_ — 
POSSIBILITIES FOR REMOTE SENSING OF 
CHLOROPHYLL BY OPTICAL METHODS 
by 
H. ARST 
and 
J. LOKK 
Tallinn, Institute of Thermophysics and 
Electrophysics 
Academy of Sciences of the Estonian 
USSR 
The liaht measured over the sea surface contains infor- 
mation about two characteristics of the sea: I) light reflected 
from the sea surface is influenced by the sea state; 2) light 
diffusely reflected from the sea is influenced by the quantity 
and type of optically active matter in the water. In the exper- 
iments carried out at lower levels heights the great  variabi- 
lity of signal is caused mainly by the variability of light 
directly reflected from the surface. That explains why we have 
quite a bad correlation between the spectral brightness and 
the matter composition in water in such experiments. Measure- 
ments carried out in at the same time and place under the sea 
surface yield much better results. Lifting up the instruments 
to the heights from where the spatial diameter of the pixel is 
about 20- 30 meters, we come to the situation when the reflection 
from the sea surface (including sun glitters) formaly a steady 
background and the signal variability is influenced by the col- 
our of the sea. Higher than 200 meters atmospheric influence on 
the spectrum of the upwelling light could be felt. The strong 
influence of the atmosphere causes more changes in the short 
wavelength region of the spectrum. The main part of information 
about water is contained in longer wavelengths (up to NIRed). 
727 
TT aa m