The GEWEX Atmospheric Boundary Layer Study
The overall objective of the GEWEX Atmospheric Boundary Layer Study (GABLS) is to improve the understanding and the representation of the atmospheric boundary layer in regional and largescale climate models. GABLS aims to provide a platform in which scientists working on boundary layers at different scales will interact. Such activity is important in itself and also very relevant for other activities in GEWEX, and more generally for the activities within WCRP and the International Geosphere-Biosphere Program (Holtslag and Randall, 2001).
The first focus of GABLS is on the representation of the stable atmospheric boundary layer (SBL). It appears that much of the warming predicted by climate models occurs during stable conditions over land (either in winter or at night). At the same time, it is realized that the understanding and parameterization of the SBL is still poor.
As an example, the figure shows the difference in the temperature at a height of 2
meters for January 1996 as calculated from two model runs with the same
forcings, but with (slightly) different stability functions in the mixing scheme
of the ECMWF model in stable conditions.