Transforming Atmospheric Observations to Enhance Urban Weather and Climate Services
As urban populations continue to grow globally, cities face escalating challenges in managing the impacts of climate change, air pollution, and environmental extremes on the well-being of their residents. Recognizing the critical need for comprehensive, real-time environmental intelligence, the eurbanisphere (urbisphere) research project is pioneering a transformative approach to investigating city-atmosphere interactions across multiple scales.
Centered in Berlin, Germany, the urbisphere-Berlin campaign combines an extensive network of ground-based instruments with high-resolution numerical modeling to provide unprecedented insights into how the physical structure and human activity within a city modify the overlying atmosphere. By strategically deploying a diverse array of sensors, from Doppler wind lidars to eddy covariance flux towers, the research team is able to dynamically monitor the three-dimensional characteristics of the urban atmospheric boundary layer (ABL) and surface-atmosphere exchanges.
The overarching goal of this multifaceted investigation is to enhance the delivery of integrated urban services (IUS) – tailored weather, climate, and environmental information to support decision-making across a wide range of city operations and public services. To achieve this, the urbisphere-Berlin campaign takes a systematic, multiscale approach, exploring how urban form and function influence ABL processes, from the neighborhood scale to the regional scale.
Mapping the Urban Landscape: Characterizing Form and Function
At the heart of the urbisphere-Berlin study is a detailed understanding of the city’s physical structure and human activities – the key drivers of urban-atmosphere interactions. The research team has developed a comprehensive, data-driven framework to characterize the urban landscape, leveraging a variety of spatial datasets (Table 1).
Table 1. Key datasets used to quantify urban form and function in the urbisphere-Berlin study.
| Dataset | Description | Spatial Resolution |
|---|---|---|
| Amtliches Liegenschaftskatasterinformationssystem (ALKIS) | Official cadastral data, including building footprints and land use | Vector data |
| Digitales Oberflächenmodell (DOM) | Digital surface model, capturing building heights and urban topography | 1 m |
| Copernicus Global Land Service | Satellite-derived land cover classification | 100 m |
| Population Density (Umweltatlas) | Detailed population distribution within the city | 1 km |
| Energieverbrauch – Fernwärme (Umweltatlas) | District heating energy consumption | Vector data |
By analyzing these datasets within a geographic information system (GIS), the research team has developed a series of 300-meter grid cells that characterize the urban form and function across the Berlin metropolitan region. This includes metrics such as the ratio of non-residential to residential building volumes, which provides insights into the spatial distribution of workplace and residential areas (Figure 1a). Additionally, the team has quantified temporal variations in human activity patterns, as observed through measurements of carbon dioxide (CO2) fluxes at selected sites (Figure 1b).
Understanding the complex interplay between urban form and human activity is crucial for accurately modeling the impacts on the local atmosphere. The urbisphere-Berlin framework allows the research team to systematically investigate how variations in building density, land use, and behavioral patterns influence surface-atmosphere exchanges and the development of the urban ABL.
Observing the Urban Atmosphere: A Comprehensive Sensor Network
To capture the spatial and temporal dynamics of the urban ABL, the urbisphere-Berlin campaign has deployed a dense network of ground-based remote sensing instruments, strategically positioned across the city and surrounding rural areas (Figure 2). This network includes:
- Automatic Lidars and Ceilometers (ALCs): Providing vertical profiles of attenuated backscatter, cloud-base height, and aerosol-concentration-derived mixed-layer height (MLH)
- Doppler Wind Lidars (DWLs): Measuring profiles of wind speed, wind direction, and turbulence-derived boundary layer height (MH)
- Eddy Covariance (EC) Flux Towers: Quantifying surface-atmosphere exchanges of sensible heat, latent heat, and carbon dioxide
- Radiation Sensors: Measuring incoming and outgoing shortwave and longwave radiation, as well as surface temperature
The observation network is designed to capture both urban-rural gradients and intraurban variability, with sensor transects aligned along the prevailing wind direction and a dense grid of instruments within the city center. This comprehensive approach allows the research team to investigate the complex interplay between urban form, human activity, and the evolution of the urban ABL at multiple scales.
Probing the Urban Atmosphere: Insights from Observations and Modeling
The urbisphere-Berlin dataset provides a wealth of information on how the city modifies the overlying atmosphere, with two contrasting case studies illustrating the diverse and dynamic nature of these interactions.
Spring Day: Upwind-City-Downwind Effects on the ABL
On a clear spring day (April 18, 2022), the observations reveal systematic differences in ABL characteristics between the urban and rural areas, driven largely by variations in surface heat fluxes (Figure 3). During the daytime, the urban area experiences higher net radiation and sensible heat fluxes compared to the surrounding rural regions, leading to a deeper and more turbulent ABL over the city. This urban-induced ABL modification is then observed downwind, with the ABL height gradually transitioning back to rural conditions.
The high-resolution numerical modeling conducted as part of the urbisphere-Berlin campaign provides further insights into the spatial and temporal evolution of the ABL, complementing the observations. The model accurately captures the upwind-city-downwind effects, demonstrating the importance of properly resolving urban land surface characteristics and their impacts on surface energy partitioning.
Heatwave Day: Extreme Conditions and the Urban Heat Island
In contrast, during an extreme heatwave event (August 4, 2022), the observed ABL characteristics reveal a more homogeneous regional pattern, with a remarkably deep ABL across both urban and rural areas (Figure 4). The regional drought and dry soil conditions during this period led to similar surface heat fluxes across the study domain, reducing the typical urban-rural differences in ABL development.
While the ABL height was not strongly differentiated, the urban heat island effect was still evident in the near-surface air temperatures and land surface temperatures, with the city center experiencing warmer conditions compared to the surrounding areas (Figure 5). These findings highlight the importance of understanding how extreme weather events can modulate the typical urban-rural contrasts, with implications for human health and infrastructure resilience.
Unlocking the Potential of Integrated Urban Services
The comprehensive dataset and insights generated by the urbisphere-Berlin campaign demonstrate the value of combining systematic observations and high-resolution modeling to enhance our understanding of urban-atmosphere interactions. By capturing the multiscale dynamics of the urban ABL, the research team is poised to support the development of IUS that can better inform decision-making in areas such as:
- Urban Planning and Design: Optimizing building layouts, materials, and green infrastructure to mitigate urban heat island effects and improve thermal comfort.
- Transportation and Air Quality Management: Predicting the transport and dispersion of air pollutants within the city, informing traffic management and emission reduction strategies.
- Emergency Response and Resilience: Anticipating the impacts of extreme weather events on urban populations and infrastructure, enabling targeted preparedness and adaptation measures.
- Energy and Resource Efficiency: Integrating meteorological and environmental data to optimize the performance of building heating, cooling, and energy systems.
By placing the city-atmosphere interactions at the center of their research, the urbisphere-Berlin team is pioneering a new era of urban climate science that can directly support the development of more sustainable, resilient, and livable cities. As urban centers across the globe face escalating environmental challenges, the lessons learned from this groundbreaking campaign can serve as a blueprint for future investigations, ultimately enhancing the ability of cities to thrive in the face of a changing climate.
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