On gust characteristics of cold pools

Cold pools are mesoscale atmospheric phenomena associated with showers and thunderstorms, they are characterized by a sudden temperature drop, pressure jump and strong gusty winds. At their edges, cold pools may trigger the onset of deep convection. Many studies focused on the temperature distribution and dynamics associated with cold pools while the wind field has found much less attention.

This study investigated the dynamics of gust fronts associated with cold pool events observed during the FESSTVaL (Field Experiment on Sub-mesoscale Spatio Temporal Variability in Lindenberg) field campaign which was conducted in and around Falkenberg, Germany, between May and August 2021. Utilizing a ground-based network of 19 automatic weather stations (WXT-536, Vaisala Oy), the analysis covered an area of approximately 30 km in diameter and it focused on nine significant cold pool events identified from a total of 42 cold pool occurrences recorded during the experiment.

These nine events showed an average maximum wind speed increase of 2.8 m/s, the onset of which was observed a few minutes before the temperature drop. The Python package tobac was employed to detect the cold pool centers. The analysis of gust front intensity with propagation distance revealed an increase within the first 4 km from the cold pool center, and a subsequent decrease with distance. Variations in gust front intensity in relation to the background wind appeared to be dependent on wind direction, with headwind conditions showing the highest gust intensities. Vertical wind and gust profiles obtained from measurements at the 99m tower at the Falkenberg boundary layer field site further elucidated the flow dynamics within gust fronts and indicated the dominance of a lateral cold pool expansion compared to vertical air motion.