Linking pollution, meteorology and climate change

Abstract

This thesis examines the relationship between synoptic meteorology and particulate matter (PM10). PM10 is a pollutant of high interest to UK health policy (DEFRA, 2016) and this study evaluates the importance of Rossby wave breaking (RWB) on UK PM10 concentration ([PM10]). RWB can result in atmospheric blocking, which is one extreme of mid-latitude synoptic meteorological variability that favours the accumulation of PM10. This study finds significant increases (p<0.01) in UK Midlands [PM10] resulting from winter-time northeast Atlantic/ European RWB. Furthermore, this study shows that northeast Atlantic/ European RWB increases the probability of exceeding a hazardous [PM10] threshold. We have identified the Omega block as the most hazardous RWB subset, with a probability of exceeding a hazardous [PM10] threshold (0.383) over three times that for days without RWB (0.129). We have implemented a tracer framework within a Hadley centre Met-Office climate model (HADGEM3-GA4) to identify flow regimes influencing the UK throughout northeast Atlantic/European RWB events. A present-day HADGEM3-GA4 simulation, nudged to ERA-Interim reanalysis data, is used to verify the tracer framework and to identify the flow regimes influencing Omega block events. This study finds that the advection of European tracer and the accumulation of locally sourced tracer contribute to hazardous [PM10] throughout Omega block events. This study’s principal aim is to determine climatic shifts in both the frequency of synoptic meteorological conditions conducive to UK PM10 accumulation and in the corresponding flow regimes. Using a further two HADGEM3-GA4 simulations, we find a north-eastward climate shift in northeast Atlantic/ European RWB, with an overall reduction in events. Additionally, we find that uture RWB events result in significantly (p<0.01) increased European and reduced stagnant air masses within the UK. This result indicates a reduced frequency of UK [PM10] exceedances, however a tendency for increased transport of toxic particles from Europe