An atmospheric approach to the flood disaster in the Western Black Sea region (Turkey) on 10–12 August 2021

Abstract. Precipitation is one of the important climate elements that directly affect disasters with its high spatial and temporal variability. In addition to the changes in precipitation amounts between years, precipitation intensity and duration are also necessary for precipitation climatology. The Black Sea coast is one of the regions that attract attention in terms of precipitation amounts, intensity and duration in the world. Countries bordering the Black Sea have been struggling with flash floods, which have arisen due to excessive rainfall in recent years. The flood has had the most loss of life and devastating effect in recent times, especially in the summer season, which occurred after heavy rains on August 10–12, 2021. In this disaster, 82 people lost their lives due to the flood. In addition, the flood damaged energy, transportation, access to drinking water, communication, and shelter areas. From 10 to August 12, total accumulated rainfall amounts of 452.5, 389.2, 386.2 and 281.1 mm were measured in the Bozkurt Mamatlar Village, Devrekani Kuzköy, Küre and Abana settlements of Kastamonu city, respectively. Additionally, precipitation was recorded 235.9 mm in Ulus Ceyüpler Village of Bartın, 317.9 mm in Ayancık and 225.8 mm in Türkeli of Sinop. In this study, the atmospheric conditions of the flood disaster were examined. The Basra low pressure settled over the eastern Black Sea during this period. On August 8–9, a trough developed above Anatolia at the level of 500 hPa. Due to the low pressure remaining on the region, the system coming to the Black Sea Basin from the north turned towards the east of the Black Sea as of August 8. Especially at this date, while high-pressure conditions continued in most western parts of the Black Sea, the pressure falling from the Sevastopol-Kastamonu line to the east attracted the system coming from the north. On August 10 2021, the surface temperature of the Black Sea, especially the eastern part, reached 28.3 °C (3.5 °C higher than average). The temperature difference between sea surface temperatures and 850 hPa reached 13 °C degrees. These conditions resulted in a strong low-level moisture convergence development that continued for three days in the Black Sea Basin. Thus, the developing convective cell gradually became more vigorous, expanded its area of influence in the interior of the land due to the cyclone movement as of the morning of August 10 and caused heavy rains with the effect of the topography.