Assessment of multi-year change tendency in the number of hot, cold and normal months in the territory of Azerbaijan based on extreme indices of air temperature

The article considers the change tendency in the number of hot, cold and normal months in most natural-climatic zones of Azerbaijan over the years 1936-2022, against the background of the increase in the extremes of climate change over the past decades. These indicators are determined on the basis of air temperature extreme indices. For each month of the year, a hot month is considered to be a case where the average monthly air temperature is greater than the sum of the climate norm and the root mean square (RMS) tendency coefficient of this series, a cold month is considered to be a case where the average monthly air temperature is less than the difference between the climate norm and the root mean square tendency coefficient, and a normal month is considered to be a case where the average monthly air temperature is in the range between the sum and the difference between the climate norm and the root mean square tendency coefficient. The average monthly air temperature is calculated based on the data for the period 1961-1990. In the study, the average multi-year values of the percentage shares of the number of hot, cold and normal months for each month over 87 years were calculated and analyzed, the multi-year change tendency in these series was evaluated both for the years 1936-2022 and separately for the years 1936-1972 (global cooling period) and 1973-2022 (global warming period), and the results were presented in the form of tables and graphs. It was determined that in terms of air temperature extremes in different natural-climatic zones of Azerbaijan, February, March, August, September and October were the months with the highest frequency of hot months, while December, all months of spring and summer, and November were the months with the highest frequency of cold months. There were statistically significant increases in the number of hot months during the year, hot months were not recorded in 1936-1994, and there were statistically significant decreases in the number of cold months during the year. The highest frequency of years with zero cold months occurred in various years between 1940 and 1970. There were also statistically significant decreases in the multi-year dynamics of the number of normal months. During 1973-2022, there were significant increases in the number of hot months, which were of a regular nature, and a decrease in the number of cold and normal months.