Introduction

Abstract

The exchanges of momentum, heat, and moisture between the atmosphere and the earth’s surface have a fundamental influence on the dynamics and thermodynamics of the atmosphere. The oceans and continents store a portion of the incoming solar energy and eventually return it to the atmosphere. Over land, this delay is short because most of the net radiation returns to the atmosphere through turbulent exchanges that have rather small characteristic time scales and are very efficient. Part of the returned energy is immediately usable in the form of the sensible heat flux. The other and larger part is the latent heat (or moisture) flux. The energy transfer from the surface to the atmosphere approximately compensates for the loss by radiative transfer. Thus on the global scale (typically the whole globe for a space scale and 1 year for a time scale) the atmosphere maintains a constant level of energy (internal + potential + kinetic). However, this global energy balance is not achieved on smaller space and time scales, and atmospheric motions act to transfer energy among the different regions of the globe. A workshop was held in Banyuls in 1988 with the objective of improving the understanding of how land surface processes affect this transfer and the local climates.