Analysis Of The Formation Mechanism Of A Super Cold Wave In January 2016

The correlation of potential vorticity(PV)at upper Asian and the meteorological elements in the eastern part of China is analyzed in January from 1979 to 2017 using ERA-Interim data and CMAP precipitation data.The anomalies of high altitude PV response to the anomalies of ground meteorological elements in January 2016 are verified through the equation of linear regression.Then the PV of super cold wave is analyzed and the budget of PV isstudied during the development of the cold wave.The conclusions are as following:The PV at upper Asian has a strong correlation with the meteorological elements in the eastern part of China,and the correlation with wind field is most,and the correlation with precipitation is least.Pressure and temperature field aremost sensitive and the wind field is least to the anomalies of PV.The impacts of middle-to-high atmosphere PV on the sea level pressure,2m temperature and 10 m wind field are higher than that of the lower atmosphere.The anomalies of ground meteorological elements are verified during the eruption of the cold wave at 23 January 2016 through the equation of linear regression.Although the meteorological elements are different degrees of approximation or break the historical extreme during the extreme cold wave,it is found that the correlation between the PV at upper level and the meteorological elements at surface is identical with the results of statistic.Then the extreme cold wave is analyzed by the isentropic potential vorticity(IPV).The result shows that high potential vorticity was divided by the polar vortex,and the blocking of the front low PV and the proceeding northward of the rear low PV strengthen the meridional exchange of the PV.The high PV air continuously moved from the polar to the south,making the main body of high PV continue to strengthen.On the other hand,the high vortex moved from the north to the south.And also transported downward from the troposphere.The cold wave,which includes three strands of main cold air,developed from the upper to the bottom,settling in the north side of the upper-level jet.In the southern tip a sinking air is most exuberant,which resulted from its interaction with the upper-level jet.The sinking of the strong cold air made the cold wave influence the South China.As the high PV transmitted towards the south area,the low vortex system developed rapidly at high-level troposphere.When it moved to the east of China,The East Asian Trough deepened rapidly,and finally induced the outbreak of strong cold air behind the trough.On the other hand,in the process of high PV transportation,the rear strongly sinking movement occurred,to render the rapid development of the cold high on the ground,and lead to the outbreak of cold wave weather.Lastly,The budget of PV is calculated.From the horizontal distribution of PV budget,we can seethe horizontal advection PV is always beneficial for the development of PV,and the intensity is the strongest at the lower troposphere,.The vertical advection PV is not conducive to the development of the high PV in the establishment stage and the enhancement stage of the cold wave,and it makes contribution to high PV in the outbreak stage and becomes stronger.The intensity of the non-advection PV is always weak,which is favorable to the development of the cold wave in the establishment stage.It is not conducive to the development of the high PV in the cold wave enhancement and the outbreak stage.From the vertical distribution of PV budget,We can see the horizontal advection PV make contribution to PV at higher troposphere and lower troposphere,and the intensity is stronger than vertical advection PV and non-advection PV.The vertical advection PV is favorable to the development of high PV in the higher troposphere,and the change caused by non-advection PV is mainly in the lower troposphere.The change of PV caused by advection PV and non-advection PV is positive,and enhance the cold vortex,which is favorable to the development of cold wave.