Academic Journal
Effect of latitudinally displaced gravity wave forcing in the lower stratosphere on the polar vortex stability
| العنوان: | Effect of latitudinally displaced gravity wave forcing in the lower stratosphere on the polar vortex stability |
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| المؤلفون: | Samtlebeng, Nadja, Jacobi, Christoph, Pišoft, Petr, Sacha , Petr, Kuchař, Aleš |
| بيانات النشر: | Annales Geophysicae |
| سنة النشر: | 2019 |
| المجموعة: | University of Vigo: Investigo (Repositorio Institucional de la Universidade de Vigo) |
| مصطلحات موضوعية: | 2501 Ciencias de la Atmósfera |
| الوصف: | In order to investigate the impact of a locally confined gravity wave (GW) hotspot, a sensitivity study based on simulations of the middle atmosphere circulation during northern winter was performed with a nonlinear, mechanistic, general circulation model. To this end, we selected a fixed longitude range in the East Asian region (120–170∘ E) and a latitude range from 22.5 to 52.5∘ N between 18 and 30 km for the hotspot region, which was then shifted northward in steps of 5∘. For the southernmost hotspots, we observe a decreased stationary planetary wave (SPW) with wave number 1 (SPW 1) activity in the upper stratosphere and lower mesosphere, i.e., fewer SPWs 1 are propagating upwards. These GW hotspots lead to a negative refractive index, inhibiting SPW propagation at midlatitudes. The decreased SPW 1 activity is connected to an increased zonal mean zonal wind at lower latitudes. This, in turn, decreases the meridional potential vorticity gradient (qy) from midlatitudes towards the polar region. A reversed qy indicates local baroclinic instability, which generates SPWs with wave number 1 in the polar region, where we observe a strong positive Eliassen–Palm (EP) divergence. As a result, the EP flux increases towards the polar stratosphere (corresponding to enhanced SPW 1 amplitudes), where the SPWs with wave number 1 break, and the zonal mean zonal wind decreases. Thus, the local GW forcing leads to a displacement of the polar vortex towards lower latitudes. The effect of the local baroclinic instability indicated by the reversed qy also produces SPWs with wave number 1 in the lower mesosphere. The effect on the dynamics in the middle atmosphere due to GW hotspots that are located northward of 50∘ N is negligible, as the refractive index of the atmosphere is strongly negative in the polar region. Thus, any changes in the SPW activity due to the local GW forcing are quite ineffective ; Deutsche Forschungsgemeinschaft | Ref. JA836/32-1 ; Xunta de Galicia | Ref. ED481B 2018/103 ; Ministerio de Ciencia e Innovación | ... |
| نوع الوثيقة: | article in journal/newspaper |
| اللغة: | English |
| تدمد: | 14320576 |
| Relation: | info:eu-repo/grantAgreement/MICINN//CGL2015-71575-P/ES; Annales Geophysicae, 37(4): 507-523 (2019); http://hdl.handle.net/11093/4199; https://angeo.copernicus.org/articles/37/507/2019/ |
| DOI: | 10.5194/angeo-37-507-2019 |
| الاتاحة: | http://hdl.handle.net/11093/4199 https://doi.org/10.5194/angeo-37-507-2019 https://angeo.copernicus.org/articles/37/507/2019/ |
| Rights: | Attribution 4.0 International ; https://creativecommons.org/licenses/by/4.0/ ; openAccess |
| رقم الانضمام: | edsbas.7AEF036B |
| قاعدة البيانات: | BASE |
Full Text Finder | تدمد: | 14320576 |
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| DOI: | 10.5194/angeo-37-507-2019 |