Suppressed migrating diurnal tides in the mesosphere and lower thermosphere region during El Niño in northern winter and its possible mechanism
Suppressed migrating diurnal tides in the mesosphere and lower thermosphere region during El Niño in northern winter and its possible mechanism
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北方冬季厄尔尼诺现象对中层和低热层区日潮迁移的抑制及其可能机制
DOI：
10.5194/acp-22-7861-2022
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发表时间：
2022-06
影响因子：
6.3
通讯作者：
Xiankang Dou
中科院分区：
文献类型：
--
作者：
Yetao Cen;Chengyun Yang;Tao Li;James M. Russell III;Xiankang Dou
抽象的。根据宽带辐射探测大气（SABER）的观测结果，在2002 - 2020年北方半球冬季（12 - 1 - 2月）厄尔尼诺期间，中层上层和低热层（MLT）区域的迁移日潮（DW 1）减少了约10%。根据多元线性回归（MLR）分析，在SABER观测和SD-WACCM（全大气共同体气候模式的特定动力学版本）模拟中，厄尔尼诺对热带MLT DW 1的线性影响都是显著负的。北半球冬季DW 1对厄尔尼诺的响应比其年平均响应强得多。SD-WACCM模拟结果表明，热带MLT区DW 1分潮的变化以Hough模态（1，1）为主。对流层顶区和MLT区（1，1）模的一致性以及15 ~ 100 km的向下位相变化表明，DW 1是从对流层激发源直接向上传播的。在厄尔尼诺冬季期间，热带对流层（平均高度为100 -16 km，35 ° S-35 ° N）的DW 1加热率受到抑制，导致DW 1潮汐减弱。为了评估重力波（GW）对潮汐的影响，GW强迫计算为GW阻力加权DW 1 GW阻力和DW 1风之间的相位关系。在厄尔尼诺冬季，热带上层中层的负GW强迫将显著抑制MLT DW 1潮。这种潮汐-GW相互作用可能是MLT中DW 1对厄尔尼诺响应的主导机制。在厄尔尼诺冬季，绝对涡度和行星涡度（R）之比的增加抑制了波导，从而抑制了副热带中层的DW 1振幅。然而，由于波导的响应相对较弱，波导的作用可能起次要作用。
Abstract. As observed by the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER), the migrating diurnal tide (DW1) in the upper mesosphere and lower thermosphere (MLT) region decreased by ∼ 10 % during El Niño in the Northern Hemisphere (NH) winter (December–January–February) from 2002 to 2020. According to the multiple linear regression (MLR) analysis, the linear effects of El Niño on the tropical MLT DW1 are significantly negative in both SABER observations and SD-WACCM (the Specified-Dynamics version of the Whole Atmosphere Community Climate Model) simulations. The DW1 response to El Niño in NH winter is much stronger than its annual mean response. As suggested by SD-WACCM simulation, Hough mode (1, 1) dominates the DW1 tidal variation in the tropical MLT region. The consistency between the (1, 1) mode in the tropopause region and the MLT region and the downward phase progression from 15 to 100 km indicates the direct upward propagation of DW1 from the excitation source in the troposphere. The suppressed DW1 heating rates in the tropical troposphere (averaged over ∼ 0–16 km and 35∘ S–35∘ N) during El Niño winter contribute to the decreased DW1 tide. To evaluate the effect of the gravity waves (GWs) on the tide, the GW forcing is calculated as the GW drag weighted by the phase relation between DW1 GW drag and DW1 wind. The negative GW forcing in the tropical upper mesosphere would significantly suppress the MLT DW1 tide during El Niño winter. This tide–GW interaction could be a dominant mechanism for DW1 response in the MLT to El Niño. During El Niño winter, the increased ratio of the absolute and planetary vorticity (R) suppresses the waveguide and thus the DW1 amplitude in the subtropical mesosphere. However, the effect of the waveguide might play a secondary role due to its relatively weak response.
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DOI：
10.1186/1880-5981-66-103
发表时间：
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期刊：
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