The researchers studied extremely cold months in south China over 45 years. They found that high geopotential in the north and low in the south of the Asian-Pacific region, along with meridional circulation, are common during severely cold months. Anomalies in the geopotential field were observed in previous periods. Sea surface temperatures showed a continuous pattern leading up to severely cold months, with El Niño in January and La Niña in February and December. The researchers concluded that predicting severely cold winter months is possible using geopotential and sea surface temperature data.