Research on the Characteristics of High-Temperature Heat Waves and Outdoor Thermal Comfort: A Typical Space in Chongqing Yuzhong District as an Example

For the high-density urban space heat wave problem, take the core urban area of the mountainous city of Chongqing as an example, four types of typical urban functional spaces, including commercial areas, residential areas, mountain parks, and riverfront parks, were measured during a heat wave cycle, and the characteristics of high-temperature heat waves in different urban spaces were compared through the analysis of air temperature, surface temperature, relative humidity, solar thermal radiation, and other thermal environment parameters. Combined with the questionnaire research related to the heat comfort of the urban population, the physiological equivalent temperature (PET) was selected to describe the heat sensation of the human body, to summarize the elements and patterns of the influence of heat waves on heat comfort of the population in urban spaces, and to establish a prediction model of outdoor heat comfort in summer. It shows that: (1) temperatures recorded during the heat waves are influenced by urban space elements and are differentiated, with older residential areas recording the highest temperatures, followed by commercial areas, and green park areas comparing favorably with both; (2) crowd thermal comfort is correlated with the thermal environment formed by space elements, PET is significantly positively correlated with air temperature, thermal radiation and surface temperature, and significantly negatively correlated with relative humidity, air temperature and thermal radiation have more influence on thermal comfort has a greater impact, while relative humidity and surface temperature have a relatively small impact; (3) reasonable spatial form and shade planning, vegetation and water body settings, high thermal storage substrate and other design elements can alleviate high-temperature heat waves, reduce the thermal neutral temperature and improve thermal comfort. The research results provide some basis for the investigation of the formation mechanism of high-temperature heat waves in mountainous cities and the optimal design of urban spatial thermal environment.

Modeling the Relationships Between Historical Redlining, Urban Heat, and Heat-Related Emergency Department Visits: An Examination of 11 Texas Cities

Place-based structural inequalities can have critical implications for the health of vulnerable populations. Historical urban policies, such as redlining, have contributed to current inequalities in exposure to intra-urban heat. However, it is unknown whether these spatial inequalities are associated with disparities in heat-related health outcomes. The aim of this study is to determine the relationships between historical redlining, intra-urban heat conditions, and heat-related emergency department visits using data from eleven Texas cities. At the zip code level, the proportion of historical redlining was determined, and heat exposure was measured using daytime and nighttime land surface temperature (LST). Heat-related inpatient and outpatient rates were calculated based on emergency department visit data that included ten categories of heat-related diseases between 2016 and 2019. Regression or spatial error/lag models revealed significant associations between higher proportions of redlined areas in the neighborhood and higher LST (Coef. = 0.0122, 95% CI = 0.0039 - 0.0205). After adjusting for indicators of social vulnerability, neighborhoods with higher proportions of redlining showed significantly elevated heat-related outpatient visit rate (Coef. = 0.0036, 95% CI = 0.0007-0.0066) and inpatient admission rate (Coef. = 0.0018, 95% CI = 0.0001-0.0035). These results highlight the role of historical discriminatory policies on the disparities of heat-related illness and suggest a need for equity-based urban heat planning and management strategies.

Approaches for identifying heat-vulnerable populations and locations: A systematic review

Heat related morbidity and mortality, especially during extreme heat events, are increasing due to climate change. More Americans die from heat than from all other natural disasters combined. Identifying the populations and locations that are under high risk of heat vulnerability is important for urban planning and design policy making as well as health interventions. An increasing number of heat vulnerability/risk models and indices (HV/R) have been developed based on indicators related to population heat susceptibility such as sociodemographic and environmental factors. The objectives of this study are to summarize and analyze current HV/R's construction, calculation, and validation, evaluate the limitation of these methods, and provide directions for future HV/R and related studies. This systematic review used the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) framework and used 5 datasets for the literature search. Journal articles that developed indices or models to assess population level heat-related vulnerability or risks in the past 50 years were included. A total of 52 papers were included for analysis on model construction, data sources, weighting schemes and model validation. By synthesizing the findings, we suggested: (1) include relevant and accurately measured indicators; (2) select rational weighting methods and; (3) conduct model validation. We also concluded that it is important for future heat vulnerability models and indices studies to: (1) be conducted in more tropical areas; (2) include a comprehensive understanding of energy exchanges between landscape elements and humans; and (3) be applied in urban planning and policy making practice.

Human health outcomes at the neighbourhood scale implications: Elderly's heat-related cardiorespiratory mortality and its influencing factors

The excessively warm weather, especially in cities, can lead to several adverse impacts, including heat-related mortality, becoming an increasingly important public health issue. Previous studies on heat-related mortality have assessed risk factors at the municipal scale, missing the intra-urban variability in heat risk and vulnerability. The knowledge of the spatial intra-variability can help to design spatially targeted measures to better protect citizens' health. Through hot spot analysis, we identified the neighbourhood-scale spatial pattern of heat-related cardiorespiratory mortality in the elderly, during the yearly warmest five months of a three years period. Potential associations between spatial variability in heat-related mortality and several independent factors in each neighbourhood were investigated and their predictions. Two approaches were adopted: one is eminently statistical, using Generalized Linear Models (GLM) and another using Geographically Weighted Regression (GWR). This new recent regression technique is increasing in international attention on spatial modelling. The spatial model explains about 60% of the spatial variations in elderly's heat-related cardiorespiratory mortality. The two-analyses produced an overlapping set of predictor variables, with emphasis on the elderly, vegetation cover and employment. The results also show that the areas where heat-related mortality is high, are also the areas where the number of deaths is higher than expected. These neighbourhoods should be considered as the most vulnerable to heat-related mortality. We concluded that studying human health outcomes at neighbourhood-scale is relevant for public health heat-related plans. Essential suggestions are provided to decision-making support and city planners designing strategies to reduce heat-related mortality.

Message Sent, Now What? A Critical Analysis of the Heat Action Plan in Ahmedabad, India

To protect public health, heat-related policies are increasingly being adopted by city authorities to address the unequal impact of heatwaves. Ahmedabad’s Heat Action Plan (HAP) is an acclaimed and successful policy response in India and beyond. While the pilot evaluation of the initiative suggests that almost a thousand deaths were avoided annually after its implementation, it is not yet clear whose lives were saved, and to what extent this statistic was due to the HAP, rather than other factors. By reviewing the published and grey literature centering on the HAP target groups, outreach strategies, and impacts on urban services, this paper points out major knowledge gaps concerning the potentials and impacts of the HAP, which may lead to the systematical exclusion of vulnerable and disadvantaged groups from the intended benefits. In this paper, it is argued that the effectiveness and inclusiveness of the HAP predominantly depend on its integration into urban development projects, which is a challenging task given the existing horizontal and vertical fragmentation in the planning of city projects. Moreover, urban plans and policies, including the HAP, are shown to be overly focused on technology, and as a consequence, they do not realize their limited scope in addressing the associated issues, which are fundamentally social, deep, and structural, such as spatial inequality in Indian cities.

A New Method to Assess Fine-Scale Outdoor Thermal Comfort for Urban Agglomerations

In urban areas, high air temperatures and heat stress levels greatly affect human thermal comfort and public health, with climate change further increasing the mortality risks. This study presents a high resolution (100 m) modelling method, including detailed offline radiation calculations, that is able to efficiently calculate outdoor heat stress for entire urban agglomerations for a time period spanning several months. A dedicated measurement campaign was set up to evaluate model performance, yielding satisfactory results. As an example, the modelling tool was used to assess the effectiveness of green areas and water surfaces to cool air temperatures and wet bulb globe temperatures during a typical hot day in the city of Ghent (Belgium), since the use of vegetation and water bodies are shown to be promising in mitigating the adverse effects of urban heat islands and improving thermal comfort. The results show that air temperature reduction is most profound over water surfaces during the afternoon, while open rural areas are coolest during the night. Radiation shading from trees, and to a lesser extent, from buildings, is found to be most effective in reducing wet bulb globe temperatures and improving thermal comfort during the warmest moments of the day.

Appraisal of the heat vulnerability index in Punjab: a case study of spatial pattern for exposure, sensitivity, and adaptive capacity in megacity Lahore, Pakistan

In this study, the heat vulnerability index has been developed for a megacity Lahore. Although Pakistan stands at 12th rank among highly exposed countries to climate change, very little research has been dedicated in exploring the heat-related vulnerability of exposed populations. We have applied the principal component analysis with varimax rotation on well-established indicators of exposure, sensitivity, and adaptive capacity to determine the heat vulnerability. This study has resulted in two principal components sharing 70.4% variance. Principal component 1 comprises pre-existing illness, population density, housing density, education, and normalized difference vegetation index with following significant (> 0.4) loading values 0.91, 0.91, 0.91, 0.57, and - 0.773, respectively, and principal component 2 combines the nature of housing material (0.964) followed by the water availability (0.962) and minority status (0.539). The hot spot analysis and overlay analysis have also been applied on the extracted component, and the resultant co-occurrence of high variable class, high vulnerability, and hot spots of vulnerability helped to grip those areas which imperatively require the applications of heat-related health interventions. The heat vulnerability index developed in our study clarifies that the most vulnerable populations are confined in the central vicinities of Lahore and less vulnerable are those which inhibit towards the outskirts of the city.

Heat risk assessment for the Brussels capital region under different urban planning and greenhouse gas emission scenarios

Urban residents are exposed to higher levels of heat stress in comparison to the rural population. As this phenomenon could be enhanced by both global greenhouse gas emissions (GHG) and urban expansion, urban planners and policymakers should integrate both in their assessment. One way to consider these two concepts is by using urban climate models at a high resolution. In this study, the influence of urban expansion and GHG emission scenarios is evaluated at 100 m spatial resolution for the city of Brussels (Belgium) in the near (2031-2050) and far (2081-2100) future. Two possible urban planning scenarios (translated into local climate zones, LCZs) in combination with two representative concentration pathways (RCPs 4.5 and 8.5) have been implemented in the urban climate model UrbClim. The projections show that the influence of GHG emissions trumps urban planning measures in each period. In the near future, no large differences are seen between the RCP scenarios; in the far future, both heat stress and risk values are twice as large for RCP 8.5 compared to RCP 4.5. Depending on the GHG scenario and the LCZ type, heat stress is projected to increase by a factor of 10 by 2090 compared to the present-day climate and urban planning conditions. The imprint of vulnerability and exposure is clearly visible in the heat risk assessment, leading to very high levels of heat risk, most notably for the North Western part of the Brussels Capital Region. The results demonstrate the need for mitigation and adaptation plans at different policy levels that strive for lower GHG emissions and the development of sustainable urban areas safeguarding livability in cities.

[Assessment of health risks due to heat and fine particles in Germany: an epidemiological study approach]

BACKGROUND

Exposure to heat and particulate matter is a cause of increased mortality. Climate change and increasing climate variability exacerbate these problems. Experts require assessments with which health risks and the success of preventative measures can be estimated. We implemented an ecological study approach to assess these risks at both small and large scales of reference levels (Federal Republic of Germany and territorial authority).

METHODS

We utilised a case-crossover design to investigate the relationship between exposure and mortality. This study design uses a logistic regression model. Analogously to a matched case-control study, the odds ratio maps the effect strength. The study period included the years 2002-2006.

RESULTS

The analysis demonstrated health risks from exposure to heat for the German population (OR 1.1529, 95% CI 1.1517-1.1541; adjusted OR 1.0658). Significant evidence of a health risk was also documented for exposure to particulate matter (PM_10; OR 1.2987, 95% CI 1.2951-1.3024; adjusted OR 1.0128). The risk does not significantly differ for women versus men; the variable age was also not significant at the level of the country-wide analysis, but for a few subordinate units of space. This study approach can be adapted for assessments at varying levels of reference and periods of time as well as for different populations.

DISCUSSION

The methodological approach is useful for a reproducible study design. Nevertheless, other influencing factors such as ozone or PM_2.5 should be incorporated in subsequent analyses to clarify whether these factors skew the results. Further analysis would also be useful to investigate if and to what extent socio-structural and socio-economic factors affect the associated risk.

A Raster-Based Subdividing Indicator to Map Urban Heat Vulnerability: A Case Study in Sydney, Australia

Assessing and mapping urban heat vulnerability has developed significantly over the past decade. Many studies have mapped urban heat vulnerability with a census unit-based general indicator (CGI). However, this kind of indicator has many problems, such as inaccurate assessment results and lacking comparability among different studies. This paper seeks to address this research gap and proposes a raster-based subdividing indicator to map urban heat vulnerability. We created a raster-based subdividing indicator (RSI) to map urban heat vulnerability from 3 aspects: exposure, sensitivity and adaptive capacity. We applied and compared it with a raster-based general indicator (RGI) and a census unit-based general indicator (CGI) in Sydney, Australia. Spatial statistics and analysis were used to investigate the performance among those three indicators. The results indicate that: (1) compared with the RSI framework, 67.54% of very high heat vulnerability pixels were ignored in the RGI framework; and up to 83.63% of very high heat vulnerability pixels were ignored in the CGI framework; (2) Compared with the previous CGI framework, a RSI framework has many advantages. These include more accurate results, more flexible model structure, and higher comparability among different studies. This study recommends using a RSI framework to map urban heat vulnerability in the future.

On the Science-Policy Bridge: Do Spatial Heat Vulnerability Assessment Studies Influence Policy?

Human vulnerability to heat varies at a range of spatial scales, especially within cities where there can be noticeable intra-urban differences in heat risk factors. Mapping and visualizing intra-urban heat vulnerability offers opportunities for presenting information to support decision-making. For example the visualization of the spatial variation of heat vulnerability has the potential to enable local governments to identify hot spots of vulnerability and allocate resources and increase assistance to people in areas of greatest need. Recently there has been a proliferation of heat vulnerability mapping studies, all of which, to varying degrees, justify the process of vulnerability mapping in a policy context. However, to date, there has not been a systematic review of the extent to which the results of vulnerability mapping studies have been applied in decision-making. Accordingly we undertook a comprehensive review of 37 recently published papers that use geospatial techniques for assessing human vulnerability to heat. In addition, we conducted an anonymous survey of the lead authors of the 37 papers in order to establish the level of interaction between the researchers as science information producers and local authorities as information users. Both paper review and author survey results show that heat vulnerability mapping has been used in an attempt to communicate policy recommendations, raise awareness and induce institutional networking and learning, but has not as yet had a substantive influence on policymaking or preventive action.

The Construction and Validation of the Heat Vulnerability Index, a Review

The occurrence of extreme heat and its adverse effects will be exacerbated with the trend of global warming. An increasing number of researchers have been working on aggregating multiple heat-related indicators to create composite indices for heat vulnerability assessments and have visualized the vulnerability through geographic information systems to provide references for reducing the adverse effects of extreme heat more effectively. This review includes 15 studies concerning heat vulnerability assessment. We have studied the indicators utilized and the methods adopted in these studies for the construction of the heat vulnerability index (HVI) and then further reviewed some of the studies that validated the HVI. We concluded that the HVI is useful for targeting the intervention of heat risk, and that heat-related health outcomes could be used to validate and optimize the HVI. In the future, more studies should be conducted to provide references for the selection of heat-related indicators and the determination of weight values of these indicators in the development of the HVI. Studies concerning the application of the HVI are also needed.