PROCESSING PROCEDURES 

 120° 



19 



)17° 



Figure 21. — Contours of dynamic height anomahes (dynamic meters) for surface over 500 decibars. Current direction 

 is indicated by arrows on contours, velocity by contour spacing using scale at lower left. 



When the contours are drawn at equal inter- 

 vals of dynamic height anomaly, the velocity 

 of the current is in-versely proportional to the 

 distance between contours. An insert graph is 

 normally given on the chart to relate dynamic 

 height contour spacing to current speed. 

 Charts showing the dynamic topography of an 

 isobaric surface relative to a lower isobaric 

 STirfacc thus not only present a complete picture 

 of motion at the upper sin-face relative to any 

 motion at the lower surface, but eliminate the 

 need for luimerical calculation of the com- 

 ponents of currents between stations from 

 dynamic height differences. 



Certain limitations to the accm-acy of the 

 current calculations outlined above should be 

 borne in mind: (1) Currents deduced are rela- 

 tive to any unknown current at the reference 

 level rather than absolute values. (2) Ac- 

 celerations have been neglected; if currents are 

 changing, the results of the calculations are less 



valid. (3) Frictional forces have been neg- 

 lected. (4) Observations taken at different 

 times at the different stations have been as- 

 sumed simultaneous. In some areas the in- 

 fluence of internal waves (LaFond, 1949) {23) and 

 tidal influence on dynamic height are taken into 

 account. These limitations may, however, be 

 largely offset by the familiarity with a region 

 which comes with repeated observations (pro- 

 vided conditions are quasi-permanent). 



D.4— EXAMPLES OF PROCESSED SE- 

 RIAL TEMPERATURE AND SALINITY 

 DATA 



The observed data collected at sea, the com- 

 puted values determined during processing, and 

 the final tabulated summary of results are 

 usually all recorded on specially printed forms. 

 The printed columns and spaces on these forms 

 have appropriate designations for the specific 

 information required by the groups concerned 



