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The urban heat island (UHI) concept describes heat trapping that elevates urban temperatures relative to rural temperatures, at least in temperate/humid regions. In drylands, urban irrigation can instead produce an urban cool island (UCI) effect. However, the UHI/UCI characterization suffers from uncertainty in choosing representative urban/rural endmembers, an artificial dichotomy between UHIs and UCIs, and lack of consistent terminology for other patterns of thermal variation at nested scales. We use the case of a historically well-enforced urban growth boundary (UGB) around Portland (Oregon, USA): to explore the representativeness of the surface temperature UHI (SUHI) as derived from Moderate Resolution Imaging Spectroradiometer (MODIS) land surface temperature data, to test common assumptions of characteristically “warm” or “cool” land covers (LCs), and to name other common urban thermal features of interest. We find that the UGB contains heat as well as sprawl, inducing a sharp surface temperature contrast across the urban/rural boundary. The contrast ranges widely depending on the end-members chosen, across a spectrum from positive (SUHI) to negative (SUCI) values. We propose a new, inclusive “urban thermal deviation” (UTD) term to span the spectrum of possible UHI-zero-UCI conditions. We also distinguish at finer scales “microthermal extremes” (MTEs), discrete areas tending in the same thermal direction as their LC or surroundings but to extreme (hot or cold) values, and microthermal anomalies (MTAs), that run counter to thermal expectations or tendencies for their LC or surroundings. The distinction is important because MTEs suggest a need for moderation in the local thermal landscape, whereas MTAs may suggest solutions.
Kevan B. Moffett; Yasuyo Makido; Vivek Shandas. Urban-Rural Surface Temperature Deviation and Intra-Urban Variations Contained by an Urban Growth Boundary. Remote Sensing 2019, 11, 2683 .
AMA StyleKevan B. Moffett, Yasuyo Makido, Vivek Shandas. Urban-Rural Surface Temperature Deviation and Intra-Urban Variations Contained by an Urban Growth Boundary. Remote Sensing. 2019; 11 (22):2683.
Chicago/Turabian StyleKevan B. Moffett; Yasuyo Makido; Vivek Shandas. 2019. "Urban-Rural Surface Temperature Deviation and Intra-Urban Variations Contained by an Urban Growth Boundary." Remote Sensing 11, no. 22: 2683.
Urban heat is a growing environmental concern in cities around the world. The urban heat island effect, combined with warming effects of climate change, is likely to cause an increase in the frequency and intensity of extreme heat events. Alterations to the physical, built environment are a viable option for mitigating urban heat, yet few studies provide systematic guidance to practitioners for adapting diverse land uses. In this study, we examine the use of green infrastructure treatments to evaluate changes in ambient temperatures across diverse land uses in the city of Portland, Oregon. We apply ENVI-met® microclimate modeling at the city-block scale specifically to determine what built environment characteristics are most associated with high temperatures, and the extent to which different physical designs reduce ambient temperature. The analysis included six green infrastructure interventions modeled across six different land-use types, and indicated the varying degrees to which approaches are effective. Results were inconsistent across landscapes, and showed that one mitigation solution alone would not significantly reduce extreme heat. These results can be used to develop targeted, climate- and landscape-specific cooling interventions for different land uses, which can help to inform and refine current guidance to achieve urban climate adaptation goals.
Yasuyo Makido; Dana Hellman; Vivek Shandas. Nature-Based Designs to Mitigate Urban Heat: The Efficacy of Green Infrastructure Treatments in Portland, Oregon. Atmosphere 2019, 10, 282 .
AMA StyleYasuyo Makido, Dana Hellman, Vivek Shandas. Nature-Based Designs to Mitigate Urban Heat: The Efficacy of Green Infrastructure Treatments in Portland, Oregon. Atmosphere. 2019; 10 (5):282.
Chicago/Turabian StyleYasuyo Makido; Dana Hellman; Vivek Shandas. 2019. "Nature-Based Designs to Mitigate Urban Heat: The Efficacy of Green Infrastructure Treatments in Portland, Oregon." Atmosphere 10, no. 5: 282.
Recent evidence suggests that many densely populated areas of the world will be uninhabitable in the coming century due to the depletion of resources, climate change, and increasing urbanization. This poses serious questions regarding the actions that require immediate attention, and opportunities to stave off massive losses of infrastructure, populations, and financial investments. The present study utilizes microclimate modeling to examine the role of landscape features as they affect ambient temperatures in one of the fastest growing regions of the world: Doha, Qatar. By modeling three study sites around Doha—one highly urbanized, one newly urbanizing, and one coastal low-density urbanized—the research indicates that at the neighborhood scale, the most effective scenario was that of adding mature trees along the sides of roads. In the coastal study area, the model results estimated a maximum hourly air temperature reduction of 1.35 °C, and in the highly urbanized inland site, surface temperature reductions were up to 15 °C at 12:00. While other scenarios were effective at reducing air and surface temperatures, the mean radiant temperature was also increased or nearly neutral for most of the other scenarios. This result highlights the need to develop improved shading measures for pedestrian pathways and outdoor recreational areas, especially for highly urbanized inland areas in Doha and cities with similar climatic conditions.
Salim Ferwati; Cynthia Skelhorn; Vivek Shandas; Yasuyo Makido. A Comparison of Neighborhood-Scale Interventions to Alleviate Urban Heat in Doha, Qatar. Sustainability 2019, 11, 730 .
AMA StyleSalim Ferwati, Cynthia Skelhorn, Vivek Shandas, Yasuyo Makido. A Comparison of Neighborhood-Scale Interventions to Alleviate Urban Heat in Doha, Qatar. Sustainability. 2019; 11 (3):730.
Chicago/Turabian StyleSalim Ferwati; Cynthia Skelhorn; Vivek Shandas; Yasuyo Makido. 2019. "A Comparison of Neighborhood-Scale Interventions to Alleviate Urban Heat in Doha, Qatar." Sustainability 11, no. 3: 730.
Recent evidence suggests that urban forms and materials can help to mediate temporal variation of microclimates and that landscape modifications can potentially reduce temperatures and increase accessibility to outdoor environments. To understand the relationship between urban form and temperature moderation, we examined the spatial and temporal variation of air temperature throughout one desert city—Doha, Qatar—by conducting vehicle traverses using highly resolved temperature and GPS data logs to determine spatial differences in summertime air temperatures. To help explain near-surface air temperatures using land cover variables, we employed three statistical approaches: Ordinary Least Squares (OLS), Regression Tree Analysis (RTA), and Random Forest (RF). We validated the predictions of the statistical models by computing the Root Mean Square Error (RMSE) and discovered that temporal variations in urban heat are mediated by different factors throughout the day. The average RMSE for OLS, RTA and RF is 1.25, 0.96, and 0.65 (in Celsius), respectively, suggesting that the RF is the best model for predicting near-surface air temperatures at this study site. We conclude by recommending the features of the landscape that have the greatest potential for reducing extreme heat in arid climates.
Yasuyo Makido; Vivek Shandas; Salim Ferwati; David Sailor. Daytime Variation of Urban Heat Islands: The Case Study of Doha, Qatar. Climate 2016, 4, 32 .
AMA StyleYasuyo Makido, Vivek Shandas, Salim Ferwati, David Sailor. Daytime Variation of Urban Heat Islands: The Case Study of Doha, Qatar. Climate. 2016; 4 (2):32.
Chicago/Turabian StyleYasuyo Makido; Vivek Shandas; Salim Ferwati; David Sailor. 2016. "Daytime Variation of Urban Heat Islands: The Case Study of Doha, Qatar." Climate 4, no. 2: 32.