F, W. Very — Sky Radiation and Isothermal Layer. 383 



The curve of apparent sky temperature and altitude above 

 the horizon for July 5th is plotted in fig. 2. The curve is 

 rather flat-topped. There is a slow change from the zenith to 

 an altitude of 30°, but below 20° altitude the negative radiation 

 to the sky diminishes rapidly, and at 5° altitude it sometimes 

 hardly differs from the radiation to the ground. 



Fig. 2. 



24° 



Cesriti 



qrtode. 

















20 





Q 

















<6 



\ + 



















19 





















8 





f\ 

















4 





+ 







































0° 



\o c 



20' 



30' 



40 £ 



50° 



60 c 



l° c 



80< 



qo< 



^Jii&ticcLe. cdrtvc 



rriQ*07i. 



Final Conclusions. 



As an example of an average sounding-balloon ascent to the 

 lower limit of the isothermal layer at latitude 52° and in the 

 tropics we may take 



Air density at the surface = 1*26 kgra / cu. m. = 1 atm. 

 (Lat.52°)" " " 12000 m =0*3928 " = 0*312 " 



(Tropics) " " " 15000 m = 0*2810 " = 0*223 " 



That is to say, about one-fourth of the atmosphere is included 

 in the isothermal layer, or there are 2000 cubic meters = 

 2586 kgm. of standard air over each square meter of surface at 

 the isothermal limit. The specific heat of air being 0*239, if 

 35 large calories are received from the sun's rays at the outer 

 surface on each square meter each minute, "then (2856 X 

 0*239) / 35 = 19*5 minutes will be required for a rise of 1° C., 

 if all the energy is absorbed ; or if no more than 7 per cent of 



