Transcript Theme3_summary_Strong

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
Overview
 Polar Stratospheric Ozone Trends
 The Need for Arctic Measurements
 The Arctic Middle Atmosphere Chemistry Theme
 The First Year of AMAC Activities
 Outlook
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
Polar Total Ozone Trends
WMO Ozone Assessment 2006
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
Largest Arctic trend is
1.04 ± 0.39 % per year in March
Eq. Latitude a potential
vorticity
coordinate
with vortex
centre at 90°
WMO Ozone
Assessment
2002
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
Latitudinal Total Ozone Trends
Measured
and
modelled
latitudinal
total ozone
trends
WMO Ozone
Assessment
2006
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, T<195 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.
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 ?
= BrO + BrCl
Frieler at al., 2006; WMO Ozone Assessment 2006
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
Processes Affecting Stratospheric
Ozone and Temperature
Stratospheric circulation
Chemical reaction rates
Stratospheric
temperature
UV
Stratospheric
ozone
Brasseur, SPARC Lecture 2004,
after Schnadt et al., Climate Dynamics 2002
Processes Affecting Stratospheric
Ozone and Temperature
Stratospheric circulation
Chemical reaction rates
Stratospheric
temperature
UV
Stratospheric
ozone
Vertical propagation of
planetary and gravity waves
Brasseur, SPARC Lecture 2004,
after Schnadt et al., Climate Dynamics 2002
Processes Affecting Stratospheric
Ozone and Temperature
Stratospheric circulation
Chemical reaction rates
Stratospheric
temperature
UV
Stratospheric
ozone
Greenhouse
gases
Vertical propagation of
planetary and gravity waves
Anthropogenic emissions of
CO2, CFCs, CH4, N2O
Brasseur, SPARC Lecture 2004,
after Schnadt et al., Climate Dynamics 2002
Processes Affecting Stratospheric
Ozone and Temperature
Stratospheric circulation
Chemical reaction rates
Stratospheric
temperature
UV
Greenhouse
gases
Stratospheric
ozone
Stratospheric chlorine,
bromine, and nitrogen
oxides
Troposphere-stratosphere exchange
Vertical propagation of
planetary and gravity waves
Anthropogenic emissions of
CO2, CFCs, CH4, N2O
Brasseur, SPARC Lecture 2004,
after Schnadt et al., Climate Dynamics 2002
Processes Affecting Stratospheric
Ozone and Temperature
Stratospheric circulation
Chemical reaction rates
Stratospheric
temperature
UV
Stratospheric
ozone
PSC formation
Greenhouse
gases
Stratospheric chlorine,
bromine, and nitrogen
oxides
Troposphere-stratosphere exchange
Vertical propagation of
planetary and gravity waves
Stratospheric
water vapour
CH4 oxidation
Anthropogenic emissions of
CO2, CFCs, CH4, N2O
Brasseur, SPARC Lecture 2004,
after Schnadt et al., Climate Dynamics 2002
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
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)
mid-Jantotolate
late March)
March)
mid-Jan
km, km,
(~14-25(14-25
loss [ DU
columnloss
Ozone
DU] ]
column
Ozone
Sensitivity of Arctic Ozone Loss to T
squares, red line
- ozonesondes
circles, green
line - HALOE
B&W circles,
black lines SLIMCAT
~80 DU
ozone loss
~5-6 K temperature change
~ 15 DU additional chemical ozone loss
per Kelvin cooling of the Arctic stratosphere
Overall
cooling trend
in the globalmean lower
stratosphere
is ~0.5
K/decade
(1979-2005)
Rex et al., GRL 2004, 2006; WMO Ozone Assessment 2006
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
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
WMO Ozone
Assessment
2006
Recovery of Stratospheric Ozone
Changes in
total ozone
from 60°S
to 60°N
IPCC/TEAP
SROC 2005
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
WMO Ozone Assessment 2006
Spring Polar
Ozone Anomalies
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
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
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.
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)?
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.
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.
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.
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
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
DA8 FTS Measurements: HNO3
Farahani et al., JGR 2007
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
2006-2007 AMAC Highlights
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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
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February-March 2007 - ACE Arctic validation campaign
May 2007 - P-AERI ordered
July 2007 - Bruker / Bomem intercomparison campaign
August 2006 - installation of new UV-visible grating
spectrometer (PEARL-GBS)
 August-October 2006 - first data from both instruments
August-September 2007 - NDACC Aura validation campaign
Ongoing - daily measurements, implementation and
optimization of retrieval algorithms, data analysis
AMAC Students and PDFs
 Bruker FTS measurements and data analysis
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 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 - )
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
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 ACEFTS 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: 2004–2006. 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
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
Outlook: Tasks and Issues
 Installation of new sun-trackers for FTS and UV-visible
 Maximization and automation of Bruker FTS
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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