Radiative and turbulent fluxes in the nocturnal boundary layer

This study examines the relative contributions of turbulent and radiative flux divergences to nocturnal cooling by analyzing data from the 60-m flux tower in CASES99 and using an offline model of the radiative flux. The sensitivity of radiative cooling to structure of the atmosphere near the surface is first examined in terms of artificial profiles. In general, the radiative cooling is proportional to the negative curvature of the temperature profile, magnitude of the specific humidity and the deficit of the ground surface temperature. For the days examined, the radiative flux divergence appears to control the initial formation of the surface inversion at the beginning of the night when the turbulence collapses.