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Lei Song
and
Renguang Wu

Abstract

The present study shows that winter cold events over eastern China can be induced by Madden–Julian oscillation (MJO)-associated anomalous convection over the Maritime Continent. We conduct composite analysis separately for identified intraseasonal cold events over eastern China that occur following anomalous convection over the Maritime Continent and the tropical Indian Ocean. For cold events related to anomalous convection over the Maritime Continent, the southward intrusion of cold air into eastern China takes an eastward path in association with an eastward location of an anomalous Siberian high compared to cold events related to anomalous convection over the tropical Indian Ocean. The Maritime Continent convection-related cold events tend to occur with a negative Arctic Oscillation (AO), whereas the relationship between the tropical Indian Ocean convection-related cold events and the AO is weak. Anomalous convective heating over the Maritime Continent triggers a poleward Rossby wave train, which, together with an AO-related southward wave train from northern Eurasia, contributes to the deepening of the East Asian trough. The poleward wave energy dispersion is similarly triggered by anomalous convective heating over the tropical Indian Ocean. In both types of cold events, anomalous tropical heating induces a meridional vertical circulation, with large-scale airmass convergence in the upper midtroposphere and descending of air on the northern branch of the vertical cell over Siberia. The upper-level mass convergence and the radiative cooling over Siberia work together for the enhancement and southeastward expansion of the Siberian high and the southward intrusion of cold anomalies to eastern China.

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