Propagation of the Arctic Oscillation from the stratosphere to the troposphere
Propagation of the Arctic Oscillation from the stratosphere to the troposphere
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DOI：
10.1029/1999jd900445
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发表时间：
1999-12-27
影响因子：
4.4
通讯作者：
Dunkerton, TJ
中科院分区：
文献类型：
--
作者：
Baldwin, MP;Dunkerton, TJ
从地球表面到北半球平流层中部的地势异常由一种称为北极涛动（AO）的变率模式主导。冬季地势在1000 ~ 10 hPa之间低频变率的主导模态（第一经验正交函数）表示AO。在平流层中部，AO的特征是一个几乎纬向对称的模式，代表一个强或弱的极涡。在1000 hPa时，AO与北大西洋涛动相似，但具有更多的纬向对称性，特别是在高纬度地区。在纬向平均风中，AO被看作是一个以北纬40度-45度为中心的南北向偶极子；在纬向平均温度中，它被视为从对流层上层到类似于10 hPa的深暖或冷极异常。对流层中AO型与平流层极涡强度调制的关联，可能是平流层和对流层之间耦合的最佳测量方法。通过检查;对流层和平流层AO特征的时间序列分析表明，AO异常通常首先出现在平流层，然后向下传播。当地表距平时间序列滞后约3周时，90 d低通滤后10-hPa距平与1000-hPa距平的隆冬相关性超过0.65。AO异常的对流层特征表现为风暴路径和对流层中气流强度的显著变化，特别是北大西洋和欧洲上空。讨论了大平流层异常作为对流层天气模式变化前兆的含义。
Geopotential anomalies ranging from the Earth's surface to the middle stratosphere in the northern hemisphere are dominated by a mode of variability known as the Arctic Oscillation (AO). The AO is represented herein by the leading mode (the first empirical orthogonal function) of low-frequency variability of wintertime geopotential between 1000 and 10 hPa. In the middle stratosphere the signature of the AO is a nearly zonally symmetric pattern representing a strong or weak polar vortex. At 1000 hPa the AO is similar to the North Atlantic Oscillation, but with more zonal symmetry, especially at high latitudes. In zonal-mean zonal wind the AO is seen as a north-south dipole centered on 40 degrees-45 degrees N; in zonal-mean temperature it is seen as a deep warm or cold polar anomaly from the upper troposphere to similar to 10 hPa. The association of the AO pattern in the troposphere with modulation of the strength of the stratospheric polar vortex provides perhaps the best measure of coupling between the stratosphere and the troposphere. By examining; separately time series of AO signatures at tropospheric and stratospheric levels, it is shown that AO anomalies typically appear first in the stratosphere and propagate downward. The midwinter correlation between the 90-day low-pass-filtered 10-hPa anomaly and the 1000-hPa anomaly exceeds 0.65 when the surface anomaly time series is lagged by about three weeks. The tropospheric signature of the AO anomaly is characterized by substantial changes to the storm tracks and strength of the midtropospheric flow especially over the North Atlantic and Europe. The implications of large stratospheric anomalies as precursors to changes in tropospheric weather patterns are discussed.