Methane budget estimates in Finland from the CarbonTracker Europe-CH₄ data assimilation system

Figures & data

Table 1. List of observations over Finland and surrounding regions.

Site code	Site name	Country	Contributor	Latitude [°N]	Longitude [°E]	Height${}^{*}$ [m a.s.l.]	Obs. Unc. [ppb]	Date range${}^{**}$ [mm/yyyy]
SMR	Hyytiälä	Finland	UHEL	61.85	24.28	306 (125)	25	11/2011–12/2014
KJN	Kjølnes	Norway	MPI&UE	70.85	29.24	30 (5)	15	10/2013–12/2014
KMP	Kumpula	Finland	FMI	60.20	24.96	53 (30)	30	5/2010–12/2014
PAL${}^{†}$	Pallas	Finland	FMI	67.97	24.12	572 (7)	15	2/2004–12/2014
PAL${}^{†}$	Pallas	Finland	NOAA	67.97	24.12	570 (7)	15	1/2004–12/2014
PUI	Puijo	Finland	FMI&UEF	62.91	27.66	316 (80)	30	6/20110–12/2014
SOD	Sodankylä	Finland	FMI	67.36	26.64	227 (48)	25	6/20128–12/2014
UTO	Utö	Finland	FMI	59.78	21.37	65 (57)	25	3/2012–12/2014

Observation Uncertainty (Obs. Unc.) is used to define diagonal values in the observation covariance matrix. This contains both measurement and model representativity error.

* Sampling heights from which atmospheric CH₄ is sampled in TM5. The numbers in the parenthesis are the measurement heights above ground.

** Date range for this study period, 2004–2014. Note that most of the observations are continuously updated, and measurements at Pallas (NOAA) started as early as in 2001.

^† Observations from Pallas are coordinated by FMI and NOAA, of which NOAA observations are from discrete, and FMI observations are from continuous air samples.

Table 2. List of inversion setups.

Inversion	Prior [anthropogenic]	Prior [biospheric]	Observations	Period
J1	EDGAR v4.2 FT2010	LPX-Bern-DYPTOP	All available	2004–2014
J2	EDGAR v4.2 FT2010	LPX-Bern-DYPTOP	All but KMP and PUI	2010–2014
J3	EDGAR v4.2 FT2010	LPJG-WHyMe	All available	2010–2014
J4	EDGAR v4.2 FT2010	LPX-Bern v1.0	All available	2010–2014
J5	FIN-EDGAR	LPX-Bern-DYPTOP	All available	2010–2014

Fig. 1. Statistics (bias, correlation and root mean squared error (RMSE)) of posterior atmospheric CH₄ compared with assimilated observations from sites in Finland and surrounding regions. Negative bias shows model underestimation. The statistics were calculated from 2010–2014 observations, except for KJN, where 2013–2014 data were used. The statistics for Puijo (PUI) and Kumpula (KMP) for J2 were plotted separately, as those were not assimilated in J2, and the statistics are calculated from posterior estimates and all prepossessed daily observations.

Fig. 2. Observed and simulated atmospheric CH₄ at sites in Finland and surrounding regions for 2012, except for Kjølnes which shows data from 2014. For continuous observations, the daily averaged values are shown. For complete time series for all inversions, see Supplementary Material.

Fig. 3. [Top and middle] Monthly prior and posterior anthropogenic and biospheric emission estimates for Finland. The shaded areas show uncertainty ranges of the prior (grey) and the J1 posterior (blue). [Bottom] Number of Fennoscandian stations assimilated in J1 and J5. Note the number in J2 was same as in J1.

Fig. 4. Measured CH₄ fluxes at Lompolojänkkä and Siikaneva, and estimated regional monthly mean biospheric CH₄ fluxes around the sites.

Fig. 5. Mean annual emission estimates for 2010–2014 [10^–8mol m⁻² s⁻¹], their uncertainty reduction ($1-{\sigma }_{\text{posterior}}^2/{\sigma }_{\text{prior}}^2$), and locations of observations in Fennoscandia. The triangles show sites with continuous observations and the star shows the site with both continuous and discrete observations. For other inversions, see Supplementary Material.

Table 3. Average annual CH₄ emission estimates between 2010 and 2014 in Finland [Tg CH₄ yr⁻¹].

	Anthropogenic	Biosphere
(Prior)
EDGAR v4.2 FT2010	0.39
FIN-EDGAR	0.38
LPX-Bern-DYPTOP		0.19
LPJG-WHyMe		2.15
LPX-Bern v1.0		1.29
(Posterior)
J1	0.27 ± 0.34	0.27 ± 0.23
J2	0.41 ± 0.34	0.27 ± 0.23
J3	0.19 ± 0.34	0.73 ± 1.43
J4	0.20 ± 0.34	0.87 ± 1.02
J5	0.44 ± 0.33	0.26 ± 0.22