GES-card heat stress — condition 2003

Area-covering map of Health Effects Screening score (GES) of heat stress in Flanders. The indicator is based on the number of heat wave days (°C.dag) in Flanders in the year 2003, modelled for the Flemish environmental company (2018). The Heat Wave Degree Day (HGD) indicator indicates where and by how many degrees Celsius the thresholds for minimum and maximum temperatures (18.2 °C and 29.6 °C respectively) indicated by the FPS Public Health are exceeded. The number of heat wave days per location is added to all days of the year 2003. For the creation of the GES card we use the 2003 HGD card, a very warm year that is also used as a reference in the study of the Flemish environmental company (2018). It has been chosen to work with the card for an extreme year rather than an annual average map, because the health problems arise mainly during this type of summer, and in this way the potential problem locations are well pictured and not underestimated. The GES classes were defined in this way: GES 2 = 0-20 (°C.dag) = “reasonable”; GES 3 = 20-30 (°C.day) = “free moderate”; GES 4 = 30-40 (°C.day) = “moderate”; GES 5 = 40-60 (°C.day) = “very moderate”; GES 6 = 60-80 (°C.day) =“insufficient”; GES 7 = 80-100 (°C.day) = “Very insufficient”; GES 8 > 100 (°C.day) = “very insufficient”. GES 6 corresponds to at least 60 heat wave days, a value that occurs in Antwerp in the year 2003 and is known to have many victims due to heat stress. However, a lower number of heat wave days also has negative effects on health. The map can be used to detect potential problem areas for heat stress in Flanders. In addition to air temperature, however, radiation loads (both short-gollow and longgolvig), humidity and wind speed are important factors in determining heat stress and human thermal comfort. Modelling does not take this into account. Local heat stress can therefore be higher (e.g. local radiation from concrete or asphalt hardening) or lower (e.g. because of shade by trees).