68 



model of turbulent boundary layer processes occurring at the sea-air 

 interface. This modeling should be best applicable when the windspeed is 

 high and the static stability is near neutral - that is, for near-zero 

 values of the Richardson number. The formulation gives increasingly bad 

 results as the Richardson number increases, to either positive (stable) or 

 negative (unstable) values. 



This is not the place to develop the transfer formulas nor to discuss 

 further their range of validity, although a lot of work and consideration has 

 been recently devoted to this topic (Roll, 1965; Garstang, 196^1) . The fact 

 remains that flux computations based upon them, good or bad, form one of the 

 primary cornerstones upon which tropical meteorology has been built. Sjxst 

 checks of these flux computations have been made, by methods which are 

 themselves indirect and subject to errors and assumptions . Two main ways 

 of checking are the energy budget method, which involves assessment of 

 radiative fluxes, and the so-called "direct" method by aircraft measurements 

 made at some height above the surface (Malkus, I962) . These results nearly 

 always agree with those of the transfer formulas within a factor of two, 

 and often to better than 25 percent. It is all very well to reiterate the 

 truism that these fluxes Just must be more accurately specified, to go 

 forward with tropical meteorology, but no one has jret produced a way to do 

 thiS;, particularly on the necessary routine and frequent basis over wide 

 expanse of ocean. 



The second important point to make here about the Jacobs transfer 

 formulas is that, to the extent that they are valid, they tell us that the 

 atmosphere itself mainly controls the extent of its own heat and moisture 

 input from the sea. We see this in the form of the equations, which is 



Flax = Coefficient x (Air-Sea Proi)erty Difference) x Windsi)eed (l) 



Since time fluctuations in the air-sea property difference are mainly 

 governed by those in the lower air, we can see that the atmosphere opens 

 and closes its own fuel line, making a very intriguing feed-back linkage; 

 the fine beginning made by Kraus (1959) in modeling this has not been 

 pursued as it deserves. 



The coefficient in the transfer equations needs consideration prior to 

 inteiT)retation of any of its results. In most climatological maps of heat 

 and moisture exchange, this coefficient is used as a constant. In his 

 classical work, Jacobs (l95l) obtained his constant coefficient by 

 "calibration" with the energy budget method. There are more sophisticated 

 but probably no physically sounder ways of evaluating the coefficient 

 nowadays . 



Boundary layer modeling indicates that the coefficient is a function 

 of Cp, the so-called "drag coefficient, " which relates momentum exchange at 

 the interface to the windspeed. C^ must be empirically determined. 

 Recently a number of workers have examined its dependence upon the atmospheric 

 variables (cf . Garstang 196*1; Roll, I965; Deacon and Webb, 1962; Deacon, 



