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Multi-model assessment of the late-winter stratospheric response to El Niño and La Niña
Climate Dynamics ( IF 4.6 ) Pub Date : 2021-06-13 , DOI: 10.1007/s00382-021-05836-3
Bianca Mezzina , Froila M. Palmeiro , Javier García-Serrano , Ileana Bladé , Lauriane Batté , Marianna Benassi

The impact of El Niño-Southern Oscillation (ENSO) on the late-winter extra-tropical stratosphere (January–March) is assessed in a multi-model framework. Three state-of-the-art atmospheric models are run with prescribed SST anomalies representative of a strong ENSO event, with symmetric patterns for El Niño and La Niña. The well-known temperature perturbation in the lower stratosphere during El Niño is captured by two models, in which the anomalous warming at polar latitudes is accompanied by a positive geopotential height anomaly that extends over the polar cap. In the third model, which shows a lack of temperature anomalies over the pole, the anomalous anticyclone is confined over Canada and does not expand to the polar cap. This anomalous center of action emerges from the large-scale tropospheric Rossby wave train forced by ENSO, and shrinking/stretching around the polar vortex is invoked to link it to the temperature response. No disagreement across models is found in the lower stratosphere for La Niña, whose teleconnection is opposite in sign but weaker. In the middle-upper stratosphere (above 50 hPa) the geopotential height anomalies project on a wavenumber-1 (WN1) pattern for both El Niño and, more weakly, La Niña, and show a westward tilt with height up to the stratopause. It is suggested that this WN1 pattern arises from the high-latitude lower-stratospheric anomalies, and that the ENSO teleconnection to the polar stratosphere can be interpreted in terms of upward propagation of the stationary Rossby wave train and quasi-geostrophic balance, instead of wave breaking.



中文翻译:

晚冬平流层对厄尔尼诺和拉尼娜反应的多模式评估

厄尔尼诺-南方涛动 (ENSO) 对晚冬温带平流层(1 月至 3 月)的影响在多模式框架中进行评估。三个最先进的大气模型使用代表强 ENSO 事件的规定 SST 异常运行,厄尔尼诺和拉尼娜具有对称模式。厄尔尼诺现象期间平流层下层众所周知的温度扰动由两个模型捕捉,其中极地纬度的异常变暖伴随着延伸到极冠的正位势高度异常。在第三个模型中,极地没有温度异常,异常反气旋被限制在加拿大上空,没有扩展到极冠。这个异常的活动中心来自由 ENSO 强迫的大规模对流层罗斯比波列,并调用极涡周围的收缩/拉伸以将其与温度响应联系起来。拉尼娜现象在平流层下层没有发现不同模型的分歧,其遥相关符号相反但较弱。在平流层中上层(50 hPa 以上),对于厄尔尼诺和更弱的拉尼娜,位势高度异常投射在波数 1 (WN1) 模式上,并显示向西倾斜,高度达到平流层顶。建议这种 WN1 模式源于高纬度低平流层异常,并且 ENSO 与极地平流层的遥相关可以解释为静止罗斯比波列和准地转平衡的向上传播,而不是波打破。拉尼娜现象在平流层下层没有发现不同模型的分歧,其遥相关符号相反但较弱。在平流层中上层(50 hPa 以上),对于厄尔尼诺和更弱的拉尼娜,位势高度异常投射在波数 1 (WN1) 模式上,并显示出随着高度上升到平流层顶而向西倾斜。建议这种 WN1 模式源于高纬度低平流层异常,并且 ENSO 与极地平流层的遥相关可以解释为静止罗斯比波列和准地转平衡的向上传播,而不是波打破。拉尼娜现象在平流层下层没有发现不同模型的分歧,其遥相关符号相反但较弱。在平流层中上层(50 hPa 以上),对于厄尔尼诺和更弱的拉尼娜,位势高度异常投射在波数 1 (WN1) 模式上,并显示向西倾斜,高度达到平流层顶。建议这种 WN1 模式源于高纬度低平流层异常,并且 ENSO 与极地平流层的遥相关可以解释为静止罗斯比波列和准地转平衡的向上传播,而不是波打破。在平流层中上层(50 hPa 以上),对于厄尔尼诺和更弱的拉尼娜,位势高度异常投射在波数 1 (WN1) 模式上,并显示出随着高度上升到平流层顶而向西倾斜。建议这种 WN1 模式源于高纬度低平流层异常,并且 ENSO 与极地平流层的遥相关可以解释为静止罗斯比波列和准地转平衡的向上传播,而不是波打破。在平流层中上层(50 hPa 以上),对于厄尔尼诺和更弱的拉尼娜,位势高度异常投射在波数 1 (WN1) 模式上,并显示出随着高度上升到平流层顶而向西倾斜。建议这种 WN1 模式源于高纬度低平流层异常,并且 ENSO 与极地平流层的遥相关可以解释为静止罗斯比波列和准地转平衡的向上传播,而不是波打破。

更新日期:2021-06-14
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