Scan angle (in degrees) 
Figure 3.2. Error introduced on surface temperature 
by ignoring the effects from the varying scan angle. 
The numbers refer to the atmospheres applied in the 
calculations presented in figure 3.1. 
data from the Arctic are introduced from the weather 
conditions. Very often the presence of clouds reduce 
the data availability. For testing the complete algo 
rithm, a project which included collection of in-situ 
SST's and radiosondes data together with the NOAA- 
satellite data, was done summer 1981 off the coast of 
Northern Norway. Unfortunately the bad weather condi 
tions resulted in no available satellite surface data. 
Instead, for real application of the algorithm, a 
NOAA-6 data set from the island Jan Mayen, acquired 
at Troms0 Telemetry Station on August 20. 1984, was 
chosen. The approximate geographical coverage of the 
data set is illustrated by the square marked A in fig 
ure 4.1. 
As input for atmospheric correction, a radiosonde 
profile from the meteorological station at the island 
was applied. In-situ measured SST's from the area were 
available from the Norwegian Institute of Marine Rese 
arch (private communication). Although these measure 
ments were taken about one week off the satellite data, 
they were applied for comparisons of temperatures. 
Figure 4.1. Approximate geographical coverage of the 
data sets applied in this report: 
A: Jan Mayen 
B: The Troms0 area 
C: Southern Norway. 
The water content of the applied atmosphere was app. 
1.3 cm. From the atmospheric profile, an averaged 
transmittance, t a = 0.89 was calculated for the NOAA- 
6/AVHRR channel 4. The error introduced if the atmos 
pheric correction was not performed was of the order 
0.5 K. In figure 4.2, the resulting atmospheric cor 
rected SST image data for the Jan Mayen data set are 
presented. 
At the top of the image in figure 4.2 there is a 
scale showing the correspondence between the grey lev 
els and the temperatures. Comparisons of the satellite 
derived SST's and the in-situ measured temperatures 
indicate an average, absolute error of 1 K. Having in 
mind the one week difference between the compared 
data, this error agrees well with the commonly accep 
ted error in deriving SST's from a single infrared 
band. 
Figure 4.2. SST image from the Jan Mayen area derived 
from the NOAA-6/AVHRR data set. A temperature value of 
1.25 or 1.75 means the actual temperature is within 
the range 1.-1.5 o'r 1.5-2.0 degrees Celsius respec 
tively . 
The data from the NOAA-satellites have also been 
applied for studying the strong currents often obser 
ved off the coast of southern Norway. A group at the 
Geophysical Institue at the University of Bergen has 
undertaken projects related to studies of the currents. 
In the worst case, the strong currents can be of dan 
ger to the activities at the important oil-fields 
located in the area of observed strong current gradi 
ents. In figure 4.3 an image showing eddies off the 
coast of Southern Norway is presented. The image is 
generated at Troms0 Telemetry Station from NOAA- 6 
thermal infrared data acquired on April 13. 1981. 
Off the western coast of Norway a pattern of eddies is 
observed. The different grey levels in the pattern 
represent surface temperatures ranging from approxi 
mately 1.5 to approximately 6.0 degrees Celcius. For 
this application, there has been no atmospheric cor 
rection, and the derived temperatures have not been 
compared to in-situ measurements. 
5. SST STUDIES FROM LANDSAT/TM 
The increased spatial resolution of the TM thermal 
infrared channel, as compared to the AVHRR, offers the 
possibility of applying the operated SST-algorithm to 
coastal-zone studies from the TM. 
During flight, the TM is calibrated against internal 
blackbodies. Although the calibration data is located 
in the spacecraft downlink datastream, at present