Radiative scaling of the nocturnal boundary layer and the diurnal temperature range

Abstract

A radiative scaling for the warm season nocturnal boundary layer (NBL) is proposed, based on the daily mean surface net longwave radiation flux. Using this scaling, a conceptual model is proposed for the NBL, with parameters estimated from multiple linear regression of model data from the European Centre reanalysis, averaged over river basins from the tropics to high latitudes. A radiative temperature scale, computed from surface net longwave radiation flux and the slope of the Stefan-Boltzmann law, primarily determines the strength of the NBL and the amplitude of the diurnal temperature range, although the length of the nighttime period and the surface wind stress play important subsidiary roles, A related radiative velocity scale or radiative conductance, the duration of the nighttime period and the ratio of the scaled surface heat flux (which increases with wind stress) to the NBL strength determine the depth of the NBL. From an observational perspective, this suggests that the diurnal temperature range may give a useful estimate of surface net longwave radiation flux. From a modeling perspective, this provides a framework for relating model physical parameterizations, especially the coupling at night between the surface, the ground and the atmosphere, to observables, the diurnal temperature range and the strength and depth of the NBL. The model is then applied to estimate the nocturnal rise in concentration of gases such as CO 2 and radon that are emitted at the surface. Copyright 2006 by the American Geophysical Union.