NCC - TDF-1I - ONE DEGREE SUMMARIZATION 



NOAA - NflTIONRL MARINE FISHERIES SERVICE 



PHCIFIC ENVIRONMENTAL GROUP 



MONTEREY. CALIFORNIA 



ONSHORE SURFACE STRESS 



( DYNE CM-2 ) 



LONGSHORE TIMESERIES GRID SECTION ( 1 ) 



LONG TERM MEAN 



1B57 - 1972 



JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC 



JAN FEB MAR RPR MAY JUN JUL AUG SEP CC 



. WIND STRESS VECTOR 



^ 



C? 



~~X EKMAN TRANSPORT VECTOR 



~"N UPWELLING-DOWNWELLING VECTOR 



A 



POSITIVE 



CURL 



NEGATIVE 

 CURL 



Figure 15. — A conceptual diagram of the relationship of wind stress 

 curl to the divergence and convergence of surface Kkman transport 

 offshore of the primary coastal upwelling zone. 



Direct measurements of wind stress curl are not 

 available; however, the curl of the monthly mean sur- 

 face wind stress fields has been computed. The vertical 

 component of the curl of the wind stress in spherical 

 coordinates is defined by: 



*• (V Xr ) 



1 



R cos 



ax 



J? (t cos 



(7) 



where R is the radius of the earth, </> and A denote geo- 

 graphic latitude and longitude, respectively, and t x and 

 r y denote the eastward and northward components of the 

 mean surface wind stress. A finite difference equation 

 approximating the curl at the grid point (i,j) in Figure 16 

 is given by: 



(Vx 



R cos. 



'i" + i.j *i-i.j 



-f 



( T, COS f ) 



■>+ I 



2AX 



(fjCOSvp),- 



2A*p 



-) 



(8) 



where A^ = A X = 1°. The method is similar to calcula- 

 tions described by Hantel (1970). Centered differences 

 were utilized throughout the interior of the data grid. 

 Forward and backward differences were required along 

 the boundaries. As a result, certain artificial features 

 may have been introduced at these boundaries. 



Monthly Curl Distributions 



Monthly fields of surface wind stress curl are dis- 

 played in Appendix III (Charts 37 to 48). These dis- 

 tributions correspond to the monthly mean wind stress 

 distributions shown in Appendix I. Values are plotted in 

 units of dyne cm" 2 per 100 km. A value of 1 dyne cm -2 



Figure 14. — Seasonal cycle of onshore surface wind stress near the 

 coast. Means of the onshore components of wind stress were com- 

 puted by month for the 1 -degree squares immediately adjacent to the 

 coast. Units are dyne cm . The contour interval is 0.5 dyne cm* 2 . 

 Offshore stress is shaded. Numbers along ordinate are degrees north 

 latitude. 



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