COASTAL OCEANOGRAPHIC USE OF THE U.S. AIR FORCE DATA ACQUISITION 

 AND PROCESSING PROGRAM (DAPP) 



I. INTRODUCTION 



This report has three objectives: to introduce the coastal oceanographic capabilities 

 of the U.S. Air Force meteorological Data Acquisition and Processing Program, to briefly 

 define and illustrate a coastal oceanographic problem area for which it is most useful 

 (figure 1), and to outline techniques for obtaining the most useful products. The valuable 

 characteristics of this remote sensing system are the global availability of high resolution 

 (1/3 and 2 n.mi ,) imagery, (figs. 2-10) the high repetition rate (minimum of 4 times daily), 

 and the capability of the infrared sensors to detect thermally distinct surface waters and 

 oceanic fronts. This study is centered about the utility of the film products, the nearly 

 distortion free film transparencies of the visual range and infrared data available at scales 

 of 1:15,000,000 and 1:7,500,000 in near real time. 



A major problem in studies of narrow continental shelf regions of the globe is the 

 detection and measurement of the influence of impinging offshore ocean currents on coastal 

 waters. Permanent or semipermanent currents, the major circulation elements of adjacent 

 ocean basins, are time-dependent features, meandering, repositioning, and even temp- 

 orarily disappearing in the course of an experiment or survey. These currents have fund- 

 amental role as the major source of both seawater and energy to either flush the continental 

 shelf of existing waters or drive the local coastal circulation. The position, orientation, 

 structure and strength of gradients along the landward wall or coastal front of an ocean 

 current, are key indicators of mixing processes and the effects of the impinging ocean current, 

 These fronts, though difficult to observe or even detect by conventional methods, are 

 shown to be readily detected and their movement in time and space easily followed by 

 remote sensing methods. 



Coastal fronts, and oceanic fronts in general, are important but poorly known structures 

 in the sea. The term "oceanic front" has been widely adopted by the oceanographic 

 community from analogy with atmospheric fronts (Griffiths, 1965). Uda (1938) in an early 

 but most definitive paper delved deeply into the structure and origin of oceanic fronts as he 

 sought to understand the nature and mechanism of their common surface effect, current 

 rips or "siome". He defined the latter as "A comparatively narrow stretched band, which 

 appears on the sea surface with singular rippling and is commonly accompanied by foams 

 and other drifting-bodies of various kind. ,, " coinciding with the line of discontinuity 

 between two different watermasses or between currents. Uda classified siomes into three 

 types: the first caused by pure convergence at the sea surface, the second by upwelling 

 or divergence, and the third by strong current shear. He also reports that they frequently 

 though not exclusively, occur near the margin of continental shelves and that they are 

 commonly the sea surface expression of the contact of waters of different colors, chiefly 

 yellow-green coastal waters and the deep blue-green oceanic water. Major ocean fronts 

 are common in deep ocean areas, where they occur as boundary zones between major 

 currents or water types (Defant, 1961, p. 453), Laevastu and Lafond, 1970). Griffiths 

 (1965) proposed the term "frontal system" for the entire boundary between two kinds of 



