Multi-Scale Assessment of Projected Urban Expansion in the United States

Abstract:

Recent projections indicate the U.S. will add about 300 million inhabitants through the end of the current century, leading to roughly 250,000km² of new urban land use to meet the increase in commercial, housing, and transportation demand. Multi-year and multi-member continental scale numerical simulations are conducted with the WRF model, for the U.S., to assess impacts owing to end of century megapolitan expansion, and to examine consequences of commonly proposed adaptation strategies. Warming of 1-2ºC is simulated for all expanding urban areas, with local warming exceeding 3ºC for some regions during some seasons. This warming is a significant fraction of 21st century greenhouse gas-induced climate change simulated by global climate models. Widespread adoption of adaptation strategies exhibit regionally and seasonally dependent hydroclimatic impacts, displaying intended effects for some urban areas while exhibiting unintended consequences for others. To assess the multi-scale dependency of simulated results, high-resolution (2km grid spacing) seasonal timescale simulations are conducted for select rapidly urbanizing regions. In addition to emphasizing the need for integrated assessment that also incorporates biophysically induced urban impacts, I argue in favor of examining scale dependency of simulated outcomes to comprehensively address tradeoff assessment of various urban adaptation approaches.