A Sustainable Systems Approach to the Hysteresis Lag Effect of Surface Materials & Urban Heat Islands

The transition from rural to urban is means for the engineered environment of manmade civil infrastructure to flourish and expand. Urbanization is transitioning communities from the natural rural vegetation to urban infrastructure. The anthropogenic-induced change has manifested itself in microscale and mesoscale impacts for the urban inhabitants. This includes increases in temperatures in comparison to adjacent rural regions, increased environmental and environmental health impacts as well as economic and social consequences. Policy makers from the local regions play an integral part in developing and sustaining policies, incentives and regulations to mitigate the impacts of the UHI. This paper intends to present a case example in Phoenix, Arizona and a research methodology to reduce the hysteresis lag effect of surface materials and to develop policy recommendations based on sound science and engineering.

The interdependencies and interactions of the built environment with climatic and atmospheric sciences is a driving basis for the variations in the severity of the UHI effect. However, for policies to be developed and implemented at the local level, there must be an understanding of technologies and practices which are under the control of the policy making branch. There currently exists an opportunity within the engineering and scientific communities to develop a robust understanding of the coupled volumetric and material make up of surface materials within an urban region and their impacts to the UHI effect.

On December 5, 2001, the City of Phoenix adopted by City Council Resolution a revision of the General Plan which promulgated Goal 7 – The Urban Heat Island. This goal obligated the City to “explore options to minimize the impacts of the Urban Heat Island Effect” (Phoenix General Plan, page 271). Subsequent to the adoption of the General Plan, numerous editorials in the States largest newspaper, The Arizona Republic were run including a series of four full page editorials in September 2003. Beginning mid 2002, researchers from Arizona State University and from the Cambridge – MIT Institute sponsored Engineering for Sustainable Development Programme within the Department of Engineering at Cambridge University initiated a series of meetings in the greater Phoenix, Arizona region with a variety of stakeholders from all levels of government as well as representatives from industry, academics and non-governmental organizations. These discussions resulted in governmental and industrial management stakeholders articulating a need to address the Phoenix regional UHI effect via science and engineering based policies and standards for items for which the stakeholders have direct control. It was identified that those items of control lay primarily within the micro-scale and local-scale (urban canopy layer). However, these layers impact all levels including the meso-scale potentially as well as the global-scale.

The outdoor laboratory utilized for materials encompassing the regional surface urban fabric, is Phoenix Sky Harbor Airport. Sky Harbor serves the two county region of Maricopa and Pinal of central Arizona (14,600 Sq. Miles / 37,813 Sq. Kilometers), and the large Phoenix metropolitan region (urbanized land area of 1,207 Sq. Miles / 3,126.12 Sq. Kilometers). Phoenix is the largest single city within Maricopa County and is the nation’s fifth largest city by population. Its geographic area of 484.521 square miles is larger the City of Los Angeles. Phoenix is projected by 2010 to be the fourth largest City in the United States behind only New York, Los Angeles and Chicago.