function phi = temporal(phi_w, t_ref)
%si = size(phi_w);
phi = zeros(size(phi_w));
phi(:, :, :, t_ref) = phi_w(:, :, :, t_ref);
phi_diff = zeros(size(phi_w));
for i = t_ref:size(phi_w, 4)-1
    phi_diff(:, :, :, i) = phi_w(:, :, :, i+1) - phi_w(:, :, :, i);
    phi_diff(:, :, :, i) = phi_diff(:, :, :, i) + 2*pi*(phi_diff(:, :, :, i)<-pi);
    phi_diff(:, :, :, i) = phi_diff(:, :, :, i) - 2*pi*(phi_diff(:, :, :, i)>pi);
    phi(:, :, :, i+1) = phi(:, :, :, i) + phi_diff(:, :, :, i);
end
for i = t_ref-1:-1:1
    phi_diff(:, :, :, i) = phi_w(:, :, :, i+1) - phi_w(:, :, :, i);
    phi_diff(:, :, :, i) = phi_diff(:, :, :, i) + 2*pi*(phi_diff(:, :, :, i)<-pi);
    phi_diff(:, :, :, i) = phi_diff(:, :, :, i) - 2*pi*(phi_diff(:, :, :, i)>pi);
    phi(:, :, :, i) = phi(:, :, :, i+1) - phi_diff(:, :, :, i);
end