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Sudden Stratospheric Warming (SSW) is considered one extreme of polar stratospheric dynamic variability. During this extreme circulation variability, sudden warming at the stratospheric levels is seen to occur within a few days. There is a weakening of mean flow at the stratospheric level due to the strong two-way nonlinear interactions between upward propagating planetary waves and the mean flow. Recent studies have shown that the upper atmosphere's response during a particular SSW event may differ from that observed during another SSW occurrence. More studies are required to comprehensively organize the effects of SSWs on the upper atmosphere, especially in the ionosphere. This work focuses on understanding the SSW's impact on ionosphere dynamics, especially at high and mid-latitudes combining datasets obtained from atmospheric and ionospheric measurements and modeling. The individual characteristics of an SSW event are analyzed using the meteorological parameters retrieved from the reanalysis data. The global Total Electron Content (TEC) maps and the ground magnetometer data are used to understand the ionospheric response during the SSW event. The forcing due to the atmosphere-ionosphere vertical coupling during the SSW event is studied using the Chemistry Transport Model of the Leibniz Institute of Atmospheric Physics (CTM-IAP). Ionospheric responses during these event periods are analyzed using the outputs from the CTM-IAP. The study details the plasma density variability in the ionosphere during an SSW event.

Lastovicka (2021, 2023) found some differences in the dependence of yearly values foF2 on solar activity when different solar activity proxies were used. He used F10.7, F30, Mg II, solar H Lyman-α flux, sunspot numbers and He II. F30 followed by Mg II were established to be the optimum solar activity proxies, not traditionally used F10.7 and sunspot numbers, for yearly values of foF2. Here we use data of six ionospheric stations from four continents, Juliusruh, Pruhonice, Roma, Boulder, Kokubunji and Canberra, which reveal somewhat and sometimes even substantially different trends of foF2 when the effect of solar cycle is removed/reduced from foF2 data with different solar activity proxies., The 28th IUGG General Assembly (IUGG2023) (Berlin 2023)

WOS; International audience

The EU CANDIDOZ project investigated the chemical and dynamical influences on decadal ozone trends focusing on the Northern Hemisphere. High quality long-term ozone data sets, satellite-based as well as ground-based, and the long-term meteorological reanalyses from ECMWF and NCEP are used together with advanced multiple regression models and atmospheric models to assess the relative roles of chemistry and transport in stratospheric ozone changes. This overall synthesis of the individual analyses in CANDIDOZ shows clearly one common feature in the NH mid latitudes and in the Arctic: an almost monotonic negative trend from the late 1970s to the mid 1990s followed by an increase. In most trend studies, the Equivalent Effective Stratospheric Chlorine (EESC) which peaked in 1997 as a consequence of the Montreal Protocol was observed to describe ozone loss better than a simple linear trend. Furthermore, all individual analyses point to changes in dynamical drivers, such as the residual circulation (responsible for the meridional transport of ozone into middle and high latitudes) playing a key role in the observed turnaround. The changes in ozone transport are associated with variations in polar chemical ozone loss via heterogeneous ozone chemistry on PSCs (polar stratospheric clouds). Synoptic scale processes as represented by the new equivalent latitude proxy, by conventional tropopause altitude or by 250 hPa geopotential height have also been successfully linked to the recent ozone increases in the lowermost stratosphere. These show significant regional variation with a large impact over Europe and seem to be linked to changes in tropospheric climate patterns such as the North Atlantic Oscillation. Some influence in recent ozone increases was also attributed to the rise in solar cycle number 23. Changes from the late 1970s to the mid 1990s were found in a number of characteristics of the Arctic vortex. However, only one trend was found when more recent years are also considered, namely the tendency for cold winters to become colder.

ISSN : 1364-6826; International audience

The EU CANDIDOZ project investigated the chemical and dynamical influences on decadal ozone trends focusing on the Northern Hemisphere. High quality long-term ozone data sets, satellite-based as well as ground-based, and the long-term meteorological reanalyses from ECMWF and NCEP are used together with advanced multiple regression models and atmospheric models to assess the relative roles of chemistry and transport in stratospheric ozone changes. This overall synthesis of the individual analyses in CANDIDOZ shows clearly one common feature in the NH mid latitudes and in the Arctic: an almost monotonic negative trend from the late 1970s to the mid 1990s followed by an increase. In most trend studies, the Equivalent Effective Stratospheric Chlorine (EESC) which peaked in 1997 as a consequence of the Montreal Protocol was observed to describe ozone loss better than a simple linear trend. Furthermore, all individual analyses point to changes in dynamical drivers, such as the residual circulation (responsible for the meridional transport of ozone into middle and high latitudes) playing a key role in the observed turnaround. The changes in ozone transport are associated with variations in polar chemical ozone loss via heterogeneous ozone chemistry on PSCs (polar stratospheric clouds). Synoptic scale processes as represented by the new equivalent latitude proxy, by conventional tropopause altitude or by 250 hPa geopotential height have also been successfully linked to the recent ozone increases in the lowermost stratosphere. These show significant regional variation with a large impact over Europe and seem to be linked to changes in tropospheric climate patterns such as the North Atlantic Oscillation. Some influence in recent ozone increases was also attributed to the rise in solar cycle number 23. Changes from the late 1970s to the mid 1990s were found in a number of characteristics of the Arctic vortex. However, only one trend was found when more recent years are also considered, namely the tendency for cold winters to become colder. ISSN:0992-7689 ISSN:0939-4176 ISSN:1432-0576