Land Cover Change
& Atmospheric Chemistry
Implementing a New
Land Cover Module for
GEOS-Chem
IGC7
May 5, 2015
Jeffrey Geddes
Randall Martin
Colette Heald
Land Cover Change
& Atmospheric Chemistry
Implementing a New
Land Cover Module for
How might GEOS-Chem
be used
GEOS-Chem
“out of the box” to evaluate
impact of land cover changes?
Jeffrey Geddes
Randall Martin
IGC7
May 5, 2015
Colette Heald
Variety of (Conflicting?) Land Cover Data Currently Used
PFT Distribution
(Plant Functional Type)
𝐹 𝑖 = 𝛾𝑖
𝜀𝑖 , 𝑗 𝜒𝑗
BVOC emission factors
Deposition (Olson Land Map)
Soil NOx Emissions
(MODIS Biomes)
Snow/Ice
Amazon Forest
| Deciduous Forest | Coniferous Forest | Agricultural land | Shrub/Grass
| Tundra
| Desert
| Wetland
| Urban
Leaf Area Index (MODIS-derived)
New Harmonized Land Module: Starting from a Single Data Source
Community
Land Model
(15 PFTs)
Custom PFT Distribution & LAI Maps
Total
LAI
Various PFT Fractions
BVOC
Emission
Factors
Biome
Classifications
f(PFT, latitude)
Soil NOx
Custom mapping
algorithm based
on dominant land
type / PFT mix
Deposition Surface Type
New Harmonized Land Module: Starting from a Single Data Source
Custom PFT Distribution & LAI Maps
Various PFT Fractions
Started from
the bottom…
Total
LAI
Biome
BVOC
Classifications
Emission Now we’re
f(PFT, latitude)
Factors
here.
Soil NOx
Community
Land Model
(15 PFTs)
Custom mapping
algorithm based
on dominant land
type / PFT mix
Deposition Surface Type
Biomes
(N=24)
Custom Biome Mapping is Consistent with Native GEOS-Chem Inputs
Deposition Surface
(N=11)
DEFAULT MODEL
NEW LAND MODULE
Simulated Chemistry is also Consistent…
… but demonstrates role of land cover on predictions
Monthly Mean OX (August 2005)
DEFAULT MODEL
NEW LAND MODULE
Example Nested Simulation Test: Predicted Tree Mortality
Tree mortality due to insect and disease
2013 – 2027 National Insect and Disease Forest Risk Assessment (USDA Forest Service)
Tree Mortality Impacts on Tropospheric Chemistry?
PFT Distribution & LAI Maps
Total
LAI
Gridded PFT Coverage
BVOC
Emission
Factors
Biome
Classifications
f(PFT, latitude)
Soil NOx
BASE (Unaltered CLM Input File)
Deposition
NIDR (Scaled to Tree Mortality)
Significant Impacts on Sources and Sinks
Isoprene Emissions
(1012 atoms C/cm2)
NIDR (Scaled to Tree Mortality)
BASE - NIDR
O3 Deposition
Veclocity (cm/s)
BASE (Unaltered CLM Input File)
BASE - NIDR
Significant Impacts on Predicted Tropospheric Chemistry
BASE - NIDR
PAN (ppb)
NIDR (Scaled to Tree Mortality)
BASE - NIDR
O3 (ppb)
BASE (Unaltered CLM Input File)
New GEOS-Chem Land Cover Module
Not intended to …
• Replace “dynamic” ESM simulations with the land cover changes over time
• Be used in situations where atmospheric dynamics could be significantly
altered by land cover at the resolution of the model grid
• Necessarily perform more “accurate” simulations than the default model
But allows for …
• “Controlled experiments” where land cover can be easily altered, and
changes to tropospheric composition can be identified, accounting for nonlinear chemistry and global atmospheric transport
 Changes in species composition?
 Shift in species distribution?
 Historical land use change?
THANK
YOU
Now the
whole team
here
POSTER B6:
Land use change over South East Asia
Sam Silva, MIT
Extra Slides
ORIGINAL SOIL BIOME EMISSION FACTORS
ng m-2 s-1
NEW MAPPED SOIL EMISSION FACTORS
ng m-2 s-1
SOIL NOx EMISSIONS (Full year spin-up, July 2006)
x 1011
Global: 2.65 Tg
N.A. : 0.61 Tg
USE_CLM_LAND = .FALSE.
Global: 2.71 Tg
N.A. : 0.64 Tg
USE_CLM_LAND = .TRUE.
ISOPRENE EMISSIONS (Full year spin-up, July 2006)
x 1012
Global: 45.56 Tg C
N.A. : 6.39 Tg C
USE_CLM_LAND = .FALSE.
Global: 47.54 Tg C
N.A. : 7.47 Tg C
USE_CLM_LAND = .TRUE.
Harmonized Land Module: Starting from a Single Data Source