Case studies of the impact of orbital sampling on stratospheric trend detection and derivation of tropical vertical velocities: solar occultation vs. limb emission sounding

Abstract. This study investigates the representativeness of two types of orbital sampling applied to stratospheric temperature and trace gas fields. Model fields are sampled using real sampling patterns from the Aura Microwave Limb Sounder (MLS), the HALogen Occultation Experiment (HALOE) and the Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS). The MLS sampling acts as a proxy for a dense uniform sampling pattern typical of limb emission sounders, while HALOE and ACE-FTS represent coarse nonuniform sampling patterns characteristic of solar occultation instruments. First, this study revisits the impact of sampling patterns in terms of the sampling bias, as previous studies have done. Then, it quantifies the impact of different sampling patterns on the estimation of trends and their associated detectability. In general, we find that coarse nonuniform sampling patterns may introduce non-negligible errors in the inferred magnitude of temperature and trace gas trends and necessitate considerably longer records for their definitive detection. Lastly, we explore the impact of these sampling patterns on tropical vertical velocities derived from stratospheric water vapor measurements. We find that coarse nonuniform sampling may lead to a biased depiction of the tropical vertical velocities and, hence, to a biased estimation of the impact of the mechanisms that modulate these velocities. These case studies suggest that dense uniform sampling such as that available from limb emission sounders provides much greater fidelity in detecting signals of stratospheric change (for example, fingerprints of greenhouse gas warming and stratospheric ozone recovery) than coarse nonuniform sampling such as that of solar occultation instruments.

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Case Studies of the Impact of Orbital Sampling on Stratospheric Trend Detection and Derivation of Tropical Vertical Velocities: Solar Occultation versus Limb Emission Sounding

10.5194/acp-2016-356 ◽

2016 ◽

Author(s):

Luis F. Millán ◽

Nathaniel J. Livesey ◽

Michelle L. Santee ◽

Jessica L. Neu ◽

Gloria L. Manney ◽

...

Keyword(s):

Case Studies ◽

Atmospheric Chemistry ◽

Stratospheric Ozone ◽

Sampling Bias ◽

Trend Detection ◽

Trace Gas ◽

Uniform Sampling ◽

Solar Occultation ◽

Non Uniform Sampling ◽

The Impact

Abstract. This study investigates the representativeness of two types of orbital sampling applied to stratospheric temperature and trace gas fields. Model fields are sampled using real sampling patterns from the Aura Microwave Limb Sounder (MLS), the HALogen Occultation Experiment (HALOE) and the Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS). The MLS sampling acts as a proxy for a dense uniform sampling pattern typical of limb emission sounders, while HALOE and ACE-FTS represent coarse non-uniform sampling patterns characteristic of solar occultation instruments. First, this study revisits the impact of sampling patterns in terms of the sampling bias, as previous studies have done. Then, it quantifies the impact of different sampling patterns on the estimation of trends and their associated detectability. In general, we find that coarse non-uniform sampling patterns may introduce non-negligible errors in the inferred magnitude of temperature and trace gas trends and necessitate considerably longer records for their definitive detection. Lastly, we explore the impact of these sampling patterns on tropical vertical velocities derived from stratospheric water vapor measurements. We find that coarse non-uniform sampling may lead to a biased depiction of the tropical vertical velocities and, hence, to a biased estimation of the impact of the mechanisms that modulate these velocities. These case studies suggest that dense uniform sampling such as that available from limb emission sounders provides much greater fidelity in detecting signals of stratospheric change (for example, fingerprints of greenhouse gas warming and stratospheric ozone recovery) than coarse non-uniform sampling such as that of solar occultation instruments.

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Validation of MIPAS IMK/IAA methane profiles

Atmospheric Measurement Techniques ◽

10.5194/amt-8-5251-2015 ◽

2015 ◽

Vol 8 (12) ◽

pp. 5251-5261 ◽

Cited By ~ 16

Author(s):

A. Laeng ◽

J. Plieninger ◽

T. von Clarmann ◽

U. Grabowski ◽

G. Stiller ◽

...

Keyword(s):

Atmospheric Chemistry ◽

Michelson Interferometer ◽

European Space Agency ◽

Trace Gas ◽

Mixing Ratios ◽

Air Sampler ◽

Solar Occultation ◽

Space Agency ◽

Scanning Imaging ◽

Satellite Instruments

Abstract. The Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) is an infrared (IR) limb emission spectrometer on the Envisat platform. It measures trace gas distributions during day and night, pole-to-pole, over an altitude range from 6 to 70 km in nominal mode and up to 170 km in special modes, depending on the measurement mode, producing more than 1000 profiles day−1. We present the results of a validation study of methane, version V5R_CH4_222, retrieved with the IMK/IAA (Institut für Meteorologie und Klimaforschung, Karlsruhe/Instituto de Astrofisica de Andalucia, Grenada) MIPAS scientific level 2 processor. The level 1 spectra are provided by the ESA (European Space Agency) and version 5 was used. The time period covered is 2005–2012, which corresponds to the period when MIPAS measured trace gas distributions at a reduced spectral resolution of 0.0625 cm−1. The comparison with satellite instruments includes the Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS), the HALogen Occultation Experiment (HALOE), the Solar Occultation For Ice Experiment (SOFIE) and the SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY (SCIAMACHY). Furthermore, comparisons with MkIV balloon-borne solar occultation measurements and with air sampling measurements performed by the University of Frankfurt are presented. The validation activities include bias determination, assessment of stability, precision validation, analysis of histograms and comparison of corresponding climatologies. Above 50 km altitude, MIPAS methane mixing ratios agree within 3 % with ACE-FTS and SOFIE. Between 30 and 40 km an agreement within 3 % with SCIAMACHY has been found. In the middle stratosphere, there is no clear indication of a MIPAS bias since comparisons with various instruments contradict each other. In the lower stratosphere (below 25 km) MIPAS CH4 is biased high with respect to satellite instruments, and the most likely estimate of this bias is 14 %. However, in the comparison with CH4 data obtained from cryogenic whole-air sampler (cryosampler) measurements, there is no evidence of a high bias in MIPAS between 20 and 25 km altitude. Precision validation is performed on collocated MIPAS–MIPAS pairs and suggests a slight underestimation of its uncertainties by a factor of 1.2. No significant evidence of an instrumental drift has been found.

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Atmospheric impacts of short-lived chlorinated species over the recent past: a chemistry-climate perspective

10.5194/egusphere-egu21-12824 ◽

2021 ◽

Author(s):

Ewa Bednarz ◽

Ryan Hossaini ◽

Luke Abraham ◽

Peter Braesicke ◽

Martyn Chipperfield

Keyword(s):

Atmospheric Chemistry ◽

Climate Model ◽

Stratospheric Ozone ◽

Lower Boundary ◽

Montreal Protocol ◽

Recent Past ◽

Substantial Impact ◽

Ozone Depleting Substances ◽

The Impact

The emissions of most long-lived halogenated ozone-depleting substances (ODSs) are now decreasing, owing to controls on their production introduced by Montreal Protocol and its amendments. However, short-lived halogenated compounds can also have substantial impact on atmospheric chemistry, including stratospheric ozone, particularly if emitted near climatological uplift regions. It has recently become evident that emissions of some chlorinated very short-lived species (VSLSs), such as chloroform (CHCl3) and dichloromethane (CH2Cl2), could be larger than previously believed and increasing, particularly in Asia. While these may exert a significant influence on atmospheric chemistry and climate, their impacts remain poorly characterised.&#160;&#160;We address this issue using the UM-UKCA chemistry-climate model (CCM). While not only the first, to our knowledge, model study addressing this problem using a CCM, it is also the first such study employing a whole atmosphere model, thereby simulating the tropospheric Cl-VSLSs emissions and the resulting stratospheric impacts in a fully consistent manner. We use a newly developed Double-Extended Stratospheric-Tropospheric (DEST) chemistry scheme, which includes emissions of all major chlorinated and brominated VSLSs alongside an extended treatment of long-lived ODSs.&#160;We examine the impacts of rising Cl-VSLSs emissions on atmospheric chlorine tracers and ozone, including their long-term trends. We pay particular attention to the role of &#8216;nudging&#8217;, as opposed to the free-running model set up, for the simulated Cl-VSLSs impacts, thereby demostrating the role of atmospheric dynamics in modulating the atmospheric responses to Cl-VSLSs. In addition, we employ novel estimates of Cl-VSLS emissions over the recent past and compare the results with the simulations that prescribe Cl-VSLSs using simple lower boundary conditions. This allows us to demonstrate the impact such choice has on the dominant location and seasonality of the Cl-VSLSs transport into the stratosphere.

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Oxygen isotopic ratios in Martian water vapour observed by ACS MIR on board the ExoMars Trace Gas Orbiter

Astronomy and Astrophysics ◽

10.1051/0004-6361/201936234 ◽

2019 ◽

Vol 630 ◽

pp. A91 ◽

Cited By ~ 2

Author(s):

J. Alday ◽

C. F. Wilson ◽

P. G. J. Irwin ◽

K. S. Olsen ◽

L. Baggio ◽

...

Keyword(s):

Water Vapour ◽

Atmospheric Chemistry ◽

Trace Gas ◽

Oxygen Isotope Ratios ◽

Infrared Measurements ◽

History Of ◽

Oxygen Isotopic ◽

Atmospheric Loss ◽

The Impact ◽

First Time

Oxygen isotope ratios provide important constraints on the history of the Martian volatile system, revealing the impact of several processes that might fractionate them, such as atmospheric loss into space or interaction with the surface. We report infrared measurements of the Martian atmosphere obtained with the mid-infrared channel (MIR) of the Atmospheric Chemistry Suite (ACS), onboard the ExoMars Trace Gas Orbiter. Absorption lines of the three main oxygen isotopologues of water vapour (H216O, H218O, and H217O) observed in the transmission spectra allow, for the first time, the measurement of vertical profiles of the 18O/16O and 17O/16O ratios in atmospheric water vapour. The observed ratios are enriched with respect to Earth-like values (δ18O = 200 ± 80‰ and δ17O = 230 ± 110‰ corresponding to the Vienna Standard Mean Ocean Water). The vertical structure of these ratios does not appear to show significant evidence of altitudinal variations.

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On the impact of future climate change on tropopause folds and tropospheric ozone

Atmospheric Chemistry and Physics ◽

10.5194/acp-19-14387-2019 ◽

2019 ◽

Vol 19 (22) ◽

pp. 14387-14401 ◽

Cited By ~ 2

Author(s):

Dimitris Akritidis ◽

Andrea Pozzer ◽

Prodromos Zanis

Keyword(s):

Atmospheric Chemistry ◽

Tropospheric Ozone ◽

Eastern Mediterranean ◽

Stratospheric Ozone ◽

Lower Troposphere ◽

Future Climate Change ◽

Identification Algorithm ◽

The Future ◽

Projected Changes ◽

The Impact

Abstract. Using a transient simulation for the period 1960–2100 with the state-of-the-art ECHAM5/MESSy Atmospheric Chemistry (EMAC) global model and a tropopause fold identification algorithm, we explore the future projected changes in tropopause folds, stratosphere-to-troposphere transport (STT) of ozone, and tropospheric ozone under the RCP6.0 scenario. Statistically significant changes in tropopause fold frequencies from 1970–1999 to 2070–2099 are identified in both hemispheres, regionally exceeding 3 %, and are associated with the projected changes in the position and intensity of the subtropical jet streams. A strengthening of ozone STT is projected for the future in both hemispheres, with an induced increase in transported stratospheric ozone tracer throughout the whole troposphere, reaching up to 10 nmol mol−1 in the upper troposphere, 8 nmol mol−1 in the middle troposphere, and 3 nmol mol−1 near the surface. Notably, the regions exhibiting the largest changes of ozone STT at 400 hPa coincide with those with the highest fold frequency changes, highlighting the role of the tropopause folding mechanism in STT processes under a changing climate. For both the eastern Mediterranean and Middle East (EMME) and Afghanistan (AFG) regions, which are known as hotspots of fold activity and ozone STT during the summer period, the year-to-year variability of middle-tropospheric ozone with stratospheric origin is largely explained by the short-term variations in ozone at 150 hPa and tropopause fold frequency. Finally, ozone in the lower troposphere is projected to decrease under the RCP6.0 scenario during MAM (March, April, and May) and JJA (June, July, and August) in the Northern Hemisphere and during DJF (December, January, and February) in the Southern Hemisphere, due to the decline of ozone precursor emissions and the enhanced ozone loss from higher water vapour abundances, while in the rest of the troposphere ozone shows a remarkable increase owing mainly to the STT strengthening and the stratospheric ozone recovery.

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Aerosol extinction profiles at 525 nm and 1020 nm derived from ACE imager data: comparisons with GOMOS, SAGE II, SAGE III, POAM III, and OSIRIS

Atmospheric Chemistry and Physics ◽

10.5194/acp-8-2027-2008 ◽

2008 ◽

Vol 8 (7) ◽

pp. 2027-2037 ◽

Cited By ~ 16

Author(s):

F. Vanhellemont ◽

C. Tetard ◽

A. Bourassa ◽

M. Fromm ◽

J. Dodion ◽

...

Keyword(s):

Atmospheric Chemistry ◽

Trace Gas ◽

Aerosol Extinction ◽

Optical Extinction ◽

Solar Occultation ◽

Comparison Results ◽

Stellar Occultation ◽

Relative Differences ◽

Atmospheric Trace Gas ◽

Chemistry Experiment

Abstract. The Canadian ACE (Atmospheric Chemistry Experiment) mission is dedicated to the retrieval of a large number of atmospheric trace gas species using the solar occultation technique in the infrared and UV/visible spectral domain. However, two additional solar disk imagers (at 525 nm and 1020 nm) were added for a number of reasons, including the retrieval of aerosol and cloud products. In this paper, we present first comparison results for these imager aerosol/cloud optical extinction coefficient profiles, with the ones derived from measurements performed by 3 solar occultation instruments (SAGE II, SAGE III, POAM III), one stellar occultation instrument (GOMOS) and one limb sounder (OSIRIS). The results indicate that the ACE imager profiles are of good quality in the upper troposphere/lower stratosphere, although the aerosol extinction for the visible channel at 525 nm contains a significant negative bias at higher altitudes, while the relative differences indicate that ACE profiles are almost always too high at 1020 nm. Both problems are probably related to ACE imager instrumental issues.

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Investigation of strongly enhanced methane Part I: Chemical feedbacks and rapid adjustments.

10.5194/egusphere-egu2020-9786 ◽

2020 ◽

Author(s):

Franziska Winterstein ◽

Patrick Jöckel ◽

Martin Dameris ◽

Michael Ponater ◽

Fabian Tanalski ◽

...

Keyword(s):

Atmospheric Chemistry ◽

Radiative Forcing ◽

Climate Model ◽

Numerical Study ◽

Stratospheric Ozone ◽

Lower Boundary ◽

Tropospheric Chemistry ◽

Substantial Part ◽

Mixing Ratios ◽

The Impact

Methane (CH4) is the second most important greenhouse gas, which atmospheric concentration is influenced by human activities and currently on a sharp rise. We present a study with numerical simulations using a Chemistry-Climate-Model (CCM), which are performed to assess possible consequences of strongly enhanced CH4 concentrations in the Earth's atmosphere for the climate.Our analysis includes experiments with 2xCH4 and 5xCH4 present day (2010) lower boundary mixing ratios using the CCM EMAC. The simulations are conducted with prescribed oceanic conditions, mimicking present day tropospheric temperatures as its changes are largely suppressed. By doing so we are able to investigate the quasi-instantaneous chemical impact on the atmosphere. We find that the massive increase in CH4 strongly influences the tropospheric chemistry by reducing the OH abundance and thereby extending the tropospheric CH4 lifetime as well as the residence time of other chemical pollutants. The region above the tropopause is impacted by a substantial rise in stratospheric water vapor (SWV). The stratospheric ozone (O3) column increases overall, but SWV induced stratospheric cooling also leads to enhanced ozone depletion in the Antarctic lower stratosphere. Regional&#160; patterns of ozone change are affected by modification of stratospheric dynamics, i.e. increased tropical up-welling and stronger meridional transport&#160; towards the polar regions. We calculate the net radiative impact (RI) of the 2xCH4 experiment to be 0.69 W m-2 and for the 5xCH4 experiment to be 1.79 W m-2. A substantial part of the RI is contributed by chemically induced O3 and SWV changes, in line with previous radiative forcing estimates and is for the first time splitted and spatially asigned to its chemical contributors.This numerical study using a CCM with prescibed oceanic conditions shows the rapid responses to significantly enhanced CH4 mixing ratios, which is the first step towards investigating the impact of possible strong future CH4 emissions on atmospheric chemistry and its feedback on climate.

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Brominated VSLS and their influence on ozone under a changing climate

Atmospheric Chemistry and Physics ◽

10.5194/acp-17-11313-2017 ◽

2017 ◽

Vol 17 (18) ◽

pp. 11313-11329 ◽

Cited By ~ 11

Author(s):

Stefanie Falk ◽

Björn-Martin Sinnhuber ◽

Gisèle Krysztofiak ◽

Patrick Jöckel ◽

Phoebe Graf ◽

...

Keyword(s):

21St Century ◽

Atmospheric Chemistry ◽

Lower Stratosphere ◽

Atmospheric Transport ◽

Stratospheric Ozone ◽

Chemical Transformations ◽

Mixing Ratios ◽

Ocean Atmosphere ◽

The Impact

Abstract. Very short-lived substances (VSLS) contribute as source gases significantly to the tropospheric and stratospheric bromine loading. At present, an estimated 25 % of stratospheric bromine is of oceanic origin. In this study, we investigate how climate change may impact the ocean–atmosphere flux of brominated VSLS, their atmospheric transport, and chemical transformations and evaluate how these changes will affect stratospheric ozone over the 21st century. Under the assumption of fixed ocean water concentrations and RCP6.0 scenario, we find an increase of the ocean–atmosphere flux of brominated VSLS of about 8–10 % by the end of the 21st century compared to present day. A decrease in the tropospheric mixing ratios of VSLS and an increase in the lower stratosphere are attributed to changes in atmospheric chemistry and transport. Our model simulations reveal that this increase is counteracted by a corresponding reduction of inorganic bromine. Therefore the total amount of bromine from VSLS in the stratosphere will not be changed by an increase in upwelling. Part of the increase of VSLS in the tropical lower stratosphere results from an increase in the corresponding tropopause height. As the depletion of stratospheric ozone due to bromine depends also on the availability of chlorine, we find the impact of bromine on stratospheric ozone at the end of the 21st century reduced compared to present day. Thus, these studies highlight the different factors influencing the role of brominated VSLS in a future climate.

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The Impact of Non-uniform Sampling on Stratospheric Ozone Trends Derived from Occultation Instruments

10.5194/acp-2017-575 ◽

2017 ◽

Author(s):

Robert P. Damadeo ◽

Joseph M. Zawodny ◽

Ellis E. Remsberg ◽

Kaley A. Walker

Keyword(s):

Stratospheric Ozone ◽

Primary Source ◽

Data Sets ◽

Sampled Data ◽

Uniform Sampling ◽

Ozone Trends ◽

Long Term Trends ◽

Non Uniform Sampling ◽

The Impact

Abstract. This paper applies a recently developed technique for deriving long-term trends in ozone from sparsely sampled data sets to multiple occultation instruments simultaneously without the need for homogenization. The technique can compensate for the non-uniform temporal, spatial, and diurnal sampling of the different instruments and can also be used to account for biases and drifts between instruments. These problems have been noted in recent international assessments as being a primary source of uncertainty that clouds the significance of derived trends. Results show potential recovery trends of ~ 2–3 %/decade in the upper stratosphere at mid-latitudes, which are similar to other studies, and also how sampling biases present in these data sets can create differences in derived "recovery" trends of up to ~ 1 %/decade if not properly accounted for. Limitations inherent to all techniques (e.g., relative instrument drifts) and their impacts (e.g., trend differences up to ~ 2 %/decade) are also described and a potential path forward towards resolution is presented.

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Stratospheric lifetime ratio of CFC-11 and CFC-12 from satellite and model climatologies

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-14-16865-2014 ◽

2014 ◽

Vol 14 (11) ◽

pp. 16865-16906 ◽

Cited By ~ 3

Author(s):

L. Hoffmann ◽

C. M. Hoppe ◽

R. Müller ◽

G. S. Dutton ◽

J. C. Gille ◽

...

Keyword(s):

Global Warming ◽

Atmospheric Chemistry ◽

Climate Model ◽

Transport Model ◽

Stratospheric Ozone ◽

Michelson Interferometer ◽

Coupled Model ◽

Model System ◽

Satellite Observations ◽

The Impact

Abstract. Chlorofluorocarbons (CFCs) play a key role in stratospheric ozone loss and are strong infrared absorbers that contribute to global warming. The stratospheric lifetimes of CFCs are a measure of their global loss rates that are needed to determine global warming and ozone depletion potentials. We applied the tracer-tracer correlation approach to zonal mean climatologies from satellite measurements and model data to assess the lifetimes of CFCl3 (CFC-11) and CF2Cl2 (CFC-12). We present estimates of the CFC-11/CFC-12 lifetime ratio and the absolute lifetime of CFC-12, based on a reference lifetime of 52 yr for CFC-11. We analyzed climatologies from three satellite missions, the Atmospheric Chemistry Experiment-Fourier Transform Spectrometer (ACE-FTS), the HIgh Resolution Dynamics Limb Sounder (HIRDLS), and the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS). We found a CFC-11/CFC-12 lifetime ratio of 0.47±0.08 and a CFC-12 lifetime of 111(96–132) yr for ACE-FTS, a ratio of 0.46±0.07 and a lifetime of 112(97–133) yr for HIRDLS, and a ratio of 0.46±0.08 and a lifetime of 112(96–135) yr for MIPAS. The error-weighted, combined CFC-11/CFC-12 lifetime ratio is 0.47±0.04 and the CFC-12 lifetime estimate is 112(102–123) yr. These results agree with the recent Stratosphere-troposphere Processes And their Role in Climate (SPARC) reassessment, which recommends lifetimes of 52(43–67) yr and 102(88–122) yr, respectively. Having smaller uncertainties than the results from other recent studies, our estimates can help to better constrain CFC-11 and CFC-12 lifetime recommendations in future scientific studies and assessments. Furthermore, the satellite observations were used to validate first simulation results from a new coupled model system, which integrates a Lagrangian chemistry transport model into a climate model. For the coupled model we found a CFC-11/CFC-12 lifetime ratio of 0.48±0.07 and a CFC-12 lifetime of 110(95–129) yr, based on a ten-year perpetual run. Closely reproducing the satellite observations, the new model system will likely become a useful tool to assess the impact of advective transport, mixing, and photochemistry as well as climatological variability on the stratospheric lifetimes of long-lived tracers.

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