Classification of Sudden Stratospheric Warmings Using the Method of Extreme Rates of Temperature and Wind Changes

The objective of the study is to modify the classification of sudden stratospheric warmings (SSWs) based on a new method for revealing moments of extreme rates of changes in dynamic parameters using JRA-55 reanalysis data for the period from 1958 to 2017. The time of the onset and end of a sudden stratospheric warning was identified with the moments of extremes rates of changes in temperature and zonal mean wind speed at an altitude of 30 km and latitudes north of 60° N. Algorithms and programs have been developed to search for zero values of the second time derivative of temperature and zonal wind speed, which correspond to extreme values of the rate of change in these parameters. Over the 60-year period, 140 mid-winter SSWs were detected (an average was 2.4 events per year), among which 63 complete ones (with a reversal of zonal wind), 41 partial ones (without a reversal of zonal wind), and 36 weak ones were found. The moments of the maximum temperature rise rate are on average a day ahead of the moments of the fastest decrease in zonal wind at the beginning of an SSW.