scholarly journals 20 Years of ClO Measurements in the Antarctic Lower Stratosphere

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.

scholarly journals 20 years of ClO measurements in the Antarctic lower stratosphere

2016 ◽  
Vol 16 (16) ◽  
pp. 10725-10734 ◽  
Author(s):  
Gerald E. Nedoluha ◽  
Brian J. Connor ◽  
Thomas Mooney ◽  
James W. Barrett ◽  
Alan Parrish ◽  
...  
Keyword(s):  
Montreal Protocol ◽  
Strong Increase ◽  
Interannual Variations ◽  
Chlorine Oxide ◽  
Chlorine Monoxide ◽  
Highly Correlated ◽  
The Antarctic ◽  
Long Term Trend ◽  
Underlying Trend

Abstract. We present 20 years (1996–2015) of austral springtime measurements of chlorine monoxide (ClO) over Antarctica from the Chlorine Oxide Experiment (ChlOE1) ground-based millimeter wave spectrometer at Scott Base, Antarctica, as well 12 years (2004–2015) 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 28 August to 17 September 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 strongly anti-correlated with 30 hPa temperature anomalies, both on a daily and an interannual timescale. Making use of this anti-correlation we calculate the linear dependence of the 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 total chlorine (Cly  =  HCl + ClONO2 + HOCl + 2  ×  Cl2 + 2  ×  Cl2O2 + ClO + Cl). The resultant trends in Cly, which determine the long-term trend in ClO, are estimated to be −0.5 ± 0.2, −1.4 ± 0.9, and −0.6 ± 0.4 % year−1, for zonal MLS, Scott Base MLS (both 2004–2015), and ChlOE (1996–2015) respectively. These trends are within 1σ of trends in stratospheric Cly previously found at other latitudes. The decrease in ClO is consistent with the trend expected from regulations enacted under the Montreal Protocol.

scholarly journals An Arctic Ozone Hole in 2020 If Not For the Montreal Protocol

2021 ◽  
Author(s):  
Catherine Wilka ◽  
Susan Solomon ◽  
Doug Kinnison ◽  
David Tarasick
Keyword(s):  
Ozone Depletion ◽  
Total Ozone ◽  
Lower Stratosphere ◽  
Montreal Protocol ◽  
Ozone Hole ◽  
Boreal Spring ◽  
Polar Stratospheric Cloud ◽  
The Antarctic

Abstract. Without the Montreal Protocol the already extreme Arctic ozone losses in boreal spring of 2020 would be expected to have produced an Antarctic-like ozone hole, with an area of total ozone below 220 DU of about 20 million km2. Record observed local lows of 0.1 ppmv at some altitudes in the lower stratosphere would have reached 0.01, again similar to the Antarctic. This provides an opportunity to test parameterizations of polar stratospheric cloud impacts on denitrification, and thereby to improve stratospheric models. Spring ozone depletion would have begun earlier and lasted longer without the Montreal Protocol, and by 2020 the year-round ozone depletion would have begun to dramatically diverge from the observed case. This study reinforces that the historically extreme 2020 Arctic ozone depletion is not cause for concern over the Montreal Protocol's effectiveness, but rather demonstrates that the Montreal Protocol indeed merits celebration for avoiding an Arctic ozone hole.

On the quality of eddy heat flux calculations in the vicinity of the Antarctic lower stratosphere

1990 ◽  
Vol 17 (11) ◽  
pp. 1901-1904
Author(s):  
Richard D. Rosen ◽  
David A. Salstein ◽  
Alvin J. Miller
Keyword(s):  
Heat Flux ◽  
Lower Stratosphere ◽  
Eddy Heat Flux ◽  
The Antarctic

scholarly journals Long-range transport of volcanic aerosol from the 2010 Merapi tropical eruption to Antarctica

2018 ◽  
Author(s):  
Xue Wu ◽  
Sabine Griessbach ◽  
Lars Hoffmann
Keyword(s):  
Long Range ◽  
Lower Stratosphere ◽  
Polar Vortex ◽  
Volcanic Eruptions ◽  
Long Range Transport ◽  
Volcanic Plume ◽  
Volcanic Aerosol ◽  
The South ◽  
Range Transport ◽  
The Antarctic

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.

scholarly journals Seasonal and interannual variations in HCN amounts in the upper troposphere and lower stratosphere observed by MIPAS

2015 ◽  
Vol 15 (2) ◽  
pp. 563-582 ◽  
Author(s):  
N. Glatthor ◽  
M. Höpfner ◽  
G. P. Stiller ◽  
T. von Clarmann ◽  
B. Funke ◽  
...  
Keyword(s):  
Biomass Burning ◽  
Annual Cycle ◽  
Lower Stratosphere ◽  
Tape Recorder ◽  
Time Shift ◽  
Interannual Variations ◽  
High Latitudes ◽  
Tropical Africa ◽  
Upper Troposphere ◽  
Fire Emissions

Abstract. We present a HCN climatology of the years 2002–2012, derived from FTIR limb emission spectra measured with the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) on the ENVISAT satellite, with the main focus on biomass burning signatures in the upper troposphere and lower stratosphere. HCN is an almost unambiguous tracer of biomass burning with a tropospheric lifetime of 5–6 months and a stratospheric lifetime of about 2 years. The MIPAS climatology is in good agreement with the HCN distribution obtained by the spaceborne ACE-FTS experiment and with airborne in situ measurements performed during the INTEX-B campaign. The HCN amounts observed by MIPAS in the southern tropical and subtropical upper troposphere have an annual cycle peaking in October–November, i.e. 1–2 months after the maximum of southern hemispheric fire emissions. The probable reason for the time shift is the delayed onset of deep convection towards austral summer. Because of overlap of varying biomass burning emissions from South America and southern Africa with sporadically strong contributions from Indonesia, the size and strength of the southern hemispheric plume have considerable interannual variations, with monthly mean maxima at, for example, 14 km between 400 and more than 700 pptv. Within 1–2 months after appearance of the plume, a considerable portion of the enhanced HCN is transported southward to as far as Antarctic latitudes. The fundamental period of HCN variability in the northern upper troposphere is also an annual cycle with varying amplitude, which in the tropics peaks in May after and during the biomass burning seasons in northern tropical Africa and southern Asia, and in the subtropics peaks in July due to trapping of pollutants in the Asian monsoon anticyclone (AMA). However, caused by extensive biomass burning in Indonesia and by northward transport of part of the southern hemispheric plume, northern HCN maxima also occur around October/November in several years, which leads to semi-annual cycles. There is also a temporal shift between enhanced HCN in northern low and mid- to high latitudes, indicating northward transport of pollutants. Due to additional biomass burning at mid- and high latitudes, this meridional transport pattern is not as clear as in the Southern Hemisphere. Upper tropospheric HCN volume mixing ratios (VMRs) above the tropical oceans decrease to below 200 pptv, presumably caused by ocean uptake, especially during boreal winter and spring. The tropical stratospheric tape recorder signal with an apparently biennial period, which was detected in MLS and ACE-FTS data from mid-2004 to mid-2007, is corroborated by MIPAS HCN data. The tape recorder signal in the whole MIPAS data set exhibits periodicities of 2 and 4 years, which are generated by interannual variations in biomass burning. The positive anomalies of the years 2003, 2007 and 2011 are caused by succession of strongly enhanced HCN from southern hemispheric and Indonesian biomass burning in boreal autumn and of elevated HCN from northern tropical Africa and the AMA in subsequent spring and summer. The anomaly of 2005 seems to be due to springtime emissions from tropical Africa followed by release from the summertime AMA. The vertical transport time of the anomalies is 1 month or less between 14 and 17 km in the upper troposphere and 8–11 months between 17 and 25 km in the lower stratosphere.

scholarly journals Comparison of SMMR and SSM/I passive microwave data collected over Antarctica

1993 ◽  
Vol 17 ◽  
pp. 131-136 ◽  
Author(s):  
Kenneth C. Jezek ◽  
Carolyn J. Merry ◽  
Don J. Cavalieri
Keyword(s):  
Brightness Temperature ◽  
Microwave Radiometer ◽  
Correlated Data ◽  
Data Sets ◽  
Microwave Brightness Temperature ◽  
Brightness Temperatures ◽  
Scatter Plots ◽  
Microwave Imager ◽  
Highly Correlated ◽  
The Antarctic

Spaceborne data are becoming sufficiently extensive spatially and sufficiently lengthy over time to provide important gauges of global change. There is a potentially long record of microwave brightness temperature from NASA's Scanning Multichannel Microwave Radiometer (SMMR), followed by the Navy's Special Sensor Microwave Imager (SSM/I). Thus it is natural to combine data from successive satellite programs into a single, long record. To do this, we compare brightness temperature data collected during the brief overlap period (7 July-20 August 1987) of SMMR and SSM/I. Only data collected over the Antarctic ice sheet are used to limit spatial and temporal complications associated with the open ocean and sea ice. Linear regressions are computed from scatter plots of complementary pairs of channels from each sensor revealing highly correlated data sets, supporting the argument that there are important relative calibration differences between the two instruments. The calibration scheme was applied to a set of average monthly brightness temperatures for a sector of East Antarctica.

scholarly journals Polar processing in a split vortex: early winter Arctic ozone loss in 2012/13

2015 ◽  
Vol 15 (4) ◽  
pp. 4973-5029 ◽  
Author(s):  
G. L. Manney ◽  
Z. D. Lawrence ◽  
M. L. Santee ◽  
N. J. Livesey ◽  
A. Lambert ◽  
...  
Keyword(s):  
Nitric Acid ◽  
Lower Stratosphere ◽  
Polar Vortex ◽  
The Arctic ◽  
Early Winter ◽  
Sudden Stratospheric Warming ◽  
Ozone Loss ◽  
Chlorine Monoxide ◽  
Polar Stratospheric Cloud ◽  
Vortex Split

Abstract. A sudden stratospheric warming (SSW) in early January 2013 caused the polar vortex to split. After the lower stratospheric vortex split on 8 January, the two offspring vortices – one over Canada and the other over Siberia – remained intact, well-confined, and largely at latitudes that received sunlight until they reunited at the end of January. As the SSW began, temperatures abruptly rose above chlorine activation thresholds throughout the lower stratosphere. The vortex was very disturbed prior to the SSW, and was exposed to much more sunlight than usual in December 2012 and January 2013. Aura Microwave Limb Sounder (MLS) nitric acid (HNO3) data and observations from CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations) indicate extensive polar stratospheric cloud (PSC) activity, with evidence of PSCs containing solid nitric acid trihydrate particles during much of December 2012. Consistent with the sunlight exposure and PSC activity, MLS observations show that chlorine monoxide (ClO) became enhanced early in December. Despite the cessation of PSC activity with the onset of the SSW, enhanced vortex ClO persisted until mid-February, indicating lingering chlorine activation. The smaller Canadian offspring vortex had lower temperatures, lower HNO3, lower hydrogen chloride (HCl), and higher ClO in late January than the Siberian vortex. Chlorine deactivation began later in the Canadian than in the Siberian vortex. HNO3 remained depressed within the vortices after temperatures rose above the PSC existence threshold, and passive transport calculations indicate vortex-averaged denitrification of about 4 ppbv; the resulting low HNO3 values persisted until the vortex dissipated in mid-February. Consistent with the strong chlorine activation and exposure to sunlight, MLS measurements show rapid ozone loss commencing in mid-December and continuing through January. Lagrangian transport estimates suggest ~ 0.7–0.8 ppmv (parts per million by volume) vortex-averaged chemical ozone loss by late January near 500 K (~ 21 km), with substantial loss occurring from ~ 450 to 550 K. The surface area of PSCs in December 2012 was larger than that in any other December observed by CALIPSO. As a result of denitrification, HNO3 abundances in 2012/13 were among the lowest in the MLS record for the Arctic. ClO enhancement was much greater in December 2012 through mid-January 2013 than that at the corresponding time in any other Arctic winter observed by MLS. Furthermore, reformation of HCl appeared to play a greater role in chlorine deactivation than in more typical Arctic winters. Ozone loss in December 2012 and January 2013 was larger than any previously observed in those months. This pattern of exceptional early winter polar processing and ozone loss resulted from the unique combination of dynamical conditions associated with the early January 2013 SSW, namely unusually low temperatures in December 2012 and offspring vortices that remained well-confined and largely in sunlit regions for about a month after the vortex split.

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

2011 ◽  
Vol 11 (3) ◽  
pp. 9743-9767 ◽  
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.

scholarly journals How sensitive is the recovery of stratospheric ozone to changes in concentrations of very short-lived bromocarbons?

2014 ◽  
Vol 14 (19) ◽  
pp. 10431-10438 ◽  
Author(s):  
X. Yang ◽  
N. L. Abraham ◽  
A. T. Archibald ◽  
P. Braesicke ◽  
J. Keeble ◽  
...  
Keyword(s):  
Climate Model ◽  
Stratospheric Ozone ◽  
Montreal Protocol ◽  
Background Concentrations ◽  
Future Situation ◽  
Antarctic Ozone ◽  
The Antarctic ◽  
The Impact ◽  
Ozone Column ◽  
Policy Question

Abstract. Naturally produced very short-lived substances (VSLS) account for almost a quarter of the current stratospheric inorganic bromine, Bry. Following VSLS oxidation, bromine radicals (Br and BrO) can catalytically destroy ozone. The extent to which possible increases in surface emissions or transport of these VSLS bromocarbons to the stratosphere could counteract the effect of halogen reductions under the Montreal Protocol is an important policy question. Here, by using a chemistry–climate model, UM-UKCA, we investigate the impact of a hypothetical doubling (an increase of 5 ppt Bry) of VSLS bromocarbons on ozone and how the resulting ozone changes depend on the background concentrations of chlorine and bromine. Our model experiments indicate that for the 5 ppt increase in Bry from VSLS, the ozone decrease in the lowermost stratosphere of the Southern Hemisphere (SH) may reach up to 10% in the annual mean; the ozone decrease in the Northern Hemisphere (NH) is smaller (4–6%). The largest impact on the ozone column is found in the Antarctic spring. There is a significantly larger ozone decrease following the doubling of the VSLS burden under a high stratospheric chlorine background than under a low chlorine background, indicating the importance of the inter-halogen reactions. For example, the decline in the high-latitude, lower-stratospheric ozone concentration as a function of Bry is higher by about 30–40% when stratospheric Cly is ~ 3 ppb (present day), compared with Cly of ~ 0.8 ppb (a pre-industrial or projected future situation). Bromine will play an important role in the future ozone layer. However, even if bromine levels from natural VSLS were to increase significantly later this century, changes in the concentration of ozone will likely be dominated by the decrease in anthropogenic chlorine. Our calculation suggests that for a 5 ppt increase in Bry from VSLS, the Antarctic ozone hole recovery date could be delayed by approximately 6–8 years, depending on Cly levels.

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