Dataset: P3_SST_chl

   PI:              Frank Hoge
   of:              NASA/Goddard Space Flight Ctr., Wallops Island, VA
   dataset:         Aircraft observed sea surface temperature and chlorophyll
   dates:           May 21, 1989
   location:        N: 63.872  S: 51.6826  W: -22.7278  E: -9.1751
   project/cruise:  NABE/NASA P3 flight of May 21, 1989
   ship:            NASA P3 aircraft
 
   
   Flight track
 
   Flight leg notes:
   Flight leg 1
   Starting Coordinates:  52 36.6 N 09 10.5 W
   Ending Coordinates:    52 24.7 N 14 59.7 W
   Flight leg 2
   Starting Coordinates:  52 18.2 N 15 49.2 W
   Ending Coordinates:    52 05.3 N 17 19.3 W
   Flight leg 3 not reported
   Flight leg 4
   Starting Coordinates:  51 40.8 N 20 00.1 W
   Ending Coordinates:    55 22.8 N 19 51.6 W
   Flight leg 5
   Starting Coordinates:  55 42.3 N 19 59.8 W
   Ending Coordinates:    59 32.1 N 20 03.5 W
   Flight leg 6
   Starting Coordinates:  59 32.4 N 20 04.6 W
   Ending Coordinates:    59 40.6 N 22 01.3 W
   Flight leg 7
   Starting Coordinates:  60 01.0 N 22 03.6 W
   Ending Coordinates:    63 52.3 N 22 43.7 W
 

Airborne
Oceanographic Lidar (AOL) data description

for the JGOFS North Atlantic Bloom Experiment (NABE)

21 May 1989 Frank Hoge

NASA/Goddard Space Flight Ctr., Wallops Island, VA

The laser-induced chlorophyll fluorescence has been normalized by the water
Raman backscatter to correct for variations in the optical attenuation properties
of the upper water column along the flight track. A discussion of the AOL
instrumentation and the water Raman normalization procedure are given in
the references listed below. The laser-induced chlorophyll fluorescence
was acquired using 532 nm excitation from a frequency doubled Nd:YAG laser
with an output power of ~15 mjoule/pulse. The laser was operated at 10 pulses/second.
At the nominal 120 m/sec velocity of the NASA P-3A aircraft, this sampling
rate yields an observation every 1.2 m along the flight track. The data
contained in these files are 30 point simple averages providing an observation
approximately every 0.4 km. The 532 nm laser excitation also stimulates
fluorescence from the phycoerythrin pigment contained in some strains of
marine phytoplankton. The amount of laser-induced phycoerythrin fluorescence
found during the 21 May 1989 survey was found to be low (below the detection
limitation of the AOL sensor) and accordingly is not included with the data
set contained on this disk.



The relationship between water Raman normalized laser-induced chlorophyll
fluorescence ratio and chlorophyll concentration varies somewhat due to
changes in the fluorescence pigment quantum efficiency of the in situ chlorophyll
molecules much as chlorophyll fluorescence from a continuous underway fluorometer
does. Changes in the fluorescence quantum efficiency are affected by such
factors as available light, nutrients, etc., however from previous experiments
we have seldom seen variations in excess of 20% within a single mission
over a period of 4 to 5 hours under daylight conditions. In comparing the
data set with available chlorophyll data from the R/V Discovery (U.K.) over
a contemporaneous span between 52.5 N and 53.5 N (over a period of 9 - 17
hours after the airborne sampling) we found that a scale factor 4.95 applied
to the water Raman normalized laser-induced chlorophyll provided reasonable
agreement. The data set from the R/V Discovery and the Raman normalized
laser-induced chlorophyll fluorescence data from the AOL were resampled
at 0.02 degree increments as a function of latitude and combined. A linear
regression between the absolute chlorophyll values and the chlorophyll fluorescence
yielded an R coefficient of 0.80 and the above 4.95 scale factor between
the Raman normalized laser-induced chlorophyll fluorescence values and chlorophyll
in ug/liter units. The 4.95 scale factor was applied to all data sets obtained
during the May 21 mission. The SST observations were collected from an auxiliary
Barnes PRT-5 infrared radiometer. A linear regression of the PRT-5 ocean
surface temperature values along all 7 flight lines with the ocean surface
temperature values from the Airborne Expendable Bathythermographs (AXBT's)
yielded a r coefficient of 0.95. Note that Leg 3 was not included because
of some instrument problems experienced at that point in the mission.

References:

Hoge, F. E., and R. N. Swift, Airborne dual laser excitation and mapping
of phytoplankton photopigments in a Gulf Stream warm core ring, Appl.
Opt. 22, 2272-2281, 1983.

Smith, R. C., O. B. Brown, F. E. Hoge, K. S. Baker, R. H. Evans, R.
N. Swift, and W. E. Esaias, Multiplatform sampling (ship, aircraft, and
satellite) of a Gulf Stream warm core ring, Appl. Opt. 26, 2068-2081,
1987a.