Climate change and the middle atmosphere: 5. Paleostratosphere in cold and warm climates
Climate change and the middle atmosphere: 5. Paleostratosphere in cold and warm climates
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气候变化与中层大气：5.寒冷和温暖气候下的古平流层
DOI：
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发表时间：
2001
期刊：
影响因子：
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通讯作者：
J. Lerner
中科院分区：
文献类型：
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作者：
D. Rind;M. Chandler;P. Lonergan;J. Lerner
GISS全球气候中层大气模型用于研究平流层在两个古时期的变化：寒冷的末次冰期最大期（2.21万年前）和温暖的古新世（5800万年前）。在敏感性实验中，研究了海面温度和山脉波拖曳冰盖的不稳定性。在许多方面，平流层的气候和动力强迫在这些时期是相反的，减少二氧化碳，增加地形，并增加纬度温度梯度在冰河时期，增加二氧化碳，减少地形和纬度温度梯度在古新世，代表了第三纪的大部分。结果表明，平流层的反应往往是相反的性质，以及与冰河时代的特点是一个温暖的平流层，增加剩余环流在平流层下部（和减少以上），并削弱极涡，而古新世模拟有一个寒冷的平流层，减少剩余环流在平流层下部（和增加以上），加强极涡。分析表明，平流层的响应是非常个性化的特定的气候制度，相反的效果不一定是由反向相关的机制。在这两种气候中，特别重要的是高纬度地区的纬度梯度降低，这削弱了高纬度的纬向风，限制了波能的垂直传播。平流层下部行星波强迫的增加加速了冰河时期的环流。在古新世纬向风的强烈增加是由于行星波强迫减少，与地形减少，并减少山波阻力。敏感性试验表明，热带海表温度越高，平流层剩余环流越强，而平流层增温对精确的海表温度规格和山波阻力越敏感。
The GISS Global Climate Middle Atmosphere Model is used to investigate how the stratosphere would have changed during two paleotime periods: the cold Last Glacial Maximum (∼21,000 years ago) and the warm Paleocene (58 million years ago). Uncertainties in sea surface temperatures and mountain wave drag over the ice sheets are investigated in sensitivity experiments. In many respects the climate and dynamical forcing of the stratosphere was opposite in these time periods, with reduced CO2, increased topography, and increased latitudinal temperature gradients during the ice age, and increased CO2, reduced topography and latitudinal temperature gradients during the Paleocene, representative of much of the Tertiary. The results show that the stratospheric response was often of an opposite nature as well, with the ice ages featuring a warmer stratosphere, increased residual circulation in the lower stratosphere (and decreased above), and weakened polar vortices, while the Paleocene simulation had a colder stratosphere, decreased residual circulation in the lower stratosphere (and increased above), with strengthened polar vortices. Analysis shows that the stratospheric response is very individualistic to the particular climate regime, and the opposite effects are not necessarily produced by inversely related mechanisms. Of particular importance in both climates is the reduced latitudinal gradient at high latitudes, which weakens high-latitude zonal winds and limits wave energy vertical propagation. Increased planetary wave forcing in the lower stratosphere accelerates the circulation during the ice ages. A strong increase in zonal winds during the Paleocene is the result of both decreased planetary wave forcing, associated with the reduced topography, and decreased mountain wave drag. The sensitivity experiments show that if tropical sea surface temperatures were warmer, the stratospheric residual circulation was enhanced, while stratospheric warmings are sensitive to the precise sea surface temperature specifications and mountain wave drag.