Influence of topography on the Phoenix CO₂ dome: A computational study

Recent measurements reveal that atmospheric carbon dioxide (CO₂) concentrations in the urban core of Phoenix, Arizona, are often 200 ppmv above the surrounding areas. This increase is up to two orders of magnitude higher than comparable values in other cities. In this investigation, we examine the role of topographically induced circulation as a contributor to the CO₂ dome. A three-dimensional time-dependent regional model shows that frequently occurring katabatic winds generate a mesoscale circulation in Phoenix conducive to the accumulation of CO₂ in the center of the city. We conclude that local topography and associated circulation regimes are important in understanding the high levels of CO₂ in the Phoenix metropolitan area.