B. INTERNAL WAVES 



Internal wave activity in the ocean is of considerable research 

 interest, and groups of internal waves have been detected by SAR, particularly 

 in coastal regions. However, the detection of internal waves from their 

 surface manifestations is certainly very selective, limited probably to the 

 low-mode, large-amplitude waves, usually tidally generated near the shelf 

 break, and constitute only a small subset of all internal wave motions. 

 Nevertheless, there is interest in the measurement of group and phase 

 velocities of these waves since this gives information on the density 

 structure below the water surface. There is interest in determining the 

 source of these particular waves and their mechanisms of attenuation and the 

 processes of their interaction with current shear. There is also interest in 

 the dissipation of these waves which may produce local mixing and thus affect 

 the primary energy production and diffusion in coastal waters. 



C. MARINE METEOROLOGY 



Operational and research needs in this area include determination of 

 wind speed and direction over both water and ice, measurement of atmospheric 

 stability, particularly in the lower atmosphere, the 2-dimensional structure 

 of weather patterns and their movements, the location and characteristics of 

 intense storms, and mesoscale atmospheric variability. SAR imagery appears to 

 provide information on mesoscale variability (scales 1-10 km) that is not 

 readily obtainable in other ways, but the range of conditions over which 

 useful information can be extracted may be limited to low wind speeds. SAR is 

 capable of providing the precise location of atmospheric fronts and this 

 ability may be useful in conditions in which a general cloud cover is present. 

 Capabilities in this area are still somewhat unexplored and there may be 

 useful information in existing SAR data that has not as yet been extracted. 



D. CURRENTS 



Oceanic current systems exist over a wide range of scales, spatially and 

 temporally, and the usefulness of SAR varies widely in different context. 



(a) At the largest scale are the general circulation synoptic scale 

 disturbances at 50-200 km with temporal scales greater than 5 days. These 

 represent large-scale currents and major oceanic fronts along the boundaries 

 of different water masses and associated eddies. Dynamically, they are quasi- 

 geostrophic below the surface frictional layer and have associated currents of 

 10-200 cm; they are delineated by variations in sea surface temperature, and 

 the currents are associated with a variation of sea surface level relative to 

 the geoid. In decreasing order of success, they are measurable and mappable 

 by means of altimetry, infrared radiometry and the Doppler SAR (SARD) if ever 

 it becomes operational. In addition, there is the wind driven component of 

 the current (the surface Ekman layer), 30-50 m in depth, which can be 

 associated with regional winds over past time, and also equatorial currents 

 which do not have geostrophic surface slopes. These cannot be measured by 

 altimetry or IR but could be measured by SARD. 



4-3 



