Classification of Fog Life‐Cycle Phases Using Ground‐Based and Satellite‐Based Observations

Abstract A complete understanding of the fog life cycle—defined as formation, maturity, and dissipation phases—provides a basis for better predictions of fog formation and dissipation. While satellites can observe fog and low stratus (FLS) over a large spatial extent, ground‐based instruments provide more detailed vertical and temporal information about fog at specific locations. In this study, we classify the life‐cycle phases of radiation fog events during autumn 2009–2015 at a ground station in Southwest Germany by combining geostationary satellite observations with ceilometer and in situ measurements. For this, we develop a life‐cycle phase classification algorithm that automatically detects the start and end times of each phase based on visibility trends and thresholds. Unlike other methodologies, we define fog life cycles not only through a visibility threshold of 1000 m but also by the processes involved during fog formation and dissipation. These processes are identified through changes in visibility trends and values and validated against backscatter patterns. Furthermore, we demonstrate that ground‐based visibility detects radiation fog phases effectively, while its combination with ceilometer data has the potential to detect the life‐cycle phases of cloud‐base‐lowering fog events. Thus, combining these data sources is essential for detecting the life‐cycle phases of different fog types effectively. Finally, we find that ground‐based data perform better in phase detection at individual locations compared with a satellite‐based FLS life‐cycle dataset.