PARAFOG v2.0: a near-real-time decision tool to support nowcasting fog formation events at local scales

Abstract. An improved version of the near-real-time decision tool PARAFOG (PFG2) is presented to retrieve pre-fog alert levels and discriminate between radiation (RAD) stratus lowering (STL) fog situations. PFG2 has two distinct modules monitor physical processes involved in RAD STL formation evaluated at European sites. The are based on innovative fuzzy logic algorithms (low, moderate, high) specific RAD/STL conditions, minutes hours prior onset. PFG2-RAD module assesses also thickness fog. Both PFG2-STL rely combination visibility observations automatic lidar ceilometer (ALC) measurements. overall performance 9 years measurements SIRTA (Instrumented Site for Atmospheric Remote Sensing Research) observatory near Paris up seasons Paris-Roissy, Vienna, Munich, Zurich airports. At all sites, retrieved by found be consistent with local weather analysis. advanced algorithm performs a hit rate about 100 % both considered types presents false alarm ratio order 10 (30 %) Finally, first high alerts that result subsequent event occur periods time ranging from −120 min onset, occurring earlier than cases.