Implications of Ural Blocking for East Asian Winter Climate in CMIP5 GCMs. Part II Projection and Uncertainty in Future Climate Conditions

• Published in: Journal of climate Vol. 28; no. 6; pp. 2217 - 2233
• Main Authors: Cheung, Hoffman H. N., Zhou, Wen
• Format: Journal Article
• Language: English
• Published: Boston American Meteorological Society 15-03-2015
• Subjects: 21st century; Atmospheric circulation; Atmospherics; Climate; Climate change; Climate models; Climatic analysis; Climatic conditions; Climatic zones; Climatology; Cold; Future climates; Ice; Jet stream; Jet streams (meteorology); Meteorology; Planetary waves; Regression analysis; Rossby waves; Sea ice; Sea surface; Sea surface temperature; Seas; Siberian High; Statistical variance; Studies; Surface temperature; Uncertainty; Ural blocking; Wave propagation; Winter; Winter climates; East Asia; Ural Mountains; Arctic region; Siberia; Russia; Russia, Ural Mts; PNE, Laptev Sea; INW, Asia; Russia, Siberia; PNE, Eurasia
• ISSN: 0894-8755; 1520-0442
• DOI: 10.1175/jcli-d-14-00309.1

Multiple model ensembles (MMEs) of Ural blocking frequency in 20 CMIP5 GCMs show no apparent increase or decrease in RCP4.5 and 8.5 runs throughout the twenty-first century. However, a significant increasing or decreasing trend of the Ural blocking index (UBI) is identified in individual GCMs, and the trend appears to be correlated with the trend of the Siberian high index (SHI), which measures the East Asian winter climate. Regression analyses reveal that the trend of UBI is related to upstream circulation over the Euro-Atlantic region, such as the intensification of the Atlantic jet stream and the propagation of a quasistationary Rossby wave across Eurasia.
In the late twenty-first century, the year-to-year variation of UBI appears to show a stronger linkage with the large-scale circulation over the Kara and Laptev Seas. Meanwhile, UB likely exerts a stronger impact on East Asia on synoptic and seasonal time scales. The uncertainty of UB might present a challenge for accurate prediction of the subseasonal and long-term variation of the East Asian winter climate. To further evaluate the uncertainty in projections of UB, additional work should assess the atmospheric response to the sea surface temperature over the Atlantic and the reduction of sea ice.