Abstract
Abstract. Coarse particulate matter (PM10) has long been understood to be hazardous to human health, with mortality rates increasing as a result of raised ground level concentrations. We explore the influence of synoptic-scale meteorology on daily mean observed PM10 concentration ([PM10]) using Rossby wave breaking (RWB). Meteorological reanalysis data for the winter months (DJF) between January 1999 and December 2008 and observed PM10 data for three urban background UK (Midland) sites were analysed. Three RWB diagnostics were used to identify RWB that had significant influence on UK Midland PM10. RWB events were classified according to whether the RWB was cyclonic or anticyclonic in its direction of breaking and whether the RWB event was influenced more by poleward or equatorial air masses. We find that there is a strong link between RWB events and UK [PM10]. Significant increases (p < 0.01) in UK [PM10] were seen 1 day following RWB occurring in spatially constrained northeast Atlantic–European regions. Analysis into episodic PM10 exceedance events shows increased probability of [PM10] exceedance associated with all RWB subsets. The greatest probability of exceeding the UK [PM10] threshold was associated with cyclonic RWB preceded by anticyclonic RWB forming an Ω block synoptic pattern. This mechanism suggests an easterly advection of European PM10 followed by prolonged stagnant conditions within the UK and led to an almost threefold increase in the probability of the UK Midlands exceeding a hazardous [PM10] threshold (0.383), when compared to days where no RWB was detected (0.129).
Highlights
The influence of large-scale flow patterns upon pollutant concentrations within the UK is often overlooked in relation to the contribution of local sources, sinks and smaller-scale boundary layer transport processes
The influence that Rossby wave breaking has on UK PM10 concentration ([PM10]) has been analysed, with significant relationships present
Positive correlations exist within the northeast Atlantic–European region, between UK [PM10] and the blocking index, a metric used to diagnose Rossby wave breaking (RWB)
Summary
The influence of large-scale flow patterns upon pollutant concentrations within the UK is often overlooked in relation to the contribution of local sources, sinks and smaller-scale boundary layer transport processes. Some source receptor (Charron et al, 2013) and source attribution (Yin and Harrison, 2008) studies have shown the influence that external (continental European) sources have upon pollutant levels within the UK. Both studies highlight the strong influence of large-scale advected inorganic species on UK particulate matter (PM) with an aerodynamic diameter ≤ 10 μm (PM10). The health impacts of PM depend greatly on its size and composition, with finer particles able to travel further down the human respiratory tract, increasing its anthropogenic toxicity. Throughout the period of this study, the monitoring of fine PM (PM2.5) was spatially poor, and so PM10 was analysed
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