Heat and Health in Cities – H2C

Study of the urban climate at climatological and event scales - The first component is dedicated to a state of the art of the current knowledge on the urban climate of the Paris region, and the feedbacks on meteorology and AQ at the local scale. It is based on available observations and modelling configurations at different spatial and temporal resolutions, from the climatological study on the Ile-de-France (2000-2020) to the event scale on Paris (notably in heatwave conditions).
Evaluation of the influence of temperature and air pollution on mortality and morbidity - The second component is devoted to the epidemiological study aiming at evaluating the influence of meteorological and air pollution indicators (resulting from the first part) on mortality and morbidity, by statistically cross-referencing long series of exposure parameters and health data at the scale of the municipality and of the counties.
Strengthening of observation systems and cross-analysis of multiple data sources - The third component aims to develop a complete observation database, combining the acquisition of meteorological parameters and pollutants at the surface and vertical profiles (temperature, humidity, wind) in the atmospheric boundary layer. The existing academic and institutional observation systems (IPSL, Météo France, Airparif) will be reinforced by long-term measurements and an intensive campaign in the summer of 2022, and by exploring the contribution of opportunity data. Cross-analysis of these multi-source data will allow advanced process studies and fine evaluation of numerical models.
High resolution and short term weather and AQ forecasting systems in cities - The fourth component, based on the results and data of the previous stages, aims at developing a prototype urban forecasting modelling chain at the hectometric scale over the Paris region for meteorology, AQ, indoor thermal comfort and heat exposure. In particular, we will seek to establish the link between the outdoor microclimate and comfort conditions in the indoor space, through thermo-aerodynamic modelling of buildings «sensitive to heat wave risks«. An important issue will be the design of multi-criteria forecasting products.
Knowledge transfer and information and decision-making tool - At the end of this work, a final component will aim to implement an information and decision-making tool for risk management and the promotion of adaptation and prevention. It could be used in the short term (during heat waves) to support the warning plan by helping to allocate resources or design local adaptation strategies, and in the long term to provide recommendations for documents relating to urban planning, health and the environment.

During summer, preventing risks related to heat and air pollution is a major public health issue in cities. A better understanding of the infra-urban variations of exposure to heat and air pollutants during summer and of the link to mortality and morbidity is needed to adapt prevention measures. This implies good prediction of temperature and AQ conditions in cities (through better treatment in current models of the complex interactions between urban cover and local meteorological phenomena and through new observations), and integration of the UHI effect in epidemiological studies.

The H2C project addresses this issue through an interdisciplinary approach, with the aim of improving urban climate services to support heat prevention policies, with the Paris region as a case study. This is based on several scientific objectives:
1) Better understand impacts of urban covers on UHI, thermal comfort, local meteorology and AQ.
2) Strengthen the synergy between numerical modelling and multi-sources observations for the study of environmental phenomena, and for the estimation of infra-urban exposure to heat and air pollution, and associated health risks.
3) Develop useful information for decision-making action, in terms of assessment of UHI, consequences on outdoor/indoor exposure, and prevention of health impacts.

To meet these objectives, the consortium brings together eight institutes covering various areas of expertise: specialists in atmospheric physics, meteorology and urban climatology, and atmospheric chemistry (numerical modelling and experimental methods), specialists in building sciences and techniques, researchers in epidemiology, and institutional stakeholders in the world of urban planning, the environment and health.

The first workpackage will be dedicated to an inventory of current knowledge on the urban climate of the Paris region, and feedback on meteorology and AQ at local scale. It will be based on available observations and modelling configurations at different spatial and temporal resolutions, from the climatological study over the Ile-de-France region to the event-scale for Paris. This work will feed into the second workpackage on the epidemiological study. It will assess the influence of meteorological and air pollution indicators on mortality and morbidity by statistically crossing long series of exposure parameters and health data at the level of municipalities and arrondissements depending on building types. A large experimental workpackage will also be carried out throughout the project to strengthen the observation systems by combining long-term measurements and an intensive campaign during summer 2022. Cross-analysis of data from multiple sources will allow advanced process studies and fine evaluation of models. The results of these three workpackages will contribute to the development of a prototype modeling chain for urban forecasting at the hectometric scale over the Paris region for meteorology, AQ, indoor comfort and heat exposure. In particular, we will seek to make the link between outdoor microclimate and thermal comfort conditions in the indoor space, by thermo-aerodynamic modelling of "sensitive to heatwaves" buildings. At the end of this work, a final workpackage will aim to implement an information and decision-making tool for risk management and promotion of adaptation and prevention. It could be used for short-term applications (during heat waves) to support the warning plan by helping to allocate resources or design local adaptation strategies, and for long-term applications to provide recommendations for urban planning, health and environmental documents.