Models for mortality associated with heatwaves: update of the Portuguese heat health warning system

摘要

In Portugal a Heat Health Watch Warning exists since 1999 - the iCARO Surveillance System. It is a system for monitoring heatwaves with potential impacts on population's morbidity and mortality, which is set in motion every year between May and September. This system was based on a model for the relation between heat and mortality calibrated with the district of Lisbon data for the big heatwaves of June 1981 and July 1991. The occurrence of 2003's big heatwave brought opportunity for updating existing models. The fact that this heatwave has been particularly long and had characteristics that were not described in the previously known heatwave episodes also allowed the chance to investigate the mechanism of the relation between occurrence of extreme heat and mortality. The aim of this work was to update the existing iCARO model and contribute to increase the knowledge on the phenomena of the heatwave's impact on mortality. Thus, four models were assayed, that represent four distinct proposals for reference temperature's thresholds and in the generalization of the main used variable accumulated thermal overcharge (ATO). All the assayed models showed a good adaptation to the observed mortality data for the district of Lisbon for the three known big heatwaves. It is concluded that the rational generalized accumulated thermal overload (GATO) adapts well to the relation between heat and mortality. The best model was chosen as the one that considered a dynamic threshold that follows the ascending phase of the temperatures of summer until reaching its maximum level in the end of the month of August remaining thereafter constant until the end of the summer, thus recurring to a rational of population's adaptation to heat, contrarily to what happens to air temperatures that decrease at end of the summer. Copyright (C) 2007 Royal Meteorological Society.