Title: Numerical Modeling of the Stratosphere, Mesosphere and Thermosphere
1Numerical Modeling of the Stratosphere,
Mesosphere and Thermosphere
- Dan Marsh
- National Center fo Atmospheric Research
- Boulder, USA
2Outline
- 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
3Why 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
4Numerical 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
5Continuity equation
Mathematically describes the dynamical and
chemical processes that determine the
distribution of chemical species
Transport
Chemical forcing
6Solving 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
7Chemistry Solving df/dt S/?
8Chemical 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
9Typical 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
10Composition
11E 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)
12Transport method I Eulerian Transport
13Transport method II Semi-Lagrangian transport
(x, t)
Accuracy depends greatly on Interpolation scheme
used. Common in GCMs such as WACCM
trajectory
(x0, t-?t)
14Un-resolved transport Diffusion
For more than one dimension, each dimension is
treated separately
15Thermodynamic equation
Heat advection
Diabatic heating/cooling
Adiabatic heating
16Sources 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
17Solar UV Energy Deposition in the Upper Atmosphere
S.Solomon, private communication
18Global average heating rates
19Global average cooling rates
20Modeled auroral ionization rates
21Example 1 Modeling the Antarctic ozone hole
2001/2002
GSFC, NASA
22NCEP CPC Temperatures, 200180S, Zonal Mean,
50hPa
2001
1978-2003
23Total Column Ozone (DU) September 25, 2001
1.25? lon x 1.0? lat
1.9? lon x 1.9? lat
EPTOMS
MZ3/ECMWF
24NCEP CPC Temperatures, 200280S, Zonal Mean,
50hPa
1978-2003
2002
25Total Column Ozone (DU) September 25, 2002
1.25? lon x 1.0? lat
1.9? lon x 1.9? lat
EPTOMS
MZ3/ECMWF
26Example 2 UARS/HALOE Ozone and Water Vapor
27UARS/HALOE observations0.01 mbar (80 km)
Marsh, JGR 2003
28Mesospheric odd-oxygen(Ox O O3) chemistry
29Zonal mean Ox loss rates 2.5ºN
30Monthly anomalies
Ozone
Water Vapor
Marsh, JGR 2003
31Ozone trends
sunrise
sunset
Large response
32Water vapor trends
sunrise
sunset
(SPARC Assessment of Upper Tropospheric and
Stratospheric Water Vapour 2000)
33ROSE 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
34Modeled ozone change
Marsh, JGR 2003
35Sunrise/Sunset Sensitivity
SS
SR
Simulations indicate ozone trends consistent with
water trends
36Example 3 The HALOE Nitric Oxide Anomaly
37Nitric Oxide in the lower-thermosphere
Equatorial NO
(Barth et al., 2003)
38Sources of N(2D)
(Barth et al., 2003)
Produced by (1-10 keV) precipitating electrons
and solar soft X-rays (2-7 nm)
39HALOE 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).
40MLT 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
41GSWM-98 diurnal tide amplitude and phase
42Sunrise
Sunset
43TIME-GCM Diurnal amplitudes and phase
NO24
6 hr diff at 90 km
w24
44TIME-GCM SR/SS ratios
89 km
45The 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
46Motivation 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
47Motivation 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
48Heritage 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)
49WACCM-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
50Diurnal T tide (k1 westward) January and March
ALTITUDE
LATITUDE
51V' structure of 2-day wave (January) Modeled and
observed
ALTITUDE
Wu et al (GRL, 1993) HRDI data
LATITUDE
52Forkman 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
53Water Vapor Trends model vs. observations
- Good agreement in lower stratosphere ( z lt 30-35
km) - Calculated trends 1/2 of observed in upper
stratosphere
54WACCM-2
- Includes in-line interactive chemistry
- Direct and chemical heating calculated
consistently - Improved parameterizations for thermospheric
processes
55Future 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?
56WACCM-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 (?)
57THE END
- References
- Atmospheric Chemistry and Global Change editors
Brasseur, Orlando, and Tyndall, Oxford University
Press, 1999. - Aeronomy, Banks and Kockarts, Academic Press,
1973