Wunsch, C. 1976. Geographical variability of the internal wave 

 field: a search for sources and sinks. J. Phys. Oc. 6:473- 

 485, (MODE contrib. 54). 



Wunsch, C. 1976. The Mid-Ocean Dynamics Experiment-1 . 

 Oceanus 19:45-53. 



North Pacific Experiment (NORPAX) 



The long-term objective of NORPAX is to understand 

 fluctuations in the upper layers of the North Pacific Ocean and 

 their relation to the overlying and adjoining atmosphere. These 

 fluctuations have time scales of months to years and a space 

 scale in excess of 1,000 km. Achievement of this goal should 

 lead to improved prediction of weather and climate for the 

 northeast Pacific Ocean and North America. NORPAX is 

 working to attain its long-range objective through analysis of 

 historical data, experiments to identify and understand im- 

 portant processes, monitoring of low-frequency fluctuations, 

 and integration of observations with theoretical and numerical 

 studies. 



NORPAX is jointly sponsored by the NSF, IDOE Office 

 and the Office of Naval Research. The coprincipal investigat- 

 ors form the nucleus of NORPAX (table 10). They annually 

 elect an executive committee that oversees the entire program, 

 formulates plans and policy, coordinates activities requiring 

 cooperation, and represents NORPAX in dealing with the 

 granting agencies and the rest of the scientific community. The 

 five members of the executive committee select a chairman 

 who is assisted by the program administrator. 



Most principal investigators belong to at least one of the 

 various groups and task forces formed within the program. 

 These groups are related to certain scientific problem areas 

 (Climate Group), to specific experiments (Anomaly Dynamics 

 Study, Equatorial Program) or to important organizational 

 tasks (XBT Panel, Satellite Data Evaluation Panel). Member- 

 ship in these groups is voluntary and by self-appointment; 

 scientists who are not NORPAX investigators, but who are 

 willing to contribute to the program, may also be members of 

 these groups. 



Climate Studies 



The objectives of the Climate Studies are to understand 

 long period, large scale, temperature and circulation changes 

 in the North Pacific and to relate these cnanges to variations m 

 atmospheric circulation. 



Perhaps the most striking accomplishment of the Climate 

 group was the prediction of the abnormal winter weather of 



1976-77 in the United States. This forecast is given in figure 

 7. Temperatures were forecast in three categories: below, near, 

 and above normal, each category having equal climatological 

 probability of occurrence as determined from 30 years of 

 record. Similarly, precipitation was also forecast in three likely 

 categories: light, moderate, and heavy. Forecasts for both 

 elements show appreciable skill. They were mainly based on a 

 computerized model of large-scale air/sea interactions devel- 

 oped for the North Pacific. More specifically the sea-surface 

 temperature patterns in the fall were predicted kinematically 

 to evolve into a winter pattern. This was then translated by 

 the model into a compatible midtropospheric (atmospheric) 

 flow pattern, which indicated an abnormally strong Aleutian 

 low with its maximum anomaly centered at 50°N, 180°W. 

 This prognosis made it possible to use a newly developed set 

 of teleconnections (cross-correlations) (fig. 8) to predict a 

 strong ridge over western North America and a strong trough 

 over the U.S. east coast, which brought frigid air and snows 

 to the eastern two-thirds of the United States and drought to 

 the Far West. 



During the past year, climate group scientists have also 

 been engaged in a study of seasonal and interannual fluctua- 

 tions of the Subtropical Gyre in the western North Pacific from 

 1954 to 1974. To accomplish this, temperature data from 

 historical mechanical bathythermograph (MBT), expendable 

 bathythermograph (XBT), and hydrographic data files were 

 combined. From this combined data set, the seasonal clima- 

 tology at standard depths (down to 400 m) was computed. 

 Also computed was the integral of temperature, called "steric 

 height," as shown in figure 9. This parameter shows significant 

 seasonal variability, particularly in the center of the Sub- 

 tropical Gyre at 17.5°N, in the ridge between the North Equa- 

 torial Current and the North Equatorial Countercurrent at 

 7.5 °N, and in the region of the Kuroshio south of Japan at 

 33 °N. The Subtropical Gyre and the component currents are 

 most energetic in the spring and summer, and least energetic 

 in the fall and winter. 



Figure 10 shows the annual climatology of steric height 

 anomaly for the western North Pacific, together with a 20-year 

 record of the relative surface current speed for the major 

 zonal currents in this part of the North Pacific Ocean. All these 

 currents show a significant seasonal cycle, together with sub- 

 stantial year-to-year changes. The Kuroshio ( not shown in 

 fig. 10) and the North Equatorial Countercurrent fluctuate 

 from year to year more or less in phase, but out of phase with 

 the strength of the North Equatorial Current and the Sub- 

 tropical Countercurrent. 



These results show that the equatorial and midlatitude 

 portions of the Subtropical Gyre are linked in a definite way, 

 indicating that the entire Subtropical Gyre must be studied if 

 variability in any one part is to be understood. 



Anomaly Dynamics Study 



The objective of the Anomaly Dynamics Study is to ex- 

 plain the origin of the large heat storage anomalies that are 

 observed in the surface layer of the Pacific Ocean. One im- 



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