Heatwaves in Romania -Frequency and Duration

Abstract

Heatwaves are recognized, although there is still no general acknowledged definition, as periods of unusually hot and dry or hot and humid weather, which occur gradually and cease in the same way, lasting at least 2 to 3 days with visible impact on human activities. Episodes characterized by heatwaves induce excessively hot weather compared to the local climatic specific features. The period with or without heatwaves is different from a region to another, depending on the particularities of each area. This climatological hazard can be described as an advection of tropical air mass which, compared to the climatological standards, leads to reaching large positive temperature deviations, that in some cases will set new thermal records. In the northern hemisphere, in the area of temperate latitudes, which includes Romania, the highest values of air temperature are generally recorded from mid-June to the end of August. Heatwaves in Romania are mainly generated by the advection of continental hot air masses from North Africa, leading to a stable stratification of the atmosphere from ground levels to more higher ones. The ridge of the North African anticyclone extends either over Central Europe or Central Eastern Europe, up to Romania, generating heatwaves for the first scenario in the western regions of our country, whereas or the second one outside the Carpathians, most frequently in the Romanian Plain. In Romania, the most frequent heatwaves, taken by duration in time are those between 2 and 5 days. while analysed in terms of intensity, stand out those during summer months (June to August).