The scanner image (bottom figure 11) shows incredible detail. 

 The first sharp temperature drop appears as a perpendicular band at 

 the right side of the film strip. Within the cold region there are 

 many small bands about 50 meters in width. Toward the right these 

 small bands are randomly oriented and toward the left they are par- 

 allel to the temperature step. The left edge of the cold band is 

 alined along 080°T. 



Further to the left (northeast) there is an homogeneous warm 

 region. The radiation thermometer shows that this water is cooler 

 toward the left. The scanner does not show these weak gradients. 



Still further northeast, other bands are detectable on the scan- 

 ner as the water cools. At the extreme upper left (northeast) edge 

 of the record, the water has cooled to about 11°C. 



High Altitude Flights : Flights were made at altitudes up 

 to 3 km from 1500 to 1600Z 10 March and up to 2.5 km from 0600 to 

 0700Z 11 March. ARGUS ISLAND provided surface temperatures for each 

 pass. A plot of radiation thermometer error (surface temperature 

 minus radiation thermometer) for both flights is shown in figures 

 12 and 13. The least- squares regression lines are also shown. 

 Weather charts indicated no major change in meteorological con- 

 ditions during or between these flights. During both flights the 

 sky was clear and the wind was from 030°T at 7»7 m/sec. The dif- 

 ference between daytime and nighttime data must arise, therefore, 

 from diurnal effects on the infrared radiation. 



During the daytime flights, the radiation thermometer error 

 increased about 0.9°c/km of altitude. Extrapolation to the surface 

 yields a negative bias of 1.2°C for the radiation thermometer. This 

 error is removed in routine flights by application of an environmental 

 correction (Pickett, 1966). 



At night, the error increased by 1.6°c/km of altitude. Thus, 

 the nighttime error appears to increase with altitude almost twice 

 as fast as the daytime error. Extrapolation to the surface gives a 

 negative bias of only 0.1°C for the nighttime data. Nighttime errors 

 are small at low altitudes but increase more rapidly with altitude 

 than the daytime error. This suggests that there is more water vapor 

 at low levels during the day and that night flights at low altitudes 

 will yield optimum accuracy. 



Conclusions 



The infrared scanner shows detail in regions of very strong tem- 

 perature gradients but is of limited value in regions of moderate 

 gradients. Even in regions of strong gradients, however, the scan- 

 ner shows only thermal contrast between adjacent regions. The radi- 

 ation thermometer, on the other hand, does not have two-dimensional 

 coverage but yields reasonably accurate measurements. 



21 



