Simulated seasonal cycle of atmospheric mass in four future scenarios of the CMIP6 models:a nonlinear response to increasing greenhouse gases
In the context of global warming,future climate projections have become a major research focus.The in-creasing greenhouse gas(GHG)emissions in the CMIP6 scenarios-SSPl-2.6,SSP2-4.5,SSP3-7.0,and SSP5-8.5 are accompanied by rising global mean surface air temperatures.However,the potential changes in the seasonal cycle of atmospheric mass,particularly the annual range,remain an open scientific question.This study analyzes CMIP6 data from 2015 to 2100 to examine the seasonal cycle characteristics of atmospheric mass under four GHG emission scenarios compared to historical runs.The study also examines the spatial distribution of surface air pressure and geopotential height in February and July,interpreted through temperature and wind fields.The results reveal that while the seasonal variations of global and hemispheric average atmospheric mass in the different scenarios resem-bles those in historical simulations,the annual range of hemispheric air fluctuates rather than increasing uniformly with higher GHG emissions.Specifically,the annual range decreases in SSP1-2.6 and SSP3-7.0,while it increases in SSP2-4.5 and SSP5-8.5.Globally,the annual range of atmospheric mass increases steadily with higher GHG emis-sions.Surface air pressure and geopotential height distributions in future scenarios align with reanalysis data,but in the Northern Hemisphere,a phase transition emerges,linked to the land-sea distribution dominated by Eurasia,the North Pacific,and the North Atlantic.In contrast,the Southern Hemisphere phase transitions occur along the latitudi-nal zones.The alternating positive and negative values in the February-July difference suggest regionally varying trends and amplitudes of change in surface air pressure and wind fields due to GHGs.These regional differences contribute to variations in the annual range of surface air pressure across the hemispheres.With increasing GHG e-missions,the Northern and Southern Hemispheres respond differently across seasons,and this variation is evident not only in the lower troposphere but also at higher altitudes,including the stratosphere.The Arctic and Antarctic strato-spheric vortices show nonlinear changes in intensity,weakening and strengthening in cycles as GHG emissions rise.These results suggest that the uneven distribution of GHGs in the atmosphere leads to variable temperature responses at different altitudes,altering the geopotential potential height field,layer thicknesses,and,consequently,surface air pressure.This highlights the region-specific response of atmospheric mass to increasing GHGs.The CMIP6 simula-tions provide valuable insights into atmospheric circulation changes under the conservation of atmospheric mass and their impacts on weather and climate in a warming world.Additionally,the nonlinear effects of human activities on water vapor mass and the atmospheric water-holding capacity deserve further exploration,particularly regarding their influence on the annual range of atmospheric mass.It remains uncertain whether transient and stable warming scenarios will lead to different outcomes in air mass changes.
atmospheric massseasonal cyclenonlinear changegreenhouse gas emission scenariosCMIP6 models
万方数据
维普
