THE DETERMINATION OF AVERAGE GEOSTROPHIC CURRENT VELOCITIES FROM 

 TEMPORALLY AND SPATIALLY RANDOM HYDROGRAPHIC DATA WITH AN APPLICATION 



TO THE SOUTHERN CALIFORNIA BIGHT 



INTRODUCTION 



Dynamic depth anomaly data from oceanographic stations are available as a standard product 

 from the National Oceanographic Data Center (NODC). NODC calculates these data from tem- 

 perature and salinity with depth data which it obtains from various sources. It is highly desirous 

 to analyze these data in a manner such as to obtain seasonally averaged dynamic depth anomaly 

 fields, from which can be determined seasonally averaged geostrophic current velocity fields. The 

 location of the data is, however, generally temporally and spatially random, complicating the 

 averaging procedure, and thus requiring the utilization of special methods. 

 THE METHOD 



The most direct method to analyze the data is to group together aU the dynamic depth anomaly 

 data for a particular season and then fit this data by the method of least squares with a two 



dimensional polynomial of the form: 



M N 

 dD = _2 ^ Kn ^™ ^" (1) 



m=o n=o 



where 



dj) = dynamic depth anomaly at depth D 



Aj^jj = regression coefficients 



d - latitude 



= longitude 



M,N = order of the polynomials 

 The virtue of this method is that it treats each data point for exactly what it is, an independent 

 measure of the dynamic depth field, and at the same time yields an analytic expression for the 



