224 



MALKUS 



[chap. 4 



conditions are required (Riehl, 1948) for either of these to penetrate throughout 

 the troposphere and thereby to deepen markedly. However, this whole area is a 

 wide-open frontier and will remain so until proper three-dimensional data 

 become available over the unexplored low-latitude oceans. 



Fig. 57. Schematic picture of equatorial vortex of summer season which sets off easterly 

 wave trough (heavy solid line) to north. Surface streamlines are light solid lines with 

 arrow-heads. Area of convergent low-level flow, with cloud bands and showers shown 

 by stipples. 



(n ) Synoptic and diurnal exchange fluctuations in the equatorial trough zone 



A pioneering endeavor to study at close range the exchanges and vital 

 mechanisms of the Atlantic equatorial zone was made by Garstang (1958). 

 The Woods Hole Oceanographic Institution's small research vessel Crawford 

 (125 ft length; 250 tons gross) was stationed, mostly hove to, at 11° OO'N, 

 52° 25'W from 14 August through 5 September, 1957, and accomplished a 

 detailed set of joint oceanographic and meteorological measurements, including 

 the heroic feat of decent rainfall records, six-hourly pilot balloons and twice 

 daily radiosondes ! 



During this typical wet-season period, the easterly current was well estab- 

 lished to heights above 35,000 ft. The top of the moist layer fluctuated around 

 11,000 ft, being much deeper in convergent zones of disturbances, and much 

 shallower when unusually fair -conditions and divergent flow prevailed. The 

 most significant result of the cruise was the marked variations in exchange, 

 which were clearly associated with the synoptic-scale patterns, as summarized 

 in Table XVI. The concomitant wind structure is shown in Fig. 58. The com- 

 putations oiQs and Qe were made hourly, using transfer formulas (20) and (21). 



