113 



Once the systems had been identified, time distributions of latent 

 and sensible heat could be obtained by calculating the hourly values for 

 all k6 days and obtaining average values (Q and Q ) for each of the 

 systems. Table 1 shows the initial broadsctle brelkdovn. In the first two 

 rows all undisturbed states can be compared with all disturbed states. The 

 results from both sets of obseirvations show the same trend: more heat is 

 transferred from the ocean to the atmosphere under disturbed conditions than 

 during undisturbed conditions . The increase in latent heat transfer is not 

 as large as in the case of sensible heat transfer. The ratio of Q 

 undisturbed versus Qg disturbed is 1.17 in 1957 and 1.07 in 1963; Sut for 

 Qg it is 7-7'^- and 2.0i4-, respectively. On each cruise weakly disturbed 

 modes were fairly frequent and strong trade wind conditions relatively few, 

 so that it is i)erhaps more meaningful to examine the transfers under weak 

 and moderate trades and moderately disturbed modes . Under these conditions 

 the ratio of undisturbed to_disturbed for Qe increases to 1.9i»- in 1957 

 and 1.25 in 1963; and for Qs 11-70 and 2.l6, respectively. The relative 

 increase in the Bowen ratio remains essentially the same for both of the 

 above comparisons. While the amount of sensible heat made available to the 

 atmosphere never exceeds 8 percent of the latent heat transfer, it is 

 significant to note that: 



1. This is an average figure throughout the whole disturbed period; 



2. For periods up to 6 hours within a disturbed region, the ratio 

 of sensible heat to latent heat may be greater than 0.20 as opposed to 

 undisturbed conditions when, for similar period, the sensible heat transfer 

 may be in the opposite direction, i.e., from the atmosphere to the ocean. 



3. This energy is directly available to contribute to the instability 

 of the subcloud layer and the development of convective cloud. 



Therefore, it is suggested that the role of sensible heat transfer in the 

 formative and developing stages of tropical disturbances is a critical one . 



The synoptic scale fluctuations of exchanges are examined in more 

 detail in Table 2. The mean values for each regime or mode are based_upon 

 values computed for each hour through each state . Little change in Aq _ 

 is noted between the various states. The mean temperature difference, AT 

 however, shows a systematic and fairly large change from undisturbed to 

 disturbed conditions. Mean sea-air temperature differences in excess of IC 

 occur during the disturbed modes, ■vtiile under the strong trade regime AT 

 is less than 0.3C. Sea surface temperatures were observed to vary little 

 between periods, although slightly lower temperatures were noted during the 

 strong trade wind regime as opposed to the weak regime . The dominant control 

 upon aT is produced by variations in air temperatures. Lower air temperatures 

 during the disturbed modes are ascribed to reduced Insolation due to cloud 

 cover, direct cooling by rain showers, as well as the descent from aloft of 

 cool air associated with the condensation-precipitation cycle. These processes 



