function [cd,u10]=cdnlp(sp,z)
% CDNLP: computes neutral drag coefficient following Large&Pond (1981).
% [cd,u10]=CDNLP(sp,z) computes the neutral drag coefficient and wind
% speed at 10m given the wind speed at height z following Large and
% Pond (1981), J. Phys. Oceanog., 11, 324-336.
%
% INPUT: sp - wind speed [m/s]
% z - measurement height [m]
%
% OUTPUT: cd - neutral drag coefficient at 10m
% u10 - wind speed at 10m [m/s]
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% 3/8/97: version 1.0
% 8/26/98: version 1.1 (vectorized by RP)
% 8/5/99: version 2.0
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
as_consts; % define physical constants
a=log(z./10)/kappa; % log-layer correction factor
tol=.001; % tolerance for iteration [m/s]
u10o=zeros(size(sp));
cd=1.15e-3*ones(size(sp));
u10=sp./(1+a.*sqrt(cd));
ii=abs(u10-u10o)>tol;
while any(ii(:)),
u10o=u10;
cd=(4.9e-4+6.5e-5*u10o); % compute cd(u10)
cd(u10o<10.15385)=1.15e-3;
u10=sp./(1+a.*sqrt(cd)); % next iteration
ii=abs(u10-u10o)>tol; % keep going until iteration converges
end;