Simulations of atmospheric phenomena at the Phoenix landing site with the Ames General Circulation Model

Phoenix, the first NASA Mars Scout class mission, was designed to “follow the water” and study the polar region. Landing in late northern spring, Phoenix measured soil chemistry, near-surface water ice, and studied numerous atmospheric properties and weather phenomena. Here, we use atmospheric measurements made by Phoenix to test and calibrate the Ames General Circulation Model (GCM) and start the process of analyzing and interpreting the vast data set provided by this groundbreaking mission. The GCM reproduces surface pressures and temperatures within the measured diurnal and seasonal ranges. It also reproduces measured water ice cloud profiles with ground fogs forming after L_s = 120° and a separate cloud deck between 3 km and 6 km above the surface. Near-surface water vapor pressures have daytime maxima above 1 Pa in both the data and model. We find that frosts and fogs observed by Phoenix are correlated with the formation of high-pressure weather systems over the landing site.