No sign of convective wind gust change despite stronger convective storms in future climate

Convective wind gusts, driven by the intense downdrafts and cold pool dynamics of thunderstorm systems, represent a significant hazard, especially in the warm part of the year. Yet, their climatological characteristics and response to a warming atmosphere remain scarcely investigated and poorly understood.

 

The modeling framework used here is HARMONIE-Climate (HCLIM) with two nested grids. The EC-Earth2 global climate model provides initial and boundary data to the hydrostatic HCLIM configuration with 12 km horizontal grid spacing, and the 12 km run is then further downscaled using a non-hydrostatic convection permitting HCLIM configuration with 3 km horizontal grid spacing. For the analysis, the historical (1996 - 2005) period and the end-of-century (2090 - 2099) period for the RCP8.5 scenario are used for the broader Croatian domain.

 

The convective wind gusts are detected using a two-step filter. First, the presence of convective activity using a cloud condensed water path and ice water path is ensured. After that, the maximum wind speed and wind gust are identified from the model output in the vicinity of the convective cloud. 

 

The described approach performs well in detecting convective wind gusts in a convection-permitting climate model output. While HCLIM shows an increase of extreme convective precipitation by around 18% from the historical to future climate, the projected change in convective wind gust intensity is negligible. Further, the role and intensity of cold pools in extreme convective wind gust events are investigated, and whether they could be used as a proxy for the detection of such events. Finally, the connection to large-scale dynamics will be discussed.