The role of thermal inertia in the representation of mean and diurnal range of surface temperature in semiarid and arid regions

In this article we show the possible role of thermal inertia in the large spread of the simulated surface temperature over arid and semiarid regions among climate models. The surface-atmosphere interactions are investigated based on single-column simulations of the DIurnal land-atmosphere Coupling Experiment and on global simulations. Low values of the surface thermal inertia increase the diurnal temperature range (DTR) and the daytime turbulent heat fluxes. The diurnal response of surface temperature to the thermal inertia is asymmetric between daytime and nighttime, inducing a change in the daily mean surface temperature that can reach several degrees over large areas. This asymmetrical response to thermal inertia is shown to be due to the diurnal contrast of the stability state of the atmospheric boundary layer. Thermal inertia in dry regions plays a critical role on both DTR and surface mean temperature and needs to be carefully represented in land surface models.