Project CAMS41 Phase 2
Optimization of CH4 wetland emissions in CTESSEL model using FLUXNET-CH4 dataset and GCP inversion products

The optimization is performed in two steps:

1. Optimization of the temperature dependency factor (Q10) using FLUXNET-CH4 in-situ data
2. Optimization of the scaling factor (S) using GCP inversion products

1. Optimization of Q10

For the optimization 22 sites have been selected. All site simulations are performed with the same CTESSEL configuration:

• Low vegetation fraction (CVL): 1, high vegetation fraction (CVH): 0
• Low vegetation type (TVL): PFT13 (Bogs and marshes)
• Vegetation cover (RVCOV): 1
• Reference respiration (RVR0VT): 0.27E-06 kgCO2/m2/s
• Wetland extent fraction: 1 (constant)

The optimization is performed in multiple-site mode with 23 optimized parameters: s (individual scaling factor for each site) and Q10 (temperature dependency factor). The resulting Q10 value and site time-series are shown below.

Parameter	Prior	Min	Max	Posterior
Q10	2.0	1.01	4.0	2.337

ID	MAP	TIME-SERIES
CA-SCB
DE-Hte
DE-SfN
FI-Si2
FI-Sii
IT-Cas
JP-BBY
KR-CRK
NZ-Kop
RU-Ch2
RU-Che
SE-Deg
US-A03
US-BZF
US-Bes
US-LA2
US-Los
US-Myb
US-NC4
US-PFa
US-Tw1
US-WPT

2. Optimization of S

For optimization of the scaling factor the GCP-2019 inversion products have been used (median across 11 products). The global CTESSEL simulation is performed with E2OBS forcing for 2012-2014 starting from the scratch, the last year is used in the optimization.

The optimization has been performed in three different ways:

• one global S value
• one S value per latitudinal band (>25N, 25N-25S, <25S)
• one S value per region (using 11 regions)

The resulting S values are shown below:

Region	Posterior value
Global	0.00333
North (>25N)	0.00422
Tropics (25N-25S)	0.00301
South (<25S)	0.00326
Boreal North America	0.00612
Temperate North America	0.00468
Tropical South America	0.00232
Temperate South America	0.00637
Europe	0.00238
Boreal Asia	0.00736
Temperate Asia	0.00325
Tropical Asia	0.00285
North Africa	0.00321
South Africa	0.00360
Australia & New Zealand	0.00183

The latitudinal and regional maps for S are shown below.
The maps in netcdf format can be downloaded here:

• http://dods.lsce.ipsl.fr/mosaic/VBASTRI/CAMS41/OPT_CH4/s_latitudinal.nc
• http://dods.lsce.ipsl.fr/mosaic/VBASTRI/CAMS41/OPT_CH4/s_regional.nc

The resulting mean annual maps for observations (GCP products median), CTESSEL simulations obtained with different scaling factors and their differences are presented below:

The resulting mean seasonal cycle calculated for different regions together with the components of methane emission calculation are shown in the table:

Region mask	CH4 flux	Wetland fraction	First soil layer temperature	Low vegetation respiration	High vegetation respiration