Long-Period Variability and Predictability of Heat and Cold Waves

Abstract The main definitions and quantitative characteristics of heat and cold waves are considered. According to the data of ECMWF ERA5 reanalysis using the Mann–Kendall test, statistically significant positive (negative) trends in changes of the areas occupied by positive (negative) air temperature anomalies of varying intensity and heat (cold) waves of varying duration in the winter and summer seasons of 1981–2024 in the Northern Hemisphere are revealed. A negative trend, most pronounced in winter season, has been recorded for the intraseasonal variability of the average daily air temperature. Using retrospective forecasts of the PLAV072L96 joint atmospheric model of the Institute of Numerical Mathematics, Russian Academy of Sciences (INM RAS), and the Hydrometeorological Center of Russia (HMC), the presence of a useful signal for heat (cold) waves in the integration interval of 14 days in the summer (winter) season is shown. It is noted that, against the background of the rarer recurrence of cold waves, the quality of their forecasts is significantly inferior to the quality of heat wave forecasts. Using the example of August–September 2024 in European Russia, against the background of blocking the western transfer, the possibilities of increasing the practical predictability of heat waves up to 30 days are demonstrated. The results are expected to be used in the operational practice of intraseasonal forecasting at the HMC/North Eurasian Climate Center (NEACC).