Extremely Hot Summer of 2018 and Its Observed Impacts within the Urban Environment of the City of Prague

The year 2018 has been unexpectedly warm and dry, if we take into account its context – being several year in one row in this way (hot and dry). In our work we focus on its manifestation in Central Europe, namely Czech Republic.

Warm spells in spring and heat waves later in summer have been accompanied with strong precipitation deficit. This has led to the extreme drought and caused significant economic impacts in different sectors, e.g., agriculture, forestry and water supply and management. The warm weather of 2018 has been also strongly felt in big cities of the Czech Republic due to the presence of urban heat island. The weather conditions like those in 2018 clearly occur more often within the last decades and their frequency and intensity is expected to further rise during the 21st century. We have thus focused on investigation how they manifested in the urban environment of Prague, the capital of Czech Republic, in 2018. There are ca 1.3 million inhabitants in Prague. Large parts of Prague urban landscapes are characterized by densely built up areas with practically no natural or green active surfaces. We analyse temperature data from several urban and sub-urban stations.

From April to August 2018 very warm weather prevailed in the Czech Republic with more than 80% of days warmer than the long-term normal of 1981-2010. In July and August air temperatures often exceeded 30°C (tropical day) and reached 35°C. The repeated occurrence of tropical nights with temperatures above 20°C was observed during night-time in July and August.

Results further revealed that the number of tropical days in the Prague city center in 2018 reached values that are simulated by climate models for the end of the 21st century according to RCP8.5 scenario. Moreover similar conditions were already observed in Prague in 2015.

We have also studied the urban climate in Prague from the point human thermal discomfort using the physiological equivalent temperature (PET). The highest differences between the city center and outskirts were detected in the night-time, from 10 pm to 4 am.

Acknowledgements: The GCRI was supported by project Adaptation strategies for sustainable ecosystem services and food security under adverse environmental conditions
CZ.02.1.01/0.0/0.0/16_019/0000797