You can use interp2 like this
sigma = 1:6;
OMEGA = 1:10;
T = rand(6, 10);
interp2(sigma, OMEGA, T.', 4, 5) % (4,5) is a sample query point of format (sigma, omega). You can pass vectors too
How do you want to plot? contourf?
contourf(sigma, OMEGA, T.')