4A.4 The ClearfLo project – The influence of London's urban boundary layer structure on air pollution concentrations

Monday, 9 June 2014: 4:15 PM
Queens Ballroom (Queens Hotel)
Sylvia I. Bohnenstengel, Met Office, Reading, Berks., United Kingdom; and S. E. Belcher, J. F. Barlow, O. Coceal, C. Halios, J. Lee, L. Williams, and C. Helfter

The ClearfLo project aims to understand the processes generating pollutants like ozone, NOx and particulate matter and their interaction with the urban atmospheric boundary layer. ClearfLo (www.clearflo.ac.uk) is a large multi-institution NERC-funded project that established integrated measurements of the meteorology, composition and particulate loading of London's urban atmosphere accompanied by modeling of urban meteorology and air pollution.

The project established a new long-term measurement infrastructure in London encompassing measurement capabilities at street level, in the urban background, at elevated levels and in the rural surrounding to determine the urban increment in meteorology and air pollution. These measurements were accompanied by high resolution modeling with the UK Met Office Unified model and WRF. This combined measuring/modelling approach enables us to identify the seasonal cycle in the meteorology and composition, together with the controlling processes. Two intensive observation periods in January/February 2012 and during the Olympics in summer 2012 measured London's atmosphere with higher level of detail. These IOPs will enable us (i) to determine the vertical structure and evolution of the urban atmosphere (ii) to determine the chemical controls on ozone production, particularly the role of biogenic emissions and (iii) to determine the processes controlling the evolution of the size, distribution and composition of particulate matter.

In this talk we combine the long-term air pollution measurements over two years with turbulence measurements at surface and elevated levels within London and analyse the role the meteorology plays for air pollution concentrations. In particular we show measurements that indicate the dominant regimes of London's boundary layer, and demonstrates the role of the structure of the urban boundary layer and its mixing properties on measured concentrations of O3 and NOx.

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