Chapter 3 



ENVIRONMENTAL FORECASTING 



The purpose of the IDOE Environmental 

 Forecasting Program is to provide the scien- 

 tific base necessary for an improved capability 

 in predicting changes in the environment. 



Long-range and accurate environmental 

 forecasting depends on an understanding of 

 the state of the oceans as wrell as of conditions 

 in the atmosphere. In order to enhance fore- 

 casting capabilities, data on processes at work 

 in the air and sea must be incorporated into 

 predictive models. Since knov^ledge about 

 these processes and mechanisms is incom- 

 plete, it is necessary to put major emphasis on 

 studies of the ocean surface and its interaction 

 with the lower atmosphere, and to determine 

 the dynamic processes in the deep ocean that 

 influence this interaction. Three projects 

 focus on these problems: "Mid-Ocean Dy- 

 namics Experiment" (MODE]; 'North Pacific 

 Experiment" (NORPAX); and "Climate: Long- 

 Range Investigation, Mapping, and Predic- 

 tion" (CLIMAP) program. 



PROGRAM: 



THE MID-OCEAN DYNAMICS 

 PROGRAM (MODE) 



The ultimate purpose of the Mid-Ocean Dy- 

 namics Experiment (MODE] is to establish the 

 dynamics and statistics of meso-scale eddies, 

 their energy sources and their role in general 

 ocean circulation. It is estimated that these 

 medium scale eddies, if indeed they are ubiq- 

 uitous, contain at least as much kinetic energy 

 as the mean ocean circulation and possibly 

 ten times more. Where the energy comes from, 

 how much is present and what it does are 

 questions which must be answered in order 

 to refine the numerical models that are the 

 basis of environmental prediction. It is known 

 that similar eddies exist in the atmosphere. 



that their kinetic energy content is compara- 

 ble to that of the mean flow and that this is 

 sufficient to prevent adequate numerical simu- 

 lation unless it is properly taken into account. 

 Such knowledge may be even more important 

 to the proper modeling of the temporal and 

 spatial behavior of ocean circulation. 



The MODE consists of a continuing theo- 

 retical effort and a series of field experiments, 

 two of which (MODE-0 and MODE-1] have 

 been completed. The site chosen for the 

 MODE-0 and the MODE-1 is an area of 

 600-km diameter and approximately 5-km 

 depth near the Tropic of Cancer and southeast 

 of the Bermuda Islands (Figure 8]. The region 

 was chosen for its lack of a strong mean cur- 

 rent, convenience to the U.S. east coast and 

 good Sound Fixing and Ranging (SOFAR] cov- 

 erage. The MODE-0 field experiment, de- 

 signed to provide additional information on 

 medium-scale eddies prior to a more compre- 

 hensive field experiment, began in November 

 1971 and continued until the start of MODE-1 

 in March 1973. 



MODE 



Mode-O — The MODE-0 field program con- 

 sisted of: Current measurements made with 

 four series of current meter arrays, each of 

 which contained two moorings at the same 

 site; preliminary density and bathymetric sur- 

 veys; and test deployments of SOFAR floats 

 and bottom pressure gauges. Results from 

 MODE-0 include: (1] the identification of 100 

 km as the scale (quarter-wavelength] of the 

 medium scale eddies; (2] the determination 

 that subsurface flotation for current meter 

 moorings is the most practical method of en- 

 hancing signal-to-noise ratios; and (3] the 

 discovery of numerous uncharted bottom 

 features. 



17 



