The Challenge of Urban Heat Exposure under Climate Change: An Analysis of Cities in the Sustainable Healthy Urban Environments (SHUE) Database

Cities worldwide are getting warmer due to the combined effects of urban heat and climate change. To this end, local policy makers need to identify the most thermally vulnerable areas within cities. The Local Climate Zone (LCZ) scheme highlights local-scale variations; however, its classes, although highly valuable, are to a certain extent generalized in order to be universally applicable. High spatial resolution indicators have the potential to better reflect city-specific challenges; in this paper, the Urban Heat Exposure (UHeatEx) indicator is developed, integrating the physical processes that drive the urban heat island (UHI). In particular, the urban form is modeled using remote sensing and geographical information system (GIS) techniques, and used to estimate the canyon aspect ratio and the storage heat flux. The Bowen ratio is calculated using the aerodynamic resistance methodology and downscaled remotely sensed surface temperatures. The anthropogenic heat flux is estimated via a synergy of top–down and bottom–up inventory approaches. UHeatEx is applied to the city of Athens, Greece; it is correlated to air temperature measurements and compared to the LCZs classification. The results reveal that UHeatEx has the capacity to better reflect the strong intra-urban variability of the thermal environment in Athens, and thus can be supportive for adaptation responses. High-resolution climate projections from the EURO-CORDEX ensemble for the region show that the adverse effects of the existing thermal inequity are expected to worsen in the coming decades.

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Widespread race and class disparities in surface urban heat extremes across the United States

10.31219/osf.io/r5svd ◽

2021 ◽

Author(s):

Susanne A. Benz ◽

Jennifer Burney

Keyword(s):

United States ◽

Land Surface ◽

Heat Exposure ◽

Asian Population ◽

The United States ◽

Urban Environments ◽

Race And Class ◽

Education Levels ◽

Average Education ◽

Urban Heat

Here we use 1000-m satellite land surface temperature anomaly measurements to explore the distribution of the United States' urban heating burden, both at high resolution (within cities or counties) and at scale (across the whole contiguous United States). While a rich literature has documented neighborhood-level disparities in urban heat exposures in individual cities, data constraints have precluded comparisons across locations. Here, drawing on extreme summer urban heat measurements from all 1056 U.S. counties with more than 10 developed census tracts, we find that the poorest tracts (and those with lowest average education levels) within a county are significantly hotter than the richest (and more educated) neighborhoods for 76% of these counties (54\% for education); we also find that neighborhoods with higher Black, Hispanic, and Asian population shares are hotter than the more White, non-Hispanic areas in each county. This holds in counties with both large and small spreads in these population shares, and for 71% of all counties the significant racial urban heat disparities persist even when adjusting for income. Although individual locations have different histories that have contributed to race- and class-based geographies, we find that the physical features of the urban environments driving these heat exposure gradients are fairly uniform across the country. Systematically, the disproportionate heat exposures faced by minority communities are due to higher population density, more built-up neighborhoods, and less vegetation.

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Comments about Urban Bioclimate Aspects for Consideration in Urban Climate and Planning Issues in the Era of Climate Change

Atmosphere ◽

10.3390/atmos12050546 ◽

2021 ◽

Vol 12 (5) ◽

pp. 546

Author(s):

Andreas Matzarakis

Keyword(s):

Climate Change ◽

Urban Heat Island ◽

Urban Climate ◽

Heat Island ◽

Adaptation Measures ◽

Mitigation And Adaptation ◽

Urban Heat

In the era of climate change, before developing and establishing mitigation and adaptation measures that counteract urban heat island (UHI) effects [...]

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Climate change and infrastructure risk: Indoor heat exposure during a concurrent heat wave and blackout event in Phoenix, Arizona

Urban Climate ◽

10.1016/j.uclim.2021.100787 ◽

2021 ◽

Vol 36 ◽

pp. 100787

Author(s):

Brian Stone ◽

Evan Mallen ◽

Mayuri Rajput ◽

Ashley Broadbent ◽

E. Scott Krayenhoff ◽

...

Keyword(s):

Climate Change ◽

Heat Wave ◽

Heat Exposure

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A System Dynamics Model to Facilitate the Development of Policy for Urban Heat Island Mitigation

Urban Science ◽

10.3390/urbansci5010019 ◽

2021 ◽

Vol 5 (1) ◽

pp. 19

Author(s):

Robert Dare

Keyword(s):

Climate Change ◽

System Dynamics ◽

Urban Heat Island ◽

Future Climate Change ◽

Specific Information ◽

Heat Island ◽

System Dynamics Model ◽

Dynamics Model ◽

Urban Heat ◽

Related Mortality

This article presents a customized system dynamics model to facilitate the informed development of policy for urban heat island mitigation within the context of future climate change, and with special emphasis on the reduction of heat-related mortality. The model incorporates a variety of components (incl.: the urban heat island effect; population dynamics; climate change impacts on temperature; and heat-related mortality) and is intended to provide urban planning and related professionals with: a facilitated means of understanding the risk of heat-related mortality within the urban heat island; and location-specific information to support the development of reasoned and targeted urban heat island mitigation policy.

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Heatwaves and Summer Urban Heat Islands: A Daily Cycle Approach to Unveil the Urban Thermal Signal Changes in Lisbon, Portugal

Atmosphere ◽

10.3390/atmos12030292 ◽

2021 ◽

Vol 12 (3) ◽

pp. 292 ◽

Cited By ~ 1

Author(s):

Ana Oliveira ◽

António Lopes ◽

Ezequiel Correia ◽

Samuel Niza ◽

Amílcar Soares

Keyword(s):

Climate Change ◽

Air Temperature ◽

Wind Direction ◽

Urban Heat Islands ◽

Daily Cycle ◽

Local Climate ◽

Thermal Signal ◽

Air Temperatures ◽

Local Climate Change ◽

Urban Heat

Lisbon is a European Mediterranean city, greatly exposed to heatwaves (HW), according to recent trends and climate change prospects. Considering the Atlantic influence, air temperature observations from Lisbon’s mesoscale network are used to investigate the interactions between background weather and the urban thermal signal (UTS) in summer. Days are classified according to the prevailing regional wind direction, and hourly UTS is compared between HW and non-HW conditions. Northern-wind days predominate, revealing greater maximum air temperatures (up to 40 °C) and greater thermal amplitudes (approximately 10 °C), and account for 37 out of 49 HW days; southern-wind days have milder temperatures, and no HWs occur. Results show that the wind direction groups are significantly different. While southern-wind days have minor UTS variations, northern-wind days have a consistent UTS daily cycle: a diurnal urban cooling island (UCI) (often lower than –1.0 °C), a late afternoon peak urban heat island (UHI) (occasionally surpassing 4.0 °C), and a stable nocturnal UHI (1.5 °C median intensity). UHI/UCI intensities are not significantly different between HW and non-HW conditions, although the synoptic influence is noted. Results indicate that, in Lisbon, the UHI intensity does not increase during HW events, although it is significantly affected by wind. As such, local climate change adaptation strategies must be based on scenarios that account for the synergies between potential changes in regional air temperature and wind.

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High-Resolution Modelling of Thermal Exposure during a Hot Spell: A Case Study Using PALM-4U in Prague, Czech Republic

Atmosphere ◽

10.3390/atmos12020175 ◽

2021 ◽

Vol 12 (2) ◽

pp. 175

Author(s):

Jan Geletič ◽

Michal Lehnert ◽

Pavel Krč ◽

Jaroslav Resler ◽

Eric Scott Krayenhoff

Keyword(s):

Czech Republic ◽

Urban Areas ◽

Heat Exposure ◽

Thermal Exposure ◽

Urban Environments ◽

Cooling Effect ◽

Spatiotemporal Variability ◽

Climate Index ◽

Street Canyons ◽

General Terms

The modelling of thermal exposure in outdoor urban environments is a highly topical challenge in modern climate research. This paper presents the results derived from a new micrometeorological model that employs an integrated biometeorology module to model Universal Thermal Climate Index (UTCI). This is PALM-4U, which includes an integrated human body-shape parameterization, deployed herein for a pilot domain in Prague, Czech Republic. The results highlight the key role of radiation in the spatiotemporal variability of thermal exposure in moderate-climate urban areas during summer days in terms of the way in which this directly affects thermal comfort through radiant temperature and indirectly through the complexity of turbulence in street canyons. The model simulations suggest that the highest thermal exposure may be expected within street canyons near the irradiated north sides of east–west streets and near streets oriented north–south. Heat exposure in streets increases in proximity to buildings with reflective paints. The lowest heat exposure during the day may be anticipated in tree-shaded courtyards. The cooling effect of trees may range from 4 °C to 9 °C in UTCI, and the cooling effect of grass in comparison with artificial paved surfaces in open public places may be from 2 °C to 5 °C UTCI. In general terms, this study illustrates that the PALM modelling system provides a new perspective on the spatiotemporal differentiation of thermal exposure at the pedestrian level; it may therefore contribute to more climate-sensitive urban planning.

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Disproportionate exposure to urban heat island intensity across major US cities

Nature Communications ◽

10.1038/s41467-021-22799-5 ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Angel Hsu ◽

Glenn Sheriff ◽

Tirthankar Chakraborty ◽

Diego Manya

Keyword(s):

Urban Heat Island ◽

Census Tract ◽

Demographic Data ◽

Heat Exposure ◽

Poverty Line ◽

Built Environments ◽

Heat Island ◽

Urban Heat ◽

Surface Urban Heat Island ◽

Us Cities

AbstractUrban heat stress poses a major risk to public health. Case studies of individual cities suggest that heat exposure, like other environmental stressors, may be unequally distributed across income groups. There is little evidence, however, as to whether such disparities are pervasive. We combine surface urban heat island (SUHI) data, a proxy for isolating the urban contribution to additional heat exposure in built environments, with census tract-level demographic data to answer these questions for summer days, when heat exposure is likely to be at a maximum. We find that the average person of color lives in a census tract with higher SUHI intensity than non-Hispanic whites in all but 6 of the 175 largest urbanized areas in the continental United States. A similar pattern emerges for people living in households below the poverty line relative to those at more than two times the poverty line.

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