Tables 132-134 417 



TOTAL SOLAR RADIATION AT THE TOP OF THE ATMOSPHERE 



The values given in Tables 132-134 are based on the computations of Milankovitch, 1 

 revised on the basis of a solar constant J = 1.94 cal. cm." 2 min." 1 (see p. 414). 



The basic formula for computing the amount of solar radiation h reaching a unit 

 horizontal area at the top of the atmosphere in time t is 



dl o Jo tt\ 



Tt=7 coss (1) 



where r is the radius vector of the earth (Table 169) and z is the sun's zenith distance; 

 z is given by 



cos 2 = sin sin 5 -f- cos 4> cos S cos h (2) 



where <p is the latitude, 5 is the sun's declination and h is the sun's hour angle. The 

 values of Table 132 were computed by substituting for t its value in terms of h and 

 integrating equation (1) for the period sunrise to sunset with the minor approximation 

 that 5 and r are constant during the day. 



To obtain the seasonal and annual values given in Table 133, 5 and r cannot be con- 

 sidered constant, and Milankovitch evaluated the radiation by expanding certain expres- 

 sions in series. 



Table 132 gives the total solar radiation in cal. cm." 3 falling on a horizontal surface at the 

 top of the atmosphere during one day as a function of the terrestrial latitude and the 

 solar longitude (or date). 



Table 134, prepared by Leighly, 2 presents the same data in a more convenient graphical 

 form as a direct function of the date rather than of the solar longitude. 



Table 133 gives the total solar radiation in cal. cm." 2 falling on a horizontal surface 

 at the top of the atmosphere during the whole year and also the amounts for the summer 

 and winter half-year. Summer is defined here as the period from the vernal to the 

 autumnal equinox (March 21 to September 23) and winter as the period from the autum- 

 nal to the vernal equinox. 



1 Milankovitch, M., Mathematische Klimalehre, Berlin, 1930. Handbuch der Klimatologie, Band I, 

 Teil A. 



a Leighly, J. B., private communication, 1948. 



{continued) 



SMITHSONIAN METEOROLOGICAL TABLES 



