INTRODUCTION 5 



completely absorbed in the atmosphere. It is probable that the greater 

 part of the effective radiation escapes because the water vapor is nearly 

 transparent for radiation of wave lengths between 8.5 and 11 n, at 

 which the black-body radiation of the earth's surface is nearly at a 

 maximum. 



The average value of the effective radiation over all oceans between 

 70°N and 70°S is about 0.090 g cal/cmVmin (p. 59). The effective 

 radiation from the land areas between the same latitudes is probably 

 greater, whereas that from the polar regions is smaller. The above 

 value may therefore be taken as a fair estimate of the average value for 

 the earth. Accordingly the radiation from the atmosphere must lie 

 between the limits 0.186 g cal/cm^/min and 0.276 g cal/cm'Vmin — prob- 

 ably closer to the former. Since the heat gained by the atmosphere by 

 absorption of radiation or by other processes must equal the loss by 

 radiation, the gain must also lie between the same limits. 



This gain can be further analyzed, since it may be brought about by 

 (1) condensation of water vapor in the atmosphere, (2) conduction of heat 

 from the earth's surface, (3) absorption of short-wave radiation from the 

 sun, and (4) absorption of long-wave radiation from the earth's surface. 

 The amount under item (1) could be computed if one knew approxi- 

 mately the total precipitation on the earth. According to Wiist the 

 total precipitation on the whole earth is 396,000 km^/year, corresponding 

 to an average amount of heat released by condensation equal to 0.086 

 g cal/cmVmin. Under item (2) the average amount of heat conducted 

 from the oceans to the atmosphere between latitudes 70°N and 70°S has 

 been estimated at 0.013 g cal/cm^/min. The conduction from the land 

 areas between the same latitudes is probably smaller, and in the polar 

 region heat is conducted from the atmosphere to the earth's surface. 

 On an average for the whole earth, item (2) can therefore be estimated 

 at 0.010 g cal/cm^/min. The amounts of absorbed radiation, items 

 (3) and (4), have not been estimated, but the limits of the amounts can 

 be found because the sum of all items must lie between 0.186 and 0.276 

 g cal/cm^/min. On this basis the heat budget of the atmosphere can be 

 summarized as follows: 



Minimum Maximum 



Heat gained by (g cal/cmVmin) (g cal/cmVmin) 



Condensation of water vapor .086 .086 



Conduction of heat from the earth's surface. . .010 .010 



Absorption of radiation .090 . 180 



TT86 7276 



Heat lost by radiation .186 .276 



It is probable that the true values lie closer to those listed under the 

 minimum heat budget. 



All numerical values given here are subject to revision, but such revi- 

 sion is not likely to reverse the feature which the available data bring 



