scholarly journals Influence of Enhanced Planetary Wave Activity on the Polar Vortex Enhancement Related to Energetic Electron Precipitation

2020 ◽  
Vol 125 (9) ◽  
Author(s):  
Timo Asikainen ◽  
Antti Salminen ◽  
Ville Maliniemi ◽  
Kalevi Mursula
Keyword(s):  
Planetary Wave ◽  
Energetic Electron ◽  
Polar Vortex ◽  
Wave Activity ◽  
Electron Precipitation

Influence of energetic particle precipitation on polar vortex mediated by planetary wave activity

2021 ◽  
Author(s):  
Timo Asikainen ◽  
Antti Salminen ◽  
Ville Maliniemi ◽  
Kalevi Mursula
Keyword(s):  
Planetary Wave ◽  
Energetic Electron ◽  
Polar Vortex ◽  
Analysis Data ◽  
Wave Activity ◽  
Necessary Condition ◽  
Atmospheric Conditions ◽  
Mean Flow ◽  
Ozone Loss ◽  
Near Earth Space

<p>The northern polar vortex experiences considerable inter-annual variability, which is also reflected to tropospheric weather. Recent research has established a link between polar vortex variations and energetic electron precipitation (EEP) from the near-Earth space into the polar atmosphere, which is mediated by EEP-induced chemical changes causing ozone loss in the mesosphere and stratosphere. However, the most dramatic changes in the polar vortex are due to strong enhancements of planetary wave activity, which typically result in a sudden stratospheric warming (SSW), a momentary breakdown of the polar vortex. Here we use the SSWs as an indicator of high planetary wave activity and consider their influence of SSWs on the atmospheric response to EEP in 1957-2017 using combined ERA-40 and ERA-Interim re-analysis data and geomagnetic activity as a proxy of EEP. We find that the EEP-related enhancement of the polar vortex and other associated dynamical responses are seen only during winters when a SSW occurs, and that the EEP-related changes take place slightly before the SSW onset. We show that the atmospheric conditions preceding SSWs favor enhanced wave-mean-flow interaction, which can dynamically amplify the initial polar vortex enhancement caused by ozone loss. These results highlight the importance of considering SSWs and sufficient level of planetary wave activity as a necessary condition for observing the effects of EEP on the polar vortex dynamics.</p>

Influence of sudden stratospheric warmings on the polar vortex enhancement related to energetic electron precipitation

2020 ◽  
Author(s):  
Timo Asikainen ◽  
Antti Salminen ◽  
Ville Maliniemi ◽  
Kalevi Mursula
Keyword(s):  
Planetary Wave ◽  
Energetic Electron ◽  
Polar Vortex ◽  
Analysis Data ◽  
Electron Precipitation ◽  
Necessary Condition ◽  
Atmospheric Conditions ◽  
Mean Flow ◽  
Ozone Loss ◽  
Near Earth Space

<p>The northern polar vortex experiences considerable inter-annual variability, which is also reflected to tropospheric weather. Recent research has established a link between polar vortex variations and energetic electron precipitation (EEP) from the near-Earth space into the polar atmosphere, which is mediated by EEP-induced chemical changes causing ozone loss in the mesosphere and stratosphere. However, the most dramatic changes in the polar vortex are due to sudden stratospheric warmings (SSW), a momentary breakdown of the polar vortex associated to enhanced planetary wave convergence and meridional circulation. Here we consider the influence of SSWs on the atmospheric response to EEP in 1957-2017 using combined ERA-40 and ERA-Interim re-analysis data and geomagnetic activity as a proxy of EEP. We find that the EEP-related enhancement of the polar vortex and other associated dynamical responses are seen only during winters when a SSW occurs, and that the EEP-related changes take place slightly before the SSW onset. We show that the atmospheric conditions preceding SSWs favor enhanced wave-mean-flow interaction, which can dynamically amplify the initial polar vortex enhancement caused by ozone loss. These results highlight the importance of considering SSWs and sufficient level of planetary wave activity as a necessary condition for observing the effects of EEP on the polar vortex dynamics.</p>

Final Sudden Stratospheric Warmings and the memory of the stratosphere

2021 ◽  
Author(s):  
Alain Hauchecorne ◽  
Chantal Claud ◽  
Philippe Keckhut
Keyword(s):  
Zonal Wind ◽  
Planetary Wave ◽  
Middle Atmosphere ◽  
Temperature Anomaly ◽  
Polar Vortex ◽  
Wave Activity ◽  
Late Winter ◽  
Easterly Wind ◽  
Weather Forecasts ◽  
Stratospheric Circulation

<p>Sudden Stratospheric Warming (SSW) is the most spectacular dynamic event occurring in the middle atmosphere. It can lead to a warming of the winter polar stratosphere by a few tens of K in one to two weeks and a reversal of the stratospheric circulation from wintertime prevailing westerly winds to easterly winds similar to summer conditions. This strong modification of the stratospheric circulation has consequences for several applications, including the modification of the stratospheric infrasound guide. Depending on the date of the SSW, the westerly circulation can be re-established if the SSW occurs in mid-winter or the summer easterly circulation can be definitively established if the SSW occurs in late winter. In the latter case it is called Final Warming (FW). Each year, it is possible to define the date of the FW as the date of the final inversion of the zonal wind at 60°N - 10 hPa . If the FW is associated with a strong peak of planetary wave activity and a rapid increase in polar temperature, it is classified as dynamic FW. If the transition to the easterly wind is smooth without planetary wave activity, the FW is classified as radiative.</p><p>The analysis of the ERA5 database, which has recently been extended to 1950 (71 years of data), allowed a statistical analysis of the evolution of the stratosphere in winter. The main conclusions of this study will be presented :</p><p>- the state of the polar vortex in a given month is anticorrelated with its state 2 to 3 months earlier. The beginning of winter is anticorrelated with mid-winter and mid-winter is anticorrelated with the end of winter;</p><p>- dynamic FWs occur early in the season (March - early April) and are associated with a strong positive polar temperature anomaly, while radiative FWs occur later (late April - early May) without a polar temperature anomaly;</p><p>- the summer stratosphere (polar temperature and zonal wind) keeps the memory of its state in April-May at the time of FW at least until July .</p><p>These results could help to improve medium-range weather forecasts in the Northern Hemisphere due to the strong dynamic coupling between the troposphere and stratosphere during SSW events.</p>

scholarly journals Reactive nitrogen (NO<sub><i>y</i></sub>) and ozone responses to energetic electron precipitation during Southern Hemisphere winter

2019 ◽  
Vol 19 (14) ◽  
pp. 9485-9494 ◽  
Author(s):  
Pavle Arsenovic ◽  
Alessandro Damiani ◽  
Eugene Rozanov ◽  
Bernd Funke ◽  
Andrea Stenke ◽  
...  
Keyword(s):  
Southern Hemisphere ◽  
Climate Model ◽  
Middle Atmosphere ◽  
Stratospheric Ozone ◽  
Energetic Electron ◽  
Polar Vortex ◽  
Solar Proton ◽  
Electron Precipitation ◽  
Reactive Nitrogen ◽  
High Electron

Abstract. Energetic particle precipitation (EPP) affects the chemistry of the polar middle atmosphere by producing reactive nitrogen (NOy) and hydrogen (HOx) species, which then catalytically destroy ozone. Recently, there have been major advances in constraining these particle impacts through a parametrization of NOy based on high-quality observations. Here we investigate the effects of low (auroral) and middle (radiation belt) energy range electrons, separately and in combination, on reactive nitrogen and hydrogen species as well as on ozone during Southern Hemisphere winters from 2002 to 2010 using the SOCOL3-MPIOM chemistry-climate model. Our results show that, in the absence of solar proton events, low-energy electrons produce the majority of NOy in the polar mesosphere and stratosphere. In the polar vortex, NOy subsides and affects ozone at lower altitudes, down to 10 hPa. Comparing a year with high electron precipitation with a quiescent period, we found large ozone depletion in the mesosphere; as the anomaly propagates downward, 15 % less ozone is found in the stratosphere during winter, which is confirmed by satellite observations. Only with both low- and middle-energy electrons does our model reproduce the observed stratospheric ozone anomaly.

scholarly journals The Structure and Dynamics of the Stratospheric Northern Annular Mode in CMIP5 Simulations

2014 ◽  
Vol 28 (1) ◽  
pp. 86-107 ◽  
Author(s):  
Yun-Young Lee ◽  
Robert X. Black
Keyword(s):  
Rossby Wave ◽  
Planetary Wave ◽  
Regional Analysis ◽  
Storm Track ◽  
Polar Vortex ◽  
Wave Activity ◽  
Flux Analysis ◽  
Annular Mode ◽  
Northern Annular Mode ◽  
Structure And Dynamics

Abstract The structure and dynamics of stratospheric northern annular mode (SNAM) events in CMIP5 simulations are studied, emphasizing (i) stratosphere–troposphere coupling and (ii) disparities between high-top (HT) and low-top (LT) models. Compared to HT models, LT models generally underrepresent SNAM amplitude in stratosphere, consistent with weaker polar vortex variability, as demonstrated by Charlton-Perez et al. Interestingly, however, this difference does not carry over to the associated zonal-mean SNAM signature in troposphere, which closely resembles observations in both HT and LT models. Nonetheless, a regional analysis illustrates that both HT and LT models exhibit anomalously weak and eastward shifted (compared to observations) storm track and sea level pressure anomaly patterns in association with SNAM events. Dynamical analyses of stratosphere–troposphere coupling are performed to further examine the distinction between HT and LT models. Variability in stratospheric planetary wave activity is reduced in LT models despite robust concomitant tropospheric variability. A meridional heat flux analysis indicates relatively weak vertical Rossby wave coupling in LT models consistent with the excessive damping events discussed by Shaw et al. Eliassen–Palm flux cross sections reveal that Rossby wave propagation is anomalously weak above the tropopause in LT models, suggesting that weak polar vortex variability in LT models is due, at least in part, to the inability of tropospheric planetary wave activity to enter the stratosphere. Although the results are consistent with anomalously weak vertical dynamical coupling in LT models during SNAM events, there is little impact upon attendant tropospheric variability. The physical reason behind this apparent paradox represents an important topic for future study.

scholarly journals Observations of coincident EMIC wave activity and duskside energetic electron precipitation on 18-19 January 2013

2015 ◽  
Vol 42 (14) ◽  
pp. 5727-5735 ◽  
Author(s):  
L. W. Blum ◽  
A. Halford ◽  
R. Millan ◽  
J. W. Bonnell ◽  
J. Goldstein ◽  
...  
Keyword(s):  
Energetic Electron ◽  
Wave Activity ◽  
Electron Precipitation ◽  
Emic Wave

scholarly journals Reactive nitrogen (NO<sub><i>y</i></sub>) and ozone responses to energetic electron precipitation during Southern Hemisphere winter

2018 ◽  
Author(s):  
Pavle Arsenovic ◽  
Alessandro Damiani ◽  
Eugene Rozanov ◽  
Bernd Funke ◽  
Andrea Stenke ◽  
...  
Keyword(s):  
Southern Hemisphere ◽  
Climate Model ◽  
Middle Atmosphere ◽  
Stratospheric Ozone ◽  
Energetic Electron ◽  
Polar Vortex ◽  
Solar Proton ◽  
Electron Precipitation ◽  
Reactive Nitrogen ◽  
High Electron

Abstract. Energetic particle precipitation (EPP) affects the chemistry of the polar middle atmosphere by producing reactive nitrogen (NOy) and hydrogen (HOx) species, which then catalytically destroy ozone. Recently, there have been major advances in constraining these particle impacts through a parametrization based on high quality observations. Here we investigate the effects of low (auroral) and middle (radiation belt) energy range electrons, separately and in combination, on reactive nitrogen and hydrogen species as well as on ozone during Southern Hemisphere winters from 2002 to 2010 using the chemistry-climate model SOCOL3-MPIOM. Our results show that, in absence of solar proton events, low energy electrons produce the majority of NOy in the polar mesosphere and stratosphere. In the polar vortex, NOy subsides and affects ozone at lower altitudes, down to 10 hPa. Comparing a year with high electron precipitation with a quiescent period, we found large ozone depletion in the mesosphere; as the anomaly propagates downward, 15 % less ozone is found in the stratosphere during winter, which is confirmed by satellite observations. Only with both low and middle energy electrons, our model reproduces the observed stratospheric ozone anomaly.

scholarly journals An unusual stratospheric ozone decrease linked to isentropic air-mass transport as observed over Irene (25.5° S, 28.1° E) in mid-May 2002

2005 ◽  
Vol 5 (6) ◽  
pp. 12617-12639
Author(s):  
N. Semane ◽  
H. Bencherif ◽  
B. Morel ◽  
A. Hauchecorne ◽  
R. D. Diab
Keyword(s):  
Total Ozone ◽  
Planetary Wave ◽  
Lower Stratosphere ◽  
Polar Vortex ◽  
Ozone Layer ◽  
Wave Activity ◽  
Transport Processes ◽  
Diagnostic Tools ◽  
Air Masses ◽  
Middle Stratosphere

Abstract. A prominent ozone minimum of less than 240 Dobson Units (DU) was observed over Irene (25.5° S, 28.1° E) by the Total Ozone Mapping Spectrometer (TOMS) during May 2002 with extremely low ozone value of less than 219 DU recorded on 12 May, as compared to a climatological mean of 249 DU for May between 1999 and 2005. In this study, the vertical structure of this ozone minimum is examined using ozonesonde measurements performed over Irene on 15 May 2002, when the total ozone (as given by TOMS) was about 226 DU. Indeed, it is found that the ozone minimum is of Antarctic polar origin with a low-ozone layer in the middle stratosphere above 625 K and of tropical origin with low-ozone layer between 400-K and 450-K isentropic levels in the lower stratosphere. The upper and lower depleted parts of the ozonesonde profile for 15 May, are respectively attributed to equatorward and poleward transport of low-ozone air toward the subtropics. The tropical air moving over Irene and the polar one passing over the same area associated with enhanced planetary-wave activity are simulated successfully using a high-resolution advection contour model (MIMOSA) of Potential Vorticity. Indeed, in mid-May 2002, MIMOSA maps show a polar vortex filament in the middle stratosphere above the 625-K isentropic level and they show also tropical air-masses moving southward (over Irene) in the lower stratosphere between 400-K and 450-K isentropic levels. The winter stratospheric wave driving and its associated localized isentropic mixing leading to the ozone minimum are investigated by means of two diagnostic tools: the Eliassen-Palm flux and the effective diffusivity computed from the European Center for Medium-range Weather Forecasts (ECMWF) fields. The unusual distribution of ozone over Irene during May 2002 in the middle stratosphere is closely connected to the anomalously pre-conditioned structure of the polar vortex at that time of the year. Indeed, the perturbed vortex was typically predisposed for easy erosion by dynamical transport processes, which have been driven by strong planetary wave activity and have eventually resulted in a very large latitudinal advection of polar air masses towards the subtropics. The exceptional presence of polar vortex air over the subtropics during May 2002 can be considered as the first sign of the particular polar vortex disturbances, which after being well reinforced, contributed to the unprecedented behavior of the Antarctic spring ozone hole observed during September 2002.

scholarly journals Climatology and trends in the forcing of the stratospheric zonal-mean flow

2011 ◽  
Vol 11 (24) ◽  
pp. 12751-12771 ◽  
Author(s):  
E. Monier ◽  
B. C. Weare
Keyword(s):  
Planetary Wave ◽  
Polar Vortex ◽  
Early Spring ◽  
Wave Activity ◽  
Mean Flow ◽  
Flux Divergence ◽  
Temporal Shift ◽  
Long Term Changes ◽  
Environmental Prediction

Abstract. The momentum budget of the Transformed Eulerian-Mean (TEM) equation is calculated using the European Centre for Medium-Range Weather Forecasts (ECMWF) reanalysis (ERA-40) and the National Centers for Environmental Prediction (NCEP) Reanalysis 2 (R-2). This study outlines the considerable contribution of unresolved waves, deduced to be gravity waves, to the forcing of the zonal-mean flow. A trend analysis, from 1980 to 2001, shows that the onset and break down of the Northern Hemisphere (NH) stratospheric polar night jet has a tendency to occur later in the season in the more recent years. This temporal shift follows long-term changes in planetary wave activity that are mainly due to synoptic waves, with a lag of one month. In the Southern Hemisphere (SH), the polar vortex shows a tendency to persist further into the SH summertime. This also follows a statistically significant decrease in the intensity of the stationary EP flux divergence over the 1980–2001 period. Ozone depletion is well known for strengthening the polar vortex through the thermal wind balance. However, the results of this work show that the SH polar vortex does not experience any significant long-term changes until the month of December, even though the intensification of the ozone hole occurs mainly between September and November. This study suggests that the decrease in planetary wave activity in November provides an important feedback to the zonal wind as it delays the breakdown of the polar vortex. In addition, the absence of strong eddy feedback before November explains the lack of significant trends in the polar vortex in the SH early spring. A long-term weakening in the Brewer-Dobson (B-D) circulation in the polar region is identified in the NH winter and early spring and during the SH late spring and is likely driven by the decrease in planetary wave activity previously mentioned. During the rest of the year, there are large discrepancies in the representation of the B-D circulation and the unresolved waves between the two reanalyses, making trend analyses unreliable.

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