Heat waves strike with relative frequency in the summer months across southern Europe but the Greek capital of Athens is notorious for its sweltering conditions. The city is particularly prone to high temperatures because of its dense layout, narrow streets, limited green space and long-standing air pollution problem. While the average daytime temperature for July is 33.5ºC (92.3 F), statistics show that the number of days that exceed 38ºC (100.4 F)appears to be increasing dramatically reports Science Daily.
Periods of hot weather are always felt more acutely in cities, especially at night. This is down to a phenomenon called an urban heat island, where the temperature in the city can be up to 10ºC higher than the surrounding countryside. The built-up urban environment tends to act like a giant storage heater, soaking up the heat during the day and releasing it at night. Air pollution, traffic, lack of open space and low evaporation also contribute to the heat of the city. In addition, appliances such as refrigerators and air conditioners have to work harder as the temperature rises. In turn, this adds more heat to the environment causing the situation to worsen.
Increased daytime temperatures and reduced night-time cooling have a huge impact on human health and comfort. Urban heat islands are associated with above-average rates of mortality, especially amongst the elderly. This is sadly illustrated by the 10-day heat wave that engulfed Athens in 1987 and responsible for claiming 926 lives. During this extreme event, the mercury climbed to 48ºC – the all-time highest temperature recorded for metropolitan Athens.
In order to improve our understanding of the complexities of how urban heat islands arise, so that more efficient alert systems can be developed and effective mitigation strategies adopted, ESA organised an airborne campaign that was recently carried out over Athens.
In a series of coordinated activities, a group of thermal remote-sensing and urban-climate experts from Greece and Spain carried out ground-based measurements at various sites in and around the Greek capital, whilst aircraft equipped with sensitive instrumentation passed overhead and satellites orbiting Earth acquired data simultaneously from space.
The campaign, called Thermopolis 2009 from the classical Greek terms for hot (thermo) and city (polis), was led and coordinated by Prof. Spyridon Rapsomanikis from the Democritus University of Thrace. It was carried out as part of the Urban Heat Islands and Urban Thermography project within the framework ESA’s Data User Element. Four Greek administrations also participated in the project: the city of Athens, the municipality of Amaroussion, the Hellenic National Meteorological Service and the General Secretariat for Civil Protection.
Read more here: Making summer in the City More Bearable