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Overview of the Arctic Middle Atmospheric Chemistry Theme

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Title: Overview of the Arctic Middle Atmospheric Chemistry Theme


1
Overview of the Arctic Middle Atmospheric
Chemistry Theme
  • Kimberly Strong
  • Department of Physics, University of Toronto
  • Co-Investigators J. Drummond, H. Fast, A.
    Manson, T. McElroy, G. Shepherd, R. Sica, J.
    Sloan, K. Strawbridge, K. Walker, W. Ward, J.
    Whiteway
  • Collaborators J. McConnell, P. Bernath, T.
    Shepherd
  • Students C. Adams, A. Fraser, D. Fu, F.
    Kolonjari, R. Lindenmaier, H. Popova
  • Post-docs R. Batchelor, T. Kerzenmacher, K.
    Sung, M. Wolff
  • Env. Canada M. Harwood, R. Mittermeier
  • CANDAC P. Fogal, A. Harrett, A. Khmel, C.
    Midwinter, P. Loewen, O. Mikhailov, M.
    Okraszewski (Thanks to all!)
  • CANDAC Workshop 5
  • Toronto, 24-26 October 2007

2
Overview
  • Polar Stratospheric Ozone Trends
  • The Need for Arctic Measurements
  • The Arctic Middle Atmosphere Chemistry Theme
  • The First Year of AMAC Activities
  • Outlook

3
Introduction
  • Arctic middle atmosphere chemistry
  • Focus here is on the stratosphere and the ozone
    budget
  • Coupled to troposphere mesosphere, dynamics
    radiation
  • Stratospheric ozone
  • Highly effective absorber of harmful UV-B solar
    radiation
  • Dominant source of radiative heating in the
    stratosphere
  • This heating determines the stratospheric
    temperature distribution, which, in turn,
    influences stratospheric winds
  • Consequences of a decrease in Arctic
    stratospheric ozone
  • Enhancement of UV-dependent photochemical
    reactions in the troposphere
  • Decrease in radiative forcing
  • Reduction in stratospheric temperatures
  • Change in stratospheric dynamics

4
Polar Total Ozone Trends
WMO Ozone Assessment 2006
5
Seasonal Total Ozone Trends
  • Total ozone column trends as a function of
    equivalent latitude
  • and season using TOMS and GOME data for 1978-2000

x - mean position of vortex edge Eq. Latitude -
a potential vorticity coordinate with vortex
centre at 90
Largest Arctic trend is 1.04 0.39 per year
in March
WMO Ozone Assessment 2002
6
Arctic Ozone March Averages
  • March monthly averaged total ozone from
    satellites
  • Nimbus-4 BUV
  • Nimbus-7 TOMS
  • NOAA-9 SBUV/2
  • Earth Probe TOMS
  • Aura OMI

WMO Ozone Assessment 2006
7
Latitudinal Total Ozone Trends
  • Measured and modelled latitudinal total ozone
    trends

WMO Ozone Assessment 2006
8
Polar Ozone Depletion - Processes
  • (1) Formation of the winter polar vortex (band
    of westerly winds)
  • isolates cold dark air over the polar regions
  • (2) Low temperatures in the vortex, Tlt195 K
  • PSCs form in the lower stratosphere (liquid
    solid HNO3,H2O,H2SO4)
  • (3) Dehydration and denitrification
  • remove H2O nitrogen oxides which could
    neutralize chlorine
  • (4) Release of CFCs, mixing, and transport to
    the polar regions
  • enhanced levels of chlorine and other halogen
    species
  • (5) Heterogeneous reactions on the PSCs
  • convert inactive chlorine (HCl and ClONO2) into
    reactive Cl2
  • (6) Sunlight returns in the spring
  • UV radiation breaks Cl2 apart to form Cl
  • (7) Catalytic chlorine and bromine cycles
  • destroy ozone, while recycling Cl
  • This continues until the Sun causes a dynamical
    breakdown of the winter vortex and PSCs evaporate.

9
The Role of Bromine
  • Significant source of uncertainty
  • May be more important (by 10-15) in polar
    ozone depletion than previously thought
  • BrO ClO cycle estimated to contribute up to
    50 of chemical loss of polar ozone
  • Bry may be 3-8 ppt larger than expected from
    CH3Br halons source
  • due short-lived bromocarbons and tropospheric
    BrO ?

Frieler at al., 2006 WMO Ozone Assessment 2006
10
Arctic Vortex and Ozone Loss
  • Large variation from year to year in
  • area of the Arctic vortex (dominates circulation
    from Nov. to March)
  • strength of the sudden warmings associated with
    planetary-scale waves originating in the
    troposphere
  • timing of the final vortex breakdown
  • Large variability in Arctic ozone (short long
    term) is due to
  • variability in transport of air in the
    stratosphere
  • variability in tropospheric forcing
  • variations in chemical ozone loss
  • Chemical consequences of variability in vortex
    meteorology
  • area over which T is below threshold for PSC
    formation
  • amount of sunlight available to drive chemical
    ozone loss and the volume of air processed
    through cold regions
  • timing of the cold periods
  • the location of the cold areas within the vortex
  • position of the vortex when cold areas develop

11
Processes Affecting Stratospheric Ozone and
Temperature
Brasseur, SPARC Lecture 2004, after Schnadt et
al., Climate Dynamics 2002
12
Processes Affecting Stratospheric Ozone and
Temperature
Brasseur, SPARC Lecture 2004, after Schnadt et
al., Climate Dynamics 2002
13
Processes Affecting Stratospheric Ozone and
Temperature
Brasseur, SPARC Lecture 2004, after Schnadt et
al., Climate Dynamics 2002
14
Processes Affecting Stratospheric Ozone and
Temperature
Brasseur, SPARC Lecture 2004, after Schnadt et
al., Climate Dynamics 2002
15
Processes Affecting Stratospheric Ozone and
Temperature
Brasseur, SPARC Lecture 2004, after Schnadt et
al., Climate Dynamics 2002
16
Future Impact of Climate Change
  • Will climate change enhance or reduce polar ozone
    loss?
  • Two possibilities
  • The stratospheric vortex becomes stronger and
    colder, and there is a positive Arctic
    Oscillation trend (e.g., Shindell et al., 1999).
  • increasing CO2 cools the stratosphere,
    strengthens the polar vortex
  • such cooling could increase formation of PSCs
  • results in more Arctic ozone loss
  • observations suggest 15 DU Arctic ozone loss per
    Kelvin cooling
  • Dynamical heating causes a more disturbed and
    warmer NH stratospheric vortex (e.g., Schnadt et
    al., Clim. Dyn. 2002 Schnadt Dameris, GRL
    2003).
  • enhancement of planetary wave activity
  • causes a weaker and warmer polar vortex
  • results in less Arctic ozone loss - faster
    recovery

17
Two Possibilities
(1) Cooling of stratosphere ?T (K) (July) in
response to CO2 doubling from the Hammonia
Model (Brasseur, SPARC Lecture 2004)
(2) Warming of stratosphere ?T (K) (DJF) from
1990 to 2015 from the ECHAM model (Schnadt et
al., Clim. Dyn. 2002)
18
Sensitivity of Arctic Ozone Loss to T
squares, red line - ozonesondes circles, green
line - HALOE BW circles, black lines -
SLIMCAT Overall cooling trend in the global-mean
lower stratosphere is 0.5 K/decade (1979-2005)
Ozone column loss DU (14-25 km, mid-Jan to
late March)
Ozone column loss DU (14-25 km, mid-Jan to
late March)
80 DUozone loss
5-6 K temperature change
15 DU additional chemical ozone lossper Kelvin
cooling of the Arctic stratosphere
Rex et al., GRL 2004, 2006 WMO Ozone Assessment
2006
19
An Example - Winter 2005
  • The Arctic vortex was unusually cold and stable
    in early winter 2005...

Courtesy of C.T. McElroy and J. Davies, EC
20
Montreal Protocol
  • 1985 - Vienna Convention for the Protection of
    the Ozone Layer
  • 1987 - Montreal Protocol on Substances that
    Deplete the Ozone Layer
  • Entered into force in 1989
  • Established controls on halogen source gases
  • Later strengthened by a series of Amendments

WMO Ozone Assessment 2006
21
WMO Ozone Assessment 2006
22
Recovery of Stratospheric Ozone
Changes in total ozone from 60S to 60N
IPCC/TEAP SROC 2005
23
Polar Ozone - Predictions
  • Gradual recovery of ozone is anticipated as
    stratospheric chlorine decreases
  • ozone turnaround in the Arctic likely before 2020
  • vunerable to perturbations, such as aerosols from
    volcanoes
  • coupled to stratospheric cooling
  • extreme Arctic ozone loss is not predicted

Spring Polar Ozone Anomalies
WMO Ozone Assessment 2006
24
The Need for Arctic Measurements
  • the frequency of measurements deep in the
    Arctic vortex remains low. The situation is
    unsatisfactory given the highly non-linear
    sensitivity of Arctic stratospheric ozone to cold
    winters. Chemical and dynamical perturbations
    caused by strong volcanic eruptions make it
    impossible to derive a linear trend in total
    ozone, which highlights the importance of
    continuous measurements throughout the expected
    recovery of the ozone layer during the coming
    decades.
  • IGOS 2004 Atmospheric Chemistry Report

25
The Need for Arctic Measurements
  • With regard to the Arctic, the future evolution
    of ozone is potentially sensitive to climate
    change and to natural variability, and will not
    necessarily follow strictly the chlorine loading.
    There is uncertainty in even the sign of the
    dynamical feedback to WMGHG changes. Progress
    will result from further development of CCMs
    chemistry-climate models and from comparisons
    of results between models and with observations.
  • IPCC/TEAP 2005, Special Report on Safeguarding
    the Ozone Layer and the Global Climate System

26
Arctic Middle Atmosphere Chemistry
  • Overall goal of this theme
  • To improve our understanding of the processes
    controlling the Arctic stratospheric ozone budget
    and its future evolution, using measurements of
    the concentrations of stratospheric constituents.
  • This theme addresses two of the four grand
    challenges in atmospheric chemistry identified
    in the 2004 IGOS Atmospheric Chemistry Theme
    Report, namely
  • stratospheric chemistry and ozone depletion
  • chemistry-climate interactions.

27
Arctic Middle Atmosphere Chemistry Theme
  • Science Questions
  • What is the chemical composition of the Arctic
    stratosphere above PEARL?
  • How and why is it changing with time?
  • How is the chemistry coupled to dynamics,
    microphysics, and radiation?
  • What is the polar stratospheric bromine budget?
  • Significant source of uncertainty
  • BrO ClO cycle estimated to contribute up to
    half chemical loss
  • How will the polar stratosphere respond to
    climate perturbations?
  • Particularly while Cl and Br loading is high
  • How will changes in atmospheric circulation
    affect polar ozone?
  • Cooling (more ozone depletion) or warming (less)?

28
Arctic Middle Atmosphere Chemistry Theme
  • Scientific Objectives
  • (1)To obtain an extended data set of the
    concentrations of ozone and of other key trace
    gases in the Canadian Arctic stratosphere above
    PEARL under both chemically perturbed and
    unperturbed conditions.
  • (2)To analyse these measurements, in conjunction
    with dynamical, radiative, aerosol/PSC, and
    meteorological observations also made at PEARL,
    in order to unravel the coupled processes
    controlling Arctic stratospheric composition and
    to quantify the contributions from dynamics and
    chemistry to ozone depletion.
  • (3)To investigate the seasonal and interannual
    variability of the Arctic ozone budget, as well
    as its longer-term evolution, with a focus on
    determining the impact of climate change.
  • (4)To combine the measurements with atmospheric
    models (including chemical box models, chemical
    transport models and global circulation models)
    to facilitate both improved modelling of the
    atmosphere and the interpretation of the
    measurements, and hence to better understand
    climate system processes and climate change.

29
Arctic Middle Atmosphere Chemistry Theme
  • Short-Term Outputs
  • Better understanding of diurnal, day-to-day,
    seasonal, and interannual variations in a suite
    of Arctic stratospheric constituents, including
    ozone and related trace gases, particularly
    nitrogen and halogen compounds.
  • Identification and quantification of chemical
    ozone loss at Eureka during each Arctic
    winter-spring.
  • Process studies of the relative importance of
    chemical, radiative, microphysical, and transport
    processes, including comparisons with atmospheric
    models.

30
Arctic Middle Atmosphere Chemistry Theme
  • Long-Term Outputs
  • A significant new long-term dataset of Arctic
    chemical composition measurements.
  • Determination of trends in ozone and related
    stratospheric constituents.
  • Improved understanding of processes that result
    in feedbacks between stratospheric ozone
    depletion, rising greenhouse gas concentrations,
    and climate change.
  • Better predictive capabilities regarding the
    future evolution of the Arctic stratospheric
    ozone budget.

31
Arctic Middle Atmosphere Chemistry Theme
  • Primary Composition Instruments
  • Bruker 125HR Fourier transform infrared
    spectrometer (FTS)
  • Direct solar (and lunar) absorption, 700-4500
    cm-1 at high resolution
  • UV-visible grating spectrometer
  • Zenith-scattered (and direct) solar absorption,
    300-600 nm
  • Stratospheric ozone lidar ? Differential
    Absorption Lidar (DIAL)
  • Brewer spectrophotometer ? Ozone total columns
  • Polar Atmospheric Emitted Radiance Interferometer
    (P-AERI)
  • Emission, 400-3300 cm-1 (3-25 µm) at low spectral
    resolution
  • Measurements
  • Reactive species, source gases, reservoirs,
    dynamical tracers
  • O3, NO, NO2, HNO3, N2O5, NO3, N2O, ClONO2, HCl,
    OClO, BrO, HF, CFCs, CH4, H2O, CO, OCS, ...
  • Total columns and some information on vertical
    distribution

32
Arctic Middle Atmosphere Chemistry Theme
  • Modelling
  • Interpretation will include comparisons with
    atmospheric models in order to better understand
    the underlying processes and to facilitate
    improved modelling of the atmosphere.
  • Comparisons with chemical transport models to
    quantify chemical ozone loss, and the role of
    nitrogen, chlorine, and bromine families
  • Back trajectories and box models will be used to
    investigate the history and chemical evolution of
    stratospheric air above Eureka
  • CMAM can provide a detailed global chemical
    climate model, e.g., for estimating the
    spatio-temporal variability of the measured trace
    gases
  • CMAM-DA will enable combination of the Arctic
    data with other observations and with a priori
    information

33
DA8 FTS Measurements HNO3
Farahani et al., JGR 2007
34
DA8 FTS Measurements HNO3
Comparison of solar and lunar DA8 FTS
measurements during winter 2001-2002 with SLIMCAT
chemical transport model and CMAM
Farahani et al., JGR 2007
35
2006-2007 AMAC Highlights
  • February-March 2006 - ACE Arctic validation
    campaign
  • March 2006 - installation of SEARCH / U of Idaho
    AERI
  • July 2006 - installation of new Bruker IFS 125HR
    FTS
  • August 2006 - installation of new UV-visible
    grating spectrometer (PEARL-GBS)
  • August-October 2006 - first data from both
    instruments
  • February-March 2007 - ACE Arctic validation
    campaign
  • May 2007 - P-AERI ordered
  • July 2007 - Bruker / Bomem intercomparison
    campaign
  • August-September 2007 - NDACC Aura validation
    campaign
  • Ongoing - daily measurements, implementation and
    optimization of retrieval algorithms, data
    analysis

36
AMAC Students and PDFs
  • Bruker FTS measurements and data analysis
  • PDF Rebecca Batchelor, UofT
  • MSc/PhD student Rodica Lindenmaier, UofT
  • UV-visible measurements and data analysis
  • PhD student Annemarie Fraser, UofT
  • PhD student Cristen Adams, UofT
  • Analysis of PARIS-IR Bomem DA8 data using SFIT2
  • PDF Keeyoon Sung, UofT (Sept. 2006 - April 2007)
  • PhD student Dejian Fu, U of Waterloo (just
    graduated)
  • Stratospheric ozone lidar measurements and data
    analysis
  • MSc student Andrea Moss, UWO
  • 2006 and 2007 ACE Arctic validation campaigns
  • PDF Tobias Kerzenmacher, UofT
  • P-AERI measurements and data analysis
  • PDF Mareile Wolff, UofT (IPY Dec. 2007 - )

37
External Linkages
  • Canadian Space Agency
  • Continues to support ACE Arctic validation
    campaigns, currently Canadian Arctic Validation
    of ACE for IPY 2007 2008
  • Network for the Detection of Atmospheric
    Composition Change (NDACC)
  • Contacted Co-Chairs of the NDACC UV-Visible
    Working Group about the requirements for
    certifying the UV-visible spectrometer
  • Invited to upcoming November meeting
  • Comparing Bruker FTS with Bomem DA8 for NDACC
    certification
  • Six weeks of alternating measurements from
    February-March 2007, linked by continuous
    measurements with PARIS-IR
  • Additional intercomparison campaign held in July
    2007
  • Actively collaborating with Gloria Manney, JPL
  • Working on linkages with SEARCH, IASOA, SPARC,
    modelling groups

38
AMAC-Related Publications
  • T.E. Kerzenmacher et al., Measurements of O3,
    NO2 and Temperature During the 2004 Canadian
    Arctic ACE Validation Campaign. GRL 2005.
  • A. Wiacek et al., First Detection of
    Meso-Thermospheric Nitric Oxide by Ground-Based
    FTIR Solar Absorption Spectroscopy. GRL 2006.
  • E.E. Farahani et al., Nitric acid measurements at
    Eureka obtained in winter 2001-2002 Using solar
    and lunar Fourier transform infrared absorption
    spectroscopy Comparisons with observations at
    Thule and Kiruna and with results from
    three-dimensional models. JGR 2007.
  • G. L. Manney et al., The high Arctic in extreme
    winters vortex, temperature, and MLS and ACE-FTS
    trace gas evolution. ACPD 2007.
  • R. J. Sica et al., Validation of the
    Atmospheric Chemistry Experiment (ACE) version
    2.2 temperature using ground-based and
    space-borne measurements. ACPD 2007.
  • R. Lindenmaier, First Measurements of ozone with
    the new Bruker IFS 125HR at Eureka, M.Sc. Thesis,
    U of Toronto, Toronto, 2007.
  • D. Fu et al., PARIS-IR and ACE Measurements,
    Ph.D. Thesis, U of Waterloo, 2007.
  • A. Fraser et al., Intercomparison of UV-visible
    measurements of ozone and NO2 during the Canadian
    Arctic ACE Validation Campaigns 20042006. In
    preparation. Submission to ACP is imminent.
  • E. Dupuy et al., Validation of ozone
    measurements from the Atmospheric Chemistry
    Experiment (ACE). Submission to ACP is imminent.
  • K. Sung et al., Partial and total column
    measurements at Eureka, Nunavut in spring 2004
    and 2005 using solar infrared absorption
    spectroscopy, including comparisons with ACE
    satellite measurements. Submission to ACP soon.
  • D. Fu et al., Simultaneous atmospheric
    measurements using two Fourier transform infrared
    spectrometers at the Polar Environment
    Atmospheric Research Laboratory (PEARL) during
    spring 2006. Submission to ACP soon. Also
    ACE validation

39
TCCON Opportunity
  • Invited to join proposal to NASA for expansion of
    the Total Carbon Column Observing Network (TCCON)
  • Network of Bruker 125HRs for CO2, CH4, H2O, O2,
    N2O, CO
  • One goal - validation of NASA's Orbiting Carbon
    Observatory (OCO)
  • Travel and loan of hardware (beamsplitters,
    detectors, data storage)
  • Attended TCCON meeting at May NDACC IRWG meeting
  • Provided a report to CANDAC Scientific Steering
    Committee
  • Recommended that we accept the invitation to join
    the network
  • Issues
  • TCCON measurements use different beamsplitter and
    detector from standard mid-IR configuration, with
    manual intervention needed
  • Some reduction in "middle atmosphere"
    observations
  • General thoughts
  • An interesting and positive extension of our
    capabilities, benefits outweigh challenges, links
    us to this growing network, very topical

40
Outlook Tasks and Issues
  • Installation of new sun-trackers for FTS and
    UV-visible
  • Maximization and automation of Bruker FTS
    measurements
  • Upgrade and operation of stratospheric ozone
    lidar
  • Installation of CANDAC P-AERI
  • NDACC certification for Bruker FTS and UV-visible
    spectrometer
  • Implementation of TCCON capability if proposal
    successful
  • Completion of the analysis of Bomem DA8 data
    archive
  • Analysis of CANDAC/PEARL measurements
  • Integration with complementary measurements at
    PEARL
  • Contributions to IPY atmospheric science
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