Inter-annual variability and trends of the frost-free season characteristics over Central and Southeast Europe in 1950-2019

Agriculture and forestry are two economic sectors most dependent on climate, and climate change has a direct and indirect impact on biotic and abiotic disturbances with strong implications. The air temperature is one of the major environmental factors affecting growth, development, and yields of crops. Despite the undeniable global warming, damage to crops by frost and freezing temperatures causes serious loss to farmers in many parts of the world. The frost-free season has a large influence on plant phenology, with implications for the distribution of natural vegetation and the types of crops grown in a particular region. The present study is dedicated to the climatology of the frost-free season over Central and Southeast Europe in the second half of the previous and the first two decades of this century. The climatology of the frost-free season is characterized by three indicators, namely the date of the last spring frost, the date of the first autumn frost, and the length of the frost-free season. Additionally, the middle date of the frost-free season as measure of the seasonal shift is analysed. The study, which is performed for the thresholds of -2.2 degrees C and 0 degrees C, reveals non-negligible lengthening of the frost-free season, associated primarily with an earlier date of last spring frost rather than a delayed date of first autumn frost.