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Understanding Urban Microclimate: Challenges and Solutions

Urban microclimate refers to the specific climatic conditions in a small-scale urban area, significantly influenced by the presence of buildings, roads, vegetation, and human activities. The importance of studying urban microclimate has surged due to its profound impact on the health, comfort, and overall well-being of urban residents, as well as energy efficiency of the buildings [1]. As cities continue to grow and face the challenges of climate change, understanding and managing the urban microclimate becomes crucial for urban planners, architects, municipalities, and policymakers [2].

This white paper delves into the complexities of modeling urban microclimate, explores recent government regulations aimed at promoting sustainable and eco-friendly cities, and introduces a groundbreaking solution provided by PGL through its CityDigitalTwin (CDT) platform.

The Significance of Urban Microclimate

Urban microclimates play a critical role in shaping the day-to-day experiences and overall well-being of city residents. These localized climatic conditions, influenced by a variety of factors including infrastructure, vegetation, and human activity, can have profound effects on thermal comfort, air quality, energy consumption, and wind comfort.

Thermal Comfort

Thermal comfort refers to the state of mind that expresses satisfaction with the surrounding environment. It is influenced by various factors, including air temperature, humidity, wind speed, and radiation. In urban areas, thermal comfort is often compromised due to the urban heat island (UHI) effect. UHIs occur when city centers become significantly warmer than their rural surroundings, primarily due to the extensive use of concrete, asphalt, and other heat-absorbing materials in urban construction. The lack of vegetation and green spaces exacerbates this effect, leading to higher temperatures during the day and slower cooling at night.

Urban microclimates also have a substantial impact on energy consumption. The increased temperatures in UHIs lead to higher energy demands for cooling buildings. This not only results in higher electricity bills for residents and businesses but also puts a strain on the urban power grid, increasing the likelihood of power outages during peak demand periods. Moreover, the increased energy consumption contributes to higher greenhouse gas emissions, exacerbating climate change and creating a feedback loop that further intensifies the UHI effect.

Wind Comfort

Wind comfort is another critical aspect influenced by urban microclimates. The interaction between wind and urban infrastructure can create areas with both positive and negative effects on comfort and safety.

Positive Effects: Properly managed wind flow can help disperse air pollutants, reduce heat buildup by promoting natural ventilation, and enhance pedestrian comfort during hot weather by providing cooling breezes.

Negative Effects: Conversely, poorly designed urban areas can lead to wind tunnels and high wind speeds at street level, causing discomfort and potential safety hazards for pedestrians. Strong winds can make walking difficult and uncomfortable, increase the risk of accidents, and reduce the usability of outdoor spaces. In winter, increased wind speeds can lead to wind chill, making outdoor conditions feel colder than they are.

Air Quality

Air quality in urban areas is significantly influenced by the microclimate. Higher temperatures can increase the concentration of ground-level ozone, a harmful air pollutant. Additionally, the interaction between buildings and local weather patterns can trap pollutants, leading to poor air quality. This can result in a range of health issues, from respiratory problems like asthma and bronchitis to cardiovascular diseases. The presence of pollutants such as particulate matter (PM), nitrogen dioxide (NO2), and sulfur dioxide (SO2) further deteriorates air quality, posing serious health risks to urban residents.

Challenges in Modeling Urban Microclimate

Modeling urban microclimate is inherently complex due to the multitude of parameters involved:

  • Historical and Future Climate Data: Accurate modeling requires a thorough understanding of past climate trends and future projections.

  • Human Activities: Urban areas are dynamic environments with constant human activity influencing local climatic conditions.

  • Infrastructure Interactions: Buildings, roads, and other infrastructure significantly alter wind patterns, thermal properties, and shading effects.

  • Vegetation: The presence and type of vegetation affect local temperatures, humidity levels, and air quality.

The interplay of these factors makes it challenging for urban planners, architects, and policymakers to develop accurate and reliable models. This complexity necessitates expertise in various fields of science and engineering, creating a significant barrier for comprehensive urban microclimate studies.

Government Regulations and the Need for Sustainable Urban Design

In response to the growing challenges posed by urbanization and climate change, governments worldwide are introducing new regulations to promote sustainable and eco-friendly cities. These regulations often focus on enhancing energy efficiency, improving thermal and wind comfort, and ensuring overall environmental sustainability. Compliance with such regulations requires a deep understanding of urban microclimates, making it more critical than ever for professionals involved in urban planning and design to have access to reliable and user-friendly modeling tools.

Introducing PGL and CityDigitalTwin (CDT)

At PGL, we understand the complexities and challenges faced by urban planners, architects, municipalities, and policymakers. Our mission is to simplify the process of studying and managing urban microclimates through innovative technological solutions. We proudly present CityDigitalTwin (CDT), a unique platform designed to simulate urban microclimates with unparalleled precision and ease of use.

The CDT Platform

CityDigitalTwin (CDT) is the fastest urban microclimate model available, incorporating a wide range of features to provide comprehensive insights into urban climatic conditions. The platform offers:

  • Wind Simulation: Detailed analysis of wind patterns and their interaction with urban structures.

  • Thermal and UTCI Simulation: Accurate modeling of thermal comfort using the Universal Thermal Climate Index (UTCI).

  • Building Interaction: Examination of how buildings influence and are influenced by the local microclimate.

  • Indoor and Outdoor Simulation: Two-way interaction modeling between indoor environments and outdoor conditions.

  • Solar Radiation and Shading: Assessment of solar radiation impact and shading effects on urban areas.

  • Vegetation Analysis: Integration of vegetation data to understand its role in urban microclimates.

In this report, we focus on the microclimate solver of CDT, while other features will be comprehensively introduced in future reports.

CDT Microclimate Solver: Technological Excellence

The CDT microclimate solver is based on a suite of novel numerical schemes, utilizing MultiGPU-CUDA and OpenMP technologies to maximize the computational power of modern hardware, thereby accelerating the simulation process. This advanced solver has been rigorously tested and validated through several benchmarks, demonstrating its capability to simulate urban microclimates accurately across different scales, from single building areas to vast urban regions up to 10 km by 10 km.

High-Resolution Wind and Temperature Simulation

CDT provides high-resolution simulations of wind and temperature within cities, offering valuable data for urban planners and architects to conduct wind and thermal comfort studies. These studies are increasingly mandated by city governments to ensure sustainable urban design and enhance the quality of life for urban residents.

Thermal Comfort Indices

CDT goes beyond basic temperature and wind analysis by offering various thermal comfort indexes, including UTCI and Mean Radiant Temperature (MRT). These indexes provide deeper insights into thermal comfort, helping users make informed decisions about urban design and policy.

User-Friendly Interface

One of the standout features of CDT is its web-based user-friendly interface, designed to cater to clients from diverse backgrounds with minimal technical knowledge. Users can select a region from a global map and choose a simulation period with just a few clicks. For advanced users, the platform offers customizable options such as mesh refinement and parameter adjustments, including time step and turbulence parameters. This flexibility ensures that both novice users and experts can effectively utilize the CDT platform to meet their specific needs.


Urban microclimate modeling is essential for creating sustainable, energy-efficient, and comfortable urban environments. The complexity of such modeling has traditionally posed significant challenges for professionals in urban planning and design. However, with PGL's CityDigitalTwin (CDT) platform, these challenges are addressed through a powerful yet user-friendly tool that simplifies the process while providing high-resolution, accurate simulations. As cities continue to evolve, tools like CDT will play a crucial role in ensuring that urban development is both sustainable and conducive to the well-being of city dwellers.

In future reports, we will delve deeper into the additional features of CDT, demonstrating its comprehensive capabilities in urban microclimate modeling and its potential to revolutionize the way we approach urban design and planning.


[1] Santamouris, M., 2013. Energy and climate in the urban built environment. Routledge.

[2] Stone, B., 2012. The city and the coming climate: Climate change in the places we live. Cambridge University Press.

[3] Yoshie, R., Mochida, A., Tominaga, Y., Kataoka, H. and Yoshikawa, M., 2005. Cross comparisons of CFD prediction for wind environment at pedestrian level around buildings.

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