A Note on Some Early Radiosonde Temperature Observations in the Antarctic Lower Stratosphere

Abstract. Volcanic sulfate aerosol is an important source of sulfur for Antarctica where other local sources of sulfur are rare. Mid- and high latitude volcanic eruptions can directly influence the aerosol budget of the polar stratosphere. However, tropical eruptions can also enhance polar aerosol load following long-range transport. In the present work, we analyze the volcanic plume of a tropical eruption, Mount Merapi in October 2010, using the Lagrangian particle dispersion model Massive-Parallel Trajectory Calculations (MPTRAC), Atmospheric Infrared Sounder (AIRS) SO2 observations and Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) aerosol observations. We investigate the pathway and transport efficiency of the volcanic aerosol from the tropical tropopause layer (TTL) to the lower stratosphere over Antarctica. We first estimated the time- and height-resolved SO2 injection time series over Mount Merapi during the explosive eruption using the AIRS SO2 observations and a backward trajectory approach. Then the SO2 injections were tracked for up to 6 months using the MPTRAC model. The Lagrangian transport simulation of the volcanic plume was compared to MIPAS aerosol observations and showed good agreement. Both of the simulation and the observations presented in this study suggest that a significant amount of aerosols of the volcanic plume from the Merapi eruption was transported from the tropics to the south of 60 °S within one month after the eruption and even further to Antarctica in the following two months. This relatively fast meridional transport of volcanic aerosol was mainly driven by quasi-horizontal mixing from the TTL to the extratropical lower stratosphere, which was facilitated by the weakening of the subtropical jet during the seasonal transition from austral spring to summer and linked to the westerly phase of the quasi-biennial oscillation (QBO). When the plume went to southern high latitudes, the polar vortex was displaced from the south pole, so the volcanic plume was carried to the south pole without penetrating the polar vortex. Based on the model results, the most efficient pathway for the quasi-horizontal mixing was in between the isentropic surfaces of 360 and 430 K. Although only 4 % of the initial SO2 load was transported into the lower stratosphere south of 60 °S, the Merapi eruption contributed about 8800 tons of sulfur to the Antarctic lower stratosphere. This indicates that the long-range transport under favorable meteorological conditions enables tropical volcanic eruptions to be an important remote source of sulfur for the Antarctic stratosphere.

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Response of the Antarctic stratosphere to warm pool El Niño Events in the GEOS CCM

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-11-9743-2011 ◽

2011 ◽

Vol 11 (3) ◽

pp. 9743-9767 ◽

Cited By ~ 2

Author(s):

M. M. Hurwitz ◽

I.-S. Song ◽

L. D. Oman ◽

P. A. Newman ◽

A. M. Molod ◽

...

Keyword(s):

El Niño ◽

Planetary Wave ◽

Lower Stratosphere ◽

El Nino ◽

Warm Pool ◽

Wave Activity ◽

Central Pacific ◽

Quasi Biennial Oscillation ◽

South Central ◽

The Antarctic

Abstract. A new formulation of the Goddard Earth Observing System Chemistry-Climate Model, Version 2 (GEOS V2 CCM), with an improved general circulation model and an internally generated quasi-biennial oscillation (QBO), is used to investigate the response of the Antarctic stratosphere to (1) warm pool El Niño (WPEN) events and (2) the sensitivity of this response to the phase of the QBO. Two 50-yr time-slice simulations are forced by repeating annual cycles of sea surface temperatures and sea ice concentrations composited from observed WPEN and neutral ENSO (ENSON) events. In these simulations, greenhouse gas and ozone-depleting substance concentrations represent the present-day climate. The modelled responses to WPEN, and to the phase of the QBO during WPEN, are compared with NASA's Modern Era Retrospective-Analysis for Research and Applications (MERRA) reanalysis. WPEN events enhance poleward planetary wave activity in the central South Pacific during austral spring, leading to relative warming of the Antarctic lower stratosphere in November/December. During the easterly phase of the QBO (QBO-E), the GEOS V2 CCM reproduces the observed 3–5 K warming of the polar region at 50 hPa, in the WPEN simulation relative to ENSON. In the recent past, the response to WPEN events was sensitive to the phase of the QBO: the enhancement in planetary wave driving and the lower stratospheric warming signal were mainly associated with WPEN events coincident with QBO-E. In the GEOS V2 CCM, however, the Antarctic response to WPEN events is insensitive to the phase of the QBO: the modelled response is always easterly QBO-like. OLR, streamfunction and Rossby wave energy diagnostics are used to show that the modelled QBO does not extend far enough into the lower stratosphere and upper troposphere to modulate convection and thus planetary wave activity in the south central Pacific.

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Nighttime Mesospheric Ozone During the 2002 Southern Hemispheric Major Stratospheric Warming

10.5194/acp-2016-758 ◽

2016 ◽

Author(s):

Christine Smith-Johnsen ◽

Yvan Orsolini ◽

Frode Stordal ◽

Varavut Limpasuvan ◽

Kristell Pérot

Keyword(s):

Atomic Oxygen ◽

Lower Stratosphere ◽

Climate Model ◽

Middle Atmosphere ◽

Ozone Layer ◽

Stratospheric Warming ◽

Mesospheric Ozone ◽

Northern Hemispheric ◽

Second Year ◽

The Antarctic

Abstract. A Sudden Stratospheric Warming (SSW) affects the chemistry and dynamics of the middle atmosphere. The major warmings occur roughly every second year in the Northern Hemispheric (NH) winter, but has only been observed once in the Southern Hemisphere (SH), during the Antarctic winter of 2002. Using the National Center for Atmospheric Research's (NCAR) Whole Atmosphere Community Climate Model with specified dynamics (WACCM-SD), this study investigates the effects of this rare warming event on the ozone layer located around the SH mesopause. This secondary ozone layer changes with respect to hydrogen, oxygen, temperature, and the altered SH polar circulation during the major SSW. The 2002 SH winter was characterized by three zonal-mean zonal wind reductions in the upper stratosphere before a fourth wind reversal reaches the lower stratosphere, marking the onset of the major SSW. At the time of these four wind reversals, a corresponding episodic increase can be seen in the modeled nighttime ozone concentration in the secondary ozone layer. Observations by the Global Ozone Monitoring by Occultation of Stars (GOMOS, an instrument on board the satellite Envisat) demonstrate similar ozone enhancement as in the model. This ozone increase is attributable largely to enhanced upwelling and the associated cooling of the altitude region in conjunction with the wind reversal. Unlike its NH counterpart, the secondary ozone layer during the SH major SSW appeared to be impacted more by the effects of atomic oxygen than hydrogen.

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Anomalous quasi-stationary planetary waves over the Antarctic region in 1988 and 2002

Annales Geophysicae ◽

10.5194/angeo-26-1101-2008 ◽

2008 ◽

Vol 26 (5) ◽

pp. 1101-1108 ◽

Cited By ~ 11

Author(s):

A. V. Grytsai ◽

O. M. Evtushevsky ◽

G. P. Milinevsky

Keyword(s):

Lower Stratosphere ◽

Polar Vortex ◽

Amplitude Distribution ◽

Stationary Wave ◽

Planetary Waves ◽

Late Winter ◽

Stratospheric Polar Vortex ◽

Latitudinal Position ◽

The Antarctic ◽

Peak Value

Abstract. Anomalies in the Antarctic total ozone and amplitudes of the quasi-stationary planetary waves in the lower stratosphere temperature during the winter and spring of 1988 and 2002 have been compared. Westward displacement of the quasi-stationary wave (QSW) extremes by 50°–70° relative to the preceding years of the strong stratospheric polar vortex in 1987 and 2001, respectively, was observed. A dependence of the quasi-stationary wave ridge and trough positions on the strength of the westerly zonal wind in the lower stratosphere is shown. Comparison of the QSW amplitude in the lower stratosphere temperature in July and August shows that the amplitude distribution with latitude in August could be considered as a possible indication of the future anomalous warming in Antarctic spring. In August 2002, the QSW amplitude of 10 K at the edge region of the polar vortex (60° S–65° S) preceded the major warming in September, whereas in August 1988, the highest 7 K amplitude at 55° S preceded the large warming in the next months. These results suggest that the peak value of the lower stratosphere temperature QSW amplitude and the peak latitudinal position in late winter can influence the southern polar vortex strength in spring.

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20 Years of ClO Measurements in the Antarctic Lower Stratosphere

10.5194/acp-2016-188 ◽

2016 ◽

Author(s):

Gerald E. Nedoluha ◽

Brian J. Connor ◽

Thomas Mooney ◽

James W. Barrett ◽

Alan Parrish ◽

...

Keyword(s):

Lower Stratosphere ◽

Montreal Protocol ◽

Strong Increase ◽

Interannual Variations ◽

Strong Decrease ◽

Chlorine Monoxide ◽

Highly Correlated ◽

The Antarctic ◽

Underlying Trend ◽

Wave Spectrometer

Abstract. We present 20 years of springtime measurements of ClO over Antarctica from the Chlorine monOxide Experiment (ChlOE1) ground-based millimeter wave spectrometer at Scott Base, Antarctica, as well 12 years of ClO measurements from the Aura Microwave Limb Sounder (MLS). From August onwards we observe a strong increase in lower stratospheric ClO, with a peak column amount usually occurring in early September. From mid-September onwards we observe a strong decrease in ClO. In order to study interannual differences we focus on a 3-week period from August 28 to September 17 for each year, and compare the average column ClO anomalies. These column ClO anomalies are shown to be highly correlated with the average ozone mass deficit for September and October of each year. We also show that anomalies in column ClO are anti-correlated with 30 hPa temperature anomalies, both on a daily and an interannual timescale. We calculate the dependence of interannual variations in column ClO on interannual variations in temperature. By making use of this relationship we can better estimate the underlying trend in the Cly which provides the reservoir for the ClO. The resultant trends for zonal MLS, Scott Base MLS (both 2004–2015), and ChlOE (1996–2015) were 0.5 ± 0.2 %/yr, −1.4 ± 0.9 %/yr, and −0.6 ± 0.4 %/yr, respectively. These trends are within 1σ of trends in stratospheric Cly previously found at other latitudes. This decrease in ClO is the result of changes in anthropogenic CFC emissions due to actions taken under the Montreal Protocol.

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