Abstract
The occurrence of wintertime cold surges (CSs) over East Asia is largely controlled by the surface air temperature (SAT) distribution at high latitudes and thermal advection in the lower troposphere. The thermodynamic background state over northeastern Asia is associated with the strength of the East Asian winter monsoon and the variation of Arctic Oscillation. This study assesses the importance of the SAT structure with thermal advection in determining the frequency of CS occurrences over East Asia through the analysis of nine atmosphere–ocean coupled global climate models participating in the Coupled Model Intercomparison Project Phase 5. The historical simulations can reproduce the observed typical characteristics of CS development. On the basis of this model performance, ensemble-averaged future simulations under the representative concentration pathway 8.5 project a reduction in CS frequency by 1.1 yr−1 in the late 21st century (2065–2095) compared to the present-day period (1975–2005). The major reason for less frequent CSs in the future is the weakened cold advection, caused by notable SAT warming over the northern part of East Asia. These results suggest that changes in the meridional SAT structure and the associated changes in thermal advection would play a more substantial role than local warming in determining future changes in the frequency of CS occurrences over East Asia.
Highlights
Cold surges (CSs), characterized by a steep temperature drop within one or two days, are energetic systems associated with the East Asian winter monsoon (EAWM)
We compare the spatial patterns and vertical structures of observed CSs to those simulated in the coupled global climate models (CGCMs) prior to investigating future changes in CSs and the contribution of thermal advection to those changes
The geopotential height patterns at 250 and 850 hPa are shown during the dates of CS occurrence stretches from the Ural Mountains (50◦ E–90◦ E, 50◦ N–75◦ N) to the Korea–Japan region
Summary
Cold surges (CSs), characterized by a steep temperature drop within one or two days, are energetic systems associated with the East Asian winter monsoon (EAWM). The suppression of convective activity in the maritime continent associated with the weak EAWM in El Niño years provides unfavorable conditions for CS occurrences [6,17] These large-scale climate variabilities affect CS occurrence by changing the mean state temperature distribution. Recent studies have reported that sea ice loss in the Barents-Kara sea can modulate atmospheric circulation in Eurasia by direct Rossby wave propagation [18,19,20] or by indirect modulation via stratospheric circulation [21] These remote modulations influence CS frequency through their effects on the cold advection associated with the meridional temperature gradient.
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