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

GEOS-Chem

IGC7 May 5, 2015 Jeffrey Geddes Randall Martin Colette Heald

How might GEOS-Chem be used “out of the box” to evaluate

impact of land cover changes?

Variety of (Conflicting?) Land Cover Data Currently Used

Snow/Ice | Deciduous Forest | Coniferous Forest | Agricultural land | Shrub/Grass Amazon Forest | Tundra | Desert | Wetland | Urban

BVOC emission factors

Soil NOx Emissions (MODIS Biomes)

PFT Distribution

𝐹𝑖 = 𝛾𝑖 𝜀𝑖, 𝑗 𝜒𝑗

Leaf Area Index (MODIS-derived)

(Plant Functional Type)

Deposition (Olson Land Map)

New Harmonized Land Module: Starting from a Single Data Source

Custom PFT Distribution & LAI Maps

Various PFT Fractions

BVOC Emission Factors

Biome Classifications f(PFT, latitude)

Soil NOx Deposition Surface Type

Total LAI

Custom mapping algorithm based

on dominant land type / PFT mix

Community Land Model

(15 PFTs)

New Harmonized Land Module: Starting from a Single Data Source

Custom PFT Distribution & LAI Maps

Various PFT Fractions

BVOC Emission Factors

Biome Classifications f(PFT, latitude)

Soil NOx Deposition Surface Type

Total LAI

Custom mapping algorithm based

on dominant land type / PFT mix

Community Land Model

(15 PFTs) Started from the bottom…

Now we’re here.

Bio

me

s (N

=2

4)

Custom Biome Mapping is Consistent with Native GEOS-Chem Inputs

NEW LAND MODULE DEFAULT MODEL

De

po

siti

on

Su

rfac

e

(N=1

1)

… but demonstrates role of land cover on predictions

DEFAULT MODEL NEW LAND MODULE

Monthly Mean OX (August 2005)

Simulated Chemistry is also Consistent…

Tree mortality due to insect and disease

2013 – 2027 National Insect and Disease Forest Risk Assessment (USDA Forest Service)

Example Nested Simulation Test: Predicted Tree Mortality

BASE (Unaltered CLM Input File) NIDR (Scaled to Tree Mortality)

Tree Mortality Impacts on Tropospheric Chemistry?

PFT Distribution & LAI Maps

Gridded PFT Coverage

BVOC Emission Factors

Biome Classifications f(PFT, latitude)

Soil NOx Deposition

Total LAI

BASE (Unaltered CLM Input File) NIDR (Scaled to Tree Mortality)

Iso

pre

ne

Emis

sio

ns

(10

12 a

tom

s C

/cm

2)

O3 D

epo

siti

on

V

eclo

city

(cm

/s)

BA

SE - NID

R

Significant Impacts on Sources and Sinks B

ASE - N

IDR

BASE (Unaltered CLM Input File) NIDR (Scaled to Tree Mortality)

O3 (

pp

b)

PAN

(p

pb

) B

ASE - N

IDR

Significant Impacts on Predicted Tropospheric Chemistry

BA

SE - NID

R

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 non-linear chemistry and global atmospheric transport

Changes in species composition? Shift in species distribution? Historical land use change?

New GEOS-Chem Land Cover Module

POSTER B6: Land use change over South East Asia

Sam Silva, MIT

THANK YOU

Now the whole team

here

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)

Global: 2.65 Tg N.A. : 0.61 Tg

Global: 2.71 Tg N.A. : 0.64 Tg

x 1011

USE_CLM_LAND = .FALSE.

USE_CLM_LAND = .TRUE.

ISOPRENE EMISSIONS (Full year spin-up, July 2006)

Global: 45.56 Tg C N.A. : 6.39 Tg C

Global: 47.54 Tg C N.A. : 7.47 Tg C

x 1012

USE_CLM_LAND = .FALSE.

USE_CLM_LAND = .TRUE.

Harmonized Land Module: Starting from a Single Data Source