5. CASE STUDIES 

 5. 1 North Atlantic, Labrador Current 



Early in this study, four cases were selected for areas of the North Atlantic. 

 The areas chosen exhibit high climatological SST gradients during summer months, 

 and it was expected that adequate conventional data from ship reports would be 

 available. The selected cases all occurred during late August or early September 

 of 1963. Nearly coincident TV pictures and nephanalyses were used to assure some 

 regions of clear skies within the selected areas. 



Of the four cases selected, one was found to be unusable since it included only 

 closed-mode radiometer data. While it was not a criteria for case selection, there 

 were areas of overlap between each of the remaining three cases. 



The analysis of the best of these cases is shown in Figure 5-1. These data 

 are taken from Pass 1126 of TIROS VII, on 3 September 1963 between 1234Z and 

 1238Z. The isotherms shown in this and all subsequent analyses are uncorrected 

 for atmospheric attenuation or sensor degradation. Rather, attenuation and degra- 

 dation corrections were determined for individual points or areas as required for 

 comparisons with conventional data. The isotherms are drawn at 2-1/2 K intervals. 

 The cloud edge shown in Figure 5-1 was determined by using a 10 % albedo threshold 

 and the Channel 5 data. The dashed extensions to the solid isotherms, both into the 

 cloudy area and beyond the edge of the data, are merely extrapolated best estimates. 

 The 267. 5 K isotherm shown below the edge of the Pass 1126 data was taken from an 

 earlier pass. 



Fortunately, the weather ship Bravo was located within the clear area of the 

 analysis, and provided upper air data for use in atmospheric attenuation corrections. 

 These corrections were calculated as discussed in Section 4. 3 above. They indicated 

 that, due to atmospheric attenuation, the apparent radiative temperature of the sea 

 surface would be 6 K less than the actual sea surface temperature. From the sensor 

 degradation estimates in the TIROS VII Radiation Data Catalog , it was found that 

 the measured temperatures would be approximately 2 K less than actual for these 

 temperatures and time period. The average temperature of the waters off Labrador 

 in this season is 40 F, or 277 K. Figure 5-1 suggests that 265 K is a good 



(uncorrected) representative temperature for the area involved. When increased 

 by the 8 K combined correction for attenuation and degradation, an average corrected 

 sea surface temperature of 273 K is obtained, or 4 K less the anticipated value. As 

 discussed at the end of Section 4. 3, such a difference between conventionally observed 

 surface temperatures and the corrected Channel 2 data is not unusual. 



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