Spatial Patterns and Determinants of Atmospheric Carbon Dioxide Concentrations in Phoenix metro area

The purpose of this work is to describe determinants and spatial patterns of
atmospheric carbon dioxide (CO2) in Phoenix, Arizona. Specifically, we use
geographic information systems (GIS) and regression-based analyses to identify the
human and biological factors that contribute to spatial and temporal variations in
near-surface atmospheric CO2 levels. We use these factors to create estimated
surfaces of CO2 for the urban area. We validate our surfaces using independently
collected records of CO2 from several monitoring stations and transects. To
investigate the temporal patterns and variations of CO2, we were able to generate
CO2 surfaces for the early mornings and the afternoons, and on weekdays when traffic
is heavy and spatially focused and on weekends when it is lighter and more spatially
dispersed. Our findings suggest there is a distinct relationship between the
structure of Phoenix CO2 levels and spatial patterns of human activities and
vegetation densities. Morning CO2 levels are higher than afternoon levels and
correspond closely to the density of traffic, population, and employment. The
spatial structure of human activity explains the pattern of CO2 better on weekdays
than on weekends. CO2 surfaces reflect declining densities of human activity with
distance from the city center, the pattern of irrigated agriculture in the Phoenix
area, and riparian habitats on the urban fringe. Spatial and temporal patterns of
CO2 are useful in understanding urban climate and ecosystem processes