Latent Heat Flux

Latent heat flux is the heat removed from the sea surface by evaporation, carried by water vapor as the latent heat of vaporization (about 2.5e6 J/kg). It is the largest cooling term in the ocean surface energy budget over most of the world ocean. The bulk aerodynamic formula gives Q_L = rho * L_v * C_E * U * (q_s - q_a), where q_s is the saturation specific humidity at the sea surface, q_a the air humidity, U the wind speed, and C_E a transfer coefficient near 1.1e-3. Trade-wind and western boundary current regions reach 150 to 200 W/m2 in the annual mean, with winter peaks above 500 W/m2 over the Gulf Stream and Kuroshio.