Relationships between summer air masses and mortality in Seoul: Comparison of weather-type classifications

The paper compares applicability of two sorts of ‘objective’ classifications of weather types (‘air masses’, AMs) for evaluating elevated mortality due to heat in Seoul, South Korea: the ‘Temporal Synoptic Index’ (TSI) and ‘Spatial Synoptic Classification’ (SSC). Several variants of the TSI classifications that differ in the selection of input meteorological variables and the number of AMs formed are examined. Oppressive AMs are identified as those associated with excess mortality. We conclude that the TSI classifications are superior to SSC with respect to the coverage of days with large excess mortality by the oppressive AMs; their application in models that aim at predicting increased mortality risks should be compared with SSC before the decision on the method used is made. Although the presented findings are derived for a specific location, they may have wider implications for the appropriate classification method employed in heat-watch-warning systems.