tic activity. In 
istance of 5 km 
1990) on spatial 
actual range of 
sually supposed 
et al., 1991). 
schnique in the 
:ion about both 
photosynthesis 
and Chekalyuk, 
photosynthesis 
:e Fig.5a) was 
ng influence of 
id, that due to 
A4>/<I>m indicated 
1 centers of PS 
tive). 
sis 
bution (Fig.5a) 
ical structures 
anation of the 
nthetic activity 
water streams 
tion of Chl-a 
uk, 1993) taking 
illumination in 
curacy of Chl-a 
>ution of Chl-a 
6.3. Lidar monitoring of natural biophysical processes in the sea 
Another potentially rich field of application of pump-and-probe lidar 
technique is undisturbing in situ study of natural biophysical processes at 
various temporal and spatial scales. As an example we present in Fig .6 the 
results of our measurements in the Mediterranean Sea (April 1991). One can see 
duirnal variations of Chl-a fluorescence ($) and algal photosynthesis effici 
ency (17 = caused by excessive solar illumination in near-surface water 
column. Energy-dependent quenching and photoinhibition of photosynthesis were 
found to be the main regulating mechanisms (Gorbunov and Chekalyuk, 1992). 
0° 
0.4 
0.2 
V 
0.0 
0.6 
0.4 
0.2 
0.0 
1 1 1 1 r— 
L : 
* ■ ■ ■ 1 ■ ■ ■’ 
'■/] 
. 
ui, . 
kM 
AA À . v.-m: 
-j— l'U V- ,—VWA ,—U-.Iq 
24 6 1218 24 6 1218 24 6 1218 
TIME (hours) 
Figure 6 . Lidar Measurements of Diurnal Variations of Phytoplankton 
Chlorophyll-a Fluorescence (Actual Level $) and Efficiency of 
Photosynthesis rj = A$/4>m. The Mediterranean, April 1991. 
7. - CONCLUSION 
Thus, the development of lidar implementation of pump-and-probe technique and 
its first field applications have shown the essential potential of this 
approach to remote monitoring of photosynthesis. The main advantage of this 
novel technique is the capability of direct remote real-time monitoring the 
efficiency of ongoing photosynthetic processes, as well as phytoplankton 
abundance with a high spatial (horizontal) and temporal resolution. 
On the other hand, successful transfer of lidar pump-and-probe technique 
from research environment to real operational use will strongly depend on 
solutions of a number of relevant problems: 1 ) development of airborne (using 
helicopter are aircraft as a carrier) pump-and-probe lidar system to provide 
express monitoring over large areas; 2 ) development of detecting system with 
time resolution and wide dynamic range to provide vertical profiling in the 
sea; 3) transfer from estimates of photosynthetic efficiency to the evalua 
tions of integral characteristics of photosynthesis (primary production); 4) 
development of lidar bioindication of unfavorable environmental impacts in 
industrially active areas (including monitoring in coastal zones); 5 ) 
development of a family of relatively simple and cost-effective commercially 
available lidar systems.