||Previous studies demonstrate that the tropical anticyclone on the upper troposphere blocks the southward cold-air advection so that the cold air can only flow underneath this high system, in turn, this unique phenomenon named cold surges, naturally occurs over East Asia. During January 2016, an extreme cold surge event with a dramatic cooling in East Asia occurred and introduced a surprising solid-form precipitation around the subtropical areas and leading to serious economic losses. Following the synoptic development, a prominent anticyclonic anomaly over the Siberian region was observed prior to the extreme event. It turns out that there was a westward moving anticyclone over the western Pacific, which acts as a blocking agent to prevent the regular eastward migrating cyclones activity over North Asia resulting in the accumulation of air mass over Siberia that develop into a ridge. |
The daily vertical cross-section of the streamfunction clearly shows that the anticyclone over the western Pacific evolves with a westward movement and yet provide the blocking function toward the newly developing ridge over the west Siberia. Further analysis based upon the short wave regime (wave number 4-15), it appears that the polar short wave and westerly short wave coupled with each other when they merged over East Asia, the upper-level trough was deepened. On the other hand, the air columns over East Asia exhibit a sufficient water vapor content prior to the extreme event. The water vapor flux analysis also demonstrates how the additional water vapors were transported from the deepened trough over the Indian peninsula to that over East Asia.
Chen,T.-C., 1985: Global Water Vapor Flux and Maintenance during
____, 2002: A North Pacific short-wave train during the extreme
phases of ENSO. J. Climate, 15, 2359-2376.
____, W.-R. Huang, and J.H. Yoon, 2004: Interannual variation of the
East Asian Cold Surge Activity. J. Climate, 17, 401–413.
____, M.-C. Yen, W.-R. Huang, and W.A. Gallus, 2002: An East Asian
cold surge: Case Study. Mon.Wea.Rev., 130, 2271-2290.
Hoskins, B.J., and D.J. Karoly, 1981: The steady linear response of a
spherical atmosphere to thermal and orographic forcing. J.Atmos. Sci., 38, 1179-1196.
Hovmöller, E.,1949: The Trough-and-Ridge diagram. Tellus, 1, 62–66.
Osprey, S. M., N. Butchart, J. R. Knight, A. A. Scaife, K.
Hamilton, J. A. Anstey, V. Schenzinger, and C. Zhang 2016: An unexpected disruption of the atmospheric quasi-biennial oscillation, Science, 353, 1424–1427.
Lau,K.-M.,M.-T.,Li,1984: The monsoon of East Asia and its global
associations – a survey. Bull Amer. Meteor.Soc., 65, 144-125.
Tibaldi, S., and F. Molteni, 1990: On the operational predictability
of blocking. Tellus, 42A, 343-365.
Wu, M. C., and J.C.L. Chen, 1997,: Upper-level features associated
with winter monsoon surges over South China. Mon. Wea. Rev., 125, 317-340.
Yen, M.-C., and T.-C. Chen, 2002: A revisit of the tropical–
midlatitude interaction in East Asia caused by cold surges. J. Meteor. Soc. Japan, 80, 1115–1128.