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- Title
Future Reductions in Polar Cold Air Mass and Cold Air Outbreaks Revealed From Isentropic Analysis.
- Authors
Kanno, Yuki; Iwasaki, Toshiki
- Abstract
This study quantifies future changes in the polar cold air mass (PCAM) below a threshold potential temperature of 280 K and its horizontal fluxes, which are an indicator for the intensity of cold air outbreaks, by analyzing the outputs from five climate models from the Fifth Coupled Model Intercomparison Project. Under the business‐as‐usual scenario, the multimodel means of the wintertime total hemispheric PCAM decrease by 37% in the Northern Hemisphere and by 34% in the Southern Hemisphere by the end of the 21st century. The midlatitude equatorward PCAM fluxes are projected to decrease significantly by around 2050. This is primarily due to the reduction of the PCAM and to a lesser extent due to the weakening of the extratropical meridional circulation. Finally, intermodel differences in the total hemispheric PCAM reduction are shown to be linearly related to the climate sensitivity to the global mean surface air temperature. Plain Language Summary: In winter, the polar regions are reservoirs of extremely cold air masses. Sometimes, the polar cold air outflows to the midlatitudes and results in very cold weather. This study quantitatively evaluated the future changes in the polar cold air mass and its outflow to the midlatitudes in the winter hemispheres. We found that both the polar cold air mass and its outflow are projected to decrease significantly by the end of the 21st century in the Northern and Southern Hemispheres due to the increase in the global mean surface temperature. These findings provide a possible scenario of future polar climate change. Key Points: Under the RCP8.5 scenario, the polar cold air mass is projected to decrease by 37% in the boreal winter by the end of 21st centuryThe equatorward polar cold air mass fluxes in the midlatitudes are projected to decrease significantly by around 2050Thermodynamical (dynamical) change is the main (secondary) contributor to the projected reduction in the polar cold air mass fluxes
- Subjects
AIR masses; CLIMATE sensitivity; ATMOSPHERIC temperature; POLAR climate; CLIMATE change; SURFACE temperature
- Publication
Geophysical Research Letters, 2020, Vol 47, Issue 3, p1
- ISSN
0094-8276
- Publication type
Article
- DOI
10.1029/2019GL086076