Fog in Sofia 2010–2019: Objective Circulation Classification and Fog Indices

Low visibility caused by fog events can lead to disruption of every type public transportation, and even loss life. The focus this study is the synoptic conditions associated with formation. data used in was collected over course ten years (2010–2019) Sofia, Bulgaria. forecast skills Fog Stability Index (FSI) local Sofia (SSI), as well relation between Integrated Water Vapor (IWV) from Global Navigation Satellite System (GNSS), were tested. Both indices are for nowcasting their times short unclear. Jenkinson–Collison Type method extracting predominant synoptic-scale pressure systems which provide suitable weather Surface observations two stations calculate evaluate performance ground-based GNSS receiver IWV. provided Probability Detection (POD) False Alarm Ratio (FAR), both no-fog periods, obtained discriminant analysis. Additionally, several parameters, such surface wind speed, relative humidity IWV, added order improve results index (SSI). This led a 77.9% hit rate. cyclonic system influence zonal flows west southwest responsible number cases that comparable those anticyclonic system. IWV not found skill indices. However, it its values had larger spread during periods comparison periods.