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利用美国SAGEII(Stratospheric Aerosol and Gas Experiment Ⅱ)卫星最新版(6.0版)1.020μm通道逐日气溶胶消光系数资料,得出了对流层中上层及平流层(10km以上高度)气溶胶光学厚度的平均分布和变化特征。结果表明:气溶胶光学厚度在低纬度大,在印度洋的岛屿上空有三个高值中心,气溶胶光学厚度高值中心与对流层中上层的上升气流的高值中心相对应。与17年(1984~2000年)年平均相比,近6年(1995~2000年)盂加拉湾至青藏高原东南部上空气溶胶光学厚度明显增加;中国东部地区上空气溶胶光学厚度增加,中西部地区则减小。气溶胶光学厚度存在三个经向的增加带和两个经向的减小带。中纬度与赤道之间的布鲁尔—多普森环流(Brewer—Dobson Circulation)带来的低层大气与对流层中上层及平流层之间的气溶胶输送是导致气溶胶这种经向一致变化的主要因素。气溶胶的这种输送产生的近地面大气污染物向中上层大气输送有可能产生重要的气候变化。  相似文献   
2.
Using the outputs from 16 chemistry-climate models(CCMs), the trends of lower- to mid-stratospheric water vapor(WV) during the period 1980–2005 were studied. Comparisons were made between the CCM results and European Centre for Medium-Range Weather Forecasts(ECMWF) Interim Reanalysis(ERA-Interim).The results of most of the CCMs, and those based on ERA-Interim, showed the trends of lower- to mid-stratospheric WV during the period 1980–2005 to be positive, with the extent of the trend increasing with altitude. The trend of lower- to mid-stratospheric WV in the ensemble mean of the CCMs was 0.03 ppmv per decade,which was about twice as large as that based on ERA-Interim. The authors also used a state-of-the-art general circulation model to evaluate the impacts of greenhouse gas(GHG) concentration increases and ozone depletion on stratospheric WV. The simulation results showed that the increases of lower- to mid-stratospheric WV affected by the combined effects of GHG and ozone changes happened mainly via warming of the tropopause and enhancement of the Brewer-Dobson circulation(BDC), with the former being the greater contributor.GHG increase led to a higher and warmer tropopause with stronger BDC, which in turn led to more WV entering the stratosphere; while ozone depletion led to a higher and cooler tropopause, which caused the decreases of lowerto mid-stratospheric WV, despite also causing stronger BDC.  相似文献   
3.
Using a state-of-the-art chemistry-climate model,we analyzed the atmospheric responses to increases in sea surface temperature (SST).The results showed that increases in SST and the SST meridional gradient could intensify the subtropical westerly jets and significantly weaken the northern polar vortex.In the model runs,global uniform SST increases produced a more significant impact on the southern stratosphere than the northern stratosphere,while SST gradient increases produced a more significant impact on the northern stratosphere.The asymmetric responses of the northern and southern polar stratosphere to SST meridional gradient changes were found to be mainly due to different wave properties and transmissions in the northern and southern atmosphere.Although SST increases may give rise to stronger waves,the results showed that the effect of SST increases on the vertical propagation of tropospheric waves into the stratosphere will vary with height and latitude and be sensitive to SST meridional gradient changes.Both uniform and non-uniform SST increases accelerated the large-scale Brewer-Dobson circulation (BDC),but the gradient increases of SST between 60°S and 60°N resulted in younger mean age-of-air in the stratosphere and a larger increase in tropical upwelling,with a much higher tropopause than from a global uniform 1.0 K SST increase.  相似文献   
4.
平流层剩余环流及其时间演变特征   总被引:2,自引:0,他引:2       下载免费PDF全文
陈权亮  陈月娟 《大气科学》2007,31(1):136-144
平流层剩余环流是由剩余速度-v*和-ω*构成的平流层经向-垂直环流,它对于对流层-平流层相互作用和物质交换起着十分重要的作用。作者利用1979~2003年NCEP II再分析资料计算了剩余速度-v*和-ω*,并与数值模拟结果进行了比较,再用计算的剩余环流讨论了它的季节变化、年际变化和长期变化趋势。计算结果表明,剩余环流的上升气流从低纬度赤道地区对流层顶上升到平流层下部,然后向极向下运动,在中纬度地区下沉,进入对流层,这也就是Brewer-Dobson环流。计算结果同数值模拟结果比较一致。由此可见,可以利用NCEP资料得到比较清晰的剩余环流和Brewer-Dobson环流。剩余环流有明显的季节变化,上升气流的中心随着季节的变化在赤道地区南北移动,春秋季节其中心基本上位于赤道附近,南北半球大致呈对称分布,只是北半球副热带地区的下沉气流要比南半球强。在冬夏季节,上升气流的中心分别位于南北纬10°附近。北半球夏季的上升气流要比南半球夏季的上升气流强,同时冬半球的下沉气流比夏半球的下沉气流强。剩余环流还有年际变化和准两年周期振荡特征,在纬向风为西风位相时,赤道地区的上升气流比较弱;而在东风位相时,上升气流和水平方向的输送相对比较强。剩余环流的十年际变化表现为,1979~1983年、1990~1995年、2000~2003年较强,其他年份则较弱。在过去25年,就总的变化趋势而言,剩余环流的上升气流有所增强,平流层下部向中纬度地区的输送也有所增强,环流整体形势是增强的。  相似文献   
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