Influence of the Madden-Julian oscillation on cold surges in East Asia

The variations of wintertime surface air temperature (SAT) and the occurrences of cold surges over East Asia in association with the Madden and Julian Oscillation (MJO) are examined. The MJO is defined as a combination of the two leading empirical orthogonal function modes of 850 and 200 hPa zonal winds and outgoing longwave radiation in the Tropics. The spatial pattern and magnitude of SAT anomalies over East Asia significantly change with respect to MJO phases. Composite analysis reveals that the MJO-SAT relationship is mainly affected by strong temperature advection in the lower troposphere. Also, occurrences of cold surges are identified using objectively determined synoptic criteria and their relation to the MJO is analyzed. Most extreme cold surges occur when the MJO convection center is located over the Indian Ocean, and it is suggested that MJO-induced circulation anomalies may reinforce the amplification of normal cold surges to extreme cold surges.