Atmospheric circulation types and daily mortality in Athens, Greece

We investigated the short-term effects of synoptic and mesoscale atmospheri c circulation types on mortality in Athens, Greece. The synoptic patterns i n the lower troposphere were classified in 8 a priori defined categories. T he mesoscale weather types were classified into 11 categories, using meteor ologic parameters from the Athens area surface monitoring network; the dail y number of deaths was available For 1987-1991. We applied generalized addi tive models (GAM), extending Poisson regression, using a LOESS smoother to control for tile confounding effects of seasonal patterns. We adjusted for long-term trends, day of the week, ambient particle concentrations, and add itional temperature effects. Both classifications, synoptic and mesoscale, explain the daily variation of mortality to a statistically significant deg ree. The highest daily mortality was observed on days characterized by sout heasterly flow (increase 10%; 95% confidence interval (CI), 6.1-13.9% compa red to the high-low pressure system), followed by zonal flow (5.8%; 95% CI, 1.8-10%). The high-low pressure system and the northwesterly dow are assoc iated with the lowest mortality. The seasonal patterns are consistent with the annual pattern. For mesoscale categories, in the cold period the highes t mortality is observed during days characterized by the easterly flow cate gory (increase 9.4%; 95% CI, 1.0-18.5% compared to flow without the main co mponent). In the warm period, the highest mortality occurs during the stron g southerly flow category (8.5% increase; 95% CI, 2.0-15.4% compared again to flow without the main component). Adjusting for ambient particle levels leaves the estimated associations unchanged for the synoptic categories and slightly increases the effects of mesoscale categories. In conclusion, syn optic and mesoscale weather classification is a useful tool for studying th e weather-health associations in a warm Mediterranean climate situation, sy noptic classification.