EFFECTS OF CLOUDIPffiSS ON THE THERMAL STRUCTURE 



The heat exchange calculations presented above are based on the 

 cloud amount indicated on each BT observation. Of the 901 BT's avail- 

 able for this study, U20 indicated cloud codes 0, 1, and 2 (cloud 

 amount less than 25 percent); 26o had cloud codes 3^ ^> and 5 (cloudi- 

 ness between 25 and 75 percent); and 221 had cloud codes 6, 'J, and 8 

 (cloudiness more than 75 percent). These groups therefore could be 

 considered to represent clear, partly cloudy, and cloudy skies. The 

 number of observations in each group for each hour is listed in table 

 8. Mean hourly surface temperatures for the three cloud groups are 

 shown in figure 7 along with a fitted curve which represents a Fourier 

 curve with two harmonics. This type of curve is the simplest for por- 

 traying multiple peaks and troughs in the daily curve. Average tem- 

 peratures computed from 10 or less observations generally contain 

 enough uncertainty to make fitting of the curve to match every hourly 

 mean undesirable. 



TABLE 8 

 NUMBER OF BT OBSERVATIONS, 2-21 SEPTEMBER 1959 

 Hour (Z) Cloud Code 



0-2 3-5 6-8 



00 19 



01 29 



02 32 



03 20 

 Ok 15 



05 18 



06 16 



07 15 



08 19 



09 19 



10 l6 



11 17 



12 17 



13 25 

 Ik 18 



15 19 



16 11 



17 8 



18 n 



19 1^ 



20 17 



21 17 



22 l6 



23 12 



TOTAL U20 



9 



9 



7 



10 



6 



8 



11 



8 



Ik 



6 



13 



7 



9 



13 



5 



Ik 



8 



9 



10 



10 



13 



7 



12 



7 



11 



9 



13 



12 



16 



Xk 



17 



12 



13 



6 



lii 



5 



Ik 



10 



8 



10 



8 



10 



7 



u 



9 



9 



13 



5 



!6o 



221 



15 



