Study on the Structure and Variation of the Antarctic Vortex, and an Integral Diagnostic Method

The Antarctic vortex is the main feature of the atmospheric circulation on the Southern Hemisphere. It plays an important role in the Antarctic synoptic, climatologic and environmental processes, and relationship between the Antarctic and global atmospheres. The Antarctic is a large-scale three-dimension atmospheric system, with distinguished morphological, dynamic and thermal structures. Study on the three-dimension system benefits our understanding of the Antarctic atmospheric processes and their interactions with the global atmosphere. In this study, using 1979~2014 ERA-Interim reanalysis data, the three-dimension morphological, dynamic and thermal structures, and evolution of the Antarctic vortex are investigated, and the inhomogeneity in the vertical distribution of the Antarctic vortex is revealed. Analysis of the Antarctic vortex on a given surface in the conventional specific-layer method is unable to describe the integral features of the Antarctic vortex. An integral diagnostic method based on the integral mass, momentum and enthalpy of the Antarctic vortex is introduced by this study, for better understanding of the Antarctic vortex as an integrated atmospheric system. Compared with the conventional specific-layer method, this diagnostic method has better integration and more physics in the study of the Antarctic vortex. The conclusion remarks are as the following,

The vertical distributions of the morphological, dynamic and thermal structures and evolution of the Antarctic vortex have a clear inhomogeneity. The area of the Antarctic vortex is the largest in the upper stratosphere with the value of 40^oS equivalent latitude and the smallest in the lower stratosphere with the value of 60^oS equivalent latitude. The zonal wind of the Antarctic vortex edge is the strongest in the upper stratosphere with the averaged value of 92.0 m/s and the weakest in the lower stratosphere with the averaged value of 35.0 m/s. The temperature of the Antarctic vortex is the highest in the upper stratosphere with the averaged value of 234K and lowest in the lower stratosphere with the averaged value of 186K. The establishing time is the earliest in the upper stratosphere with the value of 75^th day and latest in the lower stratosphere with the value of 145^th day; the breaking time is the earliest in the upper stratosphere with the value of 276^th day and latest in the lower stratosphere with the value of 337^th day; the persisting time is the longest in the middle stratosphere with the value of 220 days and shortest in the low stratosphere with the value of 170 days.

The integral diagnostic method introduced by our study is able to obtain the morphological, dynamic and thermal structures and evolution of the integral Antarctic vortex. The integral mass of the Antarctic vortex exists from March to November, with the average of 8.77×10¹⁵kg and the maximum of 15.7×10¹⁵kg in August. The integral momentum of the Antarctic vortex edge exists from March to November, with the average of 6.27×10⁵kg m/s and the maximum of 12.1×10⁵kg m/s in September. The integral enthalpy of the Antarctic vortex exists from March to November, with the average of 17.74×10²⁰J and the maximum of 31.0×10²⁰J in August. The establishing time of the integral Antarctic vortex is 130^th day, the breaking time of the integral Antarctic vortex is 319^th day, and the persisting time of the integral Antarctic vortex is 189 days.

The Antarctic vortex, described by the integral mass, momentum and enthalpy, and the persistence, has a significant increasing trend. In 1979~2014, the annual-mean mass, momentum and enthalpy of the integral Antarctic vortex have significant increasing trends; the establishing time of the integral Antarctic vortex is becoming earlier, the breaking time of the integral Antarctic vortex is becoming later, the persisting time of the integral Antarctic vortex is becoming longer. Decadal variations of the mass, momentum and enthalpy of the integral Antarctic vortex are different, and the persisting time of the integral Antarctic vortex has a significant decadal variation.