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首页> 外文期刊>Journal of the Atmospheric Sciences >To What Extent Does High-Latitude Wave Forcing Drive Tropical Upwelling in the Brewer-Dobson Circulation?
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To What Extent Does High-Latitude Wave Forcing Drive Tropical Upwelling in the Brewer-Dobson Circulation?

机译：高纬度波在多大程度上推动了Brewer-Dobson环流中的热带上升？

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摘要

The causes of the annual cycle and nonseasonal variability in the globally averaged, equator-to-pole Brewer Dobson circulation (BDC: defined here as the equatorially symmetric component of the Lagrangian-mean meridional circulation) are investigated based on zonally averaged, lower-stratospheric temperature data from satellite-borne Microwave Sounding Unit (MSU) and Advanced Microwave Sounding Unit (AMSU). Time-varying vertical velocities in the BDC are inferred from departures of the meridional temperature profiles from the respective radiative equilibrium temperature profiles. Equatorward of similar to 45 degrees N/S, the annual-mean profile of lower-stratospheric temperature and the seasonal and nonseasonal variations about it project almost exclusively onto the equatorially symmetric component. The climatological-mean annual cycle accounts for nearly 90% of the month-to-month variance of the equatorially symmetric component of the temperature field; January/February is colder than July/August equatorward of similar to 45 degrees N/S and warmer than July/August poleward of that latitude. The equator-to-subpolar temperature contrast roughly doubles from July/August to January/February, implying an approximate doubling of the strength of the BDC. The nonseasonal variability is dominated by a similar pattern. Tropical upwelling in the BDC, as inferred from of the temperature field, varies in response to variations in eddy heat fluxes at high latitudes with comparable strength on the intraseasonal and interannual time scales; it does not appear to be correlated with equatorial tropospheric planetary wave activity or with variations in wave forcing in subtropical lower stratosphere. It is concluded that high-latitude wave forcing plays an important role in modulating tropical upwelling in the BDC across a wide range of frequencies.
机译：基于纬向平均的低平流层，研究了全球平均的赤道至极布鲁尔·多布森环流（BDC：此处定义为拉格朗日平均子午环流的赤道对称分量）的年周期和非季节变化的原因。来自卫星微波测深仪（MSU）和高级微波测深仪（AMSU）的温度数据。从子午温度曲线与相应的辐射平衡温度曲线的偏离可以推断出BDC中的时变垂直速度。接近45度N / S的赤道，低平流层温度的年平均廓线及其附近的季节和非季节变化几乎都投影在赤道对称分量上。气候平均年周期约占温度场赤道对称部分逐月变化的90％。一月/二月比七月/八月赤道冷，大约为45度N / S，比七月/八月的赤道偏冷。从七月/八月到一月/二月，赤道到亚极的温度差大约翻倍，这意味着BDC的强度大约翻倍。非季节性变化主要由相似的模式决定。从温度场推断，BDC的热带上升变化是响应高纬度涡流通量的变化而变化的，在季节内和年际时间尺度上强度相当;它似乎与赤道对流层行星波活动或与亚热带低平流层的波强迫变化无关。结论是，高纬度的强迫作用在广泛频率范围内的BDC热带上升过程中起着重要作用。

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