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I . INTRODUCTION 



Considerations of the energy sources, conversions and transports in 

 the earth-atmosphere system soon lead to the conclusion that the tropical 

 oceans play an extremely important role in the heat and energy balance of 

 the atmosphere . The greater part of the incoming short vra,ve solar radiation 

 in either direct or diffuse form is absorbed at the earth's surface. Before 

 this energy can be utilized by the atmosphere it must be transferred across 

 the earth-atmosphere interface. Therefore, the atmosphere is fuelled mainly 

 from below. As shovn by Malkus (1962, p. 93) snd others, the most important 

 transfer process at the earth-atmosphere interface is evaporation which 

 provides about half of the atmosphere's fuel in the latent form of water 

 vapor. More than half of this water vapor fuel is supplied to the lower 

 troposphere by the tropical oceans between 30°N and 30°S latitude. If we 

 add to these considerations the observation that the overall radiation 

 balance of the earth-atmosphere system is positive between about 35°N and 

 35 S latitude and negative poleward, the validity of the opening statement 

 is justified in general terms . 



In the tropical regions of heat input the net transfer of water vapor 

 and sensible heat is from the ocean to the atmosphere . Shear turbulence 

 within the first tens of meters of the trades insures thorough mixing and 

 upward transport of both water vapor and sensible heat. Turbulent eddies 

 continue the upward transport through the subcloud layer to the cloud layer . 

 where convective cells, in the form of cumulus clouds, probably play the 

 dominant role in the vertical transport of energy. Within the undisturbed 

 trades high values of wind steadiness occur through a considerable depth of 

 the lower troposphere. Under these undisturbed conditions, gradients are 

 likely to stabilize and the energy input at the surface will reach an 

 equilibrium value dependent upon the vertical removal from the surface and 

 upward transportation of energy. Riehl, Malkus and others (l95l) demonstrated 

 that these processes create a moist convective layer gradually deepening 

 along the airflow. In the trade wind regions of high evaporation most of 

 the moisture is retained in vapor form rather than rained back into the 

 oceans . This accumulated water vapor is transported equatorward "at a rate 

 of energy export easily two orders of magnitude greater than the rate of 

 kinetic energy consumption by all the global winds and sea currents combined." 

 (Malkus, 1962.) 



Within the equatorial trough region much of this water vapor is 

 condensed, releasing its latent heat, which is carried to great heights in 

 cumulonimbus clouds. Riehl and Malkus (1958) have shown that relatively few 

 such large clouds concentrated in a limited number of synoptic scale systems 

 (e.g., the vortical and wave-like pertubations common in this region) are 

 able to transport this energy, now in the form of sensible heat and potential 

 energy. But now a distinction should be made between suggestions based upon 

 mean budget conditions and deductions based upon day-to-day synoptic changes . 

 If average trade wind conditions prevail for some period of time, gradients 



