function [Struct_a] = CalculateAlpha(Struct)
% [Struct_a] = CalculateAlpha(Struct)
% Input a mass flux struct including mass flux (in unit of kg/m^2/s) and
% saltation flux Q (in the unit of g/m/s), email: Raleigh Martin 1/9/17
% 
% Output: size-resolved sandblasting efficiency (in the unit of m^(-1))

Q = Struct.Q*10^(-3); % saltation flux, in unit of kg/m/s
Q_err = Struct.sigma_Q*10^(-3); % in unit of kg/m/s

for i = 1:7 % 7 bins
    Fd = Struct.Fd(:,i); % mass flux, in unit of kg/m^2/s
    Fd_err = Struct.Fd_err(:,i); % in unit of kg/m^2/s
    
    alpha(:,i) = Fd./Q; % sandblasting efficient, in unit of m^(-1)
    alpha_err(:,i) = sqrt((-1*Fd./Q./Q.*Q_err).^2 + (Fd_err./Q).^2); % in unit of m^(-1)     
end

%--- store the sandblasting efficienct into the Alpha struct
Struct_a.alpha = alpha;
Struct_a.alpha_err = alpha_err;
Struct_a.unit = 'm^(-1)';
Struct_a.z = Struct.z;
Struct_a.StartTimes = Struct.StartTimes;
Struct_a.EndTimes = Struct.EndTimes;
Struct_a.ustar = Struct.ustar;

end