Effect of latitudinally displaced gravity wave forcing in the lower stratosphere on the polar vortex stability

Kód výsledku v 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>

Výsledek na webu

<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>

Jazyk výsledku

angličtina

Název v původním jazyce

Effect of latitudinally displaced gravity wave forcing in the lower stratosphere on the polar vortex stability

Popis výsledku v původním jazyce

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.

Název v anglickém jazyce

Effect of latitudinally displaced gravity wave forcing in the lower stratosphere on the polar vortex stability

Popis výsledku anglicky

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.

Druh

J_imp - Článek v periodiku v databázi Web of Science

CEP obor

—

OECD FORD obor

10509 - Meteorology and atmospheric sciences

Projekt

Výsledek vznikl pri realizaci vícero projektů. Více informací v záložce Projekty.

Návaznosti

P - Projekt vyzkumu a vyvoje financovany z verejnych zdroju (s odkazem do CEP)

Rok uplatnění

2019

Kód důvěrnosti údajů

S - Úplné a pravdivé údaje o projektu nepodléhají ochraně podle zvláštních právních předpisů

Název periodika

Annales Geophysicae

ISSN

0992-7689

e-ISSN

—

Svazek periodika

37

Číslo periodika v rámci svazku

4

Stát vydavatele periodika

DE - Spolková republika Německo

Počet stran výsledku

17

Strana od-do

507-523

Kód UT WoS článku

000473681000001

EID výsledku v databázi Scopus

2-s2.0-85068471793