Evolution and customisation of the RegCM model for urban climate studies:Addressing multifaceted challenges and advancing climate science

The Regional Climate Model(RegCM)proves valuable for climate analysis and has been applied to a wide range of climate change aspects and other environmental issues at a regional scale.The model also demonstrated success in diverse areas of urban research,including urban heat island studies,extreme climate events analysis,assessing urban resilience,and evaluating urbanization impacts on climate and air quality.Recently,more studies have been conducted in utilizing RegCM to address climate change in cities,due to its enhanced ability over the years to capture meteorological phenomena at city scales.However,there are many challenges associated with its implementation in meso-scale research,which are attributed to various shortcomings and thus create room for further improvement in the model.This paper presents a comprehensive overview of the evolution of the RegCM over the years and its customisation across various parameters,demonstrating its versatility in urban climate studies and underscoring the model’s pivotal role in addressing multifaceted challenges in urban environments.By addressing these aspects,the paper offers valuable insights and recommendations for researchers seeking to enhance the accuracy and efficacy of urban climate simulations using the RegCM system,thereby contributing to the advancement of urban climate science and sustainability.

Local Climate Change Induced by Urbanization on a South China Sea Island

The South China Sea is a hotspot for regional climate research.Over the past 40 years,considerable improvement has been made in the development and utilization of the islands in the South China Sea,leading to a substantial change in the land-use of the islands.However,research on the impact of human development on the local climate of these islands is lacking.This study analyzed the characteristics of local climate changes on the islands in the South China Sea based on data from the Yongxing Island Observation Station and ERA5 re-analysis.Furthermore,the influence of urbanization on the local climate of the South China Sea islands was explored in this study.The findings revealed that the 10-year average temperature in Yongxing Island increased by approximately 1.11℃from 1961 to 2020,and the contribution of island development and urbanization to the local warming rate over 60 years was approximately 36.2%.The linear increasing trend of the annual hot days from 1961–2020 was approximately 14.84 days per decade.The diurnal temperature range exhibited an increasing trend of 0.05℃per decade,whereas the number of cold days decreased by 1.06days per decade.The rapid increase in construction on Yongxing Island from 2005 to 2021 led to a decrease in observed surface wind speed by 0.32 m s^(-1)per decade.Consequently,the number of days with strong winds decreased,whereas the number of days with weak winds increased.Additionally,relative humidity exhibited a rapid decline from 2001 to 2016 and then rebounded.The study also found substantial differences between the ERA5 re-analysis and observation data,particularly in wind speed and relative humidity,indicating that the use of re-analysis data for climate resource assessment and climate change evaluation on island areas may not be feasible.

Climate &Sustainability Implications of Land Use Alterations in an Urbanizing Region: Raleigh-Durham, North Carolina

Urban climate is the most immediate manifestation of the warming global climate for the majority of people on earth. Nearly half of those people live in small to medium sized cities, an understudied scale in urban climate research. Widespread characterization would be useful to decision makers in planning and design for land use decisions. Using a multi-method approach, the mesoscale UHI in the study region is characterized and the secular trend over the last sixty years evaluated. Under isolated ideal conditions the findings indicate a UHI of 5.3℃ ± 0.97℃ to be present in the study area, the magnitude of which is growing over time.

Assessment of Urban Climate Environment and Configuration of Ventilation Corridor:A Refined Study in Xi'an

Integrating urban spatial landscape(USL) parameters into refined climate environment assessment is important. By taking the central urban area(CUA) of Xi’an, China as an example, this study develops an evaluation method based on Urban Climatic Map(UCMap) technology. We define surface urban heat island intensity(SUHI) and surface ventilation potential coefficient(VPC), which can effectively reflect local urban climate. Based on SUHI and VPC,we analyze the influences of seven typical USL metrics including building height(BH), building density(BD), floor area ratio(FAR), sky view factor(SVF), frontal area index(FAI), surface roughness length(RL), and vegetation cover(VC). Then, we construct a comprehensive evaluation model and create an urban climate zoning map on a 100-m resolution. The climate optimization on the map is performed for configuration of possible ventilation corridors and identification of associated control indicators. The results show that the main factors affecting SUHI in the CUA of Xi’an are VC and BD, which explain 87.9% of the variation in SUHI, while VPC explains 50% of the variation in SUHI. The main factors affecting VPC are BH, FAR, FAI, and RL, all of which contribute to more than 95% of the variation in VPC. The evaluation model constructed by SUHI, VPC, and VC can divide the CUA into climate resource spaces, climate preservation spaces, climate sensitive spaces, and climate restoration spaces. On this basis, a ventilation corridor network of 3 level-1 corridors(each over 500 m wide), 6 level-2 corridors(each over 500 m wide) and 13 level-3 corridors(each over 50 m wide) is established. Meanwhile, the main quantitative control indicators selected from the USL metrics are proved to be capable of ensuring smooth implementation of the planned corridors at different levels.

Coping with Multi-scale Climate Change:Study on the Application of Urban Environmental Climate Maps of Stuttgart,Germany

The development of modern cities has brought about tremendous changes in the climate environment.Faced with complex climate conditions,research on multi-scale climate change in cities is of great significance.The urban environmental climate maps and the application of climate atlas tool in Stuttgart,Germany were studied,and the multi-scale application of urban environmental climate maps in Stuttgart,Germany was summarized through the analysis of the pre-planning,current construction situation,and landscape reconstruction of the German"Stuttgart 21"plan case.Besides,other important measures to cope with climate change in German were proposed,and finally multi-scale practical strategies to cope with urban climate and environment were summarized to provide ideas and methods for improving China’s future urban climate environment.

Influence of new town development on the urban heat island-The case of the Bundang area

Five new towns have been developed around the Seoul metropolitan area since 1996 However, these new towns generate lots of traffic and related problems in the areas including those new towns and Seoul as a result of increases in population and a lack of ecological-self-sufficiency. Currently, construction of another new town is under deliberation, and what should be a major consider is the notion that the new town be located within a wide, green zone. Many studies have revealed that green space can play an important role in improving urban eco-meteorological capability and air quality. In order to analyze the urban heat island which will be created by the new urban development, and to investigate the local thermal environment and its negative effects caused by a change of land use type and urbanization, Landsat TM images were used for extraction of urban surface temperature according to changes of land use over the last 15 years. These data are analyzed together with digital land use and topographic information. As a study result, it was found the urban heat island of the study area from 1985 to 1999 rapidly developed which showed a difference of mean temperature above +2 0 Before the Bundang new town construction the temperature of the residential area was the same as a forest, but during the new town construction in 1991 analysis revealed the creation of an urban heat island. The temperature of a forest whose size is over 50% of the investigation area was lowest, and thus the presence of a forest is believed to have a direct cooling effect on the urban environment and its surroundings. The mean temperature of the residential and commercial areas in the study was found to be +4 5 higher than the forest, and therefore this part of land use is believed to be the main factor causing the temperature increase of the urban heat island.

Influences of Structures on Urban Ventilation: A Numerical Experiment

Numerical simulations are carried out for the disturbed flow caused by three six-story buildings and a twenty-story tall tower respectively, as well as the distribution of automobile exhaust gas from a nearby road, based on the Peking University Model of Atmospheric Environment. The results show that the ventilation is better around the tall tower than around the three six-story residential buildings for the same number of households in the same urban region.

Improving the WRF/urban modeling system in China by developing a national urban dataset

Accurate modeling of urban climate is essential to predict potential environmental risks in cities.Urban datasets,such as urban land use and urban canopy parameters(UCPs),are key input data for urban climate models and largely affect their performance.However,access to reliable urban datasets is a challenge,especially in fast urbanizing countries.In this study,we developed a high-resolution national urban dataset in China(NUDC)for the WRF/urban modeling system and evaluated its effect on urban climate modeling.Specifically,an optimization method based on building morphology was proposed to classify urban land use types.The key UCPs,including building height and width,street width,surface imperviousness,and anthropogenic heat flux,were calculated for both single-layer Urban Canopy Model(UCM)and multiple-layer Building Energy Parameterization(BEP).The results show that the derived morphological-based urban land use classification could better reflect the urban characteristics,compared to the socioeconomic-function-based classification.The UCPs varied largely in spatial within and across the cities.The integration of the developed urban land use and UCPs datasets significantly improved the representation of urban canopy characteristics,contributing to a more accurate modeling of near-surface air temperature,humidity,and wind in urban areas.The UCM performed better in the modeling of air temperature and humidity,while the BEP performed better in the modeling of wind speed.The newly developed NUDC can advance the study of urban climate and improve the prediction of potential urban environmental risks in China.

The Relationship between Meteorological Variables and Clearness Index for Four Urban/Suburban Areas of Brazilian Cities

This study aimed to examine the relationship between meteorological variables and the clearness index for three sites in Cuiaba city and one site in Chapada dos Guimaraes city, Brazil during 2007. It described the microclimate of each site on the basis of constructive elements and their surroundings, considering sky coverage using a daily clearness index. The results were that micrometeorological values were influenced by the natural elements and construction within the surrounding site, with higher air temperatures in more urbanized areas and sites with high diffuse radiation. When determining the sky coverage, on average, the days were partly cloudy or cloudy due to two reasons： （a） during the wet season, rainfall created cloudy conditions and （b） during the dry season, increases of particulates in the atmosphere as a result of anthropogenic emissions of gases and aerosols in this region of the state resulted in sky conditions classified as partly cloudy and cloudy. Future research should aim to better quantify the measurements taken inside an urban area, considering the topography and vegetation cover. This will improve the models that support urban planning, therefore favoring the thermal comfort of areas already occupied or to be urbanized.

Urban Design Embracing the Wind Environment: Bezigrad Neighbourhood Case Study in Ljubljana, Slovenia

Urban climate is considered one of the most important environmental criteria in urban planning,since it significantly affects the project and its placement in the space.Climate conditions are central to the study,with winds in the urban environment,their direction,intensity and changes taken into consideration designing the new interventions in space.The results of the case study were applied to the project with the intention of supporting and guiding the urban design in order to improve the comfort and quality of the environment.In this article,I explore the question of how individual morphological models affect the micro-and macroclimate conditions.The initial urban solution of the Novi Bezigrad neighbourhood is presented as a realistic model project responding to the existing urban and architectural practices and legal provisions.The project was tested in a computer model and was analysed in terms of the positive and negative effects of its impact on the wind in the planning area and the wider area in the surrounding area.The final urban design derives from the results of wind analysis.

Effects of Forest Type and Urbanization on Carbon Storage of Urban Forests in Changchun, Northeast China

Rapid urbanization has led to dramatic changes in urban forest structures and functions, and consequently affects carbon(C) storage in cities. In this study, field surveys were combined with high resolution images to investigate the variability of C storage of urban forests in Changchun, Northeast China. The main objectives of this study were to quantify the C storage of urban forests in Changchun City, Northeast China and understand the effects of forest type and urbanization on C storage of urban forests. The results showed that the mean C density and the total C storage of urban forests in Changchun were 4.41 kg/m2 and 4.74 × 108 kg, respectively. There were significant differences in C density among urban forest types. Landscape and relaxation forest(LF) had the highest C density with 5.41 kg/m2, while production and management forest(PF) had the lowest C density with 1.46 kg/m2. These differences demonstrate that urban forest type is an important factor needed to be considered when the C storage is accurately estimated. Further findings revealed significant differences in different gradients of urbanization, and the mean C density decreased from the first ring(6.99 kg/m2) to the fourth ring(2.87 kg/m2). The total C storage increased from the first ring to the third ring. These results indicate that C storage by urban forests will be significantly changed during the process of urbanization. The results can provide insights for decision-makers and urban planners to better understand the effects of forest type and urbanization on C storage of urban forests in Changchun, and make better management plans for urban forests.

ON TEMPERATURE CHANGES OF SHANGHAI AND URBANIZATION IMPACTS

To understand how temperature varies in urban Shanghai under the background of global climate change and how it is affected by urbanization, the Shanghai temperature responses to global warming were analyzed, and then the temperature trends of urban and suburb stations under different climatic backgrounds were obtained. The urbanization effects on temperature were studied by comparing urban stations to suburb stations, the relationship between urbanization variables and temperature components were obtained, and observation data of surface and high level were combined to assess the contribution of urbanization effect. In the last part of the paper, the cause of urbanization effects on temperature was discussed. The results indicated: The long term change trend of Shanghai annual mean temperature is 1.31/100a from 1873 to 2004, the periods of 1921 – 1948 and 1979 – 2004 are warmer, and the 1979 – 2004 period is the warmest; compared to suburb stations, the representative urban station has slower decreases in the cool period and faster increases in the warm one; the urban and suburb temperatures have distinct differences resulting from urbanization and the differences are increasing by the year, with the difference of mean temperature and minimum temperature being the greatest in fall and that of maximum temperature being the largest in summer between the urban and suburban areas. The urbanization process accelerates the warming speed, with the minimum temperature being the most obvious; the urbanization effect contributes a 0.4°C increase in 1980s and 1.1°C in 1990s to the annual mean temperature.

SUSTAINABILITY ON THE URBAN SCALE:‘GREEN URBANISM’—MARK Ⅱ

In the essay entitled‘Towards a Sustainable City Centre’(published in JGB Summer 2006),the author reflected on principles how to best integrate ecologically sustainable development(ESD)into urban design.This second paper reports on his continuing research in the area of‘Green Urbanism’.1 Among the most significant environmental challenges of our time are global climate change,excessive fossil fuel de-pendency and the growing demand for energy—all likely to be major challenges of the 21st century and one of the great-est problems facing humanity.In this context,urban design and the fundamental principles of how to shape our cities has barely featured in the greenhouse debate.Much of the debate in related areas has so far circled around ideas about active technology for‘eco-buildings’.This is surprising,since almost half the energy consumed is used in cities and urban built-up areas,and given that avoiding mistakes in urban design at early stages could genuinely lead to more sustain-able cities and less greenhouse gas emission.This article reflects upon practical strategies focused on increasing sustain-ability beyond and within the scope of individual buildings.The paper deals with cross-cutting issues in architecture and urban design and addresses the question of how we can best cohesively integrate all aspects of energy systems,transport systems,waste and water management,passive and active strategies,climatisation and so on,into contemporary urban design and improved environmental performance of our cities.It provides a context for a general debate about the regeneration of the city centre,and discusses how urbanism is affected(and can be expected to be even more affected in future)by the paradigms of ecology.The significance of the research is found in the pressing need for an integration of sustainability principles in the urban design process of cities in South East Asia and the general need for a sustainable city development.It will be of particular relevance to the rapid urban growth of developing cities that have,in the past,frequently been poorly man-aged.Research in sustainable urban design recommends increased harnessing of the energies manifested in the existing fabrics—for instance,through the adaptive re-use of former industrial(brownfield)sites and the upgrade and extension of existing building structures.It is less environmentally damaging to stimulate growth within the established city cen-tre rather than sprawling into new,formerly un-built areas.Two recent examples for the application of such urban de-sign principles are the author’s proposals for the Australian city of Newcastle:the‘City Campus’and‘Port City’projects.

Multi-level CO_(2) fluxes over Beijing megacity with the eddy covariance method

Based on five years of eddy covariance measurements at multiple levels(47,140,and 280 m)of Beijing's 325-m meteorological tower,the exchange process of CO_(2) fluxes between the atmosphere and urban surface were investigated.As a result of the total vehicle control policy from 2011 in Beijing,the growth rate of annual total CO_(2) flux at 140 m is 7.8% from 2008-2010 but 2.3%from 2010-2012.With the minimum vegetation cover and largest population density,the 5-yr average annual total CO_(2) flux at 140 m is largest(6.41 kg C m^(−2) yr^(−1)),compared with that at 47 m(5.78 kg C m^(−2) yr^(−1))and 280 m(3.99 kg C m^(−2) yr^(−1)).With regards to annual total CO_(2) fluxes in Beijing,vehicle numbers and population are the main controlling factors.The measured CO_(2) fluxes were highly dependent on land cover/use in the prevailing wind direction.The CO_(2) fluxes at three layers all correlated positively with road fraction,with the R2 values being 0.69,0.57,and 0.54(P<0.05),respectively.The decreasing fraction of vegetation caused an increasing of the annual total CO_(2) flux,and there was an exponential relationship between them.The annual total CO_(2) fluxes were larger with higher population density.

Simulation of interaction between high-temperature process and heat emission from electricity system in summer

During the hot summer season,using electricity systems increases the local anthropogenic heat emission,further increasing the temperature.Regarding anthropogenic heat sources,electric energy consumption,heat generation,indoor and outdoor heat transfer,and exchange in buildings play a critical role in the change in the urban thermal environment.Therefore,the Weather Research and Forecasting(WRF)Model was applied in this study to investigate the heat generation from an indoor electricity system and its influence on the outdoor thermal environment.Through the building effect parameterization(BEP)of a multistorey urban canopy scheme,a building energy model(BEM)to increase the influence of indoor air conditioning on the electricity consumption system was proposed.In other words,the BEP+BEM urban canopy parameterization scheme was set.High temperatures and a summer heat wave were simulated as the background weather.The results show that using the BEP+BEM parameterization scheme of indoor and outdoor energy exchange in the WRF model can better simulate the air temperature near the surface layer on a sunny summer.During the day,the turning on the air conditioning and other electrical systems have no obvious effect on the air temperature near the surface layer in the city,whereas at night,the air temperature generally increases by 0.6℃,especially in densely populated areas,with a maximum temperature rise of approximately 1.2℃from 22:00 to 23:00.When the indoor air conditioning target temperature is adjusted to 25-27℃,the total energy release of the air conditioning system is reduced by 12.66%,and the temperature drops the most from 13:00 to 16:00,with an average of approximately 1℃.Further,the denser the building is,the greater the temperature drop.

Urban scale rooftop super cool broadband radiative coolers in humid conditions

The presence of water molecules in the air can impact how super cool broadband radiative coolers behave.Higher humidity in the lower atmosphere traps infrared radiation,reducing heat sent back to outer space.In this study,a mesoscale urban climate model is used to evaluate the newly developed super cool materials with broadband emissivity not selective in atmospheric window as an arsenal for urban heat management of tropical wet and dry cities like Kolkata.The results suggest that the energy balance over urban domain has substantially been altered by the city scale deployment of super cool broadband radiative cooling materials on the building rooftop.Bowen ratio and evaporative fraction values were found decreasing and increasing,respectively with a positive directional polynomial(R2=0.968)relationship,after the implementation of super cool broadband radiative cooling materials and in comparison,to the unmitigated scenario.At high solar hour(14:00 LT),additional thermal variables of urban domain such as 2 m air temperature,surface skin temperature,urban canopy temperature,and roof surface temperature decrease by 2.3℃,5.4℃,0.8℃,and 31.7℃,respectively.Reflective super cool broadband materials achieve sub-ambient temperatures up to 11.7℃during peak hours,reduce surface wind speed by 2.5 m s−1,and lower the planetary boundary layer by 1475 m.The average daytime drop is approximately 7.3℃,and at night,it is close to 2.4℃.Deployment induces a“regional high”over urban areas,disrupting sea breeze onset and lowering the planetary boundary layer.Finally,an optimal cooling performance for super cool broadband radiative coolers can be achieved in lower humidity conditions,as their efficiency decreases with increased humidity.Though needing further investigation,these findings of nano-science-based super cool broadband materials offer valuable insights for policymakers and urban planners addressing thermal management in densely packed tropical urban environments.

Data generative machine learning model for the assessment of outdoor thermal and wind comfort in a northern urban environment

Predicting comfort levels in cities is challenging due to the many metric assessment.To overcome these challenges,much research is being done in the computing community to develop methods capable of generating outdoor comfort data.Machine Learning(ML)provides many opportunities to discover patterns in large datasets such as urban data.This paper proposes a data-driven approach to build a predictive and data-generative model to assess outdoor thermal comfort.The model benefits from the results of a study,which analyses Computational Fluid Dynamics(CFD)urban simulation to determine the thermal and wind comfort in Tallinn,Estonia.The ML model was built based on classification,and it uses an opaque ML model.The results were evaluated by applying different metrics and show us that the approach allows the implementation of a data-generative ML model to generate reliable data on outdoor comfort that can be used by urban stakeholders,planners,and researchers.

Impact of building regulations on the perceived outdoor thermal comfort in the mixed-use neighbourhood of Chennai

The population in urban areas is increasing rapidly around the world in most of the cities.In India,this growth has forced the local governments to review the planning norms regularly with the main focus of making an affordable urban living.This resulted in increasing the built density without evaluating the effect of such developments on human thermal com-fort.Outdoor microclimate is one of the significant factors that determine the quality of out-door spaces.This study investigates the potential impact of the built geometry guided by the newly published development control rules of Chennai,India on the various parameters that influence microclimate.The existing and future scenario has been modelled for three locations in a typical mixed-use neighborhood of Chennai.Further,air temperature and relative humid-ity were measured in three locations on a typical summer month of May 2018.The recorded data was used for validating the simulated model and calibrating the model settings.Mostof the studies on outdoor thermal comfort compare a base case scenario and project future scenarios.This paper is a more realistic comparison of outdoor thermal comfort between the actual resultant built environment guided by the new Tamil Nadu Combined Development and Building Rules,2019 for selected locations and the existing built geometry which is the outcome of revised development control rules of 2013.The study found a significant reduction of 18℃in mean radiant temperature(Tmrt)and a reduction of 12℃in Physiological Equiv-alent Temperature(PET)between the 2013 and the predicted built geometry as per 2019 build-ing rules.Further the duration of extreme heat stress in the Physiological Equivalent Temperature(PET)scale show a reduction of 3 h during the day time,The study will assist ur-ban planners and designers to include outdoor thermal comfort also as an important factor while developing building rules.