Albedo of a water surface, spectral variation, effects of atmospheric transmittance, sun angle and wind speed

Katsaros, Kristina B.; McMurdie, Lynn A.; Lind, Richard J.; DeVault, John E.

doi:10.1029/jc090ic04p07313

Cited by 48 publications

(30 citation statements)

References 17 publications

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“…The value is 0.07, independent of wavelength, as expected for diffuse incident radiation on water with a refractive index of 1.33, and in agreement with measurements by others (Katsaros et al 1985;Kondratyev 1969;Payne 1972;Briegleb and Ramanathan 1982;Pegau and Paulson 2001).…”

Section: Spectral Albedo Measurementssupporting

confidence: 90%

Surface Albedo of the Antarctic Sea Ice Zone

et al. 2005

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In three ship-based field experiments, spectral albedos were measured at ultraviolet, visible, and nearinfrared wavelengths for open water, grease ice, nilas, young "grey" ice, young grey-white ice, and first-year ice, both with and without snow cover. From the spectral measurements, broadband albedos are computed for clear and cloudy sky, for the total solar spectrum as well as for visible and near-infrared bands used in climate models, and for Advanced Very High Resolution Radiometer (AVHRR) solar channels. The all-wave albedos vary from 0.07 for open water to 0.87 for thick snow-covered ice under cloud. The frequency distribution of ice types and snow coverage in all seasons is available from the project on Antarctic Sea Ice Processes and Climate (ASPeCt). The ASPeCt dataset contains routine hourly visual observations of sea ice from research and supply ships of several nations using a standard protocol. Ten thousand of these observations, separated by a minimum of 6 nautical miles along voyage tracks, are used together with the measured albedos for each ice type to assign an albedo to each visual observation, resulting in "ice-only" albedos as a function of latitude for each of five longitudinal sectors around Antarctica, for each of the four seasons. These ice albedos are combined with 13 yr of ice concentration estimates from satellite passive microwave measurements to obtain the geographical and seasonal variation of average surface albedo. Most of the Antarctic sea ice is snow covered, even in summer, so the main determinant of area-averaged albedo is the fraction of open water within the pack.

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Section: Spectral Albedo Measurementssupporting

confidence: 90%

Surface Albedo of the Antarctic Sea Ice Zone

et al. 2005

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“…Local variation of open water albedo can be due to several factors, including water turbidity, reflection from lake and pond bottom [70], and roughness of the water surface [71]. The solar elevation angle (SEA), i.e., the incidence of the direct radiation, however, exerts the strongest influence [72,73].…”

Section: Albedo As An Estimator Of Subpixel Water Covermentioning

confidence: 99%

“…The solar elevation angle (SEA), i.e., the incidence of the direct radiation, however, exerts the strongest influence [72,73]. Low SEAs lead to larger albedos [60,70,74], which possibly explains the larger open water albedo for PBP. SEA is lowest at PBP with 23.5…”

Section: Albedo As An Estimator Of Subpixel Water Covermentioning

confidence: 99%

Water Body Distributions Across Scales: A Remote Sensing Based Comparison of Three Arctic Tundra Wetlands

et al. 2013

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Water bodies are ubiquitous features in Arctic wetlands. Ponds, i.e., waters with a surface area smaller than 10 4 m 2 , have been recognized as hotspots of biological activity and greenhouse gas emissions but are not well inventoried. This study aimed to identify common characteristics of three Arctic wetlands including water body size and abundance for different spatial resolutions, and the potential of Landsat-5 TM satellite data to show the subpixel fraction of water cover (SWC) via the surface albedo. Water bodies were mapped using optical and radar satellite data with resolutions of 4 m or better, Landsat-5 TM at 30 m and the MODIS water mask (MOD44W) at 250 m resolution. Study sites showed similar properties regarding water body distributions and scaling issues. Abundance-size distributions showed a curved pattern on a log-log scale with a flattened lower tail and an upper tail that appeared Paretian. Ponds represented 95% of the total water body number. Total number of water bodies decreased with coarser spatial resolutions. However, clusters of small water bodies were merged into single larger water bodies leading to local overestimation of water surface area. To assess the uncertainty of coarse-scale products, both surface water fraction and the water body size distribution should therefore be considered. Using Landsat surface albedo to estimate SWC across different terrain types including polygonal terrain and drained thermokarst basins proved to be a robust approach. However, the albedo-SWC relationship is site specific and needs to be tested in other Arctic regions. These findings present a baseline to better represent small water bodies of Arctic wet tundra environments in regional as well as global ecosystem and climate models.

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“…The cloud index is defined as the difference between the clear sky (modeled) and the measured solar irradiance divided by the clear-sky irradiance. The solar transmission parameterization also directly accounts for effects of the ocean surface albedo, which varies with cloud cover and sun angle (Katsaros et al 1985).…”

Section: Implementation Of the New Solar Transmission Parameterizationmentioning

confidence: 99%

Improved Oceanic Cool-Skin Corrections Using a Refined Solar Penetration Model

Wick¹,

Ohlmann

Fairall³

et al. 2005

Journal of Physical Oceanography

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The oceanic near-surface temperature profile must be accurately characterized to enable precise determination of air-sea heat exchange and satellite retrievals of sea surface temperature. An improved solar transmission parameterization is integrated into existing models for the oceanic warm layer and cool skin within the Tropical Ocean and Global Atmosphere Coupled Ocean-Atmosphere Response Experiment (TOGA COARE) bulk flux model to improve the accuracy of predictions of the temperature profile and corresponding heat flux components. Application of the revised bulk flux model to data from 12 diverse cruises demonstrates that the improved parameterization results in significant changes to the predicted cool-skin effect and latent heat fluxes at low wind speeds with high solar radiation due to reduced absorption of solar radiation just below the surface. Daytime skin-layer cooling is predicted to increase by 0.03 K on average but by more than 0.25 K for winds below 1 m s Ϫ1 and surface irradiance exceeding 900 W m Ϫ2 . Predicted changes to the warm-layer correction were smaller but exceeded 0.1 K below 1 m s Ϫ1 . Average latent and sensible heat fluxes changed by 1 W m Ϫ2 , but the latent flux decreased by 5 W m Ϫ2 near winds of 0.5 m s Ϫ1 and surface irradiance of 950 W m Ϫ2 . Comparison with direct observations of skin-layer cooling demonstrated, in particular, that use of the improved solar transmission model resulted in the reduction of previous systematic overestimates of diurnal skin-layer warming. Similar results can be achieved using a simplified treatment of solar absorption with an appropriate estimate of the fraction of incident solar radiation absorbed within the skin layer.

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Albedo of a water surface, spectral variation, effects of atmospheric transmittance, sun angle and wind speed

Cited by 48 publications

References 17 publications

Surface Albedo of the Antarctic Sea Ice Zone

Surface Albedo of the Antarctic Sea Ice Zone

Water Body Distributions Across Scales: A Remote Sensing Based Comparison of Three Arctic Tundra Wetlands

Improved Oceanic Cool-Skin Corrections Using a Refined Solar Penetration Model

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