A flexible inversion algorithm for retrieval of aerosol optical properties from Sun and sky radiance measurements
27 Aug 2000-Journal of Geophysical Research (John Wiley & Sons, Ltd)-Vol. 105, Iss: 16, pp 20673-20696
TL;DR: The developed algorithm is adapted for the retrieval of aerosol properties from measurements made by ground-based Sun-sky scanning radiometers used in the Aerosol Robotic Network (AERONET) and allows a choice of normal or lognormal noise assumptions.
Abstract: The problem of deriving a complete set of aerosol optical properties from Sun and sky radiance measurements is discussed. Algorithm development is focused on improving aerosol retrievals by means of including a detailed statistical optimization of the influence of noise in the inversion procedure. The methodological aspects of such an optimization are discussed in detail and revised according to both modern findings in inversion theory and practical experience in remote sensing. Accordingly, the proposed inversion algorithm is built on the principles of statistical estimation: the spectral radiances and various a priori constraints on aerosol characteristics are considered as multisource data that are known with predetermined accuracy. The inversion is designed as a search for the best fit of all input data by a theoretical model that takes into account the different levels of accuracy of the fitted data. The algorithm allows a choice of normal or lognormal noise assumptions. The multivariable fitting is implemented by a stable numerical procedure combining matrix inversion and univariant relaxation. The theoretical inversion scheme has been realized in the advanced algorithm retrieving aerosol size distribution together with complex refractive index from the spectral measurements of direct and diffuse radiation. The aerosol particles are modeled as homogeneous spheres. The atmospheric radiative transfer modeling is implemented with well-established publicly available radiative transfer codes. The retrieved refractive indices can be wavelength dependent; however, the extended smoothness constraints are applied to its spectral dependence (and indirectly through smoothness constraints on retrieved size distributions). The positive effects of statistical optimization on the retrieval results as well as the importance of applying a priori constraints are discussed in detail for the retrieval of both aerosol size distribution and complex refractive index. The developed algorithm is adapted for the retrieval of aerosol properties from measurements made by ground-based Sun-sky scanning radiometers used in the Aerosol Robotic Network (AERONET). The results of numerical tests together with examples of experimental data inversions are presented.
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01 Oct 2007
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University of Illinois at Urbana–Champaign1, Joint Institute for the Study of the Atmosphere and Ocean2, Cooperative Institute for Research in Environmental Sciences3, University of Leeds4, University of Oslo5, United States Environmental Protection Agency6, University of Michigan7, Pacific Northwest National Laboratory8, German Aerospace Center9, United States Department of Energy10, Max Planck Society11, University of Tokyo12, National Oceanic and Atmospheric Administration13, Forschungszentrum Jülich14, Norwegian Meteorological Institute15, Indian Institute of Technology Bombay16, China Meteorological Administration17, Peking University18, Met Office19, Desert Research Institute20, Clarkson University21, Stanford University22, European Centre for Medium-Range Weather Forecasts23, International Institute of Minnesota24, Goddard Institute for Space Studies25, Yale University26, University of Washington27, University of California, Irvine28
TL;DR: In this paper, the authors provided an assessment of black-carbon climate forcing that is comprehensive in its inclusion of all known and relevant processes and that is quantitative in providing best estimates and uncertainties of the main forcing terms: direct solar absorption; influence on liquid, mixed phase, and ice clouds; and deposition on snow and ice.
Abstract: Black carbon aerosol plays a unique and important role in Earth's climate system. Black carbon is a type of carbonaceous material with a unique combination of physical properties. This assessment provides an evaluation of black-carbon climate forcing that is comprehensive in its inclusion of all known and relevant processes and that is quantitative in providing best estimates and uncertainties of the main forcing terms: direct solar absorption; influence on liquid, mixed phase, and ice clouds; and deposition on snow and ice. These effects are calculated with climate models, but when possible, they are evaluated with both microphysical measurements and field observations. Predominant sources are combustion related, namely, fossil fuels for transportation, solid fuels for industrial and residential uses, and open burning of biomass. Total global emissions of black carbon using bottom-up inventory methods are 7500 Gg yr−1 in the year 2000 with an uncertainty range of 2000 to 29000. However, global atmospheric absorption attributable to black carbon is too low in many models and should be increased by a factor of almost 3. After this scaling, the best estimate for the industrial-era (1750 to 2005) direct radiative forcing of atmospheric black carbon is +0.71 W m−2 with 90% uncertainty bounds of (+0.08, +1.27) W m−2. Total direct forcing by all black carbon sources, without subtracting the preindustrial background, is estimated as +0.88 (+0.17, +1.48) W m−2. Direct radiative forcing alone does not capture important rapid adjustment mechanisms. A framework is described and used for quantifying climate forcings, including rapid adjustments. The best estimate of industrial-era climate forcing of black carbon through all forcing mechanisms, including clouds and cryosphere forcing, is +1.1 W m−2 with 90% uncertainty bounds of +0.17 to +2.1 W m−2. Thus, there is a very high probability that black carbon emissions, independent of co-emitted species, have a positive forcing and warm the climate. We estimate that black carbon, with a total climate forcing of +1.1 W m−2, is the second most important human emission in terms of its climate forcing in the present-day atmosphere; only carbon dioxide is estimated to have a greater forcing. Sources that emit black carbon also emit other short-lived species that may either cool or warm climate. Climate forcings from co-emitted species are estimated and used in the framework described herein. When the principal effects of short-lived co-emissions, including cooling agents such as sulfur dioxide, are included in net forcing, energy-related sources (fossil fuel and biofuel) have an industrial-era climate forcing of +0.22 (−0.50 to +1.08) W m−2 during the first year after emission. For a few of these sources, such as diesel engines and possibly residential biofuels, warming is strong enough that eliminating all short-lived emissions from these sources would reduce net climate forcing (i.e., produce cooling). When open burning emissions, which emit high levels of organic matter, are included in the total, the best estimate of net industrial-era climate forcing by all short-lived species from black-carbon-rich sources becomes slightly negative (−0.06 W m−2 with 90% uncertainty bounds of −1.45 to +1.29 W m−2). The uncertainties in net climate forcing from black-carbon-rich sources are substantial, largely due to lack of knowledge about cloud interactions with both black carbon and co-emitted organic carbon. In prioritizing potential black-carbon mitigation actions, non-science factors, such as technical feasibility, costs, policy design, and implementation feasibility play important roles. The major sources of black carbon are presently in different stages with regard to the feasibility for near-term mitigation. This assessment, by evaluating the large number and complexity of the associated physical and radiative processes in black-carbon climate forcing, sets a baseline from which to improve future climate forcing estimates.
4,591 citations
Cites background from "A flexible inversion algorithm for ..."
...[125] Radiative inversion methods can also infer values of refractive indices from remote-sensing measurements [Dubovik and King, 2000], but only for the entire mixed aerosol, which includes water and many other constituents other than BC....
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...These instruments use informationmeasured at multiple wavelengths and multiple angles by sun- and sky-photometers [Dubovik and King, 2000]....
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TL;DR: In this paper, the AERONET network of ground-based radiometers were used to remotely sense the aerosol absorption and other optical properties in several key locations, and the results showed robust differentiation in both the magnitude and spectral dependence of the absorption, a property driving aerosol climate forcing.
Abstract: Aerosol radiative forcing is a critical, though variable and uncertain, component of the global climate. Yet climate models rely on sparse information of the aerosol optical properties. In situ measurements, though important in many respects, seldom provide measurements of the undisturbed aerosol in the entire atmospheric column. Here, 8 yr of worldwide distributed data from the AERONET network of ground-based radiometers were used to remotely sense the aerosol absorption and other optical properties in several key locations. Established procedures for maintaining and calibrating the global network of radiometers, cloud screening, and inversion techniques allow for a consistent retrieval of the optical properties of aerosol in locations with varying emission sources and conditions. The multiyear, multi-instrument observations show robust differentiation in both the magnitude and spectral dependence of the absorption—a property driving aerosol climate forcing, for desert dust, biomass burning, urban‐industrial, and marine aerosols. Moreover, significant variability of the absorption for the same aerosol type appearing due to different meteorological and source characteristics as well as different emission characteristics are observed. It is expected that this aerosol characterization will help refine aerosol optical models and reduce uncertainties in satellite observations of the global aerosol and in modeling aerosol impacts on climate.
2,653 citations
Cites background or methods from "A flexible inversion algorithm for ..."
...Comparison of retrievals from all of these techniques with the addition of the Kaashidho Climate Observatory (KCO) AERONET (‘‘KCO-AERONET’’) retrieval (Dubovik and King 2000) was presented by Ramanathan et al. (2001). The v0 values estimated for 530 nm obtained by these diverse methods for the Maldives–INDOEX region ranged from ;0.86 to 0.90 for column averages. These values show good agreement, within the uncertainty levels of the AERONET and in situ retrievals (for a more detailed discussion see R01 and Eck et al. 2001b). Unfortunately, there have not yet been any reported retrievals or measurements of v0 for the Paris region. Nevertheless, the existing aerosol chemical measurements (Rueallan and Cashier 2001; Liousse and Cashier 1992) near surface indicate high concentrations of black carbon in the Paris aerosol. The observed wide variability of v0 for the urban locations probably can be explained by differences in fuel types, emission conditions, long-range transport and environmental and meteorological conditions. Automobile traffic around GSFC is the strongest local source of pollution, while pollution transported long distances from the Gulf of Mexico, Tennessee and Ohio valleys, etc. is also present. The mixed aerosols observed over the Maldives (INDOEX) are produced primarily as a result of anthropogenic combustion processes mainly from the use of fossil fuels (Novakov et al. 2000) with some biomass fuels and also various industrial processes. The large number of diesel vehicle and two-stroke engines is also a significant factor in aerosol formation in the Indian subcontinent (Satheesh et al. 1999). Correspondingly, the relatively strong absorption properties of the aerosols observed in the Maldives (INDOEX) is due to the presence of soot primarily from fossil fuel combustion and biomass burning, which Satheesh et al. (1999) have determined contributes ;11% to the midvisible aerosol optical depth [taer(500)]....
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...Comparison of retrievals from all of these techniques with the addition of the Kaashidho Climate Observatory (KCO) AERONET (‘‘KCO-AERONET’’) retrieval (Dubovik and King 2000) was presented by Ramanathan et al....
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...The new AERONET inversion algorithm (Dubovik and King 2000) provides improved aerosol retrievals by fitting the entire measured field of radiances—sun radiance and the angular distribution of sky radiances—at four wavelengths (0....
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...Only spectral and size smoothness constraints are used, preventing unrealistic oscillations in either parameter (Dubovik and King 2000). a. Accuracy assessment of individual retrievals The accuracy of individual retrievals was analyzed by extensive sensitivity simulations (Dubovik et al. 2000),…...
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...Comparison of retrievals from all of these techniques with the addition of the Kaashidho Climate Observatory (KCO) AERONET (‘‘KCO-AERONET’’) retrieval (Dubovik and King 2000) was presented by Ramanathan et al. (2001). The v0 values estimated for 530 nm obtained by these diverse methods for the Maldives–INDOEX region ranged from ;0....
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TL;DR: Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) is a two-wavelength polarization lidar that performs global profiling of aerosols and clouds in the troposphere and lower stratosphere as discussed by the authors.
Abstract: The Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) is a two-wavelength polarization lidar that performs global profiling of aerosols and clouds in the troposphere and lower stratosphere. CALIOP is the primary instrument on the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) satellite, which has flown in formation with the NASA A-train constellation of satellites since May 2006. The global, multiyear dataset obtained from CALIOP provides a new view of the earth’s atmosphere and will lead to an improved understanding of the role of aerosols and clouds in the climate system. A suite of algorithms has been developed to identify aerosol and cloud layers and to retrieve a variety of optical and microphysical properties. CALIOP represents a significant advance over previous space lidars, and the algorithms that have been developed have many innovative aspects to take advantage of its capabilities. This paper provides a brief overview of the CALIPSO mission, the CA...
1,833 citations
Cites methods from "A flexible inversion algorithm for ..."
...Aerosol types were defined by performing a cluster analysis of aerosol parameters retrieved from the Aerosol Robotic Network (AERONET) sun-photometer network (Dubovik and King 2000)....
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TL;DR: In this paper, the spectral variation of α is typically not considered in the analysis and comparison of values from different techniques, and the spectral measurements of τ a from 340 to 1020 nm obtained from ground-based Aerosol Robotic Network radiometers located in various locations where either biomass burning, urban, or desert dust aerosols are prevalent.
Abstract: The Angstrom wavelength exponent α, which is the slope of the logarithm of aerosol optical depth (τ a ) versus the logarithm of wavelength (λ), is commonly used to characterize the wavelength dependence of τ a and to provide some basic information on the aerosol size distribution. This parameter is frequently computed from the spectral measurements of both ground-based sunphotometers and from satellite and aircraft remote sensing retrievals. However, spectral variation of α is typically not considered in the analysis and comparison of values from different techniques. We analyze the spectral measurements of τ a from 340 to 1020 nm obtained from ground-based Aerosol Robotic Network radiometers located in various locations where either biomass burning, urban, or desert dust aerosols are prevalent. Aerosol size distribution retrievals obtained from combined solar extinction and sky radiance measurements are also utilized in the analysis. These data show that there is significant curvature in the In τ a versus In λ relationship for aerosol size distributions dominated by accumulation mode aerosols (biomass burning and urban). Mie theory calculations of α for biomass burning smoke (for a case of aged smoke at high optical depth) agree well with observations, confirming that large spectral variations in α are due to the dominance of accumulation mode aerosols. A second order polynomial fit to the In τ a versus In λ data provides excellent agreement with differences in τ a of the order of the uncertainty in the measurements (-0.01-0.02). The significant curvature in In τ a versus In λ for high optical depth accumulation mode dominated aerosols results in α values differing by a factor of 3-5 from 340 to 870 nm. We characterize the curvature in In τ a versus In λ by the second derivative α' and suggest that this parameter be utilized in conjunction with α to characterize the spectral dependence of τ a , The second derivative of In τ a versus In λ gives an indication of the relative influence of accumulation mode versus coarse mode particles on optical properties.
1,788 citations
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This is the revised and greatly expanded Second Edition of the hugely popular Numerical Recipes: The Art of Scientific Computing. The product of a unique collaboration among four leading scientists in academic research and industry, Numerical Recipes is a complete text and reference book on scientific computing. In a self-contained manner it proceeds from mathematical and theoretical considerations to actual practical computer routines. With over 100 new routines (now well over 300 in all), plus upgraded versions of many of the original routines, this book is more than ever the most practical, comprehensive handbook of scientific computing available today. The book retains the informal, easy-to-read style that made the first edition so popular, with many new topics presented at the same accessible level. In addition, some sections of more advanced material have been introduced, set off in small type from the main body of the text. Numerical Recipes is an ideal textbook for scientists and engineers and an indispensable reference for anyone who works in scientific computing. Highlights of the new material include a new chapter on integral equations and inverse methods; multigrid methods for solving partial differential equations; improved random number routines; wavelet transforms; the statistical bootstrap method; a new chapter on "less-numerical" algorithms including compression coding and arbitrary precision arithmetic; band diagonal linear systems; linear algebra on sparse matrices; Cholesky and QR decomposition; calculation of numerical derivatives; Pade approximants, and rational Chebyshev approximation; new special functions; Monte Carlo integration in high-dimensional spaces; globally convergent methods for sets of nonlinear equations; an expanded chapter on fast Fourier methods; spectral analysis on unevenly sampled data; Savitzky-Golay smoothing filters; and two-dimensional Kolmogorov-Smirnoff tests. All this is in addition to material on such basic top
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26 Feb 1988
TL;DR: The Diskette v 2.04, 3.5'' (720k) for IBM PC, PS/2 and compatibles [DOS] Reference Record created on 2004-09-07, modified on 2016-08-08.
Abstract: Note: Includes bibliographical references and index.- Diskette v 2.04, 3.5'' (720k) for IBM PC, PS/2 and compatibles [DOS] Reference Record created on 2004-09-07, modified on 2016-08-08
9,345 citations
"A flexible inversion algorithm for ..." refers methods in this paper
..., Press et al. [1992]) proposes a variety of standardized mathematical methods and software for minimizing quadratic forms....
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...[1970], Rodgers [1976], and others employ matrix inversion in their methods....
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...The details of this method can be found in Press et al. [1992]. In many practical situations singular value decomposition is very helpful....
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