Environmental Forecasting Program 



Long-range and accurate environmental forecasting re- 

 quires knowledge of the processes and mechanisms of the 

 oceans and the coupling of the ocean and the atmosphere. The 

 Environmental Forecasting Program focuses on projects de- 

 signed to explain the large-scale, long-term behavior of the 

 ocean and the ocean's influence on weather and climate. 

 Experiments and studies include: the Joint U.S.-U.S.S.R. Mid- 

 Ocean Dynamics Experiment (POLYMODE); the North 

 Pacific Experiment (NORPAX); the International Southern 

 Ocean Studies (ISOS); and the Climate: Long-range Investiga- 

 tion, Mapping and Prediction Study (CLIMAP). 





MODE 



Midocean Dynamics Experiment (MODE) 



The MODE project of the United States and the United 

 Kingdom has been joined with the U.S.S.R. POLYGON project 

 in a large-scale midocean dynamics experiment, POLYMODE. 



Joint U.S.-U.S.S.R. Midocean 

 Dynamics Experiment (POLYMODE) 



The purpose of POLYMODE is t oestablish the dynamics 

 and statistics of mesoscale motions in the ocean, their energy 

 source, and their role in the general circulation of the ocean. 

 POLYMODE is based on the U. S.S.R. POLYGON project— a 

 continuing series of experiments investigating mesoscale phe- 

 nomena in the Atlantic and Pacific Oceans and in the Arabian 

 Sea — and the MODE project of the United States and the United 

 Kingdom. The POLYMODE experiment is under the direction 

 of a Joint U.S.-U.S.S.R. POLYMODE Organizing Committee, 

 established under the Agreement between the Governments of 

 the United States and the U.S.S.R. on Cooperation in Studies 

 of the World Ocean. Other countries have been invited to 

 participate in POLYMODE by the UNESCO/International 

 Oceanographic Commission's Scientific Committee on Oceanic 

 Research (SCOR) Working Group 34. 



Figure 1 is a series of maps based on MODE-I data. 

 Figures 2 and 3 show the location of current meter measure- 

 ments made as a part of the MODE-L POLYGON, and 

 POLYMODE projects to date. Results of these experiments 

 are summarized as follows: 



L There is an oceanic eddy (variability) field with definable 

 time and length scales. 



2. The eddy field is ubiquitous and normally highly energetic 

 relative to the mean general circulation. 



3. The eddy field is highly inhomogeneous on a gyre scale — 

 energy levels vary by at least two orders of magnitude and 

 vertical, horizontal, and spatial scales vary to a lesser extent. 

 At a superficial level at least, no one region can be described 

 as "typical." 



4. In some regions, the eddy field is inhomogeneous over 

 scales comparable to the eddies themselves. 



5. The local dynamics of eddies are indistinguishable from 

 geostrophic assumptions; in general, the dynamics are con- 

 sistent with quasigeostrophic assumptions. 



6. Numerical models with sufficient resolution produce sig- 

 nificant eddy activity with realistic scales. 



Based on these results, the scientific objectives for the 

 U.S. POLYMODE project are: 



1. To carry out field observations and experiments, primarily 

 in open ocean regions of the western North Atlantic, designed 

 (as far as possible) to advance our knowledge of the kinematics 

 and dynamics of the variability in that region and to determine 

 its role in the circulation of the North Atlantic subropical gyre; 

 and 



2. To pursue theoretical/numerical modelling of the phe- 

 nomenon and to apply state-of-the-art theory to the design and 

 rationalization of the POLYMODE field data via both local 

 forecast-process numerical models and high resolution numeri- 

 cal models of the North Atlantic gyre general circulation. 



United States participation in POLYMODE is jointly 

 funded by the Office of Naval Research and the National 

 Science Foundation. This participation consists of coordinated 

 research projects that range from field experiments through 

 theoretical studies. 



POLYMODE Field Experiments 



Two main types of observational activity have emerged: 

 ( 1 ) a study of the statistics of eddy motion in different geo- 

 graphical areas and (2) a local dynamics experiment. The 

 former is necessary because no one region seems to be repre- 

 sentative of the full complexity of eddies over the entire ocean 

 basin, and because dynamically different regions are known to 

 exist. The latter is necessary because one needs to penetrate 

 deeply into the dynamical balance and machinery of a few 

 eddies. These two directions are the main task of POLYMODE, 

 and this is called the "U.S. Core Program." 



There are many aspects of the eddy problem which are 

 important and which lie outside the above tasks and on which 

 important related research may occur independently. It is 

 important to maintain communication, limited coordination, 

 data exchange, and the opportunity for mutual scientific par- 

 ticipation with such programs. These are refered to as "Com- 

 plementary Programs of POLYMODE." Elements of program 

 activities follow. 



