60 Simulated AMO’s Influence on Eurasian Nonuniform Warming since the Mid-1990s

Monday, 7 January 2019
Hall 4 (Phoenix Convention Center - West and North Buildings)
Xueqian Sun, IAP, Beijing, China

Based on the ensemble experiments with three atmospheric general circulation models (AGCMs), this study investigates the role of the Atlantic Multidecadal Oscillation (AMO) in shaping the summer nonuniform warming over the Eurasian continent since the mid-1990s. The results validate that the positive phase AMO can indeed cause uneven warming, with predominant amplified warming over Europe-West Asia and Northeast Asia, respectively, but with much weaker warming over Central Asia. The underlying mechanism is then diagnosed from the perspective that the boundary forcing modulates intrinsic atmospheric variability. The results highlight the role of the Silk Road Pattern (SRP), an intrinsic teleconnection pattern across the subtropical Eurasian Continent propagating along the Asian jet. The SRP can not only be identified from the AGCM control experiments with the climatological SST, but also be excited by the AMO-related SST anomaly forcing. Furthermore, diagnostic Linear Baroclinic Model (LBM) experiments are conducted, and the results suggest that the SRP can be triggered by the AMO-related tropical diabatic heating. The AMO triggered SRP-like wave-train responses feature anticyclonic circulations over Europe-West Asia and Northeast Asia, but cyclonic circulation over Central Asia. These responses cause increased warm advection toward Europe-West Asia and Northeast Asia, reduced precipitation and cloud cover and then increased downward short wave radiation. These increased warm advection and increased downward short wave radiation together caused amplified warming in Europe-West Asia and Northeast Asia. It is opposite for Central Asia.
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