Causes of non-stationary relationships between geomagnetic activity and the North Atlantic Oscillation

Kód výsledku v IS VaVaI

<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F67985530%3A_____%2F19%3A00502274" target="_blank" >RIV/67985530:_____/19:00502274 - isvavai.cz</a>

Výsledek na webu

<a href="https://www.sciencedirect.com/science/article/abs/pii/S136468261830378X?via%3Dihub" target="_blank" >https://www.sciencedirect.com/science/article/abs/pii/S136468261830378X?via%3Dihub</a>

DOI - Digital Object Identifier

<a href="http://dx.doi.org/10.1016/j.jastp.2019.01.017" target="_blank" >10.1016/j.jastp.2019.01.017</a>

Jazyk výsledku

angličtina

Název v původním jazyce

Causes of non-stationary relationships between geomagnetic activity and the North Atlantic Oscillation

Popis výsledku v původním jazyce

The North Atlantic Oscillation (NAO) is known to be influenced by internal variability of the atmosphere and the ocean and respond to natural or anthropogenic external forcing. However, there is no consensus on the exact mechanisms. The NAO correlates with geomagnetic activity (considered as the parameter for the solar wind intensity) positively during one period (i.e. 1951-1996) but negatively in another period (i.e.1870-1950), making the Sun-climate connection a controversial subject. We try to explain this non-stationary relationship and to find the causes why the correlation had changed the sign during the past 148 years. At the times of low geomagnetic activity before 1950 and after 1997 the correlation between geomagnetic activity and the NAO was relatively weak. The variability of the NAO during those periods was mainly due to other processes. In order to answer the question why a more positive NAO phase has prevailed over the last 30 years of the past century, we study the geomagnetic signal near the surface conditioning upon the strength, shape and location of the stratospheric polar vortex and examine the immediate effect of geomagnetic storms in the troposphere. At times of prevailing high geomagnetic activity (1951-1996) the polar vortex strengthened. The effect of the solar wind was mainly over northern Europe in association with the positive phase of the NAO. A strengthened mid-latitude westerly jet kept the cold air in the Arctic and northern mid-latitudes became milder than average. When geomagnetic activity decreased, the stratospheric polar vortex also weakened. The solar wind signal prevailed over Canada in association with the negative NAO index and more of Arctic air was able to penetrate North America and Eurasia. We finally show that the geomagnetic storms may play a role in the acceleration of the downward penetration of pressure anomalies from the upper stratosphere into the troposphere.

Název v anglickém jazyce

Causes of non-stationary relationships between geomagnetic activity and the North Atlantic Oscillation

Popis výsledku anglicky

The North Atlantic Oscillation (NAO) is known to be influenced by internal variability of the atmosphere and the ocean and respond to natural or anthropogenic external forcing. However, there is no consensus on the exact mechanisms. The NAO correlates with geomagnetic activity (considered as the parameter for the solar wind intensity) positively during one period (i.e. 1951-1996) but negatively in another period (i.e.1870-1950), making the Sun-climate connection a controversial subject. We try to explain this non-stationary relationship and to find the causes why the correlation had changed the sign during the past 148 years. At the times of low geomagnetic activity before 1950 and after 1997 the correlation between geomagnetic activity and the NAO was relatively weak. The variability of the NAO during those periods was mainly due to other processes. In order to answer the question why a more positive NAO phase has prevailed over the last 30 years of the past century, we study the geomagnetic signal near the surface conditioning upon the strength, shape and location of the stratospheric polar vortex and examine the immediate effect of geomagnetic storms in the troposphere. At times of prevailing high geomagnetic activity (1951-1996) the polar vortex strengthened. The effect of the solar wind was mainly over northern Europe in association with the positive phase of the NAO. A strengthened mid-latitude westerly jet kept the cold air in the Arctic and northern mid-latitudes became milder than average. When geomagnetic activity decreased, the stratospheric polar vortex also weakened. The solar wind signal prevailed over Canada in association with the negative NAO index and more of Arctic air was able to penetrate North America and Eurasia. We finally show that the geomagnetic storms may play a role in the acceleration of the downward penetration of pressure anomalies from the upper stratosphere into the troposphere.

Druh

J_imp - Článek v periodiku v databázi Web of Science

CEP obor

—

OECD FORD obor

10510 - Climatic research

Projekt

—

Návaznosti

I - Institucionalni podpora na dlouhodoby koncepcni rozvoj vyzkumne organizace

Rok uplatnění

2019

Kód důvěrnosti údajů

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

Název periodika

Journal of Atmospheric and Solar-Terrestrial Physics

ISSN

1364-6826

e-ISSN

—

Svazek periodika

188

Číslo periodika v rámci svazku

April

Stát vydavatele periodika

GB - Spojené království Velké Británie a Severního Irska

Počet stran výsledku

7

Strana od-do

43-49

Kód UT WoS článku

000461405100005

EID výsledku v databázi Scopus

2-s2.0-85061402276