Adapting GEOS_CHEM to Mars Photochemisty

Huiqun Wang1

Kelly Chance1

Daniel Jacob2

Mark Richardson3

Michael Mischna4

1 Center for Astrophysics (CFA)2 Harvard

3 CALTECH4 JPL

• 1D photochemical model for Mars

• 3D Mars GCM

• Observations of trace gases and aerosols

in the Martian atmosphere

Motivation

Mars atmospheric compositionCO2 0.955 H2O 0-70prµm

N2 0.027 O3 0-60µm-atm

Ar 0.016 H2O2 0-40ppb

O2 1.3e-3 …

CO 8.0e-4

H2 1.7e-5

He 1.0e-5

Ne 2.5e-6

Kr 3.0e-7

CH4 1.0e-81 prµm = 3.34e+18 cm-2; 1 µm-atm = 2.69e+15 cm-2 = 0.1DU

2

2

2 22 2

CO h CO O

O O M O M

CO CO O

Photochemistry in a pure CO2 atmosphere

2

2 3

O h O O

O O M O

Prediction:

CO: 7.72e-2

O2: 3.87e-2

O3: 126DU

Observation:

CO: 7.0e-4

O2: 1.3e-3

O3: < a few DU

CO2 stability problem

HOx catalytic chemistry

2H O h H OH

2

2 2

2 2

2

CO OH CO H

H O M HO M

O HO O OH

CO O CO

2

3 2

2 3

2

CO OH CO H

H O OH O

O O M O M

CO O CO

2

2 2

2 2 2 2 2

2 2

2 2

2( )

2( )

2

2 2

CO OH CO H

H O M HO M

HO HO H O O

H O h OH

CO O CO

[McElroy & Donahue, 1972; Parkinson & Hunten, 1972]

2

2 2

2 2

2

2 2

2 2

2( )

2( )

2 2

CO OH CO H

H O M HO M

HO NO NO OH

NO h NO O

O HO O OH

CO O CO

2

2 2

2 2

2 2

2

CO OH CO H

H O M HO M

HO NO NO OH

NO O O NO

CO O CO

HOx-NOx catalytic chemistry

Heterogeneous chemistry

Mars GCMs• NASA AMESC-grid, p coord, 0-80km

• GFDL A-grid, σ-p coord, 20–40 layers, 0-80km

• LMD/AOPPA-grid/spectral, σ coord, 32 layers, 0-120/240km

• Planetary WRFC-grid, σ coord, 25 or 40 layers, 0-80km

…

CO2 IR heating

Dust visible & IR heating

Surface physics

Subgrid-scale processes

CO2 cycle

Water cycle

Dust cycle

Atmospheric chemistry

SPICAM Water Vapor Column abundance [Fedorova et al., 2006]

[Perrier et al., 2006]

MEX simultaneous observations of water vapor and ozone

MEX SPICAM observations of ozone vertical profile

3D Mars photochemical model

• Lefevre et al., 2004. Three-dimensional modeling of ozone on Mars. J. Geophys. Res.,109, doi:10.1029/2004JE002268.

• Hartogh et al., 2006. A new coupled 3D-model of the dynamics and chemistry of the Martian atmosphere. DPS 2006 abstract #60.05.

• Moudden and McConnell, 2006. Three-dimensional on-line chemical modeling in a Mars general circulation model, submitted to Icarus.

GEOS_CHEM

Mars meteorology

Mars photochemistry•Kinetic reactions•Photolysis

Mars GCM LIDORTTable for J-values

Interface with MGCM• Time

Year, Day-of-Year, Planetary-second

• ConstantsCMN_GCTM: eccentricity, g0, Rplanet, Rd, Cp, …

• File formatInput Netcdf: 40 days / GCM met file

Output Bpch: restart file & diagnostics

• Grid structure64 longitudes, 36 latitudes, 25 levels

120nm – 800nm

CO2, O2, O3, H2O, Rayleigh, dust

LIDORT→Actinic Flux→Integration→Scaling

2

1

, , , ,J T P T P I d

Look-up table for J:SZA, Surface P, O3 column, H2O column, column dust, T profile type

Phot-freq Cross section Quantum yield Actinic flux

Preliminary results from basic model