Comparative analysis of temperature and precipitation changes in the city of Shumen for the periods 1971-1980 and 2013-2023

Abstract The main climatic elements and meteorological phenomena in the area of the meteorological observatory in the city of Shumen were studied for the periods 1971-1980 and 2013-2023. A detailed analysis of changes in temperatures and precipitation has been carried out, revealing the trends in their changes. Significant differences in temperature were found between the warm and cold part of the year. For the period 1971-1980, the average January temperatures are from -3.0°C to +2.5°C, and the average June temperatures from +18.4°C to +21.3°C, while for the period 2013-2023 they are, respectively, the average January temperatures from –2.8°C to +5.7°C, and the average June temperatures from +19.1°C to +22.3°C. Temperature analysis reveals warmer months of January and June for the period 2013-2023. The average annual temperature for the period 1971-1980 is +10.73°C., while for the period 2013-2023 it is +12.48°C, i.e. for the second period an increase of 1.75°C is reported. The average maximum monthly temperatures for the city of Shumen for the period 1971-1980 in the summer range from +17.6 to +21.8°C, while for the period 2013-2023 they are from +19.1 to +24.6°C., i.e. for the second period, an increase of about 2°C is reported. The same trend is observed for the average annual temperature amplitudes, which in the period 1971-1980 were from 20°C to 24.4°C, while for the period 2013-2023. are from 19.9°C to 25.8°C. The average annual precipitation for both periods is approximately the same (1971-1980 - 608.64 mm; 2013-2023 - 648.89 mm), but by year in the period 2013-2023 there are very large differences - from 418.4 mm (2019) to 1185.4 mm (2014). Four years of the 2013-2023 period: 2019, 2020, 2022, and 2023 can clearly be identified as years of significant drought. The complex analysis of the climate of the city of Shumen allowed in the final part of the study to draw conclusions about the prevailing types and classes of weather.