Interactions between the solar radiation and the ground

Overview

The Bidirectional Reflectance Distribution Function (BRDF)

The Bidirectional Reflectance Distribution Function (BRDF) describes the directional dependence of the reflected energy of a target as a function of illumination and viewing geometries. The BRDF also depends on wavelength and is determined by the structural and optical properties of the surface, such as shadow-casting, mutiple scattering, mutual shadowing, transmission, reflection, absorption, and emission by surface elements, facet orientation distribution, and facet density.
Relevance to remote sensing of the environment:
The BRDF is needed in remote sensing for the correction of view and illumination angle effects (for example in image standardization and mosaicking), for deriving albedo, for land cover classification, for cloud detection, for atmospheric correction and other applications. It gives the lower radiometric boundary condition for any radiative transfer problem in the atmosphere and is hence of relevance for climate modeling and energy budget investigations.

Example:
View of the tested soil surfaces: (A) rough surface; (B) smooth surface; (C) uncultivated, relatively smooth; and (D) cultivated with furrows.

A

Rough surface:

850 nm
q_s = 74.3^o

B

Smooth surface:

850 nm
q_s = 74.9^o

C

Uncultivated, relatively smooth:

850 nm
q_s = 71.3^o

D

Cultivated with furrows:

850 nm
q_s = 75.4^o
f_c-s = 42^o

Distributions of the Normalized Hemispherical–Directional Reflectance Function (NHDRDF) of the tested surfaces obtained from the measured data for the wavelengths of 850 nm for chosen illumination conditions defined by the solar zenith angle θ_s and additionally by the angle f_c-s describing illumination of the furrows as a distance angle between the direction of the furrows and the sun position.

Illustration of the effect of BRDF can be viewed for the following conditions (press the arrows to run the simulations):
Simulations created by the group of Prof. Jerzy Cierniewski, Adam Mickiewicz University , Poland

q_s = 35^o	f_c-s = 264^o	t = 2.00	l = 850nm
q_s = 35^o	f_c-s = 264^o	t = 0.10	l = 850nm
q_s = 70^o	f_c-s = 264^o	t = 2.00	l = 850nm
q_s = 70^o	f_c-s = 264^o	t =0.10	l = 850nm

Collaborators:

Prof. Jerzy Cierniewski

The Department of Soil Science and Remote Sensing of Soils
Institute of Physical Geography and Environmental Planning
Faculty of Geographical and Geological Sciences (FGGS)
Adam Mickiewicz University in Poznan, Poland

Tomasz Gdala

Adam Mickiewicz University in Poznan, Poland

Uri Gilead

Ben-Gurion University of the Negev, Israel

Papers

Cierniewski, J., Gdala, T. and Karnieli, A. 2004. A hemispherical-directional reflectance model as a tool for understanding image distinctions between cultivated and uncultivated bare surfaces. Remote Sensing of Environment, 90, 505-523.

Faiman, D., Jacob, S. and Karnieli, A. 2002. Concerning the relationship between clear-sky, global and direct beam, solar spectra. Progress in Photovoltaics: Research and Applications, 10, 527-532.

Cierniewski, J. and Karnieli, A. 2002. Virtual surfaces simulating the bidirectional reflectance of semiarid soils. International Journal of Remote Sensing, 23, 4019-4037.

Karnieli, A. and Cierniewski, J. 2001. Inferring roughness of desert rocky surfaces from their bidirectional reflectance data. Advances in Space Research, 28, 171-176.