Daily mortality counts and summer heat waves in Belgrade (Serbia)

Jelena Stojilkovic, Geographical Institute "Jovan Cvijic" SASA
Vlasta Kokotovic, Geographical Institute "Jovan Cvijic" SASA
Gorica Stanojevic, Geographical Institute "Jovan Cvijic" SASA
Aleksandra Spalevic, Geographical Institute "Jovan Cvijic" SASA

Extremely high temperatures are environmental factor that can have pronounced negative consequences on population even in the 21th century, as excess mortality during summer 2003 in Western Europe has proved. The aim of this research is to assess the relation between heat waves and daily mortality counts in Belgrade (Serbia) during the summer months in period 2000-2010, with emphasize on exceptionally hot summer of 2007. We used two different measures of heat wave in order to test which one better identifies days affected by heat wave and mortality higher than expected: Warm Spell Duration Index (WSDI) based on air temperature and apparent temperature (Tapp), which uses the temperature and humidity conditions. Most of WSDI events lasted for 6 days, and Tapp events were shorter and only in few cases lasted more than 4 days. Poisson distribution was used to model mortality data in summer months and cumulative probability to define three thresholds (90th, 95th and 99th percentile) for daily extreme mortality counts. The threshold probability for 90th percentile (10% probability for death occurrence) during summer season was 65 death counts, for 95th (5%) was 68 deaths and 99th percentile of daily mortality (1%) would happened if mortality surpasses 72 dead. The expected baseline mortality is average mortality for investigated period (55.3 persons/day). We found that 75.7 % of overall time duration that WSDI identified as heat wave period and 88.5% time of Tapp are with mortality higher than expected. The main factors for unlikely high number of deaths are prolonged period with extreme temperature and higher daily average temperature excess. Also, both indices overlapped and covered the same calendar days (Tapp being on average shorter and positioned within the WSDI).