SKIT. 2] LAROK-SCAI,!; 1 NTKKACTIONS 165 



are intercisted hero in the e(]iiatorial troiiuh /.one, we employ a co-ordiruite 

 system following the mean position oi' the trough, the extremes of" which are 

 given in Figs. 22 and 23. In this way, the north south meanderings of its 

 seasonal mean position are eliminated ; we further gain vastly more data, since 

 each radiosonde station appears at different latitudinal distances relative to 

 the trough line as it migrates. Not all of the needed information for complete 

 budgets is available in this reference frame, particularly the radiation, but it is 

 assumed that, for the latter, we can employ the values computed for latitudes 

 fixed with respect to the mean trough position. 



Similar to the trade-wind studies, we shall attempt to balance the atmos- 

 j^heric heat and water- vapor conservation equations in the forms (27b) and 

 (28b), using (1) for the sea-surface heat balance to help determine exchange. 

 The oceanic storage term is uncertain and may be large even in these latitudes ; 

 in some months it has been estimated above one-third Qe by Gabites (1950) and 

 even larger by Pattullo (1957). Lacking sufficient bathythermograph observa- 

 tions in this belt, we restrict the heat-source calculations to the end of February 

 and August, when storage is known to be small and the equatorial trough 

 reaches its most poleward position. Under these conditions (1) becomes 



R = Qe + Qs + Qro. (la) 



Rather than computing B, the radiation balance of the sea surface, as done in 

 the trade-wind studies, w^e transform (la) to a suitable form to use the radiation 

 results of London directly. Substituting (26), 



Es = R + Ba, (26) 



where Bs is the radiation balance of the air-sea system and Ba the (negative) 

 radiation balance of the atmosphere, we have 



Bs = Qs + Qe + Qvo+Ba. (lb) 



London has prepared tables and diagrams giving Bs and Ba as a function of 

 latitude and season for the Northern Hemisphere. We shall use these presently 

 to supplement the transfer formula determinations of air-sea exchange with 

 (lb), but first let us consider the north-south migration of the trough. 



a. Trough position and movement in relation to energy fluxes 



The seasonal migration amplitude of the equatorial trough is from about 

 5°S to 12°N latitude, or less than half that of the sun — a strange feature which 

 has provoked much discussion in the literature. From this it has been con- 

 cluded, for instance b}^ Rossby (1949), that the classical explanation of the 

 trough as a simple thermally induced j)henomenon cannot be maintained. If 

 we now integrate London's Bs figures for the no-storage months of August and 

 February to obtain transports (similar procedure as done for the annual figures 

 in Table I), a very interesting insight into this behavior of the equatorial 

 trough is provided. 



