Impact of 20 Years of Land-Use and Land-Cover Change over the Greater Phoenix Area

Using the Regional Atmospheric Modeling System (RAMS), a state-of-the-art numerical modeling tool, and Landsat satellite data, two separate sets of ensembles are conducted to quantify the impact of anthropogenic land-use/land-cover (LULC) change on the climate and hydrologic cycle of the Greater Phoenix, Arizona area as a result of the explosive growth and urbanization that occurred between the early 1970's and early 1990's. Through modification of the Land Ecosystem-Atmosphere Feedback Model 2 (LEAF-2) biophysical parameters appropriate for the land cover enveloping the Greater Phoenix area are derived. Additionally, it is through LEAF-2, the soil and vegetation component of RAMS, prognostic in energy and water exchange between the land and atmosphere, that the different LULC scenarios are imposed on the model. The two ensembles (Dry and Wet) were determined through a derivation of a seasonal North American Monsoon System (NAMS) precipitation index defined for Arizona based on 50 years of gridded precipitation data. Furthermore, each ensemble consists of a total of 6 simulations (composed of three member years per ensemble, each including the imposed 1970's and 1990's LULC) carried out during the summer months of July and August. Using a nested grid configuration, the fine mesh grid spacing of 2-km is able to uncover specific land- atmosphere interactions and associated feedbacks controlling these impacts, relevant to the designated cover change.