SKOT. 2] LARriK-SCALE INTERACTIONS 169 



b. Lateral heat and moisture fluxes 



To complete the lieat and moisture budgets, (27b) and (2Sb) are to be 

 integrated vertically from the sea surface to the base of the stratosphere, so 

 that they may be written 



LP + Qs+Ba= I ^^Cn{CpT + Agz}dl{dplg) (27c) 



and 



Qe-LP= ( { CnLqdl{dplg). (28c) 



We use the condition of no flux across the troughline itself. It should be empha- 

 sized that this does not assume zero flux across the geographic equator ; on the 

 contrary, asymmetri<!al trough migration is bound to ensure there is a flux (see 

 discussion of Table I, p. 97). There are still, however, two unknown terms in 

 each of these equations. We must either produce an estimate of the precipita- 

 tion or calculate the export through the poleward (10° latitude) trough boundary 

 in one of them. The distribution of Lq and h = CpT + Agz is obtainable from 

 radiosonde ascents around the globe, but there are far too few available radio- 

 winds to determine a distribution of c«. Therefore, the procedure is to estimate 

 LP, to compute vertical cross sections of Lq and h and then to flt a profile of 

 Cn so that (27c) and (28c) can be jointly satisfied. Thus, an additional un- 

 certainty resides here relative to the trade-wind studies. 



Riehl (1954, p. 78) has comj^uted precipitation profiles relative to the equa- 

 torial trough using the results of Wiist (1936) and Jacobs (1942) which, as we 

 saw earlier, are probably too low. In the region here considered the precipitation 

 would be only 33 cm/season, with a heat equivalent for the belt of 1.08 units 

 (1.08 X 1015 cal/sec). For ^^ = 0.93 units, the latent heat import would be only 

 0.15 units, which would mean that almost none of the latent heat accumulated 

 in the trades reaches the equatorial trough zone. This unlikely result gives 

 further preference for Drozdov's (1953) rainfall estimation and that of Mein- 

 ardus (1934); the latter is 1.43 times that of Jacobs and Wiist. With this 

 correction, the precipitation in our belt becomes 47.5 cm/season, with heat 

 equivalent of 1.56 units. Then the divergence of Lq{Qvw)= —0.63 units and the 

 divergence of h{Qva) = + 0.94 units. The sum of these figures is the total atmos- 

 pheric export from the trough of 0.31 units which was entered in Table IX. 



An interesting overall view comes from comparison of these lateral fiuxes 

 with the trade-wind results of Colon. If we merely extrapolated his 5% sample 

 around the globe (as actually done in Fig. 30, where the numbers then read in 

 units of 10^5 cal/sec), the trades would export 1.41 units of latent heat and 

 import 0.86 units of ^. But the Caribbean winter segment is a particularly active 

 portion of the tropical circulation cell. Its lower trades are about twice as strong 

 as the global mean so that an average export of 0.6-0.7 units of latent heat 

 to equatorial regions is extremely plausible. Aloft, the agreement is apparently 

 not quite so satisfactory since Colon's required h import of 0.86 units is actually 



