PART IV — DYNAMICS OF THE ATMOSPHERE-OCEAN SYSTEM 



Ocean Circulation — Over the past 

 decade, three-dimensional numerical 

 models for calculating ocean circula- 

 tion have been developed by the So- 

 viet Hydrometeorological Service and 

 NOAA. The methods used are sim- 

 ilar to those of numerical weather 

 forecasting. Given the flux of heat, 

 water, and momentum at the upper 

 surface, the model predicts the re- 

 sponse of the currents at deeper 

 levels. The currents at deeper levels 

 in turn change the configuration of 

 temperature and salinity in the model 

 ocean. 



Although active work in develop- 

 ing these models is being conducted 

 at several universities, the only pub- 

 lished U.S. calculations are based 

 on the "box" model developed at 

 NOAA's Geophysical Fluid Dynamics 

 Laboratory. This model allows the 

 inclusion of up to 20 levels in the 

 vertical direction and a detailed treat- 

 ment of the bottom and shore con- 

 figuration of actual ocean basins. 



Cox's calculation of the circulation 

 of the Indian Ocean is perhaps the 

 most detailed application yet at- 

 tempted with the NOAA "box" 

 model. Using climatic data, it was 

 possible to specify the observed dis- 

 tribution of wind, temperature, and 

 salinity at the surface as a function of 

 season. The model was then able to 

 make an accurate prediction of the 

 spectacular changes in currents and 

 upwelling in response to the changing 

 monsoons that were measured along 

 the African coast during the Indian 

 Ocean Expedition of the early 1960's. 



Application of the Model to Prac- 

 tical Problems — The numerical mod- 

 els designed for studying large-scale 

 ocean circulation problems can be 

 modified to study more local circula- 

 tion in near-shore areas or inland 

 seas such as the Great Lakes. Thus, 

 numerical models may be useful for 

 the many problems in oceanography 

 in which steady currents play a role. 

 A partial list includes: (a) long-range 

 weather forecasting; (b) fisheries fore- 



casting; (c) pollution on a global or 

 local scale; and (d) transportation in 

 the polar ice-pack. 



Needed Advances 



The Data Base — Standard oceano- 

 graphic and geochemical data provide 

 a fairly adequate base for modeling 

 the time-averaged, mean state of the 

 ocean. The data base for modeling 

 the time-variability of the ocean is 

 extremely limited, however. Infor- 

 mation on large-scale changes in 

 ocean circulation as well as the small- 

 scale variability associated with mix- 

 ing in the ocean have not been gath- 

 ered in any comprehensive way. 



Future progress in ocean modeling 

 will depend on more detailed field 

 studies of ocean variability. Such 

 studies will establish the data base 

 for the formulation of mixing by 

 small-scale motions which must be 

 included in the circulation model. 

 Information on large-scale variability 

 will provide a means for verifying the 

 predictions of the models. 



Technical Requirements — The 

 most promising approach appears to 

 be the different arrays of automated 

 buoys that have been proposed as 

 part of the International Decade of 

 Ocean Exploration (IDOE) program. 

 Coarse arrays covering entire ocean 

 basins, as well as detailed arrays for 

 limited areas, will be required. 



Another technical requirement for 

 ocean modeling is common to a great 

 many other scientific activities: the 

 steady development of speed in elec- 

 tronic computers and the steady de- 

 crease in unit cost of calculations. 



Manpower Training — Numerical 

 models of currents have now reached 

 a point where they can be of great 

 value in the planning of observational 

 studies and the analysis of data col- 

 lected at sea. The models can be used 

 in diagnostic as well as predictive 

 modes. This is particularly true of 



the buoy networks proposed as part 

 of the IDOE. In order to do this, 

 however, more oceanographers will 

 need to be trained to use the numeri- 

 cal models and to carry out the com- 

 putations. This action will have to 

 be taken quickly if numerical models 

 are to have much signficance in IDOE 

 programs. 



Application of Ocean Modeling 

 in Human Affairs 



As pointed out by Revelle and 

 others, a large fraction of the added 

 carbon dioxide (CO-) generated by 

 the burning of fossil fuels is taken 

 up by the oceans. However, few 

 details are known concerning the 

 ocean's buffering effect and how long 

 it will continue to be effective. The 

 ability of the ocean to take up CO- 

 depends very much on how rapidly 

 surface waters are mixed with deeper 

 water. More detailed studies of geo- 

 chemical evidence and numerical 

 modeling are essential to get an un- 

 derstanding of this process. A start 

 in numerical modeling of tracer dis- 

 tributions in the ocean has been 

 made by Veronis and Kuo at Yale 

 University and Holland at the NOAA 

 Geophysical Fluid Dynamics Labora- 

 tory. 



Another urgent task is to make an 

 assessment of the effect of CO- and 

 particulate matter in the atmosphere 

 on climate. Present climatic knowl- 

 edge does not allow reliable quan- 

 titative predictions of the "green- 

 house effect" due to CO- or the 

 screening out of direct radiation by 

 particulate matter. Published esti- 

 mates have been based on highly 

 simplified models that treat only the 

 radiational aspects of climate. But 

 no climate calculation is complete 

 without taking into account the cir- 

 culation of both the atmosphere and 

 the ocean. Some preliminary climatic 

 calculations have been carried out 

 with combined numerical models of 

 the ocean and atmosphere. But 

 greater effort is required to develop 



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