The very unusual polar stratosphere in 2019–2020

2020 ◽  
Vol 65 (21) ◽  
pp. 1775-1777
Author(s):  
Yongyun Hu
Keyword(s):  
Polar Stratosphere

The Life Cycle and Variability of Antarctic Weak Polar Vortex Events

2022 ◽  
pp. 1-63
Keyword(s):  
Life Cycle ◽  
Polar Vortex ◽  
Southern Annular Mode ◽  
Austral Spring ◽  
Stratospheric Polar Vortex ◽  
Temperature And Precipitation ◽  
Scale Temperature ◽  
Precipitation Anomalies ◽  
Polar Stratosphere ◽  
The Antarctic

Abstract Motivated by the strong Antarctic sudden stratospheric warming (SSW) in 2019, a survey on the similar Antarctic weak polar events (WPV) is presented, including their life cycle, dynamics, seasonality, and climatic impacts. The Antarctic WPVs have a frequency of about four events per decade, with the 2002 event being the only major SSW. They show a similar life cycle to the SSWs in the Northern Hemisphere but have a longer duration. They are primarily driven by enhanced upward-propagating wavenumber 1 in the presence of a preconditioned polar stratosphere, i.e., a weaker and more contracted Antarctic stratospheric polar vortex. Antarctic WPVs occur mainly in the austral spring. Their early occurrence is preceded by an easterly anomaly in the middle and upper equatorial stratosphere besides the preconditioned polar stratosphere. The Antarctic WPVs increase the ozone concentration in the polar region and are associated with an advanced seasonal transition of the stratospheric polar vortex by about one week. Their frequency doubles after 2000 and is closely related to the advanced Antarctic stratospheric final warming in recent decades. The WPV-resultant negative phase of the southern annular mode descends to the troposphere and persists for about three months, leading to persistent hemispheric scale temperature and precipitation anomalies.

scholarly journals Denitrification, dehydration and ozone loss during the Arctic winter 2015/2016

2017 ◽  
Author(s):  
Farahnaz Khosrawi ◽  
Oliver Kirner ◽  
Björn-Martin Sinnhuber ◽  
Sören Johansson ◽  
Michael Höpfner ◽  
...  
Keyword(s):  
Atmospheric Chemistry ◽  
Stratospheric Ozone ◽  
Satellite Observations ◽  
The Arctic ◽  
Cold Pool ◽  
Polar Stratospheric Clouds ◽  
Airborne Measurements ◽  
Ozone Loss ◽  
Polar Stratosphere ◽  
Stratospheric Clouds

Abstract. The Arctic winter 2015/2016 was one of the coldest stratospheric winters in recent years. A stable vortex formed by early December and the early winter was exceptionally cold. Cold pool temperatures dropped below the Nitric Acid Trihydrate (NAT) existence temperature of about 195 K, thus allowing Polar Stratospheric Clouds (PSCs) to form. The low temperatures in the polar stratosphere persisted until early March allowing chlorine activation and catalytic ozone destruction. Satellite observations indicate that sedimentation of PSC particles led to denitrification as well as dehydration of stratospheric layers. Model simulations of the Arctic winter 2015/2016 nudged toward European Center for Medium-Range Weather Forecasts (ECMWF) analyses data were performed with the atmospheric chemistry–climate model ECHAM5/MESSy Atmospheric Chemistry (EMAC) for the Polar Stratosphere in a Changing Climate (POLSTRACC) campaign. POLSTRACC is a High Altitude and LOng Range Research Aircraft (HALO) mission aimed at the investigation of the structure, composition and evolution of the Arctic Upper Troposphere and Lower Stratosphere (UTLS). The chemical and physical processes involved in Arctic stratospheric ozone depletion, transport and mixing processes in the UTLS at high latitudes, polar stratospheric clouds as well as cirrus clouds are investigated. In this study an overview of the chemistry and dynamics of the Arctic winter 2015/2016 as simulated with EMAC is given. Further, chemical-dynamical processes such as denitrification, dehydration and ozone loss during the Arctic winter 2015/2016 are investigated. Comparisons to satellite observations by the Aura Microwave Limb Sounder (Aura/MLS) as well as to airborne measurements with the Gimballed Limb Observer for Radiance Imaging of the Atmosphere (GLORIA) performed on board of HALO during the POLSTRACC campaign show that the EMAC simulations are in fairly good agreement with observations. We derive a maximum polar stratospheric O3 loss of ~ 2 ppmv or 100 DU in terms of column in mid March. The stratosphere was denitrified by about 8 ppbv HNO3 and dehydrated by about 1 ppmv H2O in mid to end of February. While ozone loss was quite strong, but not as strong as in 2010/2011, denitrification and dehydration were so far the strongest observed in the Arctic stratosphere in the at least past 10 years.

scholarly journals The wintertime two-day wave in the polar stratosphere, mesosphere and lower thermosphere

2008 ◽  
Vol 8 (3) ◽  
pp. 749-755 ◽  
Author(s):  
D. J. Sandford ◽  
M. J. Schwartz ◽  
N. J. Mitchell
Keyword(s):  
Lower Thermosphere ◽  
Radar Data ◽  
The Arctic ◽  
Horizontal Wind ◽  
Meteor Radar ◽  
Polar Night ◽  
Zonal Wavenumber ◽  
Mesosphere And Lower Thermosphere ◽  
Polar Stratosphere ◽  
Striking Contrast

Abstract. Recent observations of the polar mesosphere have revealed that waves with periods near two days reach significant amplitudes in both summer and winter. This is in striking contrast to mid-latitude observations where two-day waves maximise in summer only. Here, we use data from a meteor radar at Esrange (68° N, 21° E) in the Arctic and data from the MLS instrument aboard the EOS Aura satellite to investigate the wintertime polar two-day wave in the stratosphere, mesosphere and lower thermosphere. The radar data reveal that mesospheric two-day wave activity measured by horizontal-wind variance has a semi-annual cycle with maxima in winter and summer and equinoctial minima. The MLS data reveal that the summertime wave in the mesosphere is dominated by a westward-travelling zonal wavenumber three wave with significant westward wavenumber four present. It reaches largest amplitudes at mid-latitudes in the southern hemisphere. In the winter polar mesosphere, however, the wave appears to be an eastward-travelling zonal wavenumber two, which is not seen during the summer. At the latitude of Esrange, the eastward-two wave reaches maximum amplitudes near the stratopause and appears related to similar waves previously observed in the polar stratosphere. We conclude that the wintertime polar two-day wave is the mesospheric manifestation of an eastward-propagating, zonal-wavenumber-two wave originating in the stratosphere, maximising at the stratopause and likely to be generated by instabilities in the polar night jet.

scholarly journals Nucleation of nitric acid hydrates in Polar Stratospheric Clouds by meteoric material

2017 ◽  
Author(s):  
Alexander D. James ◽  
James S. A. Brooke ◽  
Thomas P. Mangan ◽  
Thomas F. Whale ◽  
John M. C. Plane ◽  
...  
Keyword(s):  
Nitric Acid ◽  
Heterogeneous Nucleation ◽  
Ozone Depletion ◽  
Mode Of Action ◽  
Polar Stratospheric Clouds ◽  
Water Ice ◽  
Meteoric Smoke ◽  
Polar Stratosphere ◽  
Stratospheric Clouds ◽  
Meteoric Material

Abstract. Heterogeneous nucleation of crystalline nitric acid hydrates in Polar Stratospheric Clouds (PSCs) enhances ozone depletion. However, the identity and mode of action of the particles responsible for nucleation remains unknown. It has been suggested that meteoric material may trigger nucleation of nitric acid trihydrate (NAT), but this has never been directly demonstrated in the laboratory. Meteoric material is present in two forms in the stratosphere, smoke which results from the ablation and re-condensation of vapours, and fragments which result from the disruption of meteoroids entering the atmosphere. Here we show that analogues of both materials have a capacity to nucleate nitric acid hydrates. In combination with estimates from a global model of the amount of meteoric smoke and fragments in the polar stratosphere we show that meteoric material probably accounts for NAT observations in early season polar stratospheric clouds in the absence of water ice.

Condensation of HNO3on falling ice particles: Mechanism for denitrification of the polar stratosphere

1990 ◽  
Vol 17 (4) ◽  
pp. 449-452 ◽  
Author(s):  
S. C. Wofsy ◽  
R. J. Salawitch ◽  
J. H. Yatteau ◽  
M. B. McElroy ◽  
B. W. Gandrud ◽  
...  
Keyword(s):  
Ice Particles ◽  
Polar Stratosphere

Observations of clouds in the polar stratosphere and polar mesosphere from POAM II

1995 ◽  
Author(s):  
Eric P. Shettle ◽  
M. D. Fromm ◽  
D. Debrestian ◽  
John S. Hornstein ◽  
K. W. Hoppel ◽  
...  
Keyword(s):  
Polar Stratosphere

scholarly journals Chlorine nitrate in the atmosphere

2018 ◽  
Vol 18 (20) ◽  
pp. 15363-15386 ◽  
Author(s):  
Thomas von Clarmann ◽  
Sören Johansson
Keyword(s):  
Atmospheric Chemistry ◽  
Infrared Emission ◽  
Chlorine Nitrate ◽  
Rotational Bands ◽  
In Situ Techniques ◽  
Mixing Ratios ◽  
Gas Phase Chemistry ◽  
Polar Stratosphere ◽  
Phase Chemistry

Abstract. This review article compiles the characteristics of the gas chlorine nitrate and discusses its role in atmospheric chemistry. Chlorine nitrate is a reservoir of both stratospheric chlorine and nitrogen. It is formed by a termolecular reaction of ClO and NO2. Sink processes include gas-phase chemistry, photo-dissociation, and heterogeneous chemistry on aerosols. The latter sink is particularly important in the context of polar spring stratospheric chlorine activation. ClONO2 has vibrational–rotational bands in the infrared, notably at 779, 809, 1293, and 1735 cm−1, which are used for remote sensing of ClONO2 in the atmosphere. Mid-infrared emission and absorption spectroscopy have long been the only concepts for atmospheric ClONO2 measurements. More recently, fluorescence and mass spectroscopic in situ techniques have been developed. Global ClONO2 distributions have a maximum at polar winter latitudes at about 20–30 km altitude, where mixing ratios can exceed 2 ppbv. The annual cycle is most pronounced in the polar stratosphere, where ClONO2 concentrations are an indicator of chlorine activation and de-activation.

scholarly journals Why are Temperature and Upward Wave Activity Flux Positively Skewed in the Polar Stratosphere?

2017 ◽  
Vol 31 (1) ◽  
pp. 115-130 ◽  
Author(s):  
Oliver Watt-Meyer ◽  
Paul J. Kushner
Keyword(s):  
Temperature Distribution ◽  
Planetary Wave ◽  
Flux Distribution ◽  
Wave Activity ◽  
Nonlinear Dependence ◽  
Radiative Balance ◽  
Wave Phase ◽  
Wave Interference ◽  
Polar Stratosphere ◽  
Wave Activity Flux

Abstract The distribution of temperatures in the wintertime polar stratosphere is significantly positively skewed, which has important implications for the characteristics of ozone chemistry and stratosphere–troposphere coupling. The typical argument for why the temperature distribution is skewed is that radiative balance sets a firm lower limit, while planetary wave driving can force much larger positive anomalies in temperature. However, the distribution of the upward Eliassen–Palm (EP) flux is also positively skewed, and this suggests that dynamics may play an important role in setting the skewness of the temperature distribution. This study explains the skewness of the upward EP flux distribution by appealing to the ideas of linear interference. In this framework, fluxes are decomposed into a linear term (LIN) that measures the coherence of the wave anomaly and the climatological wave and an additional nonlinear term (NONLIN) that depends only on the wave anomaly. It is shown that when filtered by wavenumber, there is a clear nonlinear dependence between LIN and NONLIN: the terms cancel when LIN is negative, but they reinforce each other when LIN is positive. This leads to the positive skewness of the upward wave activity flux. A toy model of wave interference is constructed, and it is shown that the westward vertical tilt of the climatological wave is the key ingredient to a positively skewed upward EP flux distribution. The causes of the skews of the LIN and NONLIN distributions themselves are shown to be related to relationships between wave phase and amplitude, and wave phase and vertical tilt, respectively.

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