Urban Microclimate and Outdoor Thermal Comfort of Public Spaces in Warm-Humid Cities: A Comparative Bibliometric Mapping of the Literature

Intensified human population encourages urbanization changing the morphology and metabolism of urban environments, thus altering the local climate and outdoor thermal comfort (OTC) in public spaces. OTC is an increasingly urgent area of research for tropical climates. This study explores the literature from the Scopus database on urban microclimate and OTC in public spaces and contrasts the studies in warm-humid cities through a bibliometric mapping of literature. The adapted methodology includes;Bibliometric Search, Scientometric Analysis, and Content analysis using VOSviewer software to identify the evolution paths, gaps, and the most recent movement of OTC assessments in urban public spaces. Results reveal five evolution paths related to all climatic regions;1) materials and cooling strategies, 2) simulation modeling and urban planning, 3) design parameters affecting thermal perception, 4) cooling effects of green infrastructure, and 5) thermal adaptation in urban design. Although urban morphology and vegetation have been received the highest attention respectively, only a few for blue infrastructure related to warm-humid cities. This review identified five research gaps;the impact of blue infrastructure on OTC, strategies to overcome the effect of reflective materials, vegetation configurations in street canyons with wind flow, OTC improvements in asymmetrical street canyons, and how local climate zone (LCZ) classification approach could be used for OTC assessments. Past empirical studies have revealed that urban vegetation, surface materials, and morphological parameters are of paramount importance. Yet, the urban blue infrastructure has not received adequate research. Recently, the attention of researchers has been drawn to strategies in improving OTC using micro-meteorological simulation modelling to examine the impact of urban design interventions. Finally, comprehensive content analysis, bibliographic coupling based on documents, co-occurrence of all-keywords, are suggested for future bibliometric reviews. Finally, further research on recommended areas would assist decision-makers in planning and design to enhance livability by improving microclimate and OTC in urban spaces.

Urban microclimate and energy consumption:A multi-objective parametric urban design approach for dense subtropical cities

Climate change within the urban contexts is a crisis that cities are confronting globally.This issue poses numerous negative consequences such as thermal discomfort and increased energy usage within the building sector.This is especially the case in Western Sydney,Australia,where the average maximum temperature has risen by 7—8℃ within the past 30 years.This increase in temperature is highly concerning,since this region is witnessing rapid urban and infrastructural development and is proposed as the third-largest economy of Australia.Temperature changes in this region will also result in considerably increasing the electricity used for cooling purposes.This paper presents a parametric approach driven multi-objective optimization methodology to discover optimum design solution based on the urban microclimate and cooling energy demand of multi-functional buildings within this urban context.Mitigation measures including a range of design factors at both building(typology and window to wall ratio)and urban scales(aspect ratio and urban grid rotation)are further suggested for developing context sensitive optimum urban layouts.The resultant solutions indicate an improvement in urban thermal comfort,cooling and heating energy use by up to 25.85%,72.76%,and 93.67%,respectively.

Simulation of urban microclimate with uhiSolver:software validation using simplifed material data

Background:Increasing urbanization as well as global warming requires an investigation of the infuence of diferent construction methods and ground surfaces on the urban heat island efect(UHI efect).The extent of the infuence of the urban structure,the building materials used and their surfaces on the UHI efect can be signifcantly reduced already in the planning phase using a designated OpenFOAM-based solver“uhiSolver”.Results:In the frst part of this research work,it is shown that inner building details and components can be neglected while still obtaining sufciently accurate results.For this purpose,the building model was divided into two layers:a surface layer without mass,where the interaction with radiation takes place,and a component layer,which contains all relevant components and cavities of the building represented with mass-averaged material properties.It has become apparent that the three parameters—albedo,heat capacity and thermal resistance—which have a decisive infuence on the interaction,have diferent efects on the component temperatures and the surface temperatures.In the second part of this research work,dynamic 3D computational fuid dynamics(CFD)simulations are performed with uhiSolver for a residential block in Vienna.Comparing the simulation results with measurement data collected on site,it is shown that the simplifed assumption of homogeneous material data for building bodies provides very good results for the validation case investigated.However,the infuence of the greening measures in the courtyard of the residential block on the air temperature is found to be negligible.Furthermore,it was observed that due to locally higher radiation density,lower air velocities and higher air humidity,the apparent temperature in the courtyard is sometimes perceived to be higher than in the adjacent streets,despite the lower air temperature.Conclusions:Simplifying the modeling process of the uhiSolver software by reducing the model complexity helps to reduce manual work for setting up appropriate boundary conditions of buildings.Compared to market competitors,good results are obtained for the validation case Kandlgasse presented in this research work,despite the simplifcations proposed.Thus,uhiSolver can be used as a robust analytical tool for urban planning.

Addressing the Challenge of Interpreting Microclimatic Weather Data Collected from Urban Sites

This paper presents some installation and data analysis issues from an ongoing urban air temperature and humidity measurement campaign in Hangzhou and Ningbo, China. The location of the measurement sites, the positioning of the sensors and the harsh conditions in an urban environment can result in missing values and observations that are unrepresentative of the local urban microclimate. Missing data and erroneous values in micro-scale weather time series can produce bias in the data analysis, false correlations and wrong conclusions when deriving the specific local weather patterns. A methodology is presented for the identification of values that could be false and for determining whether these are “noise”. Seven statistical methods were evaluated in their performance for replacing missing and erroneous values in urban weather time series. The two methods that proposed replacement with the mean values from sensors in locations with a Sky View Factor similar to that of the target sensor and the sensors closest to the target’s location performed well for all Day-Night and Cold-Warm days scenarios. However, during night time in warm weather the replacement with the mean values for air temperature of the nearest locations outperformed all other methods. The results give some initial evidence of the distinctive urban microclimate development in time and space under different regional weather forcings.

Urban Heat Island Investigations in Arctic Cities of Northwestern Russia

Urban microclimate peculiarities in two Arctic cities in northwestern Russia--Kirovsk （67.62°N, 33.67°E） and Apatity （67.57°N, 33.38°E）-were investigated by using mobile temperature records. The experiment was carried out in and around Apatity and Kirovsk in February 2014 and December 2016. The DS 18B20 digital thermometer was in- stalled on the roof of a car （height： approximately 1.2 m） to measure and record temperature variations automatically. In addition to the digital thermometer, the car was also equipped with an onboard global positioning system, allow- ing every temperature measurement to be referenced with an altitude and a latitude/longitude position. The possibility of urban heat island formation in these polar cities, above the Arctic Circle, was studied. Our analysis indicated that on 11 February 2014, the temperature varied in accordance with the background environmental lapse rate （-0.0045℃ m^-1）, and nearly corresponded to it （-0.0165℃ m^-1） on 12 February 2014. On 6 December 2016, a strong local temperature inversion with a positive value of 0.032℃ m^-1 was detected, seemingly caused by the formation of a cold air pool in the valley near Kirovsk. It was found that the temperature variations within and outside these cities are strongly influenced by local topographic effects and the physical conditions of the atmospheric boundary layer.

The effect of Urban Heat Island mitigation strategies on outdoor human thermal comfort in the city of Baghdad

Todays,most Iraqi cities suffer from extremely hot-dry climate for long periods throughout the year.However,most urban patterns that exist inside these cities are not suitable for this harsh conditions and lead to an increase in the value of the Urban Heat Island(UHI)index.Consequently,this will increase outdoor human thermal discomfort as well as energy consumption and air pollution in cities.This study attempts to evaluate the effect of UHI mitigation strategies on outdoor human thermal comfort in three different common types of urban patterns in the biggest and most populated city in Iraq,Baghdad.Three different mitigation strategies are used here-vegetation,cool materials,and urban geometry-to build 18 different scenarios.Three-dimensional numerical software ENVI-met 4.2 is utilised to analyse and assess the studied parameters.The input data for simulations process are based on two meteorological stations in Baghdad:Iraqi Meteorological Organization&Seismology,and Iraqi Agrometeorological Network.All measurements are taken in a pedestrian walkway.The results of different scenarios are compared based on their effect on human thermal comfort.Outdoor thermal comfort is assessed according to Predicted Mean Vote index,as mentioned in ISO 7730 standard.This study provides a better understanding of the role of UHI mitigation strategies on human thermal comfort in the outdoor spaces of Baghdad’s residential neighbourhoods.This can help generate guidelines of urban design and planning practices for better thermal performance in hot and dry cities.