摘要
平流层剩余环流是由剩余速度ν^-＊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NCEPⅡ再分析资料计算了剩余速度ν^-＊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。
The stratospheric residual circulation is defined as the meridional and vertical components of the stratospheric motion while its latitudinal component is dominated, which plays an important role in the interaction and mass exchange between stratosphere and troposphere. The NCEP/NCAR Reanalysis Data from 1979 to 2003 are used to estimate the stratospheric residual circulation, and the model simulations are compared with the estimation. The results show that the estimation matches the model simulations well and the well-known Brewer-Dobson circulation can be clearly seen in the estimation. This work also shows that the residual circulation has obviously seasonal change. The center of ascending motion swings around the equator with seasonal variation. In spring and autumn, the center lies over the equator, and the ascending motion distribute symmetrically in the both hemispheres while the downwelling motion at the Northern middle latitudes is stronger than that of the Southern Hemisphere. In winter and summer, the center of upwelling lies at 10°S and 10°N, respectively. And the upwelling which appears in the Northern Hemisphere is stronger than that in the Southern Hemisphere while the downwelling in the winter hemisphere is stronger than that in the summer hemisphere. In addition, the residual circulation has interannual change and quasi-biennial oscillation. The upwelling and horizontal transport is stronger in the easterly phase than those in the westerly phase of tropical zonal winds. The residual circulation decadal variation shows that the circulation is relatively stronger in those years.. 1979 - 1983, 1990 - 1995, 2000 - 2003. Generally, the residual vertical velocity has been a little enhanced in the last 25 years, at the same time the transport towards middle latitude in low stratosphere also has become stronger.
出处
《大气科学》
CSCD
北大核心
2007年第1期137-144,共8页
Chinese Journal of Atmospheric Sciences
基金
国家自然科学基金资助项目40375012
