Abstract:

Based on the monthly mean 2m temperature observation data of more than 740 stations and NCEP/NCAR reanalysis monthly data, using dynamic diagnosis method, the abnormal warm winter phenomenon in China in 2016 to 2017 was studied. The results showed that the warm winter in China in 2016 to 2017 was mainly due to the weak Siberian high pressure and Aleutian low pressure, which led to the weak East Asian winter monsoon, so there was an abnormal southerly wind in China. The weakness of Aleutian low was caused by two factors. First, the sea surface temperature in Aleutian Islands was low, and the cold source corresponded to an abnormal high pressure, which led to the weakness of Aleutian low pressure. Second, the Aleutian low pressure was to the north of the outlet area of the upper westerly jet in the East Asian subtropical region. However, the outlet area of the westerly jet was located to the south in this winter, as a result, the Aleutian area deviated from the pressure relief zone of the jet stream outlet area, resulting in the weakening of the Aleutian low pressure. In addition, the westerlies were northward, and the zonal circulation dominated over the middle and high latitudes of the Asian continent, which was not conducive to the southward movement of cold air.

Key words: warm winter, East Asian winter wind, Aleutian low pressure, SST anomaly, subtropical westerly jet, dynamic diagnosis method