Interdecadal Variation Of Stratospheric Temperature From December To February At The End Of The 20th Century Based On MUAM Simulations

Based on NCEP/NCAR,ERA-Interim,MERRA-2 reanalysis data and Mauna Loa observatory data,the climate state and decadal changes of the zonal mean temperature and zonal wind over the whole atmosphere in December,January and February of the 1980 s and 1990 s has been simulated respectively using the Middle and Upper Atmosphere Model(MUAM).The monthly evolution characteristics of temperature,zonal wind and geopotential height in the stratosphere of the southern and northern hemisphere are analyzed.Then based on three sets of sensitivity experiments,the single and combined impacts of changes in lower boundary condition,carbon dioxide and ozone concentrations on stratospheric temperature trends are assessed,and from the point of view of atmoshpheric planetary wave energy propagation,the mechanism differences of monthly dynamical and radiative forcings in the Arctic and Antarctic are emphatically discussed.The main conclusions are as follows:(1)The MUAM can basically reproduce the zonal mean climatological distributions of the whole atmospheric temperature and zonal wind in December,January and February of the1980 s and 1990 s.For the decadal changes of the stratosphere,the temperature in the middle and lower layers increases,the geopotential height increases,and the westerly wind in the middle and high latitudes decelerates during December in the Arctic,which is in contrast to February,while January was a transitional period.In the Antarctic,the temperature in the lower(middle)stratosphere decreases(increases),the geopotential height decreases significantly,and the westerly(easterly)wind in the lower(middle and upper)stratosphere in the middle and high latitudes accelerates(decelerates)in December.The variation trends in January and February is consistent with those in December,but the intensity decreases month by month.(2)For the Arctic,the warming of the middle and lower stratosphere in December and January is mainly attributable to the significant strengthening of the upward propagation of the wavenumber-1 stationary planetary wave resulting from the change of lower boundary condition,and the warming intensity and range in December are larger.Howerver,the radiative cooling effect of ozone reduction and carbon dioxide increase weaken this warming to some extent.The cooling of the mid-lower layers in February is mainly related to the weakening of the upward propagation of the wavenumber-1 stationary planetary wave due to the change of lower boundary condition,while the radiative cooling effects of ozone and carbon dioxide play a secondary role.(3)For the Antarctic,the cooling of the lower stratosphere in December,January and February is mainly explained by the loss of ozone concentration in the region.Among them,this significant cooling in December further induces the acceleration of polar vortex,and the planetary wave propagation environment becomes more advantageous to wavenumber-1planetary wave activity to propagate higher into the stratosphere,which dominates the warming of the middle stratosphere.In addition,the dynamic heating due to the change of the lower boundary condition and the short-wave heating caused by the increase of local ozone concentration also have some contribution to the warming.The warming of the middle stratosphere in January is jointly affected by the increase of local short-wave heating of ozone and the strengthening of the upward propagation of the planetary wavenumber-1 caused by the change of the lower boundary condition,and the two effects were equivalent.The weak warming of the middle stratosphere in February is mainly related to the change of the lower boundary condition,and the increase of local ozone concentration also has a little bit of contribution.