Cities in arid or semiarid environment, like Phoenix, often face a “double devil”, viz. the elevated heat stress (aka urban heat island) combined with constant threat of water scarcity. Urban vegetation, including lawns, shade trees, green roofs, etc., offers an attractive means of heat mitigation, but imposes the requirement of outdoor irrigation that aggravates the stress of water resource management. The intricate balance of energy-water trade-off is key to the sustainable urban development, subject to challenges of emergent climate patterns and continuous growth of urbanized population. We have been continuously studying the environmental impact of urban vegetation on the dynamics and thermodynamics in urban canopy and boundary layers via interactions in the soil-vegetation-atmosphere continuum. Transdisciplinary research approaches were adopted including thermodynamic principles (e.g. Clausius-Clapeyron relation), numerical modeling of urban land surface and atmospheric processes (e.g. urban canopy and Weather Research and Forecasting models), and remotely sensed data products (e.g. MODIS land surface temperature). We used the Phoenix metropolitan in Arizona extensively (but not exclusively) as a testbed, probed into the complex dynamics of urban systems, and found that urban greening and irrigation practices are found to significantly influence the hydrological process and thermal environment of cities.
Dr. Zhihua Wang is an associate professor in the School of Sustainable Engineering and the Built Environment at Arizona State University. He obtained his B.Eng. and M. Eng. degrees from the School of Civil and Environmental Engineering at Nanyang Technological University, Singapore, in 2002 and 2004 respectively, and a Ph.D. degree from Princeton University in 2011. Dr. Wang's primary research interest focuses on the sustainable development of cities, including multiscale modeling of heat, water, and pollutant transport in the built environment, landscape and infrastructure dynamics, and building energy efficiency.