A Two-Dimensional Simulation of the Iberian Summer Thermal Low

Abstract

The forcing mechanisms of the diurnal thermal depression formed over the Iberian Peninsula in the summer and the typical air circulation induced over the Northern Plateau are analyzed by a two-dimensional hydrostatic, high-resolution, primitive equation model applied in a vertical plane perpendicular to the coastline of the Bay of Biscay. Such circulation is characterized by a low-level flow of relatively cold air that progresses inward over the elevated central plateau throughout the afternoon and evening, reaching inland distances up to 150 km at dawn, which tends to fill up the already formed thermal depression. Despite the simplicity of the model, the results obtained show a satisfactory agreement with observations. Finally, a comparison is made between results obtained from a set of simulations with different combinations of land-use types, topographic profiles, thermal stability, and synoptic wind, keeping the other conditions fixed, in order to analyze the individual effects of different terrain and atmospheric-related forcings.