Role of Radiative Flux Divergence in Stable Boundary Layer Development

摘要

The interactions between the radiative field and topography influence the evolution of the atmospheric boundary layer in complex terrain. A synergistic study of these interactions combined the analysis of a rich observational dataset collected in Arizona's Meteor Crater with model simulations made with a newly-available three-dimensional Monte Carlo radiative transfer model. The effects of topography on the receipt of short- and longwave radiative energy and on longwave radiative flux divergence (RFD) within valleys and basins were investigated and quantified. These effects include topographic shading, terrain exposure, and reflections and emissions from surrounding terrain. The strength of longwave radiative flux divergence or longwave radiative heating and cooling in idealized valleys and basins was investigated for representative day- and nighttime conditions in a modeling study in which various parameters were systematically changed, including valley or basin shape and size. The formation of terrain-following daytime superadiabatic and nighttime stable layers on radiative heating and cooling was found to produce major influences on radiative heating rates. Real-case simulations for a clear autumn night showed that nighttime radiative cooling can account for nearly 30% of the total observed nighttime cooling in the Meteor Crater basin.