Urban air quality and climate

Our research aim is to provide new insights on urban air quality and climate, for present conditions and for a future that considers climate change. It focuses on delivering accurate and detailed Essential Climate Variables (ECV) and urban impact indicators at high resolution, in support to sustainable urban planning, as well as to health assessment (dealing with the exposure to heat and air pollution). With the city as geographical unit of interest, the research spans from the high-resolution downscaling of climate models, through the emission and dispersion modelling at the urban scale, to the microscale simulation of fluxes within complex urban environments. The validation of model outputs against air quality and meteorological observations constitutes an important part of our effort to develop accurate tools, models and methods.

The work is structured into 4 interconnecting topics of research:

High resolution downscaling of urban climate

More than 70% of the European population lives in cities, together with a lot of infrastructure vulnerable to climate stress. Although existing climate data, both historical and regionally downscaled climate projections, are relevant on the regional scale, the specific conditions found inside cities are still not taken into account in a regular basis. Our goal is to better understand how different cities react to climate signals and what planning actions can be taken to meet climate change adaptation. We are currently engaged in the downscaling of existing climate data by running HARMONIE in NWP and climate mode in high resolution (1x1 km2) in order to produce urban ECV and impact indicators in support to the infrastructure and health sectors operating in major European cities.

Dynamical downscaling of air pollution to the urban scale

Urban air pollution is highly influenced by long range transport and impact from sources outside the city itself. The mix of aged and fresh pollutants requires a consistent description of aerosol dynamics and chemistry, best handled in coupled Eulerian dispersion models. We focus on the use of high resolution meteorological models as input to a new and improved urban scale MATCH model, with physics adapted to the urban scale and which can use BCs from MATCH regional air quality model. A methodology to study combined exposure to high temperatures and ozone is under development.

Emission and dispersion modelling of regulated air pollutants at the microscale

Inside cities there is a large spatial variability of air pollutant concentrations, where local traffic and residential wood combustion contribute to the formation of highly polluted hot spots. We develop model tools for emission and dispersion of regulated pollutants at the local scale, including traffic exhaust, road wear, wood combustion and ship exhaust. The downscaling of air pollution to the urban scale is tailored with the continued improvement of coupled model systems for high resolution simulations that include the microscale, such as the national SIMAIR system. We provide air pollution exposure data for epidemiology and health assessments, as well as for showing compliance to the EU directive.

Microscale simulation of urban fluxes

From a public health perspective, heat-related mortality within a city has revealed strong intra-city spatial gradients, emphasizing the interest of identifying high-risk areas and assessing the effectiveness of measures for mitigating heat stress and promoting thermal comfort. This task of detailed mapping includes the use of CFD models (OpenFOAM) and heat/radiation models (SOLWEIG) aiming to capture micro to local scale spatiotemporal patterns of urban fluxes, and ultimately to provide valuable data, guidelines and tools for urban planners and health professionals. The model tools developed under this topic will contribute to the detailed planning and prioritization of adaptation actions.