Heat Islands, Fall/Winter 2014, Issue 29

Issue 29 Fall/Winter 2014 The Kentucky Institute for the Environment and Sustainable Development F Heat Islands 2 Miles 2 Urban Heat Islands, Effects, and Mitigation Haider Taha 9 Remote Sensing and Identifying the Urban Heat Island from Space: An Overview Jeremy Sandifer Editor Allan E. Dittmer 13 The Basics of Cool Roofs: Design/Layout A Platform for Sustainability Kurt Shickman Nick Dawson University of Louisville Credit: Peter Tobia Design & Printing Services 22 Greenworks Philadelphia Alex Dews The Kentucky Institute for the Environment and Sustainable Development (KIESD) was created in July 1992 within the Credit: Peter Tobia Office of the 23 Heat Island – The More Documented Vice President for Research, Phenomenon of Urban Climate Change Matheos Santamouris University of Louisville. CONTENTS Hot Times in the City The Institute provides a forum to conduct 29 SUMMARY OF Anthony J. Brazel GREENWORKS Targets & Initiatives 2 interdisciplinary research, applied scholarly Matei Georgescu analysis, public service and educational SECTION 1 Energy 4 outreach on environmental and sustainable SECTION 2 Environment 11 36 Rise in Pavement Temperature – Making Buildings development issues at the local, state, national Part of the Road Infrastructure, Capturing Energy – SECTION 3 Equity 16 and international levels. Solutions, Possibilities and Challenges SECTION 4 Economy 22 Rajib Basu Mallick KIESD is comprised of eight thematic SECTION 5 Engagement 28 Sankha Bhowmick program centers: Environmental Education, Environmental Science, Land Use and 47 Leveraging Climate Adaptation Planning [DESIGN]: WFGD Studio for Heat Island Mitigation Environmental Responsibility, Sustainable [PRIMARY AUTHORS]: Alex Dews and Sarah Wu, Mayor’s Office of Sustainability Brendan Reed Urban Neighborhoods, Pollution Prevention, 1 Environmental and Occupational Health Sciences, Environmental Policy and Management, and 50 Climate Change in the Places We Live: Environmental Engineering. What the European Heat Wave of 2003 Reveals about Climate Change in Cities Brian Stone, Jr. Sustain is published semi-annually by the Kentucky Institute for the Environment and 53 Canopy and Carbon: The Conflicting Agendas Sustainable Development, of Local and Global Climate Change Management University of Louisville, Brian Stone, Jr. 203 Patterson Hall, Louisville, Kentucky 40292. Spatial distribution of Urban Heat Island using 56 Geographic Information System (GIS) in Greece Send electronic correspondence to Denia Kolokotsa [email protected] Kostas Gobakis This Publication is printed 61 Heat Island Mitigation - Columbus, Georgia on recycled paper. Martha L. Santana Issue 29 - Fall/Winter 2014 Heat Islands On the cover: A thermal image of Authors, William L. Heward and Jonathan W. Kimball Jefferson County, Kentucky would like to express their gratitude to Patricia Kimball for her invaluable assistance in developing the graphic elements in the article, “Sustaining Sustainability with Clueless Contingencies” which appeared in issue 28 of Sustain. The University of Louisville is an equal opportunity institution and does not discriminate against persons on the basis of age, religion, sex, disability, color, national origin or veteran status. This publication was prepared by the University of Louisville and printed with state funds KRS 57.375. Urban Heat Islands, Effects, and Mitigation By Haider Taha Altostratus Inc. Urbanization and accom- of a city) and a rural one. In other cases, the UHI is taken as an panying changes in land use average of urban temperature differences (at several locations in and land cover, energy use, urban areas) relative to one or an average of several non-urban air-pollutant emissions, and points. Another way to define UHIs is to compute the difference man-made heat, can cause a in temperature between an urban point(s) of interest and a myriad of modifications to the time-dependent (space-varying) upwind non-urban point(s). In atmosphere locally, regionally, this case, the location of the reference point changes based and globally. The Urban Heat on wind approach and thus the definition of a UHI becomes Island (UHI) is one major wind-direction-dependent, whether instantaneous or statistically- manifestation of such effects. representative. Because UHI definitions can differ, some formal Heat islands, when and standardization may become necessary, a concept that is now where they occur, can have gaining interest among many urban-climate researchers. significant impacts on energy use and the environment. Factors affecting the UHI intensity include city-size, type Annual cooling degree-days (base 65°F or 18.3°C) in U.S. cities of dominant building materials, urbanization density, land-cover can increase, because of the UHI, by 10 - 50%, depending on types and densities, energy-use intensity and fuel types, rate of climate, whereas annual heating degree-days can be reduced by release of man-made (anthropogenic) heat, pollutants emissions 5 – 15%. Every 0.5°C of warming in urban areas can cause an and concentrations, and local weather / micrometeorological increase in cooling-energy use of between 1 and 2% beyond a conditions. Thus heat islands can differ significantly from one certain temperature threshold that varies among cities. In terms area to another and also at different times at any specific point. of air-quality, an increase in urban temperatures can increase As a result, there are day- or night-time-peaking UHIs, winter- emissions from power generation, biogenic sources, and mobile or summer-peaking ones, and so on depending on the above sources, as well as fugitive emissions. It can also increase the factors. While some UHIs can remain relatively constant for rates of photochemical ozone production. While it is impossible some time, most vary seasonally and diurnally. The development to generalize, because of complexities involved, a back-of-the- of a UHI also depends on synoptic (comprehensive view) and envelope assessment would be that a reduction of 1°C in urban background conditions. For example when high winds exist, air temperatures can reduce peak one-hour ozone concentrations UHIs typically do not develop well whereas with moderate by some 1 – 5 ppbv(parts per billion in volume) in different areas winds, UHIs are displaced. At low background winds, UHIs in the U.S. develop their own circulations and can reach maximum intensity under such conditions. The background wind-speed thresholds for Urban heat and cool islands development of UHIs vary from one location or set of conditions to another, but are generally between 3 and 6 m s-1(meters per An urban heat island (UHI) can be defined as a difference second). UHIs in North America typically range from 1 to 3 C in surface (skin) temperature or in air temperature, in which case (Taha 2004), in South America up to 8°C (Lombardo 1985) or the difference is taken at a certain height above ground level, larger, and in Asia up to 3°C (Kim and Baik 2005). In Europe e.g., at 2, 5, or 10 meters. The former type of UHIs is typically a maximum summer heat island of 8°C has been reported “seen” with remote-sensing techniques using satellite or aircraft- (Kolokotsa et al. 2009). mounted thermal sensors, whereas the latter is typically measured by near-surface air-temperature probes placed at the desired Urban areas can also be cooler than their non-urban elevations above ground. UHIs are diagnosed on time scales of surroundings under certain conditions. In such cases, we define minutes to years, depending on the purpose of the analysis or an urban cool island (UCI) as an opposite to a UHI. Cool islands application at hand. can be seen in desert climates where urban areas act as “oases” that are cooler than their non-vegetated, drier surrounds. Although Quantifying UHIs requires selecting urban and non-urban occurring much less frequently than UHIs, UCIs can also be seen reference points. Depending on the purpose of analysis, UHIs in some urban areas during the morning when the surroundings are often defined as the temperature difference between two warm up faster than the urban cores (because of thermal lag, fixed points in space, e.g., an urban point (such as in the core shading, and surface moisture), then become UHIs later in the 2 Fall/Winter 2014 • Increased anthropogenic emissions, e.g., from motor vehicles / increased evaporative emissions • Increased biogenic emissions from vegetation in urban areas or downwind of them (i.e., within areas affected by heat islands) • Increased photochemical production of ground-level / tropospheric ozone • Modified radiative forcing as a result of increased ozone concentrations and particulate-matter loading • Increased evaporation and loss of surface water. Thus the main goal of heat-island mitigation research is to develop actionable information that can assist cities and reg- ulatory organizations in evaluating the effectiveness of urban-cooling measures in terms of their impacts on energy use, Figure 1. Maximum nighttime UHI (B) and morning UCI (C) over Sacramento, meteorology, thermal environmental condi- California, on 1 and 2 August (2000). The black square inset in B and C outlines tions, emissions, and air quality and, thus, the relative location of downtown Sacramento. The higher temperatures (UHI) prioritizing the deployment of such measures. plume stretching from downtown to the northeast (B) follows the extent of urban- Many studies have been carried out with these ization in the area (source: Taha 2008a, Atmospheric Environment). objectives in mind, each typically focusing on a subset of the processes and mechanisms morning, throughout the day, and at night. Figure 1, for example, of interest. For example, Akbari et al. (1999) and Akbari and shows heat and cool islands in Sacramento, California, captured Konopacki (2005) evaluated the impacts of heat-island mitigation with fine-resolution meso-urban simulations (Taha 2008a). In this on energy use. With advanced building-energy models, they example, the morning cool island is -1°C and the nighttime heat estimated that nation-wide in the U.S., implementation of cool island reaches up to 3°C.

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