Pollutant transport

Our research on the analysis and prediction of pollutant transport by weather systems (across both the tropopause and boundary-layer top) has led to nine published papers to date and has climate and air quality implications. Hence it cuts across the three different NCAS (National Centre for Atmospheric Science) directorates of weather, climate and composition. Some highlights are now given. I have quantified, for the first time, the significant role of convection in deep extratropical cross-tropopause transport of mass and chemical species (such as ozone) in weather systems (it is typically up to 40% of the total transport). This convective transport is usually neglected by the standard methods of diagnosing transport based on trajectories calculated using the resolved scale winds or based on the conservation of potential vorticity (Gray 2003). We have shown that convection and mixing acting together can double the amount of long-lived pollutants ventilated from the atmospheric boundary layer into the free troposphere in frontal cyclones compared to that ventilated by advection alone (Agusti-Panareda et al., 2005). Using idealized model simulations we were the first to demonstrate that the large-scale dynamics in extra-tropical cyclones, rather than the boundary-layer processes, control the ventilation of boundary-layer pollutants into the free atmosphere (Sinclair et al., 2010).