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Showing papers on "Urban climate published in 2020"


Journal ArticleDOI
TL;DR: A reduced form approach is proposed that is able to estimate UHI intensities based only on the number and location of urban sites as well as their distance, which can serve as a UHI rule of thumb for the comparison of urban development scenarios.
Abstract: The canopy layer urban heat island (UHI) effect, as manifested by elevated near-surface air temperatures in urban areas, exposes urban dwellers to additional heat stress in many cities, specially during heat waves. We simulate the urban climate of various generated cities under the same weather conditions. For mono-centric cities, we propose a linear combination of logarithmic city area and logarithmic gross building volume, which also captures the influence of building density. By studying various city shapes, we generalise and propose a reduced form to estimate UHI intensities based only on the structure of urban sites, as well as their relative distances. We conclude that in addition to the size, the UHI intensity of a city is directly related to the density and an amplifying effect that urban sites have on each other. Our approach can serve as a UHI rule of thumb for the comparison of urban development scenarios. How UHI intensity responds to variations of urban structure is unclear. Here the authors proposed a reduced form approach that is able to estimate UHI intensities based only on the number and location of urban sites as well as their distance.

160 citations


Journal ArticleDOI
TL;DR: In this paper, the authors assessed the efficacy of mapping hyperlocal ambient air temperatures (Tair) over Oslo, Norway, by integrating Sentinel, Landsat and LiDAR data with crowd-sourced Tair measurements from 1310 private weather stations during 2018.

90 citations


Journal ArticleDOI
TL;DR: The proposed morphology-based tree selection approach was evaluated by comparison with two uninformed selection approaches in a realistic urban neighborhood in Hong Kong and clearly indicates the proposed approach's capability in improving human thermal comfort by up two times more than either of the other approaches.

90 citations


Journal ArticleDOI
TL;DR: The authors showed that cities are particularly vulnerable to extreme weather episodes, which are expected to increase with climate change, and that cities also influence their own local climate, for example, through the relative relative...
Abstract: Cities are particularly vulnerable to extreme weather episodes, which are expected to increase with climate change. Cities also influence their own local climate, for example, through the relative ...

86 citations


Journal ArticleDOI
TL;DR: In this article, the authors investigated 147 climate change action plans (CCAPs) to understand the degree of integration of adaptation and mitigation and draw implications for the maximization of synergies and co-benefits of such a combined approach.
Abstract: Cities are major drivers of energy consumption and greenhouse gas emissions--the sources of anthropocentric climate change, whilst also concentrating people, buildings, and infrastructures and therefore potential risk and impacts of the latter. As a consequence, planning for climate change in urban areas does not only provide the opportunity but should necessitate considering interactions between mitigation and adaptation actions. However, existing research found that only a minority of urban areas consider both mitigation and adaptation in their climate action plans, i.e. 147 Climate Change Action Plans (CCAPs) were identified among a representative sample of 885 European cities. We investigate these 147 CCAPs to understand the degree of integration of adaptation and mitigation and draw implications for the maximization of synergies and co-benefits of such a combined approach. Using the developed scoring framework to evaluate the level of integration of CCAPs, the research finds that most of the plans reveal a ‘moderate’ level of integration. Moderate integration characterizes a plan that identifies sources of emissions and vulnerabilities to climate change, as well as some qualitative consideration of the synergies, but one that lacks a systematic consideration of potential integration opportunities. Furthermore, the analysis reveals that one of the main gaps of the evaluation and implementation of more integrated climate change actions in cities is the insufficient quantitative evaluation of the costs and funding schemes for adaptation and mitigation action implementation.

86 citations


Journal ArticleDOI
TL;DR: In this article, an urban ecohydrological model, Urban Tethys-Chloris (UT&C), is presented, which combines principles of ecosystem modelling with an urban canopy scheme accounting for the biophysical and ecophysiological characteristics of roof vegetation, ground vegetation and urban trees.
Abstract: . Increasing urbanization is likely to intensify the urban heat island effect, decrease outdoor thermal comfort, and enhance runoff generation in cities. Urban green spaces are often proposed as a mitigation strategy to counteract these adverse effects, and many recent developments of urban climate models focus on the inclusion of green and blue infrastructure to inform urban planning. However, many models still lack the ability to account for different plant types and oversimplify the interactions between the built environment, vegetation, and hydrology. In this study, we present an urban ecohydrological model, Urban Tethys-Chloris (UT&C), that combines principles of ecosystem modelling with an urban canopy scheme accounting for the biophysical and ecophysiological characteristics of roof vegetation, ground vegetation, and urban trees. UT&C is a fully coupled energy and water balance model that calculates 2 m air temperature, 2 m humidity, and surface temperatures based on the infinite urban canyon approach. It further calculates the urban hydrological fluxes in the absence of snow, including transpiration as a function of plant photosynthesis. Hence, UT&C accounts for the effects of different plant types on the urban climate and hydrology, as well as the effects of the urban environment on plant well-being and performance. UT&C performs well when compared against energy flux measurements of eddy-covariance towers located in three cities in different climates (Singapore, Melbourne, and Phoenix). A sensitivity analysis, performed as a proof of concept for the city of Singapore, shows a mean decrease in 2 m air temperature of 1.1 ∘ C for fully grass-covered ground, 0.2 ∘ C for high values of leaf area index (LAI), and 0.3 ∘ C for high values of Vc,max (an expression of photosynthetic capacity). These reductions in temperature were combined with a simultaneous increase in relative humidity by 6.5 % , 2.1 % , and 1.6 % , for fully grass-covered ground, high values of LAI, and high values of Vc,max , respectively. Furthermore, the increase of pervious vegetated ground is able to significantly reduce surface runoff.

84 citations


Journal ArticleDOI
TL;DR: In this article, the authors classify the required urban input data for both mesoscale state-of-the-art Urban Canopy Models (UCMs) and microscale Obstacle Resolving Models (ORM) into five categories and review the ways in which they can be obtained.
Abstract: Cities are particularly vulnerable to meteorological hazards because of the concentration of population, goods, capital stock and infrastructure. Urban climate services require multi-disciplinary and multi-sectorial approaches and new paradigms in urban climate modelling. This paper classifies the required urban input data for both mesoscale state-of-the-art Urban Canopy Models (UCMs) and microscale Obstacle Resolving Models (ORM) into five categories and reviews the ways in which they can be obtained. The first two categories are (1) land cover, and (2) building morphology. These govern the main interactions between the city and the urban climate and the Urban Heat Island. Interdependence between morphological parameters and UCM geometric hypotheses are discussed. Building height, plan and wall area densities are recommended as the main input variables for UCMs, whereas ORMs require 3D building data. Recently, three other categories of urban data became relevant for finer urban studies and adaptation to climate change: (3) building design and architecture, (4) building use, anthropogenic heat and socio-economic data, and (5) urban vegetation data. Several methods for acquiring spatial information are reviewed, including remote sensing, geographic information system (GIS) processing from administrative cadasters, expert knowledge and crowdsourcing. Data availability, data harmonization, costs/efficiency trade-offs and future challenges are then discussed.

81 citations


Journal ArticleDOI
TL;DR: In this article, a detailed understanding of the relationship between PM2.5 pollution and the urban heat island (UHI) effect is presented, which can help to design effective mitigation strategies.
Abstract: Heavy PM2.5 (particulate matter with aerodynamic diameter equal to or less than 2.5 mu m) pollution and urban heat island (UHI) pose increasing threats to human health and living environment in populated cities. However, how PM2.5 pollution affects the UHI intensity (UHII) has not been fully understood. The impacts of PM2.5 on the wintertime UHII in the Beijing-Tianjin-Hebei megalopolis of China are explored during 2013-2017. The results show that the UHII at the time of daily maximum/minimum temperature (UHIImax/UHIImin) exhibits a decreasing/increasing tendency as PM2.5 concentration increases, causing a continuous decrease in the diurnal temperature range. These effects are mediated via aerosol-radiation interaction (aerosol-cloud interaction) under clear-sky (cloudy) condition. The changes in PM2.5 concentration further cause different relative trends of UHII(ma)x/UHIImin/diurnal temperature range across different cities in the Beijing-Tianjin-Hebei region, which are likely related to the differences in both the PM2.5 composition and city size. This study provides insights on how air pollution affects urban climate and would help to design effective mitigation strategies. Plain Language Summary A detailed understanding of the relationship between PM2.5 (particulate matter with aerodynamic diameter equal to or less than 2.5 mu m) and the urban heat island (UHI) effect is significant for climate change adaption, planning, and sustainable development in urban regions. While the Beijing-Tianjin-Hebei (BTH) megalopolis of China is among the areas with the highest population densities and fastest urbanization rates in the world, the impacts of PM2.5 pollution on UHI, along with their regional differences in the BTH megalopolis, remain unclear. This study demonstrates that different PM2.5 concentrations in the BTH region pose various influences on the UHI intensities and their change rates in different cities of varying sizes. The UHI intensities during daytime and nighttime, respectively, exhibit weakening and strengthening tendency as PM2.5 concentration increases. These effects are mediated via aerosol-radiation interaction under clear-sky condition and aerosol-cloud interaction in cloudy weather. The relative changes in the UHI magnitudes were mainly determined by PM2.5 composition and city size. The asymmetrical influences of PM2.5 on the daytime and nighttime UHI intensities caused continuous decreases in the diurnal temperature ranges in the urban areas as the pollution level increased. Our study improves the understanding of urban climate affected by air pollution and provides a scientific basis for the mitigation of UHI impacts.

79 citations


Journal ArticleDOI
TL;DR: In this paper, the authors investigated the effect of urban morphology on anthropogenic heat dispersion and provided effective planning strategies to reduce UHI intensity, especially at the extreme scenarios, such as with very low wind speed and high heat emission.

78 citations


Journal ArticleDOI
TL;DR: It is argued that LCZ mapping should be considered as a scene classification task to fully exploit the environmental context and more advanced domain adaptation methods should be applied in this application.
Abstract: China, with the world’s largest population, has gone through rapid development in the last forty years and now has over 800 million urban citizens. Although urbanization leads to great social and economic progress, they may be confronted with other issues, including extra heat and air pollution. Local climate zone (LCZ), a new concept developed for urban heat island research, provides a standard classification system for the urban environment. LCZs are defined by the context of the urban environment; the minimum diameter of an LCZ is expected to be 400–1,000 m so that it can have a valid effect on the urban climate. However, most existing methods (e.g., the WUDAPT method) regard this task as pixel-based classification, neglecting the spatial information. In this study, we argue that LCZ mapping should be considered as a scene classification task to fully exploit the environmental context. Fifteen cities covering 138 million population in three economic regions of China are selected as the study area. Sentinel-2 multispectral data with a 10 m spatial resolution are used to classify LCZs. A deep convolutional neural network composed of residual learning and the Squeeze-and-Excitation block, namely the LCZNet, is proposed. We obtained an overall accuracy of 88.61% by using a large image (48 × 48 corresponding to 480 × 480 m 2 ) as the representation of an LCZ, 7.5% higher than that using a small image representation (10 × 10) and nearly 20% higher than that obtained by the standard WUDAPT method. Image sizes from 32 × 32 to 64 × 64 were found suitable for LCZ mapping, while a deeper network achieved better classification with larger inputs. Compared with natural classes, urban classes benefited more from a large input size, as it can exploit the environment context of urban areas. The combined use of the training data from all three regions led to the best classification, but the transfer of LCZ models cannot achieve satisfactory results due to the domain shift. More advanced domain adaptation methods should be applied in this application.

77 citations


Journal ArticleDOI
01 Dec 2020
TL;DR: In this article, a review of the recent literature and recommendations are formulated for future work on urban climate modeling and climate change attribution is presented, where the authors focus on the exchange of water and energy between the atmosphere and the urban surfaces.
Abstract: As an effect of climate change, cities need detailed information on urban climates at decision scale that cannot be easily delivered using current observation networks, nor global and even regional climate models. A review is presented of the recent literature and recommendations are formulated for future work. In most cities, historical observational records are too short, discontinuous, or of too poor quality to support trend analysis and climate change attribution. For climate modeling, on the other hand, specific dynamical and thermal parameterization dedicated to the exchange of water and energy between the atmosphere and the urban surfaces have to be implemented. Therefore, to fully understand how cities are impacted by climate change, it is important to have (1) simulations of the urban climate at fine spatial scales (including coastal hazards for coastal cities) integrating global climate scenarios with urban expansion and population growth scenarios and their associated uncertainty estimates, (2) urban climate observations, especially in Global South cities, and (3) spatial data of high resolution on urban structure and form, human behavior, and energy consumption.

Journal ArticleDOI
TL;DR: There is evidence, however, that the comfort achieved by sensible cooling can be offset by the increased water vapour content and that during the night blue spaces may actually exacerbate the UHI, reducing urban thermal comfort.

Journal ArticleDOI
TL;DR: This study demonstrates that both mesoscale (WRF) and microscale (ENVI-met) modeling confirm similar results in how greenery enhancements may improve the human thermal comfort in the continental climate of the GTA.

Journal ArticleDOI
TL;DR: The energy performance of urban buildings is affected by multiple climate phenomena such as heat island intensity, wind flow, solar obstructions and infrared radiation exchange in urban canyons.
Abstract: The energy performance of urban buildings is affected by multiple climate phenomena such as heat island intensity, wind flow, solar obstructions and infrared radiation exchange in urban canyons, bu...

Journal ArticleDOI
TL;DR: In this article, the authors presented the results from a self-assessment conducted by seven midsize cities in the North Sea Region through a transdisciplinary knowledge co-production process.

Journal ArticleDOI
TL;DR: The sky view factor (SVF) as discussed by the authors is defined as the ratio of the visible sky area of a point in space to the total sky area, which is the relationship between the visible Sky area and covered surroundings, such as by buildings or street trees.

Journal ArticleDOI
TL;DR: In this article, the impact of urban green infrastructure (GI) on urban climate, environmental quality and health, and their synergies and trade-offs are analyzed. But, despite the plethora of available scientific information, very little is known about the holistic and global impact of a potential increase of urban GI on urban Climate, Environmental Quality and Health.
Abstract: Urban vegetation provides undeniable benefits to urban climate, health, thermal comfort and environmental quality of cities and represents one of the most considered urban heat mitigation measures. Despite the plethora of available scientific information, very little is known about the holistic and global impact of a potential increase of urban green infrastructure (GI) on urban climate, environmental quality and health, and their synergies and trade-offs. There is a need to evaluate globally the extent to which additional GI provides benefits and quantify the problems arising from the deployment of additional greenery in cities which are usually overlooked or neglected. The present paper has reviewed and analysed 55 fully evaluated scenarios and case studies investigating the impact of additional GI on urban temperature, air pollution and health for 39 cities. Statistically significant correlations between the percentage increase of the urban GI and the peak daily and night ambient temperatures are obtained. The average maximum peak daily and night-time temperature drop may not exceed 1.8 and 2.3 °C respectively, even for a maximum GI fraction. In parallel, a statistically significant correlation between the peak daily temperature decrease caused by higher GI fractions and heat-related mortality is found. When the peak daily temperature drops by 0.1 °C, then the percentage of heat-related mortality decreases on average by 3.0% The impact of additional urban GI on the concentration of urban pollutants is analysed, and the main parameters contributing to decrease or increase of the pollutants’ concentration are presented.

Journal ArticleDOI
TL;DR: Climate projections of population-weighted heat and cold exposure that directly and simultaneously account for greenhouse gas (GHG) and urban development-induced warming are presented and it is demonstrated that Sunbelt cities are projected to undergo the largest relative increase in population heat exposure to locally defined extreme heat conditions during the 21st century.
Abstract: We use a suite of decadal-length regional climate simulations to quantify potential changes in population-weighted heat and cold exposure in 47 US metropolitan regions during the 21st century Our results show that population-weighted exposure to locally defined extreme heat (ie, “population heat exposure”) would increase by a factor of 127–295 under a high-intensity greenhouse gas (GHG) emissions and urban development pathway Additionally, end-of-century population cold exposure is projected to rise by a factor of 13–22, relative to start-of-century population cold exposure We identify specific metropolitan regions in which population heat exposure would increase most markedly and characterize the relative significance of various drivers responsible for this increase The largest absolute changes in population heat exposure during the 21st century are projected to occur in major US metropolitan regions like New York City (NY), Los Angeles (CA), Atlanta (GA), and Washington DC The largest relative changes in population heat exposure (ie, changes relative to start-of-century) are projected to occur in rapidly growing cities across the US Sunbelt, for example Orlando (FL), Austin (TX), Miami (FL), and Atlanta The surge in population heat exposure across the Sunbelt is driven by concurrent GHG-induced warming and population growth which, in tandem, could strongly compound population heat exposure Our simulations provide initial guidance to inform the prioritization of urban climate adaptation measures and policy

Journal ArticleDOI
TL;DR: In this paper, the concept of Local Climate Zones (LCZs) was introduced to compare urban heat islands (UHIs) in urban climate studies, and a systematic criteria for UHI comparisons were lacking prior to 2012.
Abstract: Urban heat islands (UHIs) are a key topic in urban climate studies. However, systematic criteria for UHI comparisons were lacking prior to 2012, when the concept of Local Climate Zones (LCZs) was i...

Journal ArticleDOI
TL;DR: In this paper, the relationship between land surface temperature and Local Climatic Zones (LCZs) in Sriniketan-Sanniketaan Planning Area (SSPA) using GIS and remote sensing techniques was examined.
Abstract: The concept Local Climatic Zones (LCZs) is a comprehensive classification scheme developed to design urban climate studies particularly to quantify the relationship in between urban morphology and urban heal islands (UHIs). Land surface temperature (LST) data obtained from satellite images were used to examine the relationship between land surface temperature and Local Climatic Zones in Sriniketan-Sanniketan Planning Area (SSPA) using GIS and remote sensing techniques. The effect of Surface Urban Heal Island was assessed using Urban Thermal Field Variance Index (UTFVI) quantitatively. The results show that land surface temperature increased by 0.34 °C per year and 0.55 °C per year during winter and summer season respectively and a significant variation of LST over the LCZs exist. The maximum and minimum LST is recorded in the month of April and January. The study landscape enjoys excellent to normal thermal conditions (UTFVI

Journal ArticleDOI
TL;DR: In this article, the relationship between the land surface temperatures (LSTs) of green and impervious surfaces was examined in Nigde, Turkey Various satellite images were used, and statistical and geographical analyses were conducted.
Abstract: The urban climate has been disrupted with increasing urbanisation and consumption concepts, revealing climatic properties that affect human comfort conditions as a result of climate change Decreasing vegetation and evaporative surfaces in cities, and increasing structural surfaces, such as concrete and asphalt, alter the topography, ecological structure, and atmospheric characteristics of nature, creating a different ecology and atmosphere In this study, the relationship between the land surface temperatures (LSTs) of green and impervious surfaces was examined in Nigde, Turkey Various satellite images were used, and statistical and geographical analyses were conducted The results revealed that the LST values changed with the changing ratio of impervious and green surfaces, and have increased in Nigde over the past three decades even though the amount of green surfaces have increased Furthermore, the LSTs of the impervious surfaces are 5–10 °C higher than that of the green surfaces A correlation analysis showed that there was a significant difference in the LST values between green and impervious surfaces Impervious surfaces contribute to the formation of the urban heat islands (UHIs), and green surfaces provide a cooling effect Thus, increasing the amount of green surfaces in cities is crucial to improve urban life quality

Journal ArticleDOI
TL;DR: In this article, the spatial variation of Urban Land Surface Temperature (ULST) is a complex function of environmental, climatic, and anthropogenic factors, and it thus requires specific techniques to quantify this phenome...
Abstract: Spatial variation of Urban Land Surface Temperature (ULST) is a complex function of environmental, climatic, and anthropogenic factors. It thus requires specific techniques to quantify this phenome...

Journal ArticleDOI
TL;DR: This paper investigated the use of narratives of change as an approach to elicit perceptions of past, present and future weather, water, and climate, and how these relate to citizens' desired futures.

Journal ArticleDOI
TL;DR: In this article, the authors estimated changes in land-use/land-cover (LULC) from 1993 to 2018, its warming (positive) and cooling (negative) effect, and their contribution to relative LST (RLST) in the city of Islamabad using satellite remote-sensing data.
Abstract: One of the essential anthropogenic influences on urban climate is land-use/land-cover (LULC) change due to urbanization, which has a direct impact on land surface temperature (LST). However, LULC changes affect LST, and further, urban heat island (UHI) still needs to be investigated. In this study, we estimated changes in LULC from 1993 to 2018, its warming (positive) and cooling (negative) effect, and their contribution to relative LST (RLST) in the city of Islamabad using satellite remote-sensing data. The LULC was classified using a random forest (RF) classifier, and LST was retrieved by a standardized radiative transfer equation (RTE). Our results reveal that the impervious surfaces has increased by 11.9% on the cost of declining barren land, forest land, grass/agriculture land, and water bodies in the last 26 years. LULC conversion contributed warming effects such as forest land, water bodies, and grass/agriculture land transformed into impervious surfaces, inducing a warming contribution of 1.52 °C. In contrast, the replacement of barren land and impervious surfaces by forest land and water bodies may have a cooling contribution of −0.85 °C to RLST. Furthermore, based on the standardized scale (10%) of LULC changes, the conversion of forest land into impervious surfaces contributed 1% compared to back conversion by −0.2%. The positive contribution to UHI due to the transformation of a natural surface to the human-made surface was found higher than the negative (cooler) contribution due to continued anthropogenic activities. The information will be useful for urban managers and decision makers in land-use planning to control the soaring surface temperature for a comfortable living environment and sustainable cities.

Journal ArticleDOI
18 Mar 2020-Energies
TL;DR: In this article, the authors summarized the findings of previous studies, assessing the main causes of urban warming along with the key investigation methods involving experimental and computational approaches, and described a description of the most common mitigations, and adaption strategies towards the attenuation of urban heating.
Abstract: The increased rates of urbanization and industrialization of the 20th and 21st centuries have dramatically changed the land use and cover of modern cities, contributing to the degradation of the urban microclimate and the rise of the ambient urban air temperatures. Given the multiple negative energy, environmental and social consequences of urban warming, the present paper summarizes the findings of previous studies, assessing the main causes of the phenomenon along with the key investigation methods involving experimental and computational approaches. There follows a description of the most common mitigations, and adaption strategies towards the attenuation of urban warming are described. The analyzed elements include the addition of green spaces such as trees, grass and green roofs; changes on the albedo of the urban surfaces and water-based techniques, as well as a combination of them. The discussion of the reported findings in the existing literature clearly reflects the impact of urban morphology on the outdoor thermal environment, providing also useful information for professionals and urban planners involved at the phase of decision-making.

Journal ArticleDOI
TL;DR: Wang et al. as discussed by the authors quantified the spatial patterns of anthropogenic heat (AH) emissions in the Yangtze River Delta (YRD) agglomeration of East China, and analyzed the temporal and spatial impacts on the urban thermal environment.

Journal ArticleDOI
TL;DR: In this article, the authors coupled the Building Effect Parameterization with Trees (BEP-Tree) vegetated urban canopy model and the Consortium for Small-scale Modeling (COSMO) mesoscale weather and climate model.
Abstract: . Street trees are more and more regarded as an effective measure to reduce excessive heat in urban areas. However, the vast majority of mesoscale urban climate models do not represent street trees in an explicit manner and, for example, do not take the important effect of shading by trees into account. In addition, urban canopy models that take interactions of trees and urban fabrics directly into account are usually limited to the street or neighbourhood scale and hence cannot be used to analyse the citywide effect of urban greening. In order to represent the interactions between street trees, urban elements and the atmosphere in realistic regional weather and climate simulations, we coupled the Building Effect Parameterisation with Trees (BEP-Tree) vegetated urban canopy model and the Consortium for Small-scale Modeling (COSMO) mesoscale weather and climate model. The performance and applicability of the coupled model, named COSMO-BEP-Tree, are demonstrated over the urban area of Basel, Switzerland, during the heatwave event of June–July 2015. Overall, the model compared well with measurements of individual components of the surface energy balance and with air and surface temperatures obtained from a flux tower, surface stations and satellites. Deficiencies were identified for nighttime air temperature and humidity, which can mainly be traced back to limitations in the simulation of the nighttime stable boundary layer in COSMO. The representation of street trees in the coupled model generally improved the agreement with observations. Street trees produced large changes in simulated sensible and latent heat flux, and wind speed. Within the canopy layer, the presence of street trees resulted in a slight reduction in daytime air temperature and a very minor increase in nighttime air temperature. The model was found to realistically respond to changes in the parameters defining the street trees: leaf area density and stomatal conductance. Overall, COSMO-BEP-Tree demonstrated the potential of (a) enabling city-wide studies on the cooling potential of street trees and (b) further enhancing the modelling capabilities and performance in urban climate modelling studies.

Journal ArticleDOI
TL;DR: It is found that cropland and forest in Nanjing are helping to cool the city with different degrees of cooling effects depending on the location and LULC composition.
Abstract: Rapid urbanization is one of the most concerning issues in the 21st century because of its significant impacts on various fields, including agriculture, forestry, ecology, and climate. The urban heat island (UHI) phenomenon, highly related to the rapid urbanization, has attracted considerable attention from both academic scholars and governmental policymakers because of its direct influence on citizens’ daily life. Land surface temperature (LST) is a widely used indicator to assess the intensity of UHI significantly affected by the local land use/cover (LULC). In this study, we used the Landsat time-series data to derive the LULC composition and LST distribution maps of Nanjing in 2000, 2014, and 2018. A correlation analysis was carried out to check the relationship between LST and the density of each class of LULC. We found out that cropland and forest in Nanjing are helping to cool the city with different degrees of cooling effects depending on the location and LULC composition. Then, a Cellar Automata (CA)-Markov model was applied to predict the LULC conditions of Nanjing in 2030 and 2050. Based on the simulated LULC maps and the relationship between LST and LULC, we delineated high- and moderate-LST related risk areas in the city of Nanjing. Our findings are valuable for the local government to reorganize the future development zones in a way to control the urban climate environment and to keep a healthy social life within the city.

Journal ArticleDOI
TL;DR: In this article, the authors investigated the interactions between urban morphology indicators and extreme weather variables and found that transforming from mesoscale to microscale can considerably dampen the magnitude of wind speed and amplify the air temperature.
Abstract: This paper investigates the interactions between urban morphology indicators and extreme weather variables. In this regard, variations of wind speed and air temperature at the urban microscale are studied for three urban morphologies by means of numerical simulations. Each urban model contains ninety-nine calculation points at different locations and heights to assess the variations during two 24-h cycles of extreme low and high wind speeds by introducing a microscale indicator. According to the results, transforming from mesoscale to microscale can considerably dampen the magnitude of wind speed (up to 66%) and amplify the air temperature (up to 39%). Moreover, the urban morphology parameters (layout geometry, final height and urban density) can change the average magnitude of wind speed (up to 23%) and air temperature (up to 16%) at microscale. For extreme low wind speeds (0.16–1.14 m/s), strong correlations exist between the mesoscale and microscale magnitude of wind speed and air temperature, while there is no significant correlation for extreme high wind speeds (12.2–14 m/s). For extreme low wind speeds, stronger buoyancy effects are observed at the urban canopies. An easy-to-setup approach is proposed to count for microscale conditions during extreme low wind speeds in urban climate studies.

Journal ArticleDOI
TL;DR: The authors investigate the political imaginaries contained within representations of urban climate futures and what silent but corollary rural dispossessions accompany them, and investigate these questions through a series of experiments.
Abstract: What are the political imaginaries contained within representations of urban climate futures? What silent but corollary rural dispossessions accompany them? I investigate these questions through th...