1 of 15

Adapting GEOS_CHEM to Mars Photochemisty

Huiqun Wang1

Kelly Chance1

Daniel Jacob2

Mark Richardson3

Michael Mischna4

1 Center for Astrophysics (CFA)

2 Harvard

3 CALTECH

4 JPL

2 of 15

Motivation

  • 1D photochemical model for Mars
  • 3D Mars GCM
  • Observations of trace gases and aerosols in the Martian atmosphere

3 of 15

Mars atmospheric composition

CO2

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-8

​

​

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

4 of 15

Photochemistry in a pure CO2 atmosphere

5 of 15

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

6 of 15

HOx catalytic chemistry

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

7 of 15

HOx-NOx catalytic chemistry

Heterogeneous chemistry

8 of 15

Mars GCMs

  • NASA AMES

C-grid, p coord, 0-80km

​

  • GFDL

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

​

  • LMD/AOPP

A-grid/spectral, σ coord, 32 layers, 0-120/240km

​

  • Planetary WRF

C-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

​

9 of 15

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

[Perrier et al., 2006]

MEX simultaneous observations of water vapor and ozone

10 of 15

MEX SPICAM observations of ozone vertical profile

11 of 15

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.

12 of 15

GEOS_CHEM

Mars meteorology

Mars photochemistry

  • Kinetic reactions
  • Photolysis

Mars GCM

LIDORT

Table for J-values

13 of 15

Interface with MGCM

  • Time

Year, Day-of-Year, Planetary-second

  • Constants

CMN_GCTM: eccentricity, g0, Rplanet, Rd, Cp, …

  • File format

Input Netcdf: 40 days / GCM met file

Output Bpch: restart file & diagnostics

  • Grid structure

64 longitudes, 36 latitudes, 25 levels

14 of 15

120nm – 800nm

​

CO2, O2, O3, H2O,

Rayleigh, dust

LIDORT→Actinic Flux→Integration→Scaling

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

15 of 15

Preliminary results from basic model