Model efekata radijacijskog prijenosa topline u graničnom sloju atmosfere

During nighttime clear-sky conditions and in the absence of significant advection the influence of divergence of net longwave radiative flux on thermodynamic processes could be dominant in the atmospheric boundary layer. The model which parameterizes such processes by height (35 grid points up to 2000 m) is accomplished based on the emissivity concept. The test of the model is performed on the Wangara experiment data. The results are analyzed and discussed concerning a complex structure of the total cooling rate, especially in the lower part of the nocturnal boundary layer (region of smaller wind speeds)

The cooling rates comparison between the longwave radiation and turbulence in nocturnal planetary boundary layer

It is shown that the process of the air-cooling is dominated by the divergence of the longwave radiative flux in cases of night-time clear-sky conditions and with weak wind conditions. The parameterization of the longwave radiative flux divergence is derived according to the emissivity concept and the Stefan-Boltzman law, assuming that the water vapor is the only absorber of longwave radiative. The parameterization of the turbulent temperature flux divergence has been based on the O’Brien’s K-profile. In a very short time increment, the effect of the turbulence is probably greater than the radiative effect, but very stable conditions and the absence of significant advection during the night change this hierarchy, and pure longwave radiative effect, like a slow-diffusive process, prevail in the total cooling rate according to the theory and experiments. The model was tested on the Wangara experiment data. The model results agree well with observations, measurements and numerical simulations made by other authors