Supervisor: Martin Weissmann (Department of Meteorology and Geophysics) in collaboration with Stefano Serafin (Department of Meteorology and Geophysics)

Funding Situation: potentially via a VISESS PhD fellowship

Project outline: Strong convective events can be associated with heavy rainfall, hail, wind gusts and tornadoes, and can cause damage to property and loss of human lives. Convection-permitting numerical weather predictions are nowadays routinely available, but storm forecasting remains a challenge, especially in the extratropics and under weak synoptic-scale forcing.

During summer, convective storms occur over and near mountains more frequently than over plains. Near the Alps, summertime storms usually intensify over the lowlands because of the inflow of low-level warm and moist air, but their initial trigger is often orographic, relating either to mechanical forcing (airflow displacement) or to thermal forcing (baroclinic breeze generation).

The project deals with lee-side convection initiation, i.e., the development of storms in the supposedly unfavourable environment downstream of major mountain ranges. The impact of mountain waves and terrain-induced breezes on convective pre-conditioning and initiation are of particular interest. These topics will be investigated through climatological analyses and high-resolution numerical simulations. The climatological study will use meteorological reanalyses and a multi-decadal archive of lightning observations to relate convection initiation patterns in the Alps to the prevailing synoptic flow. The idealized numerical simulations will explore several regimes of mechanical and thermal forcing, highlighting the favourable conditions for lee-side convection.

The research is embedded within the TEAMx programme (www.teamx-programme.org), leading in 2024 to the largest campaign of coordinated meteorological observations over the Alps since the Mesoscale Alpine Programme (1999). TEAMx was endorsed by the GEWEX Hydroclimatology Panel of the World Climate Research Programme as a crosscutting project.