Urban Meteorology Research

Urban green areas have a great potential in mitigating emissions in cities. Carbon sequestration by urban vegetation is a solution to reduce carbon dioxide (CO2) in urban areas. Urban vegetation also offers other benefits, such as cooling and wellbeing of people.​
 

We study the well-being and functioning of urban trees of different species and in different urban spaces to quantify their ability to sequester carbon and cool air through transpiration and shading, and to better understand their resilience during extreme event such as drought. ​In addition to water and carbon fluxes of trees, we investigate the fluxes of other, less studied greenhouse gases (CH4 and N2O) from managed lawns, meadows and tree pits, covering treatments from irrigation to biochar additions (GHUGS kastelu- ja biohiilikokeet). These measurements will help to complete our understanding of the role of urban greenery in total greenhouse gas balance of the city.​ In SMEAR III station, we have long-term eddy covariance measurements of CO2 and heat fluxes of Kumpula area. In order to seperate anthropogenic effect from biogenic fluxes, we have conducted measurements of carbonyl sulfide (COS) to use as proxy for photosynthesis.​ Besides measurements, we utilize urban land surface model SUEWS to study CO2 exchanges in cities. SUEWS is a local scale model, which can be used for example to examine biogenic CO2 of urban parks and spatial CO2 exchanges.

The ongoing and past projects are

• CO-CARBON, 2020-2026

• GHUGS, 2024-2028

• Kone foundation funded, 2024-2026

• CarboCity, 2019-2024

The urban heat island (UHI) effect, where urban areas are significantly warmer than their rural surroundings, is a well-known challenge in urban meteorology, with serious implications for public health and thermal comfort. As cities respond through climate-smart and sustainable urban planning, our research focuses on modelling strategies to mitigate urban heat through the use of green infrastructure. ​Our group investigates how urban vegetation and land use influence microclimates at the neighbourhood scale. In the CoolGreen project, we support the Helsinki metropolitan area by assessing the cooling potential of different greening scenarios in newly planned urban districts. Our aim is to inform planning decisions that enhance thermal comfort for future residents.  ​

​We use eddy covariance observations from the two sites in Helsinki to examine the impact of land use and weather on surface energy balance and energy partitioning as well as the Surface Urban Energy and Water balance Scheme (SUEWS) in different cities. 

The ongoing and past projects are

• CoolGreen, 2025-2026

• GHUGS, 2024-2028

• CO-CARBON, 2020-2026

• ICOSCities, 2021-2025

We study the impacts of the green transition on urban greenhouse gas (GHG) and air pollutant emissions, with a focus on local air quality and sustainable urban development. We use advanced computational methods—including large-eddy simulation (LES), geospatial modeling within local urban climate zones, and dynamic traffic emission analysis—to explore how evolving transportation systems, urban planning decisions, and green infrastructure influence air quality at the neighborhood (down to 1m) and city scale. Our work provides science-based insights to support climate-smart urban design, optimize emission mitigation strategies (i.e. increase share of battery electric vehicles), and enhance the health and livability of future cities.​

The ongoing and past projects are

• RI-Urbans, 2021-2025
• CousCous, 2020-2024
• AIForLessAuto, 2021-2024
• Katumetro, 2018-2019

The urban boundary layer (UBL) exhibits strong spatial and temporal variability, driven by surface properties, heat fluxes, and anthropogenic emissions. These local-scale inhomogeneities interact with atmospheric dynamics to enhance turbulent mixing, alter vertical stability, and significantly influence the dispersion of air pollutants. Understanding the flow and mixing processes within the UBL is essential for addressing key urban environmental challenges, including ventilation efficiency, public health, and urban planning.

To capture UBL dynamics and mixing processes at fine spatial and temporal resolution, we use the PALM model system, which has been widely used to study urban boundary layers. PALM’s modularity enables detailed simulations of turbulence, energy exchange, and pollutant transport in realistic urban environments. We combine the modelling with UBL observations such as eddy covariance from the two sites we operate in Helsinki, and eddy covariance and Lidar data collected by our collaborators.

The ongoing and past projects:
• PAUL, 2021-2025
• CATRINE, 2024-2026