Atmospheric Action Centers: Modern Features and Possible Changes According to Calculations Using CMIP6 and CMIP5 Models

The results of an analysis of changes in the parameters of the atmospheric action centers (AACs) in the Northern (NH) and Southern (SH) hemispheres using the calculation results with the ensembles of CMIP5 and CMIP6 climate model are presented. The ability of modern models to reproduce the AAC features for the historical scenario in comparison with the ERA5 reanalysis data is estimated. Prognostic estimates of changes in the AAC modes in the 21st century under the RCP8.5 scenarios for the CMIP5 models and SSP5-8.5 for the CMIP6 models are obtained. The AAC intensity is estimated as the difference between the sea level pressure in the AAC region and the average pressure for the hemisphere. In the NH, according to the reanalysis data and model calculations, the intensity of subtropical oceanic anticyclonic AACs is greater in summer than in winter. The opposite situation has been noted for the intensity of subpolar oceanic cyclonic AACs in the NH. The interannual variability of the AAC intensity in winter is generally greater than in summer. In the SH, the seasons with higher intensity of oceanic anticyclonic and cyclonic AACs and their interannual variability differ for different oceans. According to the calculations with the CMIP5 and CMIP6 models, significant changes in the AAC intensity in the 21st century are obtained. More significant trends in the strengthening of AACs in the 21st century are manifested in the SH, especially in winter. The most stable weakening trends are noted over the continents for the winter North American maximum and the summer Asian minimum. For the winter Siberian maximum, the weakening trend is more pronounced according to the calculations with the CMIP6 models than according to the calculations with the CMIP5 models.