REVIEW Ankara Esenboga International Airport (Turkey) fog analysis and synoptical investigation of the fog event dated 17–19 December 2019 Rozerin Koyuncu 1,2 | Ali Deniz 1 | Emrah Tuncay Özdemir 1 1 Department of Meteorology, _ Istanbul Technical University, _ Istanbul, Turkey 2 Batman Airport Meteorology Office, Turkish State Meteorological Service, Batman, Turkey Correspondence Rozerin Koyuncu, Department of Meteorology, _ Istanbul Technical University, _ Istanbul, Maslak 34469, Turkey. Email: koyuncu15@itu.edu.tr Abstract The aviation industry has developed greatly in recent years. Millions of peo- ple choose air transport as a means of transportation every year, and flight safety is critically important. However, meteorological conditions can cause disruptions in flight activities and lead to accidents. One of the meteorologi- cal conditions that adversely affect flight activities is fog. Prediction of fog incidents increases flight safety. In this study, fog analysis of Ankara Esenboga International Airport was carried out between 2011 and 2020. The data used in the fog analysis are taken from the observations of Aviation Rou- tine Weather Report (METAR) and Aviation Selected Special Weather Report (SPECI). The distribution of fog events in a 10-year period was determined according to years, months, days, hours, meteorological parameters (wind, pressure, cloud cover/height, temperature, and prevailing view), and types. Over a 10-year period, 802.02 hr of fog occurred. The average number of foggy days was determined as 17.9. According to the fog formation types, the fogs occurring at Esenboga Airport were classified as 62% radiation fog, 14% low- ering cloud base, 9% precipitation fog, 2% advection fog, and 12% unknown fog. CAT categories in the foggy hours of Esenboga Airport were determined. In cases where there were foggy observations for approach and landing activi- ties during the 10-year period, these were found to be 40.34% according to CAT I, 72.8% according to CAT II, 93.8% according to CAT IIIA, and 100% according to CAT IIIB. Synoptic analysis of a particular fog incident, which started at 2220 UTC on December 16 and continued for 55.83 hr, was also made. When the synoptic maps and Skew-T Log P diagrams were examined, the deepening of the high pressure center in and around Ankara and the low thermal advection caused a very stable atmosphere, resulting in a prolonged and intense fog event. KEYWORDS analysis, Esenboga Airport, fog, METAR, SPECI, synoptic Received: 8 January 2022 Revised: 13 May 2022 Accepted: 16 May 2022 DOI: 10.1002/joc.7728 Int J Climatol. 2022;1–22. wileyonlinelibrary.com/journal/joc © 2022 Royal Meteorological Society. 1