北半球极区平流层冬季12月与1—2月气候变化形势的对比

根据1980—2000年ERA-Interim再分析的风场和温度场资料,计算12月与1—2月北半球行星波的EP通量及其散度,并按冬季不同月份分析了平流层整层温度和风场从20世纪80年代到90年代变化的特征及其与行星波活动变化的关系。结果表明,12月高纬度地区中低平流层呈增温趋势;而1—2月温度变化呈冷却趋势。在12月中高纬度中上平流层纬向风明显减速;而在1—2月高纬度中高平流层,随着纬度和高度的增加,纬向风呈明显加速趋势。冬季北半球行星波主要沿低纬度和极地波导两支波导向上传播。但是,12月行星波沿低纬度波导的传播减弱,沿极地波导向平流层整层的传播则明显增强。而1—2月行星波沿低纬度波导的传播明显增强,沿极地波导向平流层的传播则减弱。因此,北半球极区平流层1980—2000年间12月与1—2月波流相互作用的年代际变化形势趋于相反,有必要针对冬季不同月份分开进行讨论。

Comparison between the situations of climate change in the Arctic stratosphere during December and January-February

In this study,fields of wind and temperature from the ERA-Interim reanalysis for the period of 1980-2000 are used to calculate the Eliassen-Palm flux and its divergence of planetary waves in the Northern Hemisphere winter.Next,the characteristics of decadal-scale variability throughout the layer of stratospheric temperature and wind and the relationships to changes in planetary wave activity during December and January-February are analyzed.While the high-latitude middle and lower stratosphere show a warming tendency in December,the same region cools during January-February.The zonal-mean zonal winds in the mid-to-high latitude middle and upper stratosphere decelerate evidently in December,but show a significant accelerated tendency during January-February with increasing latitude and altitude in the high-latitude middle and upper stratosphere.The planetary waves mainly propagate upward along the low-latitude and polar wave guides in the Northern Hemisphere winter.However,in December the propagation along the low-latitude wave guide decreases,whereas that along the polar wave guide and throughout the entire layer stratosphere increases evidently.On the contrary,during January-February the propagation along the low-latitude wave guide strengthens significantly,whereas that along the polar wave guide and throughout the stratosphere weakens.Therefore,during December and January-February for the period of 1980-2000,the respective situations of the decadal-scale changes of wave-mean flow interactions in the Arctic stratosphere tend to be opposite,and it is necessary to discuss the decadal variability during different winter months on a case-by-case basis.