1972 DYNAMIC TOPOGRAPHY SURVEYS 



As lias been the practice of IIP for many possible to compare tiie dynamic topofiraphy of 



years, the 1000 decibar surface was used as a eacli 1!)72 survey (fi^s. 53, 54, and 55) directly 



reference level in calculating dynamic heights with past surveys and the monthly normal 



from the 1972 data. Experiments as recent as charts. Such comparisons appear in later sec- 



1970 (Ettle and AVolford, 1972) have shown that tions. 

 this level is suitable for IIP work. Thus, it is 



