIS) instrument. The relationship between these results and the ones previously obtained for MISR and MODIS individually, based on comparisons with coincident ground-truth observations, is established. For the data examined, MISR and MODIS each obtain successful aerosol retrievals about 15% of the time, and coincident MISR-MODIS aerosol retrievals are obtained for about 6%-7% of the total overlap region. Cloud avoidance, glint and oblique-Sun exclusions, and other algorithm physical limitations account for these results. For both MISR and MODIS, successful retrievals are obtained for over 75% of locations where attempts are made. Where coincident AOD retrievals are obtained over ocean, the MISR-MODIS correlation coefficient is about 0.9; over land, the correlation coefficient is about 0.7. Differences are traced to specific known algorithm issues or conditions. Over-ocean ANG comparisons yield a correlation of 0.67, showing consistency in distinguishing aerosol air masses dominated by coarse-mode versus fine-mode particles. Sampling considerations imply that care must be taken when assessing monthly global aerosol direct radiative forcing and AOD trends with these products, but they can be used directly for many other applications, such as regional AOD gradient and aerosol air mass type mapping and aerosol transport model validation. Users are urged to take seriously the published product data-quality statements.
Michael J. Garay - One of the best experts on this subject based on the ideXlab platform.
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Improving MISR AOD Retrievals With Low-Light-Level Corrections for Veiling Light
IEEE Transactions on Geoscience and Remote Sensing, 2018Co-Authors: Marcin L Witek, Michael J. Garay, David J. Diner, Michael A Bull, Feng Xu, Felix C. SeidelAbstract:Operational retrievals of aerosol optical depth (AOD) from Multi-angle Imaging SpectroRadiometer (MISR) data have been shown to have a high bias in pristine oceanic areas. One line of evidence involves comparison with Maritime Aerosol Network (MAN) observations, including the areas of low aerosol loading close to Antarctica. In this paper, a principal reason for the AOD overestimation is identified, which is stray light measured by the MISR cameras in dark regions of high-contrast scenes. A small fraction of the light from surrounding bright areas, such as clouds or sea ice, is redistributed to dark areas, artificially increasing their brightness. Internal reflections and light scattering from optical elements in MISR's pushbroom cameras contribute to this veiling light effect. A simple correction model is developed that relies on the average scene brightness and an empirically determined set of veiling light coefficients for each MISR camera and wavelength. Several independent methods are employed to determine these coefficients. Three sets of coefficients are further implemented and tested in prototype MISR 4.4-km AOD retrievals. The results show dramatic improvements in retrieved AODs compared against MAN observations and the currently operational V22 MISR retrievals. For the best performing set of coefficients, the bias is reduced by 51%, from 0.039 to 0.019, the RMSE is lowered by 19%, from 0.062 to 0.050, and 84% of retrievals fall within the uncertainty envelope compared with 66% of retrievals in V22. The best performing set will be implemented operationally in the next V23 MISR AOD product release.
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development and assessment of a higher spatial resolution 4 4 km MISR aerosol optical depth product using aeronet dragon data
Atmospheric Chemistry and Physics, 2017Co-Authors: Michael J. Garay, Olga V. Kalashnikova, Michael A BullAbstract:Abstract. Since early 2000, the Multi-angle Imaging SpectroRadiometer (MISR) instrument on NASA's Terra satellite has been acquiring data that have been used to produce aerosol optical depth (AOD) and particle property retrievals at 17.6 km spatial resolution. Capitalizing on the capabilities provided by multi-angle viewing, the current operational (Version 22) MISR algorithm performs well, with about 75 % of MISR AOD retrievals globally falling within 0.05 or 20 % × AOD of paired validation data from the ground-based Aerosol Robotic Network (AERONET). This paper describes the development and assessment of a prototype version of a higher-spatial-resolution 4.4 km MISR aerosol optical depth product compared against multiple AERONET Distributed Regional Aerosol Gridded Observations Network (DRAGON) deployments around the globe. In comparisons with AERONET-DRAGON AODs, the 4.4 km resolution retrievals show improved correlation (r = 0. 9595), smaller RMSE (0.0768), reduced bias (−0.0208), and a larger fraction within the expected error envelope (80.92 %) relative to the Version 22 MISR retrievals.
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assessment of MISR cloud motion vectors cmvs relative to goes and modis atmospheric motion vectors amvs
Journal of Applied Meteorology and Climatology, 2017Co-Authors: Kevin J. Mueller, Janpeter Muller, Michael J. Garay, David J. Diner, Catherine Moroney, Veljko M. Jovanovic, Larry Di Girolamo, Dong L Wu, Akos Horvath, Steve WanzongAbstract:AbstractCloud motion vector (CMV) winds retrieved from the Multiangle Imaging SpectroRadiometer (MISR) instrument on the polar-orbiting Terra satellite from 2003 to 2008 are compared with collocated atmospheric motion vectors (AMVs) retrieved from Geostationary Operational Environmental Satellite (GOES) imagery over the tropics and midlatitudes and from Moderate Resolution Imaging Spectroradiometer (MODIS) imagery near the poles. MISR imagery from multiple view angles is exploited to jointly retrieve stereoscopic cloud heights and motions, showing advantages over the AMV heights assigned by radiometric means, particularly at low heights (<3 km) that account for over 95% of MISR CMV sampling. MISR–GOES wind differences exhibit a standard deviation ranging with increasing height from 3.3 to 4.5 m s−1 for a high-quality [quality indicator (QI) ≥ 80] subset where height differences are <1.5 km. Much of the observed difference can be attributed to the less accurately retrieved component of CMV motion along the...
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climatology of the aerosol optical depth by components from the multi angle imaging spectroradiometer MISR and chemistry transport models
Atmospheric Chemistry and Physics, 2016Co-Authors: Olga V. Kalashnikova, A. Braverman, Michael J. Garay, Kentaroh Suzuki, Ralph A KahnAbstract:Abstract. The Multi-angle Imaging SpectroRadiometer (MISR) Joint Aerosol (JOINT_AS) Level 3 product has provided a global, descriptive summary of MISR Level 2 aerosol optical depth (AOD) and aerosol type information for each month over 16+ years since March 2000. Using Version 1 of JOINT_AS, which is based on the operational (Version 22) MISR Level 2 aerosol product, this study analyzes, for the first time, characteristics of observed and simulated distributions of AOD for three broad classes of aerosols: spherical nonabsorbing, spherical absorbing, and nonspherical – near or downwind of their major source regions. The statistical moments (means, standard deviations, and skewnesses) and distributions of AOD by components derived from the JOINT_AS are compared with results from two chemistry transport models (CTMs), the Goddard Chemistry Aerosol Radiation and Transport (GOCART) and SPectral RadIatioN-TrAnSport (SPRINTARS). Overall, the AOD distributions retrieved from MISR and modeled by GOCART and SPRINTARS agree with each other in a qualitative sense. Marginal distributions of AOD for each aerosol type in both MISR and models show considerable high positive skewness, which indicates the importance of including extreme AOD events when comparing satellite retrievals with models. The MISR JOINT_AS product will greatly facilitate comparisons between satellite observations and model simulations of aerosols by type.
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aerosol optical depths over oceans a view from MISR retrievals and collocated man and aeronet in situ observations
Journal of Geophysical Research, 2013Co-Authors: Marcin L Witek, Michael J. Garay, David J. Diner, A. SmirnovAbstract:[1] In this study, aerosol optical depths over oceans are analyzed from satellite and surface perspectives. Multiangle Imaging SpectroRadiometer (MISR) aerosol retrievals are investigated and validated primarily against Maritime Aerosol Network (MAN) observations. Furthermore, AErosol RObotic NETwork (AERONET) data from 19 island and coastal sites is incorporated in this study. The 270 MISR/MAN comparison points scattered across all oceans were identified. MISR on average overestimates aerosol optical depths (AODs) by 0.04 as compared to MAN; the correlation coefficient and root-mean-square error are 0.95 and 0.06, respectively. A new screening procedure based on retrieval region characterization is proposed, which is capable of substantially reducing MISR retrieval biases. Over 1000 additional MISR/AERONET comparison points are added to the analysis to confirm the validity of the method. The bias reduction is effective within all AOD ranges. Setting a clear flag fraction threshold to 0.6 reduces the bias to below 0.02, which is close to a typical ground-based measurement uncertainty. Twelve years of MISR data are analyzed with the new screening procedure. The average over ocean AOD is reduced by 0.03, from 0.15 to 0.12. The largest AOD decrease is observed in high latitudes of both hemispheres, regions with climatologically high cloud cover. It is postulated that the screening procedure eliminates spurious retrieval errors associated with cloud contamination and cloud adjacency effects. The proposed filtering method can be used for validating aerosol and chemical transport models.
J.v. Martonchik - One of the best experts on this subject based on the ideXlab platform.
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MISR Dark Water aerosol retrievals: operational algorithm sensitivity to particle non-sphericity
Atmospheric Measurement Techniques Discussions, 2013Co-Authors: O. V. Kalashnikova, J.v. Martonchik, M. J. Garay, D. J. DinerAbstract:Abstract. The aim of this study is to theoretically investigate the sensitivity of the Multi-angle Imaging SpectroRadiometer (MISR) operational (Version 22) Dark Water retrieval algorithm to aerosol non-sphericity over the global oceans under actual observing conditions, accounting for current algorithm assumptions. Non-spherical (dust) aerosol models, which were introduced in Version 16 of the MISR aerosol product, improved the quality and coverage of retrievals in dusty regions. Due to the sensitivity of the retrieval to the presence of non-spherical aerosols, the MISR aerosol product has been successfully used to track the location and evolution of mineral dust plumes from the Sahara across the Atlantic, for example. However, the MISR global non-spherical aerosol optical depth (AOD) fraction product has been found to have several climatological artifacts superimposed on valid detections of mineral dust, including high non-spherical fraction in the Southern Ocean and seasonally variable bands of high non-sphericity. In this paper we introduce a formal approach to examine the ability of the operational MISR Dark Water algorithm to distinguish among various spherical and non-spherical particles as a function of the variable MISR viewing geometry. We demonstrate that under the criteria currently implemented: (1) Dark Water retrieval sensitivity to particle non-sphericity decreases for AOD below about 0.1 primarily due to an unnecessarily large lower bound imposed on the uncertainty in MISR observations at low light levels, and improves when this lower bound is removed; (2) Dark Water retrievals are able to distinguish between the spherical and non-spherical particles currently used for all MISR viewing geometries when the AOD exceeds 0.1; (3) the sensitivity of the MISR retrievals to aerosol non-sphericity varies in a complex way that depends on the sampling of the scattering phase function and the contribution from multiple scattering; and (4) non-sphericity artifacts occur at those view-illumination geometries where dust aerosols are indistinguishable from certain types of cirrus particles. Based on these results, we suggest that interested parties use caution with the Version 22 MISR Dark Water aerosol non-sphericity product in situations where cirrus may be present.
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Sua pan surface bidirectional reflectance: a case study to evaluate the effect of atmospheric correction on the surface products of the multi-angle imaging SpectroRadiometer (MISR) during SAFARI 2000
IEEE Transactions on Geoscience and Remote Sensing, 2006Co-Authors: Wedad A. Abdou, D. J. Diner, J.e. Conel, S.h. Pilorz, J.v. Martonchik, M.c. Helmlinger, C.j. Bruegge, Charles K. Gatebe, Michael D. King, P.v. HobbsAbstract:This paper presents a validation case study of Multi-angle Imaging SpectroRadiometer (MISR) surface products where its bidirectional reflectance (BRF) measurements during the Southern Africa Regional Science Initiative (SAFARI 2000) campaign are compared with those coincidently evaluated on the ground and from the air, using the Portable Apparatus for Rapid Acquisition of Bidirectional Observations of Land and Atmosphere (PARABOLA) and Cloud Absorption Radiometer observations, respectively. The presence of haze and smoke during the campaign provided a case study to evaluate the effect of atmospheric correction on MISR surface products. Two surface types were considered in the analyses: the bright desert-like surface of the Pan and the dark grassland that surrounds it. The results show that for the dark surface the BRF values retrieved from MISR are in good agreement, within 5%, with those obtained from field data. For the bright desert-like pan surface, better agreement, within ~10%, was found in all channels on the clear day but only in the forward scattering on the hazy day. A comparison of MISR aerosol retrievals to those obtained from three independent ground measurements suggests that, in the presence of a highly reflective surface, small uncertainties in the MISR aerosol retrievals become magnified at larger optical depths, causing errors in the surface BRF retrievals
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Improving MODIS surface BRDF/Albedo retrieval with MISR multiangle observations
IEEE Transactions on Geoscience and Remote Sensing, 2002Co-Authors: C.b. Schaaf, Xiaowen Li, A.h. Strahler, C.j. Bruegge, J.v. MartonchikAbstract:We explore a synergistic approach to use the complementary angular samplings from the Multi-angle Imaging SpectroRadiometer (MISR) and Moderate Resolution Imaging Spectroradiometer (MODIS) to improve MODIS surface bidirectional reflectance distribution function (BRDF) and albedo retrieval. Preliminary case studies show that MODIS and MISR surface bidirectional reflectance factors (BRFs) are generally comparable in the green, red, and near infrared. An information index is introduced to characterize the information content of directional samplings, and it is found that MISR angular observations can bring additional information to the MODIS retrieval, especially when the MISR observations are close to the principal plane. We use the BRDF parameters derived from the MISR surface BRFs as a priori information and derive a posteriori estimates of surface BRDF parameters with the MODIS observations. Results show that adding MISR angular samplings can reduce the relative BRF prediction error by up to 10% in the red and green, compared to the retrievals from MODIS-only observations which are close to the cross-principal plane.
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Multi-angle Imaging SpectroRadiometer (MISR) instrument description and experiment overview
IEEE Transactions on Geoscience and Remote Sensing, 1998Co-Authors: D. J. Diner, J.e. Conel, J.v. Martonchik, C.j. Bruegge, J.c. Beckert, T.h. Reilly, R.a. Kahn, T.p. Ackerman, R. Davies, S.a.w. GerstlAbstract:The Multi-angle Imaging SpectroRadiometer (MISR) instrument is scheduled for launch aboard the first of the Earth Observing System (EOS) spacecraft, EOS-AM1. MISR will provide global, radiometrically calibrated, georectified, and spatially coregistered imagery at nine discrete viewing angles and four visible/near-infrared spectral bands. Algorithms specifically developed to capitalize on this measurement strategy will be used to retrieve geophysical products for studies of clouds, aerosols, and surface radiation. This paper provides an overview of the as-built instrument characteristics and the application of MISR to remote sensing of the Earth.
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Ground-based validation of the EOS Multi-angle Imaging SpectroRadiometer (MISR) aerosol retrieval algorithms and science data products
IGARSS'97. 1997 IEEE International Geoscience and Remote Sensing Symposium Proceedings. Remote Sensing - A Scientific Vision for Sustainable Developme, 1997Co-Authors: J.e. Conel, W.c. Ledeboer, S.h. Pilorz, J.v. Martonchik, R. Kahn, W. Abdou, C. Bruegge, M.c. Helmlinger, B.j. GaitleyAbstract:A plan for the ground-based validation of MISR aerosol retrieval is outlined. Activities occur in two phases: (1) pre-launch, work is focused on technique development and MISR algorithm validation using conventional ground-based methods and a MISR simulator (AirMISR) operating from the ER-2 aircraft to simulate MISR on-orbit observations. (2) Post-launch, the validation program relies on ground campaigns, underflights with the MISR simulator and the use of local measurements of aerosol loading and properties and irradiance measurements derived from the AERONET and ISIS networks.
