MONTHLY MEAN SEA CURRENTS FOR THE 

 WEST COAST OF THE UNITED STATES AND HAWAII 

 BY 

 Dr. Kenneth A. Mooney 

 LCDR Alan Sunmy, M.S. 

 INTRODUCTION 

 In 1977 the Oceanographic Unit was given the general task of providing 

 improved current information for various areas around the coastal United States 

 and Hawaiian Islands. The problem has been that for drift calculations the 

 standard method used was to vectorial ly add a sea current, a wind current, and 

 a leeway factor. This method depends on the accuracy of the various components. 

 At the time of this study the sea current being used was one derived mainly 

 from historic ship set and drift measurements. Set and drift measurements do 

 not accurately reflect the sea current both because of the dead reckoning 

 navigation errors and the fact that they also contain an inherent wind current 

 component. Thus when these quasi sea currents are combined with a wind current 

 the result would be to over-drift the object of the search. 



The Oceanographic Unit has endeavored to improve search planning by 

 upgrading the mean sea current used. The method used to determine this 

 permanent, large scale flow of the oceans required a detailed knowledge of the 

 mean temperature, salinity, and density fields in an area. Due to the large 

 scope of area to be covered and the prohibitive cost of ship time the 

 Oceanographic Unit turned to the National Oceanographic Data Center where such 

 information is available for many parts of the world's oceans. 



The result of the analysis of this historical hydrographic data was the 

 production of mean sea current charts on a maximum grid of 1° by 1°. These 

 mean sea currents are the mean geostrophic currents computed from dynamic 



