42 



TRANSMISSION EXPERIMENTS AT ANTIGUA, WEST INDIES 



sparse and uot too reliable. A few good soundings 

 were obtained about 1 mile inland, an example of 

 which is shown in Figure 13. The data were taken dur- 

 ing the day and show clearly that no low duct existed 

 at that time. This slide is a comiDosite between a 

 sounding made on a oO-ft windmill and a kite sound- 

 ing made nearby. Tlie kite was flown to 600 ft and the 

 M curve continued at the slope representing mixed air 

 from 60 ft on irp to 600 ft. No night measurements 

 were made. 



It was possible to make a few shipboard soundings 

 to leeward of the island, beginning at a distance of SVa 

 miles and continuing on out to 30 miles. A preliminary 

 study of the results shows no appreciable change over 

 the course and no difference between conditions to lee- 



INLANO SOUNDING 

 2 MILES FROM TOWER 

 26,27 MARCH 1500-1700 



wind: 



surface: ene 8-i2 knots 



100 feet: ene ii-i6 knots 



120 



ilOO 



; 80 

 I 



: 60 



i 40 

 i 



20 



76 78 80 82 84 

 TEMPERATURE 

 IN DEGREES F 



12 13 14 



MIXING RATIO 



IN G/KG 



340 360 380 



MODIFIED 

 INDEX 



Figure 13. Inland soundings, March 26 to 27. 



ward and to windward of the island, indicating that 

 the duct is restored very close to shore. 



Some plots of certain correlations between wind 

 speed, duct thickness and 71/ deficit follow. The graphs 

 in many cases are composed of very few points and 

 due to the short time available are based on average 

 soundings which have necessarily been smoothed. 

 Figures 14, 15, 16, and 17 are based on the mean tower 

 soundings and mean winds for each run, these being the 

 only smooth data readily available for quick analysis. 



Figure 14 shows effective M deficit plotted against 

 wind speed. This piortion of the curve seems sensitive 

 to wind speed variation. 



Figure 15 shows the effective slope (height of min- 

 imum M divided by effective M deficit) plotted against 

 wind speed. Some connection between the two quan- 

 tities is indicated. 



In Figure 16 the height at which M is a minimum 

 is plotted against wind speed. The isopleths of effective 

 M deficit have been sketched in. A few of the points 



were thrown out in drawing the isopleths. For constant 

 duct height, the effective M deficit aj^parently first in- 

 creases with increasing wind sj)eed and then decreases. 

 Unfortunately there are only two points in the low 

 wind region to estal^lish this behavior. It is quite pos- 



5 10 15 20 25 30 



SURFACE WIND SPEED IN KNOTS 



Figure 14, M deficit versus wind sjieed. 



sil)le that the lines should be more nearly horizontal 

 at low wind speeds and then should slope off in the 

 manner shown for winds above 15 knots. 



An attempt to plot sea temperature minus air tem- 

 perature against wind speed showed no correlation. 



20 

 18 

 16 



14 



I- 

 uj 



ui 12 

 11. 



z 10 



u 



a. e 

 o 



5 10 15 20 25 30 



SURFACE WIND SPEED IN KNOTS 



Figure 15. Effective ^V-curve slope versus wind speed. 



Plotting mixing ratio leased on saturation at sea tem- 

 perature minus mixing ratio computed from dry and 

 wet bulb temperatures against wind speed also failed 

 to show any correlation. 



