Heatwaves of 2018: connecting large-scale to synoptic scale circulation

Abstract

The intensity of heat extremes has been increasing in recent decades, with several recent notable heatwaves afflicting highly populated areas. Previous studies have related heatwaves to slow moving amplified Rossby waves, due to the formation of circumglobal teleconnections (i.e., European heatwaves of 2003 and 2010). Other studies have found that there is a statistical link between high amplitude upper-tropospheric transient Rossby wave packets (RWPs) and increased probability of lower-tropospheric temperature extremes. These non-circumglobal RWP amplitudes were found to be better linked to temperature extremes than Fourier amplitudes quantifying circumglobal waviness, including the European heatwaves of 2003 and 2010. In the summer of 2018, several record-breaking and persistent heatwaves occurred simultaneously around the globe and were linked to an amplified hemisphere-wide wavenumber 7 circulation pattern. Here, we investigate the relation of the synoptic RWPs and the circumglobal characteristics of atmospheric circulation characteristics with the heatwaves during 1998-2018, with a focus on the heatwaves that occurred during the summer of 2018.  Preliminary results show that the dominant circumglobal pattern for the 2018 summer heat extremes was dominated by a zonal wavenumber 6 circulation pattern and that its amplitude was connected to high amplitude RWPs that occur across the Northern Hemisphere.