Reflectance and albedo differences between wet and dry surfaces

Twomey, S.; Bohren, Craig F.; Mergenthaler, J. L.

doi:10.1364/ao.25.000431

Cited by 156 publications

(94 citation statements)

References 9 publications

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“…Figure 3(a) shows the large variability in magnitude and spectral shape of surface albedo and nadir surface reflectance between 400 nm and 2,500 nm (1,700 nm for ocean albedo example) for a variety of typical surface types. For a Lambertian surface, the spectral surface reflectance and albedo are essentially equivalent [25,26] and validation studies comparing the surface reflectance retrieved from satellite measurements using a Lambertian assumption to ground-based measurements show good agreement with residual standard errors of approximately 0.02 [27]. Observational Period [19] and is the baseline surface albedo used in the forward modeling calculations of this work.…”

Section: Representation Of Error Sourcesmentioning

confidence: 99%

Characterizing a New Surface-Based Shortwave Cloud Retrieval Technique, Based on Transmitted Radiance for Soil and Vegetated Surface Types

et al. 2013

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This paper presents an approach using the GEneralized Nonlinear Retrieval Analysis (GENRA) tool and general inverse theory diagnostics including the maximum likelihood solution and the Shannon information content to investigate the performance of a new spectral technique for the retrieval of cloud optical properties from surface based transmittance measurements. The cumulative retrieval information over broad ranges in cloud optical thickness (τ), droplet effective radius (r e ), and overhead sun angles is quantified under two conditions known to impact transmitted radiation; the variability in land surface albedo and atmospheric water vapor content. Our conclusions are: (1) the retrieved cloud properties are more sensitive to the natural variability in land surface albedo than to water vapor content; (2) the new spectral technique is more accurate (but still imprecise) than a standard approach, in particular for τ between 5 and 60 and r e less than approximately 20 μm; and (3) the retrieved cloud properties are dependent on sun angle for clouds of from 5 to 10 and r e < 10 μm, with maximum sensitivity obtained for

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Section: Representation Of Error Sourcesmentioning

confidence: 99%

Characterizing a New Surface-Based Shortwave Cloud Retrieval Technique, Based on Transmitted Radiance for Soil and Vegetated Surface Types

et al. 2013

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“…[10] Most of these studies are based on laboratory experiments [Twomey et al, 1986;Lobell and Asner, 2002;Liu et al, 2002] or theoretical approach [Ishida et al, 1991;Twomey et al, 1986]. Because they are generally motivated by the fact that albedo (or surface reflectance measured in the solar spectrum) is a potential proxy for soil moisture remote sensing, the authors try to establish a relationship as general as possible by using a large number of soil types.…”

Section: Introductionmentioning

confidence: 99%

Sensitivity of bare soil albedo to surface soil moisture on the moraine of the Zongo glacier (Bolivia)

Gascoin

Ducharne

Ribstein

et al. 2009

Geophysical Research Letters

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International audienceThe dependence of bare soil albedo on soil water content is investigated using in situ data collected on the moraine of an Andean glacier (Bolivia). This study demonstrates a high negative correlation between the two variables that is best approximated by an exponential function, in agreement with previous studies. More importantly, the average snow-free albedo value during the rainy season is 40% lower than during the dry season (0.16 vs. 0.26). These results are relevant for climate and land surface modeling applications, where bare soil albedo is often considered as a constant parameter

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“…Since wetting markedly changes the reflectance of most surfaces (Twomey et al 1986), aggregates and concretes not intentionally wetted were driedaggregates on a hot plate, and concretes with a hot-air gun-prior to albedo measurement.…”

Section: Albedo Measurementsmentioning

confidence: 99%

Effects of composition and exposure on the solar reflectance of portland cement concrete

Levinson

Akbari

2002

Cement and Concrete Research

115

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Increasing the solar reflectance (albedo) of a paved surface keeps it cooler in the sun, reducing convection of heat from pavement to air and thereby decreasing the ambient air temperature. Simulations of the influence of pavement albedo on air temperature in Los Angeles predict that increasing the albedo of 1,250 km 2 of pavement by 0.25 would save cooling energy worth $15M yr -1 , and reduce smog-related medical and lost-work expenses by $76M yr -1 . Most sidewalks and a small fraction of roads and parking areas are paved with portland cement concrete, which can be made quite reflective through suitable choice of cement and aggregate. Variations with composition and environmental exposure of the albedos of portland cement concrete pavements were investigated through laboratory fabrication and exposure of 32 mixes of concrete.Twenty-four mixes yielded substandard, "rough" concretes due to high, unmet aggregate water demand. The albedos of the remaining eight "smooth" concrete mixes ranged from 0.41 to 0.77 (mean 0.59). Simulated weathering, soiling, and abrasion each reduced average concrete albedo (mean decreases 0.06, 0.05, and 0.19, respectively), though some samples became slightly more reflective through weathering or soiling. Simulated rain (wetting) strongly depressed the albedos of concretes (mean decrease 0.23) until their surfaces were dried. Concrete albedo grew as the cement hydration reaction progressed (mean increase 0.08), but stabilized within six weeks of casting.White-cement concretes were on average significantly more reflective than gray-cement concretes. The albedo of the most-reflective white-cement concrete was 0.18 to 0.39 higher than that of the most-reflective gray-cement concrete, depending on state of exposure. Concrete albedo generally correlated with cement albedo and sand albedo, and, after abrasion, with rock albedo. Cement albedo had a disproportionately strong influence on the reflectance of concrete. Efflorescence and surface carbonation whitened some gray-cement mixes.

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Reflectance and albedo differences between wet and dry surfaces

Cited by 156 publications

References 9 publications

Characterizing a New Surface-Based Shortwave Cloud Retrieval Technique, Based on Transmitted Radiance for Soil and Vegetated Surface Types

Characterizing a New Surface-Based Shortwave Cloud Retrieval Technique, Based on Transmitted Radiance for Soil and Vegetated Surface Types

Sensitivity of bare soil albedo to surface soil moisture on the moraine of the Zongo glacier (Bolivia)

Effects of composition and exposure on the solar reflectance of portland cement concrete

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