Indian summer monsoon as a driver of summer heatwaves in the Eastern Mediterranean

Boreal summer circulation over the Eastern Mediterranean is characterized by background subsidence, which is linked to both mid-latitude wave activity and to convective activity generated in the tropical belt. Background subsidence is accompanied by northerly winds over the Aegean Sea and the Eastern Mediterranean basin, which bring cooler air from the Eurasian landmass towards the Middle East and northeast Africa. These winds, also known as Etesians, can thus mitigate heatwaves in the region. Using the Peter and Clark momentary conditional independence (PCMCI) algorithm, the causal drivers of the Etesians have been identified (Di Capua et al. in preparation). This set of causal drivers consists of (i) Rossby waves propagating from North America via the North Atlantic and (ii) convective activity over the Indian summer monsoon (ISM) region, which affects the Eastern Mediterranean circulation via a geopotential height ridge forming over the Middle East. In this new work, the aim is first to quantify the effect of enhanced Etesians in mitigating heatwaves in the Middle East. Secondly, given the causal pathway identified between the Etesians and the ISM, the aim is to quantify the effect of interannual ISM activity as a potential amplifying (or inhibiting) factor of heatwaves activity. As future projection under different anthropogenic global warming scenarios predict an intensification of rainfall activity in the ISM region, it is crucial to understand how the ISM-Mediterranean teleconnection can affect heatwave activity in the Eastern Mediterranean.

 

Di Capua G., Tyrlis E., Matei D., Donner R. “Tropical and mid-latitude causal drivers of the summer Etesians in the eastern Mediterranean” (in preparation)