Special Issue "Urban Design and City Microclimates"

A special issue of Atmosphere (ISSN 2073-4433). This special issue belongs to the section "Biometeorology".

Deadline for manuscript submissions: closed (30 June 2018)

Special Issue Editor

Guest Editor
Prof. Dr. Robert Brown

Department of Landscape Architecture and Urban Planning, Texas A&M University, College Station, USA
Website | E-Mail
Interests: microclimate modification; human energy budget modeling; urban design, landscape architecture

Special Issue Information

Dear Colleagues,

More than half the people in the world now live in cities and this proportion is expected to continue to increase. Global Climate Change (GCC) and Urban Heat Island (UHI) intensification are making cities hotter places to live. Hot cities can have both a chronic and an acute effect on human health. Uncomfortably hot conditions discourage people from spending time outdoors, which has various negative physiological and mental health implications. Current heat waves are more intense, more frequent, and last longer than in the past, leading to acute health effects including hyperthermia and death. Urban designers require solid evidence on how to either reverse or dampen these trends, and they need evidence-based adaptation strategies for redesigning cities so that they will be more thermally-comfortable every day, and particularly safer during extreme heat events.

This Special Issue will explore three important questions that have not been widely addressed in related literature, yet are critical to designing thermally-safe cities. 

 

The first question is: how does the built urban environment modify the climate, at all scales?  Papers that address this issue will measure atmospheric variables before and after modifications to the urban environments. Results will quantify the relative effects of different design interventions.

 

The second question is: how does microclimate affect the energy budget (or heat balance), safety, and thermal comfort level of humans? Studies will measure microclimatic conditions and survey people experiencing those conditions, and will use the results to develop and/or validate human energy budget models. They might also measure physiological characteristics of people, such as core temperature, heart rate variability, or skin temperatures as subjects experience different microclimates.

 

And the third question is: are there new, innovative instruments that can be used to measure microclimates and/or human thermal comfort in urban environments? One example might be an inexpensive miniature anemometer that could be deployed in a network to measure the wind in urban areas. Another example may be the use of unmanned air vehicles in understanding attributes of the urban environment (such as surface temperatures) as compared to in situ or satellite measurements.

Each paper in this Special Issue will include field measurements of microclimatic conditions and/or surveys, perceptions or physical measures of how people experience those conditions. Of particular importance will be the ability of contributions to move beyond simulations or even single point/case measures and to ground-truth and/or calibrate multiple measurement techniques. Finally, each will explain how their conclusions will help to design or redesign cities to make them safer and more thermally comfortable for residents in the context of a changing climate.

Prof. Dr. Robert Brown
Guest Editor

Manuscript Submission Information

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Keywords

  • microclimate modification
  • urban heat islands
  • global climate change
  • urban design
  • microclimate measurement
  • instrumentation
  • human thermal comfort
  • human health

Published Papers (6 papers)

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Research

Open AccessArticle Development of a Distributed Modeling Framework to Estimate Thermal Comfort along 2020 Tokyo Olympic Marathon Course
Atmosphere 2018, 9(6), 210; https://doi.org/10.3390/atmos9060210
Received: 12 March 2018 / Revised: 24 May 2018 / Accepted: 26 May 2018 / Published: 30 May 2018
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Abstract
Heat stress is an issue for marathon races in the summer, such as the one planned for the 2020 Tokyo Summer Olympic games. The Tokyo Metropolitan Government is planning to grow existing street trees’ canopies to enlarge their shade to reduce air temperature
[...] Read more.
Heat stress is an issue for marathon races in the summer, such as the one planned for the 2020 Tokyo Summer Olympic games. The Tokyo Metropolitan Government is planning to grow existing street trees’ canopies to enlarge their shade to reduce air temperature and solar radiation. To formulate a baseline to assess the effect of street trees and buildings on human thermal comfort, Distributed-COMfort FormulA (D-COMFA), a prototype of a distributed computer model using a geographic information system (GIS) was developed. D-COMFA calculates the energy budget of a human body on a 1 m cell basis, using readily available datasets such as weather measurements and polygon data for street structures. D-COMFA was applied to a street segment along the marathon course in Tokyo on an hourly-basis on 9 August 2016, the hottest day in Tokyo in 2016. Our case study showed that the energy budget was positively related to the sky view factor, air temperature, and solar radiation. The energy budget was reduced on average by 26–62% in the shade throughout the day. Full article
(This article belongs to the Special Issue Urban Design and City Microclimates)
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Open AccessArticle Evaluation of the ENVI-Met Vegetation Model of Four Common Tree Species in a Subtropical Hot-Humid Area
Atmosphere 2018, 9(5), 198; https://doi.org/10.3390/atmos9050198
Received: 29 March 2018 / Revised: 27 April 2018 / Accepted: 15 May 2018 / Published: 21 May 2018
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Abstract
Urban trees can significantly improve the outdoor thermal environment, especially in subtropical zones. However, due to the lack of fundamental evaluations of numerical simulation models, design and modification strategies for optimizing the thermal environment in subtropical hot-humid climate zones cannot be proposed accurately.
[...] Read more.
Urban trees can significantly improve the outdoor thermal environment, especially in subtropical zones. However, due to the lack of fundamental evaluations of numerical simulation models, design and modification strategies for optimizing the thermal environment in subtropical hot-humid climate zones cannot be proposed accurately. To resolve this issue, this study investigated the physiological parameters (leaf surface temperature and vapor flux) and thermal effects (solar radiation, air temperature, and humidity) of four common tree species (Michelia alba, Mangifera indica, Ficus microcarpa, and Bauhinia blakeana) in both spring and summer in Guangzhou, China. A comprehensive comparison of the observed and modeled data from ENVI-met (v4.2 Science, a three-dimensional microclimate model) was performed. The results show that the most fundamental weakness of ENVI-met is the limitation of input solar radiation, which cannot be input hourly in the current version and may impact the thermal environment in simulation. For the tree model, the discrepancy between modeled and observed microclimate parameters was acceptable. However, for the physiological parameters, ENVI-met tended to overestimate the leaf surface temperature and underestimate the vapor flux, especially at midday in summer. The simplified calculation of the tree model may be one of the main reasons. Furthermore, the thermal effect of trees, meaning the differences between nearby treeless sites and shaded areas, were all underestimated in ENVI-met for each microclimate variable. This study shows that the tree model is suitable in subtropical hot-humid climates, but also needs some improvement. Full article
(This article belongs to the Special Issue Urban Design and City Microclimates)
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Open AccessArticle Microclimate Variation and Estimated Heat Stress of Runners in the 2020 Tokyo Olympic Marathon
Atmosphere 2018, 9(5), 192; https://doi.org/10.3390/atmos9050192
Received: 31 March 2018 / Revised: 10 May 2018 / Accepted: 10 May 2018 / Published: 17 May 2018
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Abstract
The Tokyo 2020 Olympic Games will be held in July and August. As these are the hottest months in Tokyo, the risk of heat stress to athletes and spectators in outdoor sporting events is a serious concern. This study focuses on the marathon
[...] Read more.
The Tokyo 2020 Olympic Games will be held in July and August. As these are the hottest months in Tokyo, the risk of heat stress to athletes and spectators in outdoor sporting events is a serious concern. This study focuses on the marathon races, which are held outside for a prolonged time, and evaluates the potential heat stress of marathon runners using the COMFA (COMfort FormulA) Human Heat Balance (HBB) Model. The study applies a four-step procedure: (a) measure the thermal environment along the marathon course; (b) estimate heat stress on runners by applying COMFA; (c) identify locations where runners may be exposed to extreme heat stress; and (d) discuss measures to mitigate the heat stress on runners. On clear sunny days, the entire course is rated as ‘dangerous’ or ‘extremely dangerous’, and within the latter half of the course, there is a 10-km portion where values continuously exceed the extremely dangerous level. Findings illustrate which stretches have the highest need for mitigation measures, such as starting the race one hour earlier, allowing runners to run in the shade of buildings or making use of urban greenery including expanding the tree canopy. Full article
(This article belongs to the Special Issue Urban Design and City Microclimates)
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Open AccessArticle Microclimate Metrics Linked to the Use and Perception of Public Spaces: The Case of Chillán City, Chile
Atmosphere 2018, 9(5), 186; https://doi.org/10.3390/atmos9050186
Received: 22 March 2018 / Revised: 3 May 2018 / Accepted: 7 May 2018 / Published: 14 May 2018
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Abstract
This paper presents research carried out in the city of Chillán, a medium size city located on the southern limit of the Chilean Mediterranean domain, at 36°36′s south latitude. Chillán provides a good representative example of warm summers in central and southern Chilean
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This paper presents research carried out in the city of Chillán, a medium size city located on the southern limit of the Chilean Mediterranean domain, at 36°36′s south latitude. Chillán provides a good representative example of warm summers in central and southern Chilean cities. Five public spaces were selected, representing different typologies and relating to different urban background conditions. Users in these public spaces were observed, counted and photographed five times a day (12, 14, 16, 18 and 20 h, local time) during a heat wave event in the summer of 2016, while meteorological parameters were measured at different points within the public space. The variables evaluated were impervious surfaces, sky view factor, H/W, azimuth, shadow, and radiation. Local public environmental management should pay attention to the complex relations between urban climate, public spaces and thermal comfort since they affect the quality of life of the most vulnerable sectors of the population. This is particularly important given the increasing episodes of elevated temperatures and intense heat waves which have occurred in the city of Chillán in recent summers, which are related to urban heat islands and climate change. Full article
(This article belongs to the Special Issue Urban Design and City Microclimates)
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Open AccessArticle Analysis and Comparison of Shading Strategies to Increase Human Thermal Comfort in Urban Areas
Atmosphere 2018, 9(3), 91; https://doi.org/10.3390/atmos9030091
Received: 13 November 2017 / Revised: 23 February 2018 / Accepted: 27 February 2018 / Published: 1 March 2018
Cited by 2 | PDF Full-text (4898 KB) | HTML Full-text | XML Full-text
Abstract
With the expected increase in warmer conditions caused by climate change, heat-related illnesses are becoming a more pressing issue. One way that humans can protect themselves from this is to seek shade. The design of urban spaces can provide individuals with a variety
[...] Read more.
With the expected increase in warmer conditions caused by climate change, heat-related illnesses are becoming a more pressing issue. One way that humans can protect themselves from this is to seek shade. The design of urban spaces can provide individuals with a variety of ways to obtain this shade. The objective of this study was to perform a detailed evaluation and comparison of three shading strategies that could be used in an urban environment: shade from a building, from a tree, and from an umbrella. This was done through using field measurements to calculate the impact of each strategy on a thermal comfort index (Comfort Formula (COMFA)) in two urban settings during sunny days of the summer of 2013 and 2014 in London, Canada. Building shade was found to be the most effective cooling strategy, followed by the tree strategy and the umbrella strategy. As expected, the main determinant of this ranking was a strategy’s ability to block incoming shortwave radiation. Further analysis indicated that changes in the convective loss of energy and in longwave radiation absorption had a smaller impact that caused variations in the strategy effectiveness between settings. This suggests that under non-sunny days, these rankings could change. Full article
(This article belongs to the Special Issue Urban Design and City Microclimates)
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Open AccessArticle The Impact of Tipuana tipu Species on Local Human Thermal Comfort Thresholds in Different Urban Canyon Cases in Mediterranean Climates: Lisbon, Portugal
Atmosphere 2018, 9(1), 12; https://doi.org/10.3390/atmos9010012
Received: 11 October 2017 / Revised: 19 December 2017 / Accepted: 4 January 2018 / Published: 7 January 2018
Cited by 1 | PDF Full-text (7921 KB) | HTML Full-text | XML Full-text
Abstract
Based upon the case of Lisbon, this article examined the in-situ effects of vegetation upon pedestrian thermal comfort levels. Focussing specifically upon the historic quarter that often witnesses the highest Tamb values and Urban Heat Island (UHI) intensities during the summer, the
[...] Read more.
Based upon the case of Lisbon, this article examined the in-situ effects of vegetation upon pedestrian thermal comfort levels. Focussing specifically upon the historic quarter that often witnesses the highest Tamb values and Urban Heat Island (UHI) intensities during the summer, the most common urban canyon cases (UCCs) were modelled, along with one of the most commonly used vegetative semi-deciduous species found in the city, Tipuana tipu. Based upon a reference point (RP) system, the assessments were undertaken through the use of a new version of the SkyHelios model, local obtained Grad values, and the modified physiologically equivalent temperature (mPET) index calculated through the human-biometeorological model RayMan. The study identified the in-situ thermo-physiological influences of Tipuana tipu during different periods of the year: (1) during the summer, which revealed considerable reductions of PET/mPET of up to 15.6 °C/11.6 °C during a very hot day (where daily maximum Tamb surpassed 35 °C); and (2) during the winter, which revealed the risks of oversharing as a result of the species keeping its foliage during the winter with reductions of PET/mPET of up to 2.7 °C/2.6 °C. Furthermore, the study utilised the climate tourism/transfer information scheme (CTIS) to categorise and facilitate the interpretation of the results. Full article
(This article belongs to the Special Issue Urban Design and City Microclimates)
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