Identifying and analyzing fog and low stratus life cycle regimes over central Europe

This contribution presents spatially distinct fog and low stratus (FLS) formation and dissipation regimes derived from satellite and reanalysis data and their sensitivities to meteorological and land surface conditions over central Europe.
FLS formation and dissipation processes are strongly governed by meteorological and land-surface conditions and vary geographically and across seasons. The timing of FLS formation and dissipation further has implications for traffic and solar energy production. While climatological analyses of FLS formation and dissipation exist, the influence of meteorological and land surface conditions on specific FLS formation and dissipation regimes is not clear yet.
In this study, satellite-derived fog and low stratus life cycle information is explicitly linked to land surface and meteorology in Europe. Pixel-based correlations of FLS formation and dissipation times with environmental conditions were analyzed in a hierarchical clustering approach. Spatially distinct regimes of FLS formation and dissipation can be identified, and a dependency on the background geography and climate is apparent. FLS formation and dissipation regimes are analyzed on multiple hierarchy levels, i.e. various cluster numbers are explored, to investigate the spatial division of larger regional regimes to smaller sub-regional and local regimes. Monthly mean sensitivities for selected sub-regional regimes suggest a dependency of those sensitivities on FLS type. A case study of a regime covering the Po valley in northern Italy is used to showcase the quantification of FLS drivers regionally using explainable machine learning. Future work will expand this approach to analyze and compare FLS drivers in regional regimes with different background geography and climate.