Urban Heat Wave Research Articles

Synergistic Influence of Local Climate Zones and Wind Speeds on the Urban Heat Island and Heat Waves in the Megacity of Beijing, China

Large-scale modifications to urban underlying surfaces owing to rapid urbanization have led to stronger urban heat island (UHI) effects and more frequent urban heat wave (HW) events. Based on observations of automatic weather stations in Beijing during the summers of 2014–2020, we studied the interaction between HW events and the UHI effect. Results showed that the UHI intensity (UHII) was significantly aggravated (by 0.55°C) during HW periods compared to non-heat wave (NHW) periods. Considering the strong impact of unfavorable weather conditions and altered land use on the urban thermal environment, we evaluated the modulation of HW events and the UHI effect by wind speed and local climatic zones (LCZs). Wind speeds in urban areas were weakened due to the obstruction of dense high-rise buildings, which favored the occurrence of HW events. In detail, 35 HW events occurred over the LCZ1 of a dense high-rise building area under low wind speed conditions, which was much higher than that in other LCZ types and under high wind speed conditions (< 30 HW events). The latent heat flux in rural areas has increased more due to the presence of sufficient water availability and more vegetation, while the increase in heat flux in urban areas is mainly in the form of sensible heat flux, resulting in stronger UHI effect during HW periods. Compared to NHW periods, lower boundary layer and wind speed in the HW events weakened the convective mixing of air, further expanding the temperature gap between urban and rural areas. Note that LCZP type with its high-density vegetation and water bodies in the urban park area generally exhibited, was found to have a mitigating effect on the UHI, whilst at the same time increasing the frequency and duration of HW events during HW periods. Synergies between HWs and the UHI amplify both the spatial and temporal coverage of high-temperature events, which in turn exposes urban residents to additional heat stress and seriously threatens their health. The findings have important implications for HWs and UHII forecasts, as well as for scientific guidance on decision-making to improve the thermal environment and to adjust the energy structure.

Research Progress of Urban Heat Wave Environment

High temperature heat wave is one of the disasters with higher frequency and greater impact in extreme weather. This article starts with the definition, disaster and health, influencing factors, prevention and control of high temperature heat wave. The results show that: (1) The current situation of high-temperature heat waves is obvious. After 2000, my country’s high-temperature heat waves showed a rapid growth trend. The high-temperature heat waves lasted for a long time and the highest temperature exceeded the historical extreme. ②High temperature and heat waves have a major impact on human health, and at least they may induce heatstroke and other symptoms, and may cause death. And high temperature not only directly harms human health, but also indirectly affects the human body from the environment, such as inducing malaria. ③ Currently, the research on the influencing factors of high temperature heat wave generally conducts quantitative and qualitative research on the thermal environment from the on-site environmental assessment, high temperature heat wave model, and thermal simulation. ④At present, my country’s prevention and control of high-temperature heat waves started relatively late, and the construction of developed countries such as Japan, the United States, and Germany, which are more comprehensive in prevention and control, is less complete.

Spatial assessment of urban heatwave vulnerability of coupling adaptability based on BPNN model: a case study of Xiamen City, China

The continuous advancement of urbanization and the acceleration of global climate warming have severely aggravated the heatwave vulnerability of the urban complex human–land system. Therefore, the scientific assessment of urban heatwave vulnerability (UHV) is particularly critical. We used Xiamen City, one of the representative heatwave disaster-prone cities, as a case study area. We then constructed a UHV index system that coupled adaptability and selected 12 indicators from the three dimensions: exposure, susceptibility, and adaptability. The back propagation neural network (BPNN) model was used to composite each indicator layer and produce UHV results. Finally, we analyzed the spatial distribution characteristics of UHV. We found that the BPNN model had good training performance, with an overall accuracy of 0.92986. The value of UHV ranged from 0 to 1 and was divided into five grades, from low to high were 18.45%, 18.72%, 17.16%, 28.76%, and 16.91. In terms of spatial characteristics, high adaptability significantly improved UHV. The high value of UHV presented specific agglomeration characteristics, and the extremely vulnerable and disordered areas were mainly located in Huli District and the junction of Siming District and Huli District. The research will provide a new theoretical perspective and framework for urban heatwave assessment and help for disaster management and sustainable development in a high-risk area.

The future urban heat-wave challenge in Africa: Exploratory analysis

Urbanization and climate change are among the most important global trends affecting human well-being during the twenty-first century. One region expected to undergo enormous urbanization and be significantly affected by climate change is Africa. Studies already find increases in temperature and high temperature events for the region. How many people will be exposed to heat events in the future remains unclear. This paper attempts to provide a first estimate of the number of African urban residents exposed to very warm 15-day heat events (>42 °C). Using the Shared Socio-economic Pathways and Representative Concentration Pathways framework we estimate the numbers of exposed, sensitive (those younger than 5 and older than 64 years), and those in low-income nations, with gross national products of $4000 ($2005, purchasing power parity), from 2010 to 2100. We examine heat events both with and without urban heat island estimates. Our results suggest that at the low end of the range, under pathways defined as sustainable (SSP 1) and low relative levels of climate change (RCP 2.6) without including the urban heat island effect there will be large populations (>300 million) exposed to very warm heat wave by 2100. Alternatively, by 2100, the high end exposure level is approximately 2.0 billion for SSP 4 under RCP 4.5 where the urban heat island effect is included.

The Migration of the Warming Center and Urban Heat Island Effect in Shanghai During Urbanization

Urbanization leads to many negative climatic and environmental issues, such as urban heat island, environment pollution, and species extinctions. Based on the monthly air temperature data from 11 national meteorological stations in Shanghai, the construction land areas from 1980 to 2015 which derived from the satellite remote sensing TM image and population density of each district in Shanghai, the migration of urban warming center and its relationships with the expansion of construction land area and the increase of population density were analyzed in Shanghai. The temporal and spatial variations of urban heat island(UHI) were investigated as well. The results showed that the location of warming centers changed with the acceleration of urbanization since the 1980s. It migrated from Baoshan to Pudong and then moved towards Songjiang and Nanhui. The shifting of urban warming centers were highly related to the growth of construction land area and population density. The warming centers in all decades were located in the areas with the fastest development of construction land and population density. The air temperature in Shanghai increased significantly during 1961-2017 due to global warming and regional urbanization, and the intensity of UHI displayed three stages successively: slow growth, rapid growth, and obvious deceleration. The intensity of UHI in winter was stronger than that in summer, and it was greater in the nighttime than that during the daytime. With the accelerating process of urbanization, the UHI in Shanghai gradually expanded from the urban areas to the surrounding suburbs and even began to expand radially towards the southwest of rural areas in the 21st century. The results can provide references for urban heatwave prediction and mitigation of the UHI effect in Shanghai.

Research progress on urban heat wave vulnerability assessment: A geographical perspective

Research progress on urban heat wave vulnerability assessment: A geographical perspective

A System Dynamics Analysis of Urban Heat Waves

In this study, we analyzed the potential determinants of urban heat waves in Korea and their dynamic relationship using a system dynamics analysis approach. We developed an integrated causal loop diagram and identified the direct and indirect factors influencing urban heat waves. The followings are the main findings of this study. First, the rise of temperature in Korea is not simply due to the increase of impervious areas affected by urbanization but should be seriously recognized as a critical issue of heat waves which may lead to the annihilation of the areas. Second, for more accurate prediction of the temperature increase and development of effective policy responses, we need a new approach that focuses on a non-linear and dynamic relationship between urban heat wave process and urban safety. Third, it is critical to explore policy measures for maintaining socioeconomic conditions and improving the level of urban safety based on the multi-dimensional examination of causal relationships across various determinants for urban heat waves in South Korea.

Assessing heat wave vulnerability in Beijing and its districts, using a three dimensional model

An urban Heat Wave Vulnerability Index (HWVI) is created and tested in Beijing and different districts in the city. It is based on a limited number of indicators, but enough indicators to effectively measure heat wave vulnerability. The HWVI developed uses data on 9 individual indicators covering the three core components exposure, sensibility and adaptive capacity. Testing the HWVI shows that heat wave vulnerability increased slightly in Beijing in the period of 2008 to 2016. Vulnerability differs between the 16 districts of Beijing. High vulnerability is observed in the urban downtown area and development areas, lower vulnerability is measured in the urban periphery. Very low vulnerability is found in the ecological conservation areas of some districts. This study develops and applies a methodological approach that could serve other mega cities in developing heat wave adaptation policies. Findings are relevant for Beijing to develop its climate change adaptation actions.

Increasing Probability of Heat-Related Mortality in a Mediterranean City Due to Urban Warming.

Extreme temperatures impose thermal stress on human health, resulting in increased hospitalizations and mortality rate. We investigated the circulatory and respiratory causes of death for the years 2007 to 2014 inclusive for the urban and rural areas of Nicosia, Cyprus under urban heatwave and non-heatwave conditions. Heatwaves were defined as four or more consecutive days with mean urban daily temperature over the 90th percentile threshold temperature of the eight investigated years. Lag period of adverse health effects was found to be up to three days following the occurrence of high temperatures. The relative risk (RR) for mortality rate under heatwave and non-heatwave conditions was found taking in consideration the lag period. The results showed the increase of mortality risk particularly for men of ages 65–69 (RR = 2.38) and women of ages 65–74 (around RR = 2.54) in the urban area, showing that women were more vulnerable to heat extremities. High temperatures were also associated with high ozone concentrations, but they did not impose an excess risk factor, as they did not reach extreme values. This analysis highlights the importance of preparing for potential heat related health impacts even in Cyprus, which is an island with frequent heatwaves.

World War I and Southern Modernism by David A. Davis (review)

Reviewed by: World War I and Southern Modernism by David A. Davis Joy Landeira David A. Davis. World War I and Southern Modernism. Jackson: U of Mississippi P, 2018. 233 p. After setting an icy tone with Robert Penn Warren's epigraph, "World War I changed everything. It was a great shock to the whole country, but the war broke open a frozen culture like the southern world," David A. Davis not only demonstrates how WWI cracked the South's frozen culture, but convincingly delineates how it "played a pivotal role in the emergence of Modernism." Both a cultural and literary phenomenon, Southern Modernism's experimentation, awareness of rural versus urban discontinuity, critique of the past, and exposure to modernity characterize this unstoppable movement. No longer valorizing the "lost cause" of the civil war, the Southern Renaissance--or Renasence—between the two World Wars (1920–40) challenged established frigid and rigid social structures, particularly the treatment of African Americans and women, and the glacial expectations of cotton growing and poverty. Combining literary technique with critical perspective, writers including Faulkner, both Fitzgeralds, Frances Newman, and Zora Neale Hurston observed the effects of modernity in the South and warmed to new ideas, technologies, social practices and divergent cultures. The key word to understanding Southern Modernism is disruption—disruption of the frozen culture, and disruption of literary tradition. After 1848, modernism ushered in an urban heat wave radiating from European capitals in Paris, London, Madrid and Vienna that sparked new perspectives and ignited a blaze of literary conflagration that reflected similar outbreaks and variants of urban modernism in Mexico and Latin America as well. Out of the nineteenth century's smoldering and moldering cinders, modernity disrupted old forms and instigated new approaches. Futurist and vanguardist dictums to "make it new" kindled fresh attitudes in US urban centers from New York, to Chicago, to Detroit to California and even sprung to life in the South with the New Negro movement, the New Southern Woman, and the New Mechanical Order. [End Page 203] The South's old ice age with its subordination of black Americans didn't just melt away. African American soldiers had defended their nation, and yet were expected to return to the same segregated and disenfranchised states they had left. The war incited a confrontational period for civil rights and for African American modernism—in particular, the Harlem Renaissance. Davis interprets three literary texts that fictionalize the experience of returning veterans. Victor R. Daly's Not Only war: A Story of Two Great Conflicts is the only novel written by a black American veteran. The titular conflicts are the war in France and the experience of being a Southern black. Walter White's The Fire in the Flint depicts racial violence, lynching, torching and murder in an attempt to illustrate social inequalities and promote civil rights. The exploitation of blacks and the effects of the war in Home to Harlem, by Claude McKay, one of Harlem's leading black radicals, profiles the international black experience of racial oppression. Some urban proximal sites of modernity like Harlem promised a cosmopolitan modernist space, but offered another sort of exile and fugitive experience. The freedom found in urban centers did not extend to the small towns and the South, revealing more hypocrisy and white supremacy, and the mandate to use writing as combat. For women, too, the war disrupted domestic life and fragmented society. To mirror these changes, linear narrative gives way to fragmented, nonlinear experiments. Social changes and the instability of identity and female roles inspire women's modernist writing. The "New Southern Woman" displaces the archetypal nineteenth century Southern belle. A particularly astute reading of Jonah's Gourd Vine illuminates how Zora Neale Hurston conveys the sense of disruption and "whirling cacophony of wartime" through disjointed montage and disembodied voices. By blending history, sociological profiles and literary textual analysis throughout World War I and Southern Modernism, David A. Davis upholds his clearly stated argument that World War I played "a pivotal role in the emergence of southern modernism." Factual evaluations of societal and economic sectors underscore the theme of disruption that begets modernism. WWI meant profitability, particularly in the South where President Woodrow...

Urban heat wave hazard and risk assessment

Abstract Heat waves are one of the largest causes of environmentally-related deaths globally. The intensification of the effects of heat waves by the urban heat island during extended periods of extreme heat, combined with urban demographics, are key elements leading to these disasters and are likely to become more numerous as a result of climate change. Climatological weather station data, moderate resolution thermal imagery from Earth-orbiting satellites, and demographic information for selected cities were use in this research to develop a heat wave risk product as a potential warning tool for public health decision makers and the general public.

Urban warming in the 2013 summer heat wave in eastern China

The impact of urban warming during the 2013 July–August extreme heat wave event across the Yangtze River Delta (YRD) in China was assessed. Using a newly developed high-resolution, land-use dataset, urban stations were identified from a total of 101 stations in the YRD. The difference between urban and non-urban/rural stations indicates that urban warming reached 1.22 °C in the 2013 summer heat wave. The new land-use dataset was then input to the Weather Research and Forecasting model to further understand the dynamical/physical processes of the urban warming during the heat wave. The model-simulated urban warming is ~1.5 °C. Impacts of urbanization on near-surface temperature had strong diurnal variation, reaching a peak at 19:00 LST, around sunset. In the daytime, urban warming was mainly caused by enhanced sensible heat fluxes and longwave radiation from the surface. Because of reduced latent heat flux and increased heat capacity, urban ground stored much more heat than rural ground during the daytime, which is later released as sensible heat flux from the surface at night, leading to the nocturnal urban warming. The simulation results also suggest a positive feedback between urban warming and heat wave intensity, which makes the heat wave more intense in urban than rural areas and the urban warming during the extreme heat wave stronger than its climatological mean.

Avoided climate impacts of urban and rural heat and cold waves over the U.S. using large climate model ensembles for RCP8.5 and RCP4.5.

Previous studies examining future changes in heat/cold waves using climate model ensembles have been limited to grid cell-average quantities. Here, we make use of an urban parameterization in the Community Earth System Model (CESM) that represents the urban heat island effect, which can exacerbate extreme heat but may ameliorate extreme cold in urban relative to rural areas. Heat/cold wave characteristics are derived for U.S. regions from a bias-corrected CESM 30-member ensemble for climate outcomes driven by the RCP8.5 forcing scenario and a 15-member ensemble driven by RCP4.5. Significant differences are found between urban and grid cell-average heat/cold wave characteristics. Most notably, urban heat waves for 1981-2005 are more intense than grid cell-average by 2.1°C (southeast) to 4.6°C (southwest), while cold waves are less intense. We assess the avoided climate impacts of urban heat/cold waves in 2061-2080 when following the lower forcing scenario. Urban heat wave days per year increase from 6 in 1981-2005 to up to 92 (southeast) in RCP8.5. Following RCP4.5 reduces heat wave days by about 50%. Large avoided impacts are demonstrated for individual communities; e.g., the longest heat wave for Houston in RCP4.5 is 38 days while in RCP8.5 there is one heat wave per year that is longer than a month with some lasting the entire summer. Heat waves also start later in the season in RCP4.5 (earliest are in early May) than RCP8.5 (mid-April), compared to 1981-2005 (late May). In some communities, cold wave events decrease from 2 per year for 1981-2005 to one-in-five year events in RCP4.5 and one-in-ten year events in RCP8.5.

Retrofitting Precincts for Heatwave Resilience: Challenges and Barriers in Australian Context

As the frequency and intensity of heatwaves are growing in Australia, strategies to combat heat are becoming more vital. Cities are exposed to urban heat islands (UHIs) due to excess urbanisation. In this study, a definition of urban heatwave (UHW) is conceptualised to investigate the combined impacts of heatwaves and UHIs. To quantify the negative impacts of UHW, indicators—such as excess morbidity, electricity and water consumption—are considered. The intensity of UHWs is calculated using the unit of excess heat factor (EHF), developed by the Australian Bureau of Meteorology. EHF enables the comparability of UHWs in different geographical locations. Using the indicators and the intensity of UHWs, a calculation method to quantify heatwave resilience at a precincts scale is proposed. The study summarises the assumed influential factors of precinct heatwave resilience based on the existing literature and propose a “cool retrofitting toolkit” (CRT). CRT creates the framework to assess the adaptation to and mitigation of UHWs available to retrofit existing precincts, and to evaluate potential retrofitting strategies in terms of energy and carbon efficiency, financial affordability and perceived acceptability by population. This study illuminates the importance of climate, function, built environment and population characteristics-conscious retrofitting.

Patterns of urban heat-wave deaths and implications for prevention: Data from New York and St. Louis during July, 1966

Patterns of urban heat wave deaths in New York and St. Louis during July 1966 indicate not only the impact of environmental stress on heat-susceptible segments of the population but provide clues to the possible prevention of such deaths. While mortality from all causes increased by 36% in New York and by 56% in St. Louis certain subgroups were at substantially higher risk (persons over age 65; censustract residents with low income, crowding, or poor housing; those with hypertensive, arteriosclerotic, cardiovascular, or other circulatory disease, diabetes, or chronic respiratory disease). The oppressiveness of heat waves in cities is emphasized by increased rates of homicide and by clashes with police in the streets. On the brighter side, pediatric deaths were controlled during heat episodes in both cities, suggesting that medical, social, and environmental measures can intervene. Unless the general approach to urban heat waves becomes prospective rather than retrospective, one can anticipate episodes of excess mortality during the summers of the 1970's with a human cost of about 136 excess deaths per million per week of heat stress.