Guidance documents on measurements and modelling of novel air quality pollutants: Atmospheric boundary layer dynamics

This document is connected to the Directive of the European Parliament and of the Council on ambient air quality and cleaner air for Europe (recast). This document was prepared as part of the "Research Infrastructures Services Reinforcing Air Quality Monitoring Capacities in European Urban & Industrial
AreaS” (RI-URBANS) EU-project that connects the atmospheric observation expertise from the Aerosols, Clouds and Trace gases Research InfraStructure (ACTRIS), as well as the urban air quality observation capacities of the regulatory air quality monitoring networks.

The proposed directive underlines the emerging importance of pollutants to air quality and the well-being of citizens. Particulate matter (PM), and in particular some of its components such as ultrafine particles (UFPs), black carbon (BC) and elemental carbon (EC), need to be monitored in both rural and urban supersites in order to support the scientific understanding of their effects on health and the environment, as recommended by WHO.

Currently, most Air Quality Monitoring Networks (AQMNs) miss information about important processes and quantities in the vertical dimension that are necessary to better understand surface-level pollution data. The vertical dimension is especially relevant when considering potential non-local sources of aerosols (e.g. those arriving via medium-to-long-range transport) and for evaluating vertical dilution of locally emitted pollutants and, in specific conditions, episodes associated with new particle formation and related particle growth processes.

Several atmospheric products can efficiently complement regulated in situ air quality measurements for different applications, including assessment, monitoring, and forecast. Here authors highlight the added value provided by knowledge of the dynamics of the atmospheric boundary layer that can be traced through measurements of atmospheric boundary layer heights and profiles of wind and turbulence. To provide an overview of the underlying measurements that allow for the monitoring of boundary layer dynamics, authors introduce the core instruments and briefly outline operation requirements. Finally, the document presents a few selected examples of measurements and retrievals that are applied in different RI-URBANS pilot cities and beyond