Impact of wind shear on aerosol–cloud interactions and convective precipitation

The impact of wind shear on aerosol-cloud interactions and convective
precipitation is investigated with real-case simulations using the ICOsahedral
Non-hydrostatic (ICON) model over central Europe. Three days with severe
convective storms have been simulated using a double-moment microphysics
scheme on a 1-km grid. For each day, twenty simulations with varied initial vertical
wind shear and cloud condensation nuclei (CCN) concentrations were
performed. In these simulations, a higher convective potential is found for
stronger wind shear. However, this is not necessarily reflected in the amount
of precipitation, which shows no systematic dependency on the wind shear for
the days analyzed. Changing the CCN concentration generally has a smaller
impact on the precipitation amount than changing the wind shear. Even if
hydrometeor amounts and microphysical process rates respond similarly to
changing CCN concentrations in the different shear cases, the convective
precipitation shows no systematic CCN dependency. Furthermore, it is shown
that this dependency even changes for a different simulation duration. If the
amount of precipitation is related to its generation processes, a systematic
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relationship emerges: the precipitation efficiency always increases with
increasing CCN concentrations, and this increase is greater the higher the
initial wind shear of the simulations is. The findings of the present paper
demonstrate that the impact of wind shear on aerosol-cloud interactions is
complex, and previous results from idealized simulations cannot be transferred to
realistic simulations.