function tau=stresslp(sp,z,rhoa)
% STRESSLP: computes neutral wind stress following Large and Pond (1981).
% tau = STRESSLP(sp,z,rhoa) computes the neutral wind stress given the wind
% speed at height z following Large and Pond (1981), J. Phys. Oceanog.,
% 11, 324-336. Air density is an optional input, otherwise assumed to
% be constant (1.22 kg/m^3).
%
% INPUT: sp - wind speed [m/s]
% z - measurement height [m]
% rhoa - air_density (optional) [kg/m^3]
%
% OUTPUT: tau - wind stress [N/m^2]
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% 3/8/97: version 1.0
% 8/26/98: version 1.1 (revised by RP)
% 4/2/99: version 1.2 (optional air density added by AA)
% 8/5/99: version 2.0
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% get constants
as_consts;
if nargin == 2
rhoa = rho_air;
end
[cd,u10]=cdnlp(sp,z);
tau=rhoa.*(cd.*u10.^2);