Numerical Modeling of the Stratosphere, Mesosphere and Thermosphere

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Numerical Modeling of the Stratosphere,
Mesosphere and Thermosphere

• Dan Marsh
• National Center fo Atmospheric Research
• Boulder, USA

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Outline

• Motivation
• Basic techniques and concepts in numerical
  modeling
• Continuity equation
• Chemical production and loss
• Chemical solvers
• Transport advection and diffusion
• Thermodynamic equation
• 3 Examples of model/data analysis
• Stratospheric antartic ozone hole
• Mesospheric HALOE water vapor
• Lower thermospheric HALOE nitric oxide
• WACCM - a general circulation model from the
  surface to the thermosphere

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Why study the Stratosphere, Mesosphere and Lower
Thermosphere

• A transition region
• Chemistry and dynamics are closely coupled
• Encompasses the turbopause and the lower boundary
  of the ionosphere
• MLT (80-120km) is perhaps the least understood
  region of the atmosphere
• Difficult to measure
• Part of the ignorosphere
• Remote sensing via satellite has dramatically
  increased the amount and quality of data

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Numerical modeling concepts

• Attempts to describe the physical world (its
  chemistry and dynamics) within a mathematical
  framework
• Developed to test our understanding in comparison
  with observations (diagnostic)
• Models can make predictions about future state of
  the atmosphere (prognostic)
• Typically, models are seperated according to the
  number of dimensions
• 1-D column models (at one location or global
  mean)
• 2-D zonally averaged models (height latitude
  only)
• 3-D global

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Continuity equation
Mathematically describes the dynamical and
chemical processes that determine the
distribution of chemical species
Transport
Chemical forcing
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Solving the continuity equation

• N species leads to N coupled non-linear equations
  which rarely have an analytic solution.
• System is solved with numerical methods at
  discrete locations (grid-points)
• Differentials replaced by finite differences
• Finite resolution (time or space) implies some
  transport processes are unresolved (e.g.
  diffusion)
• Chemistry and transport handled as separate
  operations

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Chemistry Solving df/dt S/?
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Chemical forcing (S)(i.e. production and loss)
First-order forcing Photolysis, airglow,
External forcing Independent of f
Non-linear forcing Bi-molecular and tri-molecular
reactions
For N species, A and B are NxN matrices
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Typical Middle Atmosphere Neutral Chemistry
50 species 41 photolysis rates, 93 gas phase
reactions, 17 heterogeneous reactions
Long-lived Species (17 species, 2 constant)
Misc CO2, CO, CH4, H2O, N2O, H2, O2 CFCs
CCl4, CFC-11, CFC-12, CFC-113 HCFCs HCFC-22
Chlorocarbons CH3Cl, CH3CCl3, Bromocarbons
CH3Br Halons H-1211, H-1301 Constant
Species N2, N(2D) Short-lived Species (31
species) OX O3, O, O(1D) NOX N, NO, NO2,
NO3, N2O5, HNO3, HO2NO2 ClOX Cl, ClO, Cl2O2,
OClO, HOCl, HCl, ClONO2, Cl2 BrOX Br, BrO,
HOBr, HBr, BrCl, BrONO2 HOX H, OH, HO2, H2O2
HC Species CH2O, CH3O2, CH3OOH
Radiatively important species
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Composition
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E region ion chemistry

• Ion species
• N2 , O2 , N , O , NO , and e
• reactions
• r1 O O2 -gt O2 O
• r2 O N2 -gt NO N
• r3 N2 O -gt NO N(2D)
• r4 O2 N -gt NO O
• r5 O2 NO -gt NO O2
• r6 N O2 -gt O2 N
• r7 N O2 -gt NO O
• r8 N O -gt O N
• r9 N2 O2 -gt O2 N2
• r10 O2 N2 -gt NO NO
• r11 N2 O -gt O N2
• ra1 NO e -gt N O (20)
• -gt N(2D) O (80)
• ra2 O2 e -gt 2O (15)

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Transport method I Eulerian Transport
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Transport method II Semi-Lagrangian transport
(x, t)
Accuracy depends greatly on Interpolation scheme
used. Common in GCMs such as WACCM
trajectory
(x0, t-?t)
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Un-resolved transport Diffusion
For more than one dimension, each dimension is
treated separately
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Thermodynamic equation
Heat advection
Diabatic heating/cooling
Adiabatic heating
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Sources of diabatic heating/cooling

• Absorption of solar radiation and energetic
  particles (e.g. ozone)
• Chemical heating through exothermic reactions (A
  B -gt AB E)
• Collisions between ions and neutrals (Joule
  heating)
• IR cooling (e.g. CO2 and NO)
• Airglow

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Solar UV Energy Deposition in the Upper Atmosphere
S.Solomon, private communication
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Global average heating rates

• From Roble, 1995

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Global average cooling rates

• From Roble, 1995

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Modeled auroral ionization rates
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Example 1 Modeling the Antarctic ozone hole
2001/2002
GSFC, NASA
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NCEP CPC Temperatures, 200180S, Zonal Mean,
50hPa
2001
1978-2003
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Total Column Ozone (DU) September 25, 2001
1.25? lon x 1.0? lat
1.9? lon x 1.9? lat
EPTOMS
MZ3/ECMWF
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NCEP CPC Temperatures, 200280S, Zonal Mean,
50hPa
1978-2003
2002
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Total Column Ozone (DU) September 25, 2002
1.25? lon x 1.0? lat
1.9? lon x 1.9? lat
EPTOMS
MZ3/ECMWF
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Example 2 UARS/HALOE Ozone and Water Vapor
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UARS/HALOE observations0.01 mbar (80 km)
Marsh, JGR 2003
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Mesospheric odd-oxygen(Ox O O3) chemistry

• Chapman chemistry

• HOx Catalytic cycles

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Zonal mean Ox loss rates 2.5ºN
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Monthly anomalies
Ozone
Water Vapor
Marsh, JGR 2003
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Ozone trends
sunrise
sunset
Large response
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Water vapor trends
sunrise
sunset
(SPARC Assessment of Upper Tropospheric and
Stratospheric Water Vapour 2000)
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ROSE 3-D mechanistic model
Chemistry 27 species, 101 gas-phase rxns
(JPL-2000) 83 to 1.5(-4) hPa (17.5 to 110 km by
2.5 km) 5º lat. x 11.25º lon. 7.5 min time
step Semi-lagrangian transport scheme Dynamics Gri
d-point model Hines gravity wave param. NCEP and
GSWM forcing at lower boundary Physics Airglow
package Offline D-region ion chemistry Photolysis
rates based on TUV Optimized to run on Intel
workstations
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Modeled ozone change
Marsh, JGR 2003
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Sunrise/Sunset Sensitivity
SS
SR
Simulations indicate ozone trends consistent with
water trends
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Example 3 The HALOE Nitric Oxide Anomaly
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Nitric Oxide in the lower-thermosphere
Equatorial NO
(Barth et al., 2003)
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Sources of N(2D)
(Barth et al., 2003)
Produced by (1-10 keV) precipitating electrons
and solar soft X-rays (2-7 nm)
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HALOE nitric oxide observations
there is a puzzling sunrise/sunset asymmetry
in the mesospheric NO This is puzzling because
according to photochemical theory, NO should have
no diurnal variation in the mesosphere (Siskind
et al., JGR 102, 3527-3545, 1997).
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MLT dynamics - solar tides

• Global scale waves in wind,T,P with periods that
  are harmonics of a 24 hour day
• Migrating tides propagate westward with suns
  motion
• Thermally driven by absorption of solar radiation
  (O3 and H2O)

McLandress, JGR, 1996
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GSWM-98 diurnal tide amplitude and phase
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Sunrise
Sunset
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TIME-GCM Diurnal amplitudes and phase
NO24
6 hr diff at 90 km
w24
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TIME-GCM SR/SS ratios
89 km
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The Whole Atmosphere Community Climate Model

• HAO
• Ben Foster
• Maura Hagan
• Han-Li Liu
• Art Richmond
• Ray Roble
• Stan Solomon

• ACD
• Rolando Garcia
• Doug Kinnison
• Dan Marsh
• Anne Smith
• Stacy Walters
• CGD
• Byron Boville
• Bill Collins
• Brian Eaton
• Fabrizio Sassi

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Motivation for the WACCM Model

• Coupling between atmospheric layers
• Waves transport energy and momentum from the
  lower atmosphere to drive the QBO, SAO, sudden
  warmings, mean meridional circulation
• Solar and geomagnetic inputs, e.g., auroral
  production of NO in the mesosphere and downward
  transport to the stratosphere
• Stratosphere-troposphere exchange
• Climate Variability and Climate Change
• What is the impact of the stratosphere on
  tropospheric variability, e.g., the Artic
  oscillation or annular mode?
• How important is coupling among radiation,
  chemistry, and circulation? (e.g., in the
  response to O3 depletion or CO2 increase)
• (Roble, Geophysical Monographs, 123, 53, 2000)

Jarvis, Bridging the Atmospheric
Divide Science, 293, 2218, 2001
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Motivation for the WACCM Model

• Response to Solar Variability
• Recent satellite observations have shown that
  solar cycle variation is
• 0.1 for total Solar Irradiance
• 5-10 at ? 200nm
• - Radiation at wavelengths near 200 nm is
  absorbed in the stratosphere
• gt Impacts on tropospheric climate may be
  mediated by stratospheric chemistry and dynamics
• Satellite observations
• There are several satellite programs that can
  benefit from a comprehensive model to help
  interpret observations
• e.g., UARS, TIMED, EOS Aura

UARS / SOLSTICE
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Heritage and Structure of the WACCM Model
(Thermosphere-Ionosphere-Mesosphere
Electrodynamics GCM)
TIME GCM
Mesospheric Thermospheric Processes
MOZART

WACCM
Chemistry
(Model for Ozone and Related Tracers)
WACCM1 Non-interactive chemistry WACCM2
Interactive chemistry Valid to 100
km Current Work Include ionosphere
Extend validity to 150 km
Dynamics Physical processes
CAM3
(Community Atmosphere Model, version 3)
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WACCM-1 Status

• WACCM-1b frozen and released, Summer 2003
• WACCM Web Site http//acd.ucar.edu/models/WACCM/
  
• Source code and instructions
• Selected datasets
• geov viewer (idl-based)
• Several science studies

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Diurnal T tide (k1 westward) January and March
ALTITUDE
LATITUDE
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V' structure of 2-day wave (January) Modeled and
observed
ALTITUDE
Wu et al (GRL, 1993) HRDI data
LATITUDE
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Forkman et al Long, continuous ground-based
measurements of mesospheric CO (GRL, 2003)

• CO is an excellent tracer of vertical transport
  because of strong vertical gradients in MLT

WACCM simulation
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Water Vapor Trends model vs. observations

• Good agreement in lower stratosphere ( z lt 30-35
  km)
• Calculated trends 1/2 of observed in upper
  stratosphere

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WACCM-2

• Includes in-line interactive chemistry
• Direct and chemical heating calculated
  consistently
• Improved parameterizations for thermospheric
  processes

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Future WACCM study

• How does the atmosphere respond to varying solar
  input?
• What is the response of the thermosphere and
  mesosphere to the 11-year solar cycle?
• What is the response of the stratosphere?
• Does variability in the upper atmosphere affect
  the troposphere?

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WACCM-2 Status

• Model is under development
• Interactive chemistry, radiation and dynamics
• Complete middle atmosphere chemistry is working
  (except for aurora)
• SW heating, IR to Lyman-alpha, NLTE IR cooling
  parameterization working
• Under development
• EUV SW heating
• Auroral module
• Ion drag and Joule heating
• Approximately 1 day / year of simulation on
  NCARs super-computer
• Expected release sometime in 2004 (?)

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THE END

• References
• Atmospheric Chemistry and Global Change editors
  Brasseur, Orlando, and Tyndall, Oxford University
  Press, 1999.
• Aeronomy, Banks and Kockarts, Academic Press,
  1973