1980—2000年北极平流层冬季十年际变化形势的逐月演变

Winter month-to-month evolution of decadal changes in the Arctic stratosphere during 1980—2000

摘要:

采用1980—2000年的ERA-Interim再分析资料，计算北半球冬季各月（12月、1月、2月）行星波的Eliassen-Palm（EP）通量及其散度，并按冬季不同月份分析平流层整层温度和纬向风场的十年际变化特征与行星波活动变化的关系。结果表明，温度的十年际变化在高纬度中下平流层12月呈明显增温趋势，1月转为较弱的冷却趋势，2月为明显的冷却趋势。纬向风在中高纬平流层12月呈明显的减速变化，1月减速区与加速区相间分布但强度均较弱，而2月为明显的加速趋势。12月行星波沿低纬度波导向热带对流层顶的传播减弱，沿极地波导向平流层整层的传播明显加强；1月沿两支波导的传播趋势未变但均较弱；而2月行星波沿低纬度波导的传播转为加强趋势，沿极地波导的传播转为减弱趋势。相应地，EP通量散度场的十年际变化形势沿两支波导在12月与2月相反，1月为过渡阶段。因此，北极平流层温度、纬向风、EP通量及其散度场的十年际变化在冬季内呈现一个从北半球环状模（Northern Hemisphere Annular Mode，NAM）的负极趋势向正极趋势逐月演变的过程。

Abstract:

Using ERA-Interim reanalysis data from 1980 to 2000, this study calculates the Eliassen-Palm (EP) flux and its divergence of the planetary wave in the Northern Hemisphere winter (December-February).In the following sections, this study examines the characteristics of decadal changes in stratospheric temperature and zonal wind, as well as changes in planetary wave activity during different winter months.The results show that the changes for decadal temperature show a significant warming trend in the high-latitude mid-to-lower stratospheres in December, followed by a weak cooling trend in January, and an apparent cooling trend in February.Zones of significant deceleration in the mid-to-high latitude stratosphere in December deceleration and acceleration weak intensities in January, and significant acceleration in February, are alternately distributed in the stratosphere every month.Planetary waves propagating into the tropopause along with the low-latitude waveguide weaken in December, while those propagating along with the polar waveguide into the stratosphere strengthen.During January, both propagations along two waveguides are unchanged, but their intensities are declining.As for February, it turns into an evident strengthened tendency along the low-latitude waveguide and a noticeable weakened tendency along with the polar waveguide.In addition, December and February remain transitional months for EP flux divergence, while January is decadal.Therefore, the annual decadal changes of Arctic stratospheric temperature, zonal winds, and EP flux present an evolution from the NAM (Northern Hemisphere Annular Mode) index negative polarity tendency to positive polarity tendency throughout the winter.