An imaging SAR is capable of providing support information in the areas 

 of (b), (c) and possibly (e) and is of utility in special-purpose 

 oceanographic and bathymetric studies. It is difficult, however, to discern a 

 strong need for long-term monitoring in these areas. 



E. DEEP CONVECTION 



Deep convection events occur in Arctic and Antarctic waters and in the 

 Mediterranean Sea as intermediate ocean water by transfer downwards of surface 

 water. The convection leads to a sink-type converging flow near the surface, 

 and is of small to medium scale (tens of kilometers), localized and organized 

 within larger scale phenomena. The associated vertical velocities are in the 

 range of 10-100 m per day; the horizontal velocities are unknown. These 

 events are of great oceanographic interest, but as yet, they have not been 

 detected by remote sensing (or, at least, not identified), but SARD may 

 provide a characteristic signature that would allow detection. 



F, ICE LEADS 



The heat transfer through leads in pack ice is crucially important in 

 the heat budgets of models of polar regions as discussed in Chapter 1. They 

 have horizontal scales from 0.01-5 km, though are sometimes larger and subject 

 to change as a result of local and nonlocal wind. SARD provides the best 

 measurement tool. 



The wind field over ice is an important determinant of the ice motion 

 and its measurement provides an interesting challenge. One possible method is 

 to use the length and direction of we 'shadows' in the lee of ice flows in SAR 

 imagery, though it remains to be seen if this technique is useful. One would 

 anticipate that its usefulness may be limited to the summer season when the 

 leads do not contain sheet or much ice. 



G. SAR SPECIFICATIONS FOR OCEANOGRAPHIC PURPOSES 



(1) Frequency: The choice of frequency involves somewhat of a 

 compromise. High frequencies are attractive for the best imagery 

 of short surface waves (C-band or above). High frequencies also 

 yield the maximum wind-speed sensitivity but data on possible 

 cross-section saturation at high winds are not yet available. On 

 the other hand, lower frequencies (L-band) are known to produce 

 increasing cross sections at high wind speeds, and low frequencies 

 may possibly be preferable in terms of interpretation since the 

 wave dynamics of short gravity waves are simpler than gravity- 

 capillary waves or small-scale wave breaking. 



(2) Resolution: 25 x 25 m. 



(3) Swath width: 100 km or greater. 



4-5 



