  The results of an analysis of changes in the characteristics of atmospheric
centers of action (ACAs) in the Northern (NH) and Southern (SH) hemispheres
using results of simulations with the CMIP5 and CMIP6 ensembles of climate
models are presented. The ability of models to simulate ACA features is
estimated for the historical scenario in comparison with ERA5 reanalysis data.
The projected changes are evaluated under RCP8.5 and SSP5-8.5 scenarios for
CMIP5 and CMIP6 models, respectively. The ACA intensity is evaluated that
defined as the difference in sea level pressure averaged over the ACA region
and the entire hemisphere. In NH, reanalysis and models show greater intensity
of subtropical oceanic anticyclonic ACAs in summer than in winter. The opposite
is found for the intensity of NH subpolar oceanic cyclonic ACAs. The
interannual variability of the ACA intensity in winter is generally greater
than in summer. In SH, the season with greater intensity of oceanic
anticyclonic and cyclonic ACAs and its interannual variability varies from
ocean to ocean. CMIP5 and CMIP6 models show substantial changes of ACAs
characteristics in the XXI century. More significant trends in the
strengthening of ACAs in the 21st century appear in the SH, especially in the
winter seasons. The most consistent weakening trends are found over continents
for winter North American maximum and the summer Asian minimum. For the winter
Siberian maximum, the weakening trend is found more pronounced in CMIP6 models
than in CMIP5.
