134 



[chap. 4 



Table IX 

 Comparison of Poleward Atmospheric Heat-Energy Transports by Latitude 



Unit : 1015 cal/sec 



a After Palmen, Riehl and Vuorela (1958) 

 ft After Riehl and Malkus (1958) 



d. The annual heat balance of the atmosphere 



The heat budget of the free atmosphere is now readily balanced separately. 

 Its radiation balance, Ua, may be obtained by subtracting the radiation balance 

 of the earth's surface, i2, from that of the whole system, Rs (Fig. 13), namely, 



Ra = Rs — R- 



(26) 



The radiation balance of the underlying surface is in all latitudes greater than 

 that of the earth-atmosphere system, so that Ra is everywhere negative. This 

 is due to the famous "greenhouse effect" : the water vapor in the atmosphere 

 absorbs long-wave terrestrial radiation and reradiates it both downward and 

 upward. The mean annual Ra distribution with latitude of Bagrov-Budyko is 

 given by the dash-dotted curve in Fig. 15. It is important to note that the 

 atmosphere's rate of heat loss by radiation varies extremely little with latitude, 

 being everywhere about 65 kg cal/cm^ year or equivalent to a radiative cooling 

 of approximately 0.75°C per day. London's results for Ra are not too different 

 from these, but his atmospheric heat sink is every where greater (average 20%). 

 While this discrepancy is not excessive in view of the uncertainties involved, it 

 accounts almost entirely for the difference between London's and Budyko's 

 total transports in Table I. We have seen that the earth's surface radiation 

 balances, R, of the two authors departed little from each other and thus their 

 deduced oceanic transports were in good agreement. However, if we accepted 

 London's Ra instead of Budyko's, the total air transports in Table I (Northern 

 Hemisphere) would be reduced to 63% of their presented values, implying 

 among other things that the ocean provides nearly 40% of the critical poleward 



