BEAUFORT FORCE 



The ocean surface forms a vast background against which and occasionally through 

 which observations are made. The sea surface can have an appreciable effect on the 

 detectability and observability of organisms depending upon waves related to wind, rain, 

 and depth, as well as other factors. Sea surface state was recorded using the Beaufort 

 Force Index. Table 43 details the percentage of observations made under Beaufort states 

 1 through 4. Although flights were terminated any time sea states stabilized at or above 

 4, a few observations were made under these conditions in the vicinity of local 

 thunderstorms. States 1 and 2 are characterized by a smooth water surface without 

 waves breaking. State 3 includes conditions with scattered white caps which provide 

 some visual noise for aerial observers and may reduce detectability of those organisms of 

 small size, those with white coloration, and animals which have a low profile in the 

 water. The percentage of observations made at sea states of 3 or 4, summarized in Table 

 43, clearly shows that sea states during November flights were higher than those during 

 August except in STEX. The future collection of seasonal data over the entire annual 

 cycle and at more frequent intervals is necessary to allow rigid analysis of the effect of 

 sea state on quantitative estimation of occurrence and abundance. 



GLARE 



The amount of reflected sunlight from the ocean's surface has a significant effect 

 on the observer's ability to detect and observe the organisms of interest. Glare can 

 severely impair otherwise ideal conditions, even calm sea states. Since the location of 

 the survey aircraft, the position of the sun, and the intensity of the sunlight are dynamic 

 factors, the effect of glare is most easily determined by comparing simultaneous sighting 

 records made from opposite sides of the aircraft. In the Cessna Skymaster used in the 

 Pilot Study, observers utilized observation windows on opposite sides of the plane and 

 glare, when present, was usually on one side of the aircraft or the other. Flight paths at 

 three survey subunits (STEX, NFLA, and SFLA) were in an east-west direction and 

 comparison of observations on the north and south sides of the aircraft allow glare to be 

 considered independent of subjective estimates of the intensity of the glare present. In 

 those subunits flown on east-west axes, observations made from the north and south sides 

 of the aircraft were comparable during August, but November observations made from 

 the south side of the aircraft were markedly lower than those made from the north 

 (Table 44). 



In the NTEX subunit, which was surveyed on a northwest-southeast axis, seasonal 

 differences are less obvious; but observation totals on the southwest side were 

 consistently lower than comparable sightings on the opposite side (Table 45). In fact, 

 both sides of transect line were affected by glare but it was more severe on the 

 southwest side. Since these results span flights in both landward and seaward directions 

 and include systematic rotation of observers and their positions, these factors cannot be 

 used to explain differences observed. 



As suggested above, the percentage of observations recorded on the side of the 

 aircraft with glare will be significantly lower in winter months than in summer. Table 46 

 summarizes the expected effects on glare vs. nonglare situations. Pending confirmation 

 of these trends, it may be necessary to adjust abundance estimates to compensate for 

 glare factors. 



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