Site Latitude	89° 58' 48.00" S (-89.98000 °N)	Go to interactive map
Site Longitude	24° 48' 0.00" W (-24.80000 °E)
Site Elevation	2810.0 masl
Site code	SPO
Dataset	ch4c13_spo_surface-flask_7_representative
Assimilated	Yes Switch to unassimilated subset
Data provider	Sylvia Englund Michel, University of Colorado, Institute of Arctic and Alpine Research, Stable Isotope Laboratory, Campus Box 450, University of Colorado, Boulder, CO, United States, and Reid Clark, University of Colorado, Institute of Arctic and Alpine Research, Stable Isotope Laboratory, Campus Box 450, University of Colorado, Boulder, CO, United States, and Bruce Vaughn, University of Colorado, Institute of Arctic and Alpine Research, Stable Isotope Laboratory, Campus Box 450, University of Colorado, Boulder, CO, United States
Partner(s)	No partner information available.
Laboratory

(a) Time series of δ¹³C-CH₄, both observed and simulated, at this CarbonTracker-CH4 observation site. The measured stable carbon isotope ratio values relative to ratio values of standard (Pee Dee Belemnite, 0.0112372) (black circles) are plotted along with CarbonTracker-CH4 simulated values with prior fluxes (green circles), assimilated fluxes (blue circles), and withheld (yellow circles).

(b) The time series of model residuals, the difference between the measured and simulated δ¹³C-CH4, for simulation with prior fluxes (dark green circles) and posterior fluxes (blue circles).

(c) Summary statistics for model residuals from to . Residuals are defined as observed values minus simulated values. "Bias" is the mean of the residuals; "std. dev." is the standard deviation, and RMSE is root-mean-square error. All quantities are in permil (‰) of δ¹³C-CH₄. The time period over which these quantities are computed is set by the graphs (a) and (b).

(d) Seasonal histograms of residuals

(d) Seasonal histograms of the residuals for this dataset. See caption for top figure for the definition of residuals. The left panel collects all residuals for each northern hemisphere summer (June through September); the right panel is the northern hemisphere winter (November through April). Residuals before 1 Jan 2001 are excluded from this analysis to avoid an effect of CarbonTracker burn-in from a poorly-known initial CO2 distribution. The tan color shows the histogram of the residuals themselves; the blue lines and statistics shown in blue text are a summary of the residuals interpreted as a normal distribution. For this assimilated dataset, the assumed model-data mismatch averaged over the seasonal span is shown in green (lines and text). The vertical scales are relative, determined by the number of observations and how tightly they are grouped, with the area under the histogram forced to unity.