the greatest likelihood of having at least minimally adequate periods of clear skies. 

 Analyses for individual days and running averages of the data over several more 

 or less consecutive days should be investigated. These averaged maps should 

 provide a good basis for tracing the gradual changes of large scale SST patterns, 

 while comparisons of the individual days should reveal capabilities as regards 

 smaller scale and more rapid changes and developments. 



As a first pilot study to investigate the general feasibility of such an approach, 

 a six day case was run, using both the listing and the mapping formats, for the area 

 off the western coast of Australia. The time span covered by the six days processed 

 was from 29 July to 8 August 1963; and the TIROS VII data used included Passes 

 589, 647, 662, 691, 706, and 735. For the fir st few passes , an albedo threshold 

 value of 10% was used with the Channel 5 listings to outline clear areas. This 

 resulted in areas which were too restricted for practical use. By locating abrupt 

 changes in the Channel 2 temperature values, it was determined that a 20 % albedo 

 threshold could be safely used in this case, revealing a much larger apparent clear 

 sky area. All six passes were then processed using the 20 % albedo limit. Of the 

 six passes, only one appeared completely overcast. The outlined clear areas of 

 the several maps were then hand averaged producing the final average analysis 

 in Figure 6-1. 



Mean monthly SST maps for this region show isotherms running east-west 

 across the Indian Ocean, and then dipping southward as they reach Australia. From 



the southern to the northern tip of western Australia the mean monthly SST rises 



o 

 approximately 7 K , in agreement with the results in Figure 6-1. No upper air 



data or ship reports were available for this area, but, even with reasonable atten- 

 uation and degradation corrections, the IR observed SST's would again be colder 

 than those anticipated for this region. The individual maps which were used to 

 make up the final analysis in Figure 6-1 were also analyzed, but revealed no 

 obvious continuous or significant change in SST patterns. The individual analyses 

 showed more complex SST patterns than are seen in the averaged mapping. Apparently 

 one advantage of the averaging process is its ability to ferret out the more significant 

 patterns from the background of extraneous noise of both the natural and the sensor 

 produced varieties. The positive results of this trial case have seemed to reaffirm 

 both the utility of the TIROS IR observations as a source of valid SST data, and our 

 feeling that, for extensive studies or operational uses of satellite IR data for SST 

 determiinations, the types of extensive processing methods proposed above will have 

 to be employed. 



42 



