PART V — SEVERE STORMS 



ing. Observations are needed to 

 document more thoroughly the nat- 

 ural variability of hurricanes; to de- 

 termine the distribution of water in 

 all its phases in the inner portions of 

 both natural storms and before, dur- 

 ing, and after seeding in experimental 

 storms; and to quantify further the 

 interactions among physical processes 

 on the various scales important to 

 hurricanes. Theoretical models and 

 associated computer simulations need: 

 (a) to be improved in the way in 

 which smaller-scale processes are 

 treated implicitly through parameter- 

 ized relationships; (b) to be gen- 

 eralized such that the effects of in- 

 ternal processes on the motion of 

 the storm can be treated; and (c) to 

 utilize improved observations as 



varying boundary and initial condi- 

 tions for the models. 



Time-Scale — The urgency of sat- 

 isfying these needs is undoubtedly 

 relative. In terms of clarifying the 

 scientific basis for Project STORM- 

 FURY, the need is very urgent. To 

 substantiate the encouraging, but 

 inconclusive, results from past ex- 

 perience and, thereby, provide a solid 

 foundation for modification experi- 

 ments on storms threatening inhab- 

 ited coastlines, their importance can- 

 not be overemphasized. 



These advances in scientific back- 

 ground are needed within one to two 

 years. Instrumentation and observa- 

 tional platforms needed to fill most 

 of the known gaps in the scientific 



data base for both natural and experi- 

 mental hurricanes are available. Sim- 

 ilarly, significant improvement in 

 computer simulation is possible with 

 existing computers. 



Legal Implications — The greatest 

 potential policy problems associated 

 with hurricane modification will arise 

 from the legal questions that will be 

 raised at both national and interna- 

 tional levels when modification ex- 

 periments are carried out on storms 

 which shortly thereafter affect in- 

 habited coastal regions or islands. 

 When and if we are able to predict 

 what will result from such modifica- 

 tion attempts, who will make the 

 decisions? A study of these problems 

 is sorely needed. 



A Note on the Importance of Hurricanes 



Necessity 



Our understanding of the physical 

 laws governing the behavior of the 

 atmosphere has not advanced to the 

 point where we can deduce from 

 these laws that hurricanes, or any 

 tropical circulation systems resem- 

 bling hurricanes, must occur. It is 

 just reaching the stage where we can 

 deduce theoretically that systems of 

 this sort may occur. Recent numeri- 

 cal experiments aimed at simulating 

 hurricanes have produced cyclonic 

 circulations of hurricane intensity 

 from initial conditions containing 

 weak vortices. Other experiments 

 aimed at simulating the global circu- 

 lation have produced concentrated 

 low-pressure centers within the trop- 

 ics, but the horizontal resolution 

 has been so coarse that it is impos- 

 sible to say whether the models are 

 trying to simulate hurricanes. 



Nevertheless, from our general 

 knowledge of atmospheric dynamics 

 together with the observation that 

 hurricanes do occur and continue to 

 occur year after year, we can safely 

 conclude that hurricanes not only 



may but must occur if nature is left 

 to its own devices. We could make 

 a similar statement about other at- 

 mospheric motion systems (e.g., tor- 

 nadoes) that occur repeatedly. 



Such reasoning does not apply to 

 everything that is observed in nature. 

 It would be incorrect to conclude, 

 for example, that a particular species 

 of animal is necessary simply because 

 it exists. If we should destroy all 

 members of the species, there is no 

 assurance that evolutionary processes 

 would ultimately create the same 

 species again. However, hurricanes 

 are not a species; new hurricanes are 

 not ordinarily born of old ones. On 

 the contrary, they, or the weaker 

 tropical disturbances that mark their 

 origin, appear to be spontaneously 

 generated when the proper distribu- 

 tions of atmospheric temperature, 

 moisture, wind, oceanic temperature, 

 and probably certain other quantities 

 occur in the tropics on a worldwide 

 or ocean-wide scale. 



Strictly speaking, therefore, we 

 should modify the statement that 

 hurricanes are necessary by saying 



that they are necessary only if the 

 larger-scale conditions characterizing 

 the tropical environment are main- 

 tained over the years. The absence 

 of hurricanes in the southern Atlantic 

 Ocean is presumably due to the 

 local absence of favorable large-scale 

 conditions, as is the relative scarcity 

 of hurricanes in other oceans during 

 the winter season. 



What If Hurricanes Could Be De- 

 stroyed? — Assuming that the tropi- 

 cal environment is favorable to the 

 formation of hurricanes, the latter, 

 in forming, will exert their own ef- 

 fects on the environment. Hurricanes, 

 by virtue of the active cumulonimbus 

 clouds that they contain, are effective 

 in transporting large amounts of heat 

 and moisture upward to high levels. 

 They may also carry significant 

 amounts of heat, moisture, and mo- 

 mentum from one latitude to another. 

 In any event, they act to alter the 

 environment; in the long run, their 

 effect on the environment must be 

 exactly canceled by that of other 

 processes. 



Suppose, then, that nature is not 

 allowed to take its course. Suppose 



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