Cold waves: approaches to definition and examples for Khabarovsk

The author gives a critical review of the scientific literature on the definition of cold waves. On the example of Khabarovsk, for the period of 1999-2017, the episodes with extremely low temperatures were identified. It was used two approaches to the determination of cold waves were: threshold values of 3% percentile of long - term annual distribution of average daily temperatures, calculated as an average for 8 observation periods, and 2.5% percentile-average daily temperatures, calculated as an average between the minimum and maximum per day. It is shown that cold waves are recorded mainly in December and January; most waves are observed in the period from 10 to 20 January; in February, the temperature background rises markedly, and extreme temperature drops are recorded much less often. The winter of 2010/2011 was the coldest for the entire study period; in January the revealed wave lasted 11 days with a total excess of negative temperatures above the threshold value of 43.5°C, and the minimum temperature -40,0°C was on January 14, 2011. For the dynamics of the minimum, average and maximum temperatures of the winter season, the absence of a pronounced trend is established, but interannual variations can reach ±6°C. Climatic extremes vary markedly during the study period, but generally they rarely exceed two standard deviations.