Month-to-month variability of winter temperature over northeast China linked to sea ice over the davis strait-baffin bay and the barents-kara sea

Abstract

This study focuses on the month-to-month variability of winter temperature anomalies over Northeast China (NECTA), especially the out-of-phase change betweenDecember and January-February (colder than normal in December andwarmer than normal in January-February, and vice versa), which accounts for 30%of the past 37 years (1980-2016). Our analysis shows that the variability of sea ice concentration (SIC) in the preceding November over the Davis Strait-Baffin Bay (SIC-DSBB) mainly affects NECTA in December, whereas the SIC over the Barents-Kara Sea (SIC-BKS) significantly impacts NECTA in January-February. A possible reason for the different effects of SIC-DSBB and SIC-BKS on NECTA is that the month-to-month increments (here called DM) of SIC over these two areas between October and November are different. A smaller DM of SIC- DSBB in November can generate eastward-propagating Rossby waves toward East Asia, whereas a larger DM of SIC-BKS can affect upward-propagating stationary Rossbywaves toward the stratosphere in November. Less than normal SIC-DSBB in November corresponds to a negative phase of the sea surface temperature tripole pattern over the NorthAtlantic, which contributes to a negative phase of theNorthAtlanticOscillation (NAO)- like geopotential height anomalies via the eddy-feedback mechanism, ultimately favoring cold conditions over Northeast China. However, positive November SIC-BKS anomalies can suppress upward-propagating Rossby waves that originate from the troposphere in November, strengthening the stratospheric polar vortex and leading to a positive phase of an Arctic Oscillation (AO)-like pattern in the stratosphere. Subsequently, these stratospheric anomalies propagate downward, causing the AO-like pattern in the troposphere in January- February, favoring warm conditions in Northeast China, and vice versa.