Heat Waves


Heat waves have a significant impact on society and the natural ecosystem, as was clearly
demonstrated by the severe episodes in western Europe (2003) and Russia (2010). They are extreme
weather events that are associated with physical processes across scales that are not very
well understood. The instensity and duration of heat waves pose a challenge for weather prediction
models and their impact cannot be assessed several days in advance. In addition, there
is increasing scientific evidence that the projected global warming can alter their persistence
and intensity.

Our main research question involves the role of upper-tropospheric circulation on midlatitude
temperature extremes. The hypothesis we investigate is that amplified troughs/ridges
embedded in transient Rossby wave packets constitute a large-scale setting that in conjunction
with smaller-scale physical processes lead to air masses with extreme temperatures. Analysing
the structure and propagation of Rossby wave packets on reanalysis and forecast data, we aim
at a better understanding of the causes and predictability of such events.

Temperature anomaly on Aug 8 2003

Hovmoeller diagram of meridional wind anomaly (color shading) and Rossby wave packet amplitude (black contours at 20, 22, ... m/s) during the European heat wave of 2003. The green arrow indicates the associated group velocity. (Fragkoulidis et al. 2018)