the digitized depth field. Special care was observed when comparing 

 the digitized depth fields to the bathymetry chart, especially in the 

 shelf break regions and modifications were made where necessary. 



b) Numerical integration scheme 



The multioperational alternating direction implicit algorithm 

 developed by Leendertse (1967) was adopted for time integration of 

 the finite difference equations. The following notation is used in 

 the discussion. The spatial average of a field variable X is 

 written as 



X"(I,J) = •i[X(I-J,J-^)+X(I+J,J-J)+X(I-JfJ+i>-*-X<J-4'J+i)]' <39) 



where X"(I,J) = X(Xo+lAX,4>o+JA$,to+nAt) . Time and space derivatives 

 are depicted by the standard centered differences, 



9X/at = (l/At)[X""'-^(I,J)-X""^(I,J)], 



(40) 



3X/aX = (cos<l>/AX)[X'^(I+J,J)-X'^(I-i,J)]. 



A spherical coordinate system is employed in representing the 

 gradient terms on a level surface, i.e., 



VX = (l/ae(J)){aX/3* a + e{J)dX/d\ h] (41) 



where X is any scalar field variable, a is a unit vector along lines 

 of constant $, b is a unit vector along lines of constant X, and 

 d(J) = cos($o+JA$), where 4>o is the reference latitude (18°N). 



21 



