Effect of latitudinally displaced gravity wave forcing in the lower stratosphere on the polar vortex stability
The result's identifiers
Result code in IS VaVaI
<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F00216208%3A11320%2F19%3A10405896" target="_blank" >RIV/00216208:11320/19:10405896 - isvavai.cz</a>
Result on the web
<a href="https://verso.is.cuni.cz/pub/verso.fpl?fname=obd_publikace_handle&handle=P-P8d9298e" target="_blank" >https://verso.is.cuni.cz/pub/verso.fpl?fname=obd_publikace_handle&handle=P-P8d9298e</a>
DOI - Digital Object Identifier
<a href="http://dx.doi.org/10.5194/angeo-37-507-2019" target="_blank" >10.5194/angeo-37-507-2019</a>
Alternative languages
Result language
angličtina
Original language name
Effect of latitudinally displaced gravity wave forcing in the lower stratosphere on the polar vortex stability
Original language description
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 degrees E) and a latitude range from 22.5 to 52.5 degrees N between 18 and 30 km for the hotspot region, which was then shifted northward in steps of 5 degrees. 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 (q(y)) from midlatitudes towards the polar region. A reversed q(y) 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 q(y) also produces SPWs with wave number 1 in the lower mesosphere. The effect on the dynam-ics in the middle atmosphere due to GW hotspots that are located northward of 50 degrees 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.
Czech name
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Czech description
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Classification
Type
J<sub>imp</sub> - Article in a specialist periodical, which is included in the Web of Science database
CEP classification
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OECD FORD branch
10509 - Meteorology and atmospheric sciences
Result continuities
Project
Result was created during the realization of more than one project. More information in the Projects tab.
Continuities
P - Projekt vyzkumu a vyvoje financovany z verejnych zdroju (s odkazem do CEP)
Others
Publication year
2019
Confidentiality
S - Úplné a pravdivé údaje o projektu nepodléhají ochraně podle zvláštních právních předpisů
Data specific for result type
Name of the periodical
Annales Geophysicae
ISSN
0992-7689
e-ISSN
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Volume of the periodical
37
Issue of the periodical within the volume
4
Country of publishing house
DE - GERMANY
Number of pages
17
Pages from-to
507-523
UT code for WoS article
000473681000001
EID of the result in the Scopus database
2-s2.0-85068471793