This study seeks to improve our physical understanding of the variability, structure, and evolution of the North American monsoon (NAM) in Arizona. NAM brings thunderstorm activity across Northern Mexico and the Southwest United States, often associated with flash floods, resulting in property damage and occasional deaths. We combine mesoscale model simulations and observations to gain insight into the temporal and spatial variability of NAM precipitation, airflow, and circulation response to slowly varying boundary conditions (e.g. sea surface temperature—SST and terrain forcing). This study focuses on the development of simple conceptual models for the monsoon circulation patterns and boundary layer evolution over several locations in Arizona.

We utilize a mesoscale model, remote sensing data, and surface and upper-air observations to explore the mechanisms affecting the initial onset of monsoon rainfall in Arizona. We also investigate the various contributions of Gulf of California moisture surges, mesoscale flow patterns, and surface boundary conditions in controlling the characteristics, evolution and propagation of monsoon convection. We examine the boundary layer and moisture transfer mechanisms between the Gulf of California and the atmosphere.