Radiative transfer in shrub savanna sites in Niger: preliminary results from HAPEX-Sahel. 1. Modelling surface reflectance using a geometric-optical approach

Janet Franklin, Jeff Duncan, Alfredo R. Huete, Willem van Leeuwen, Xiaowen Li, Agnès Bégué

Research output: Contribution to journalArticle

5 Citations (Scopus)

Abstract

To use optical remote sensing to monitor land surface-climate interactions over large areas, algorithms must be developed to relate multispectral measurements to key variables controlling the exchange of matter (water, carbon dioxide) and energy between the land surface and the atmosphere. The proportion of the ground covered by vegetation and the interception of photosynthetically active radiation (PAR) by vegetation are examples of two variables related to evapotranspiration and primary production, respectively. An areal-proportion model of the multispectral reflectance of shrub savanna, composed of scattered shrubs with a grass, forb or soil understory, predicted the reflectance of two 0.5 km2 sites as the area-weighted average of the shrub and understory or 'background' reflectances. Although the shaded crown and shaded background have darker reflectances, ignoring them in the area-weighted model is not serious when shrub cover is low and solar zenith angle is small. A submodel predicted the reflectance of the shrub crown as a function of the foliage reflectance and amount of plant material within the crown, and the background reflectance scattered or transmitted through canopy gaps (referred to as a soil-plant 'spectral interaction' term). One may be able to combine these two models to estimate both the fraction of vegetation cover and interception of PAR by green vegetation in a shrub savanna.

Original languageEnglish (US)
Pages (from-to)223-245
Number of pages23
JournalAgricultural and Forest Meteorology
Volume69
Issue number3-4
DOIs
StatePublished - 1994

Fingerprint

Sahel
surface reflectance
Niger
savanna
reflectance
savannas
radiative transfer
shrub
shrubs
modeling
tree crown
photosynthetically active radiation
interception
understory
vegetation
land surface
canopy gap
canopy gaps
zenith angle
vegetation cover

ASJC Scopus subject areas

  • Forestry
  • Atmospheric Science
  • Earth and Planetary Sciences(all)
  • Environmental Science(all)

Cite this

Radiative transfer in shrub savanna sites in Niger : preliminary results from HAPEX-Sahel. 1. Modelling surface reflectance using a geometric-optical approach. / Franklin, Janet; Duncan, Jeff; Huete, Alfredo R.; van Leeuwen, Willem; Li, Xiaowen; Bégué, Agnès.

In: Agricultural and Forest Meteorology, Vol. 69, No. 3-4, 1994, p. 223-245.

Research output: Contribution to journalArticle

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