ON ANGULAR DISTRIBUTION OF RADIATION REFLECTED
FROM A RUFFLED SEA ,
H. ARST
Institute of Thermonhysics and Electrophysics
Estonian Academy of Sciences
Paldiski- Str.l. Tallinn 200031
Estonian SSR , USSR
ABSTRACT
A mathematical model has been developed for describing the
angular distribution of monochromatic electromagnetic radiation
reflected from the ruffled sea surface. The reflectivity of the
; sea is calculated in view of the possibilitv ofa thin oil: fiim
= — Sites 4 on the water.The model works both in case of an incident paraliel
d area
beam radiation as well as in case of diffuse and direct solar ra-
to 5. diation.
The model may become of practical use for the interpretation
and analysis of measuring results of upwelling radiation above
the sea surface ( to estimate the relative contribution of the
A sun glitter and directly reflected sky radiation to the results
80 : of the measured sea brightness , to find the Optimum directions
= of observations for determining the zones with increased or
reduced sea radiance etc.).
The upwelling solar radiance above the sea surface
consists of two components: l)the sun and Sky radiation directly
reflected from water surface 2) solar radiation diffusely back-
Scattered by seawater . An extensive and profound investigation on
the radiance distribution over a ruffled sea has been made by
G.N. Plass with co-authors using the Monte Carlo method (Plass
et al. 1975, 1576, 1977, 1981, Guinn et'al. 1979). However, we need
id a simple mathematical model describing the field of upwelling
Area radiance above the sea in order to analyze and verify our experi-
mental results (measurings have been carried out on board of a
ed research vessel or helicopter). The computer of the research vessel
must be able to realize the program of the mathematical model.
As a; fivst. Step, .a simple mathematical model for calcula-
ting the electromagnetic radiation directly reflected from the
sea surface is developed. The model works both in case of an
incident parallel beam radiation as well as in case of the
diffuse and direct solar radiation. It describes reflected ra-
diance measured by fictitious receiver as'a function of the
zenith angle Sn ) and azimuth (Sem ) Of observation. The dis-
torting influence of the atmosphere between the receiver and
reflective surface is not taken into account. Nevertheless, in
cases of small distances between the receiver and sea surface
(vessel, helicopter) estimations made by this model could be
satisfactory enough.
El
