Large-Scale Eddies in the Unstably Stratified Atmospheric Surface Layer. Part I: Velocity and Temperature Structure

Abstract

Ensemble vertical cross sections are derived for the velocity and temperature fields associated with large-scale eddy (LSE) temperature ramp structures in the turbulent, convective atmospheric surface layer. The turbulent fluxes of heat and momentum, as well as the third-order moments that represent the fluxes of vertical and horizontal heat, stress and turbulent kinetic energy are interpreted in terms of the circulations associated with the LSE structures. Heat flux and stress correlation coefficients are related to the phase relationships between vertical velocity, longitudinal velocity, and temperature. In particular, w? and T? are found to be in phase essentially everywhere. In contrast, u? and w? have a height dependent phase lag which leads to specific regions within the LSE structure where the momentum flux is consistently counter-gradient.