Atmospheric energy fluxes over Europe

Abstract

Horizontal fluxes of atmospheric energy (sensible and latent heat, potential and kinetic energy) are computed at European aerological stations between the surface and the 150 mb level for the period 1974–1976. The fluxes are divided into their mean flow and transient eddy contributions. The main emphasis is given to the computed transient eddy fluxes and their physical and synoptic interpretation.

The vertically integrated transient eddy fluxes of sensible heat and latent heat are essentially down-gradient and reflect the “mixing” caused by the large-scale atmospheric turbulence.

The transient eddy flux of sensible heat in the upper troposphere over western Europe in winter is found to be southward and up-gradient. By using a simple averaging technique it is shown that this up gradient flux is due mainly to fluctuations with a period of less than 1 month. A synoptic example is presented showing a large-amplitude wave, typical in situations when formation of cut-off lows and shearlines takes place in the upper troposphere. In this case there is a negative spatial correlation between temperature and the meridional wind component. This kind of phenomenon, which is common over western Europe, is at least partially responsible for the observed up-gradient component of the sensible heat flux by transient eddies.