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Kenneth J. Voss

Bio: Kenneth J. Voss is an academic researcher from University of Miami. The author has contributed to research in topics: Radiance & Ocean color. The author has an hindex of 42, co-authored 155 publications receiving 7441 citations. Previous affiliations of Kenneth J. Voss include University of Maryland, College Park & University of South Florida.


Papers
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Journal ArticleDOI
TL;DR: In this paper, the AERONET program of spectral aerosol optical depth, precipitable water, and derived Angstrom exponent were analyzed and compiled into a spectral optical properties climatology.
Abstract: Long-term measurements by the AERONET program of spectral aerosol optical depth, precipitable water, and derived Angstrom exponent were analyzed and compiled into an aerosol optical properties climatology. Quality assured monthly means are presented and described for 9 primary sites and 21 additional multiyear sites with distinct aerosol regimes representing tropical biomass burning, boreal forests, midlatitude humid climates, midlatitude dry climates, oceanic sites, desert sites, and background sites. Seasonal trends for each of these nine sites are discussed and climatic averages presented.

1,891 citations

Journal ArticleDOI
TL;DR: In this article, the authors review the roles played by various seawater constituents in light backscattering and address a question of missing backscatter in the open ocean and show that due to substantial variability in water composition, different types of constituents can explain the missing back-scatter.

394 citations

Journal ArticleDOI
04 Apr 1996-Nature
TL;DR: In this paper, the authors report measurements of the light-scattering properties of North African dust delivered to Barbados by the North Atlantic trade winds and conclude that African mineral dust should be the dominant lightscattering aerosol throughout the tropical and subtropical North Atlantic region.
Abstract: ATMOSPHERIC aerosols can affect climate by scattering and absorbing solar radiation1–3. Most recent studies of such effects have focused largely on anthropogenic sulphate aerosols, which are believed to exert a substantial cooling influence2. Mineral dust aerosols have been largely ignored, because it was thought that their scattering efficiency and concentrations were too low to have a substantial effect on climate. Here we report measurements of the light-scattering properties of North African dust delivered to Barbados by the North Atlantic trade winds. Although the mass scattering efficiency of the dust is only about a quarter of that of non-seasalt sulphate over the North Atlantic5, the annual-mean dust concentration in Barbados trade-wind air is 16 times that of non-seasalt sulphate6. The net scattering by mineral dust is therefore about four times that by non-seasalt sulphate aerosols. African mineral dust should therefore be the dominant light-scattering aerosol throughout the tropical and subtropical North Atlantic region. Our observations suggest that mineral dust could be an important climate-forcing agent over this ocean region and in other regions where dust concentrations are high7,8.

347 citations

Journal ArticleDOI
TL;DR: Haugen et al. as discussed by the authors studied two coccolithophore blooms in the Gulf of Maine in 1988 and 1989 and found that coccoliths contributed approximately 75% of the backscattering signal and 50% of beam attenuation signal.
Abstract: Two coccolithophore blooms in the Gulf of Maine were studied in 1988 and 1989. Each bloom was about 50,000 km* in area and confined to the top 20 m of the water column. Maximal cell concentrations were -2,000 cells ml-* and coccolith densities of 3 x lo5 ml-’ were observed. The coccolith : cell ratio was highest in the bloom center (region of most intense reflectance) and lowest at the bloom periphery, an indication of varying organic vs. inorganic C production. Chlorophyll concentrations were generally low within the bloom and no relation could be observed between major nutrients and coccolithophore abundance. Backscattered light was profoundly affected by coccolith density and was slightly wavelength-dependent. We calculated total backscattering as well as backscattering (bh) caused exclusively by coccoliths and derived the algorithm relating coccolith density to backscattering. Although cells were efficient light absorbers, coccoliths showed negligible light absorption. Diffuse attenuation was lowest in the green and blue-green part of the visible spectrum. At the center of the bloom, coccoliths contributed ~75% of the backscattering signal and > 50% of the beam attenuation signal. The most accurate way to estimate coccolith concentrations via remote sensing is to measure water-leaving radiance in the green wavebands. The coccolithophore Emiliania huxleyi (Lohm) Hay et al. Mohler (class Prymnesiophyceae) is thought to be the most abunI Present address: Lockheed Engineering and Sciences, P.O. Box 58561, Houston, Texas 77258. Acknowledgments Many thanks to Capt. Donald Bradford and the crew of the RV Argo Maine for ship handling and help with sampling. Shiptime for leg 1 of the 1988 cruise was provided by Charles S. Yentsch. Howard Gordon provided the light scattering photometer as well as the software for calculating total backscattering. Robert Evans and Jody Splain arranged for the transfer of AVHRR data from Miami to Bigelow Lab. Janet Campbell and Thor Aarup analyzed the satellite data during the cruise and relayed the information to the ship. Stephen Groom calculated the visible band reflectance from the AVHRR data. Jeffrey Brown, Tracy Skinner, and Albert Chapin were instrumental in completing many measurements at sea and in the laboratory. Dave Townsend coordinated the CTD measurements. Elin Haugen and R. R. L. Guillard provided an inverted microscope for the 1988 cruise. Christodant calcifying organism on earth (Westbroek et al. 1985). Of all coccolithophore species, E. huxleyi is numerically dominant and can be found from tropical to subarctic regions of the Atlantic, extending into waters with temperatures

334 citations

Journal ArticleDOI
TL;DR: In this paper, the authors developed a strategy for validation of atmospheric correction over the oceans that is focused on EOS/MODIS and provided a description of the instrumentation and methods to be used in the implementation of the plan.
Abstract: By validation of atmospheric correction, we mean quantification of the uncertainty expected to be associated with the retrieval of the water-leaving radiance from the measurement of the total radiance exiting the ocean-atmosphere system. This uncertainty includes that associated with the measurement or estimation of auxiliary data required for the retrieval process, for example, surface wind speed, surface atmospheric pressure, and total ozone concentration. For a definitive validation this quantification should be carried out over the full range of atmospheric types expected to be encountered. However, funding constraints require that the individual validation campaigns must be planned to address the individual components of the atmospheric correction algorithm believed to represent the greatest potential sources of error. In this paper we develop a strategy for validation of atmospheric correction over the oceans that is focused on EOS/MODIS. We also provide a description of the instrumentation and methods to be used in the implementation of the plan.

249 citations


Cited by
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TL;DR: The second most important contribution to anthropogenic climate warming, after carbon dioxide emissions, was made by black carbon emissions as mentioned in this paper, which is an efficient absorbing agent of solar irradiation that is preferentially emitted in the tropics and can form atmospheric brown clouds in mixture with other aerosols.
Abstract: Black carbon in soot is an efficient absorbing agent of solar irradiation that is preferentially emitted in the tropics and can form atmospheric brown clouds in mixture with other aerosols. These factors combine to make black carbon emissions the second most important contribution to anthropogenic climate warming, after carbon dioxide emissions.

3,060 citations

Journal ArticleDOI
TL;DR: In this article, the authors used the Total Ozone Mapping Spectrometer (TOMS) sensor on the Nimbus 7 satellite to map the global distribution of major atmospheric dust sources with the goal of identifying common environmental characteristics.
Abstract: [1] We use the Total Ozone Mapping Spectrometer (TOMS) sensor on the Nimbus 7 satellite to map the global distribution of major atmospheric dust sources with the goal of identifying common environmental characteristics The largest and most persistent sources are located in the Northern Hemisphere, mainly in a broad “dust belt” that extends from the west coast of North Africa, over the Middle East, Central and South Asia, to China There is remarkably little large-scale dust activity outside this region In particular, the Southern Hemisphere is devoid of major dust activity Dust sources, regardless of size or strength, can usually be associated with topographical lows located in arid regions with annual rainfall under 200–250 mm Although the source regions themselves are arid or hyperarid, the action of water is evident from the presence of ephemeral streams, rivers, lakes, and playas Most major sources have been intermittently flooded through the Quaternary as evidenced by deep alluvial deposits Many sources are associated with areas where human impacts are well documented, eg, the Caspian and Aral Seas, Tigris-Euphrates River Basin, southwestern North America, and the loess lands in China Nonetheless, the largest and most active sources are located in truly remote areas where there is little or no human activity Thus, on a global scale, dust mobilization appears to be dominated by natural sources Dust activity is extremely sensitive to many environmental parameters The identification of major sources will enable us to focus on critical regions and to characterize emission rates in response to environmental conditions With such knowledge we will be better able to improve global dust models and to assess the effects of climate change on emissions in the future It will also facilitate the interpretation of the paleoclimate record based on dust contained in ocean sediments and ice cores

2,653 citations

Journal ArticleDOI
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

Journal ArticleDOI
TL;DR: In this article, a large data set containing coincident in situ chlorophyll and remote sensing reflectance measurements was used to evaluate the accuracy, precision, and suitability of a wide variety of ocean color algorithms for use by SeaWiFS (Sea-viewing Wide Field-of-view Sensor).
Abstract: A large data set containing coincident in situ chlorophyll and remote sensing reflectance measurements was used to evaluate the accuracy, precision, and suitability of a wide variety of ocean color chlorophyll algorithms for use by SeaWiFS (Sea-viewing Wide Field-of-view Sensor). The radiance-chlorophyll data were assembled from various sources during the SeaWiFS Bio-optical Algorithm Mini-Workshop (SeaBAM) and is composed of 919 stations encompassing chlorophyll concentrations between 0.019 and 32.79 μg L−1. Most of the observations are from Case I nonpolar waters, and ∼20 observations are from more turbid coastal waters. A variety of statistical and graphical criteria were used to evaluate the performances of 2 semianalytic and 15 empirical chlorophyll/pigment algorithms subjected to the SeaBAM data. The empirical algorithms generally performed better than the semianalytic. Cubic polynomial formulations were generally superior to other kinds of equations. Empirical algorithms with increasing complexity (number of coefficients and wavebands), were calibrated to the SeaBAM data, and evaluated to illustrate the relative merits of different formulations. The ocean chlorophyll 2 algorithm (OC2), a modified cubic polynomial (MCP) function which uses Rrs490/Rrs555, well simulates the sigmoidal pattern evident between log-transformed radiance ratios and chlorophyll, and has been chosen as the at-launch SeaWiFS operational chlorophyll a algorithm. Improved performance was obtained using the ocean chlorophyll 4 algorithm (OC4), a four-band (443, 490, 510, 555 nm), maximum band ratio formulation. This maximum band ratio (MBR) is a new approach in empirical ocean color algorithms and has the potential advantage of maintaining the highest possible satellite sensor signal: noise ratio over a 3-orders-of-magnitude range in chlorophyll concentration.

2,441 citations