Exploring the Meteorological Origins of Winter Mortality in England Using Back Trajectory Analysis

This paper aims to define atmospheric pathways related with the occurence of daily low temperature episodes (LTE) in England in order to reveal possible associations with increased mortality rates. For this purpose, backward air mass trajectories corresponding to LTE in five regions of England were deployed. A statistically significant increase in mortality levels, at the 0.05 level, was found for LTE compared to non-LTE days across all five regions. Seven categories of atmospheric trajectory patterns associated with LTE were identified: [East], [Local], [West], [North Atlantic], [Arctic], [South West] and [Scandinavian]. Consideration of the link between air mass trajectory patterns and mortality levels by region revealed a possible west to east split in the nature of air masses connected with elevated mortality such that for the West Midlands and North West regions relatively warm weather conditions from the west, most likely associated with the eastward progression of low pressure systems are allied with the highest daily average mortality counts, In contrast for the North East, Humberside/York and South East regions, cold continental air advection from northern or eastern Europe that lasts for several days and linked with either a blocking pattern over the western margins of Europe or an intense high pressure anomaly over eastern or northern Europe appear important in mortality terms. The duality of low temperature mortality associations identified in this study confirms that winter weather health associations are complex, such that climate setting and air mass climatology need to be taken into account when considering climate and health relationships.