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