international conference on environmental observations, modeling and information systems
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International Conference on Environmental Observations, Modeling and Information Systems ENVIROMIS-2004 17-25 July 2004, Akademgorodok, Tomsk, Russia Modeling of methane emission from natural wetlands and topography-based surface hydrology Krylova A.I. and V.N.Krupchatnikoff - PowerPoint PPT PresentationTRANSCRIPT
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International Conference on Environmental Observations, Modeling and Information Systems
ENVIROMIS-200417-25 July 2004,
Akademgorodok, Tomsk, Russia
Modeling of methane emission from natural wetlandsand topography-based surface hydrology
Krylova A.I. and V.N.Krupchatnikoff Institute of Computational Mathematics and Mathematical Geophysics of
Siberian Branch of the Russian Academy of Sciences,pr. Ac.Lavrentieva, 6, Novosibirsk, 630090, Russia,
Ph. (8-3832) 356524, e-mail:[email protected], [email protected]
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Introduction
There are two complementary approaches to determine global and regional wetland source strengths :
1) bottom-up approach: geographical coverage, spatial and temporal flux variations
a) using flux measurements and information on emission period and wetland areas to extrapolate to global and annual scales;
b) using a climate-sensitive model for methane emissions to extrapolate to the global scale;
2) top-down approach: inverse modeling Information on temporal and spatial variation of methane fluxes from soils is
deduced from observational data on CH4 mixing ratio in air, obtained on a global network of NOAA/CMDL field stations.
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climate
soil surface
soil depth
water table
rooting depth
soiltemperature
vegetation
CH4 oxidation
NPP
CH4 production
CH4 concentration
pla
nt-
med
iate
d t
ran
spo
rt
ebu
lliti
on
dif
fusi
on
CH4
emission
atmosphere
oxic soil
anoxic soil
Schematic of the one-dimensional methane model
relative pore space
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The methane emission model
),(),(),(),(4
ztQztQztFz
ztCt plantebulldiffCH
),(),( ztRztR oxidprod
Model is based on the one-dimensional continuity equation within the entire soil/water column
The diffusive flux Fdiff is calculated using Fick’s first law:
ztCz
zDztF CHCHdiff ,)(),(44
The rate Qebull at which methane in the form of bubbles is removed from depth z is calculated:
)),(()(),(44 threshCHCHebull CztCCfkztQ
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The methane production rate Rprod(t,z) at time t and depth z is described as:
10
),(
100 )()()(),(meanTztT
inorgprod QTftfzfRztR
The methane emission model
)1(),()()(),(4 oxCHgrowrootvegplant PztCtfzfTkztQ
The rate Qplant(t,z) at which methane is removed by plants from depth z at time t is calculated from:
The total methane flux to the atmosphere
)()(),()( tFtFuztFtF plantebulldifftot
)(
),()(tw
nsoil
ebullebull dzztQtF dzztQtFns
nroot
plantplant ),()(
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Boundary conditions
0),(4
nsoilztCz CH
at the lower boundary nsoil
at the upper boundary u, where u is either the water table w(t) (if w(t) > ns) or the soil surface ns
atmCH CcmuztC )4,(4
l mol M
M Catm
/ 1 1
, 076 . 0
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ResultsFigure shows a comparison between simulated and observed methane concentration profiles for the period between 1 June and 30 June 1992. Observational data were taken from Shannon and White [1994].
CHCH44 [ M ] [ M ] CHCH44 [ M ] [ M ]
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Coupled model of climate
Atmospheric model (INM/RAS) (Alexeev V., E.Volodin, V.Galin, V. Dymnikov, V. Lykosov, 1998)• Terrain-following vertical coordinate (21 σ-levels)• Semi-implicit formulation of integration in time• Energy conservation finite-difference schemes (2.5°x 2.5°)• Convection (deep, middle, shallow; mass-flux)• Radiation (H2O, CO2, O3, CH4 , N2O, O2; 18 spectral bands for SR and 10
spectral bands for LR) • PBL (5 σ-levels) Land surface model (ICMMG/SB RAS) (V. Krupchatnikov, 1998)
The Land Surface Model considered in this report is an extension of this earlier model development. The model is able to simulate:
terrestrial photosynthesis and respiration of CO2 from land surface, vegetation, methane emissions from natural wetlands, and surface hydrology,surface fluxes of energy and momentum.
Model is implemented globally, many surface type needed to be included.
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Atmosphericmodel
Land surfacemodel
soil temperature
NPP
water table
CH4
model
global wetlanddistribution
global data sets:• plant-mediated transport • rooting depth• soil depth• relative pore space
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Global methane fluxes Results : Observations and Modeling
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Global distribution of peat-rich bogs from 50-600N(from Matthews, E., and I.Fung)
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Regional CH4 emission
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Tom River basinData
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Spatial distribution of statistical moments of topographic index
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Upscaling function for obtaining 10’ equivalent of topographic index from its values for 30-arc-second DEM
''' 301062.107.0
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• This model is a component of the biosphere model in the coupled model of climate. It has allowed us to evaluate global CH4 fluxes from wetlands, seasonal change of fluxes for the basic areas of concentration peatlands in the northern latitudes.
• The model has been developed for studying the global natural emission of methane from the surface covered with bogs and lakes.
• Simulated results confirm the conclusions obtained on the basis of direct measurements, that Big Vasyugan Bog is the largest source of methane emission to the atmosphere.
• Simulated results allow us to retrieve the character of the distribution and the amount of methane fluxes from the surface earth to the atmosphere.
•The model can be considered as a basis for further research of interactions of the hydrological cycle, climate and emission of methane from the peat-bog ecosystems.
Conclusion