A Note on the Albedo of Surfaces

Nkemdirim, Lawrence C.

doi:10.1175/1520-0450(1972)011<0867:anotao>2.0.co;2

Cited by 65 publications

(33 citation statements)

References 7 publications

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“…Albedo was typically larger at dawn and dusk (when solar zenith angle is high) with a minimum value at solar noon (minimum zenith angle), a pattern of variation commonly observed for a wide range of land cover types (Stewart 1971;Nkemdirim 1972;Oguntoyinbo 1974;Pinker et al 1980, Allen et al 1994; all cited in Allen et al 1994).…”

Section: Reflection Coefficients (Albedo) (A) and Emissivities (E)mentioning

confidence: 99%

Measuring and modelling the radiation balance of a heterogeneous shrubland

Domingo

Villagarcı́a

Brenner

et al. 2000

Plant Cell & Environment

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These cycles were larger in the bare soil than in the substrate under shrubs.Key-words: Retama sphaerocarpa; sparse vegetation; semi-arid. INTRODUCTIONSemi-arid environments are commonly characterized by isolated clumps of shrubs and perennial grasses that form vegetated patches on predominantly open areas of bare soil or ephemeral annual plants. Such land surfaces possess distinctive micrometeorological properties that require a formulation of the energy balance that does not assume horizontal uniformity to correctly simulate their surface fluxes (Friedl 1995). The accurate quantification of the energy absorbed by each component of the system is important in predicting plant or soil evaporation and temperature. This in turn enables an improved understanding of how semi-arid vegetation responds to changes in climate and management. It is proposed here that radiation can be partitioned among components of sparsely vegetated surfaces using a simple model to account for heterogeneity in surface properties.It is known that the emissive and shortwave reflective characteristics of plants and soils differ, and that these differences change total surface energy balances and the energy balances of each individual component within a system. Many models have been developed to predict radiation absorption for continuous canopies (see reviews by Norman 1979;Ross 1981). Fewer have been developed to predict radiation interception by either individual plants in a stand (Grace, Jarvis & Norman 1987;Wang & Jarvis 1990) or by single, isolated plants (Charles-Edwards & Thornley 1973;Thorpe et al. 1978;Fristschen, Walker & Hsia 1980). Experimental methods have been developed to measure the radiation balance of individual plants ( Van Elsacker, Keppens & Impens 1983;MacNaughton et al. 1992;Green 1993) aiding the validation of these models. Although physically rigorous, these models have the disadvantage of requiring a large number of parameters to describe canopy architecture and light transmission, most of which are rarely available.The aim of this study was to evaluate the accuracy of a simple energy partitioning model for sparse vegetation ABSTRACTThe accurate quantification of the energy available for sensible and latent heat transfer from plant canopies is essential for the prediction of impacts of climate on vegetation water use and growth. Unlike agricultural fields and extensive forests of more humid zones, vegetation growing in semi-arid climates is usually sparse creating a heterogeneous surface of shrubs, annuals and bare soil. Under these conditions many of the assumptions of the basic equations used in microclimatology, which assume a uniform vegetated surface, may be violated. It is proposed here that heterogeneous canopies may require a formulation of their energy balance that includes a measure of the canopy complexity in order to both interpret field measurements and be used in predictive models. This paper explores the need for a more complex formulation of the vegetation energy balance through a series of experime...

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Section: Reflection Coefficients (Albedo) (A) and Emissivities (E)mentioning

confidence: 99%

Measuring and modelling the radiation balance of a heterogeneous shrubland

Domingo

Villagarcı́a

Brenner

et al. 2000

Plant Cell & Environment

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“…It cannot be simply measured but rather must be estimated on the basis of the slope of (4). Other works [e.g., Federer, 1968;Rosenberg, 1969;Nkemdirium, 1972Nkemdirium, , 1973 Subsequent works, such as Nielsen et al [1981], have attempted to improve upon this regression technique by dividing their data by cloud cover. For each category of cloud cover, a separate regression was developed.…”

mentioning

confidence: 99%

Estimation of surface net radiation in the boreal forest and northern prairie from shortwave flux measurements

Kaminsky¹,

Dubayah²

1997

J. Geophys. Res.

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“…Albedo has commonly been reported to vary inversely with solar elevation on clear days (Barkstrom, 1972;Hubley, 1955;Langleben, 1968;Nkemdirim 1972). This daily cycle for snow may be caused by the variation in the specular reflection component with sun angle, snow metamorphism during the day or instrumental error, particularly a deviation of the pyranometer response from the cosine law (Dirmhirn and Eaton, 1975).…”

Section: Resultsmentioning

confidence: 88%