CDNVE: computes neutral drag coefficient following Vera (1983).
[cd,u10]=CDNVE(sp,z) computes the neutral drag coefficient and wind
speed at 10m given the wind speed at height z. Uses the expression
for friction velocity derived by E. Vera (1983) and published as
eqn. 8 in Large, Morzel, and Crawford (1995), J. Phys. Oceanog., 25,
2959-2971. Range of fit to data is 1 to 25 m/s.
INPUT: sp - wind speed [m/s]
z - measurement height [m]
OUTPUT: cd - neutral drag coefficient at 10m
u10 - wind speed at 10m [m/s]0001 function [cd,u10]=cdnve(sp,z) 0002 % CDNVE: computes neutral drag coefficient following Vera (1983). 0003 % [cd,u10]=CDNVE(sp,z) computes the neutral drag coefficient and wind 0004 % speed at 10m given the wind speed at height z. Uses the expression 0005 % for friction velocity derived by E. Vera (1983) and published as 0006 % eqn. 8 in Large, Morzel, and Crawford (1995), J. Phys. Oceanog., 25, 0007 % 2959-2971. Range of fit to data is 1 to 25 m/s. 0008 % 0009 % INPUT: sp - wind speed [m/s] 0010 % z - measurement height [m] 0011 % 0012 % OUTPUT: cd - neutral drag coefficient at 10m 0013 % u10 - wind speed at 10m [m/s] 0014 0015 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% 0016 % 3/8/97: version 1.0 0017 % 8/26/98: version 1.1 (modified by RP) 0018 % 8/5/99: version 2.0 0019 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% 0020 0021 % constants in fit for drag coefficient 0022 A=2.717e-3; 0023 B=0.142e-3; 0024 C=0.0764e-3; 0025 0026 as_consts; % other constants 0027 a=log(z./10)/kappa; % log-layer correction factor 0028 tol=.001; % tolerance for iteration (m/s) 0029 0030 u10o=zeros(size(sp))+.1; % don't start iteration at 0 to prevent blowups. 0031 cd=(A./u10o + B + C*u10o); 0032 0033 u10=sp./(1+a.*sqrt(cd)); 0034 0035 ii=abs(u10-u10o)>tol; 0036 while any(ii(:)), 0037 u10o=u10; 0038 cd=(A./u10o + B + C*u10o); 0039 u10=sp./(1+a.*sqrt(cd)); % next iteration 0040 ii=abs(u10-u10o)>tol; % keep going until iteration converges 0041 end; 0042 0043