Global Monitoring Division

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CO2 weather. We depict the daily average of the pressure-weighted mean mole fraction of carbon dioxide in the free troposphere as modeled by CarbonTracker. Units are micromoles of CO2 per mole of dry air (μmol mol-1), and the values are given by the color scale depicted under the graphic. The "free troposphere" in this case is levels 5 through 10 of the TM5 model before 2005, and levels 6 through 10 after (due to an improvement in the vertical resolution for 2006 onwards). This corresponds to about 1.2km above the ground to about 5.5km above ground, or in pressure terms, about 850 hPa to about 500 hPa. Gradients in CO2 concentration in this layer are due to exchange between the atmosphere and the earth surface, including fossil fuel emissions, air-sea exchange, and the photosynthesis, respiration, and wildfire emissions of the terrestrial biosphere. These gradients are subsequently transported by weather systems, even as they are gradually erased by atmospheric mixing.

Click here to see animations of these CarbonTracker CO2 Weather images.

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Left Panel: The pattern of CO2 exchange calculated in CarbonTracker for the time period indicated. Negative fluxes (blue regions) indicate places where uptake of CO2 occurs. Positive fluxes (red colors) indicate places where emission of CO2 occurs. The pattern of exchange follows swings in temperature and sunlight and changes with season. Note that the two hemispheres often have opposite colors as the seasons are juxtaposed. Units are gC/m2/yr. The figures include biological and fire fluxes, no fossil fuels.

Right Panel: The uncertainty on the estimated fluxes. All estimates started with 80% uncertainty on the land parameters, and 40% on the ocean parameters. Reduction of uncertainty occurs when observations inform us on the carbon cycle and limit the possible flux strength to less than we originally prescribed. Dark red areas show relatively large uncertainty, blue is relatively little. All uncertainties indicate a one-sigma standard deviation on the fluxes estimated assuming Gaussian errors. Note that spatial covariances, which by design are very large in the tropics, are not displayed on this map giving the false impression of lowest uncertainty in these regions. In the monthly and annual averages, we show the RMS uncertainty while temporal covariances are ignored. Units are gC/m2/yr. Uncertainties reported here are formal estimates from the inversion technique and do not include all sources of error. Flux uncertainties are among the most difficult quantities to compute, and care should be taken in their interpretation.

Results Summary: The table summarizes averages with uncertainty of the data displayed in the figure. The fossil and fire emissions are prescribed in CarbonTracker; the estimated mean includes ocean and terrestrial fluxes calculated by CarbonTracker. The total flux is the sum of the components in the table. Note that fossil fuel emissions can occur over regions characterized as ocean. This is partly due to real emissions from international shipping, and partly due to emissions occurring in coastal land regions that are assigned to the ocean in our coarse 1x1 degree division scheme. The same is true for fossil fuel emissions over non-optimized regions such as ice, polar deserts, and inland seas.

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Time series of the exchange calculated with CarbonTracker aggregated over larger areas of the globe. The title reflects areas defined in the TransCom project and can be found on this map. The blue line is the final result from CarbonTracker on a weekly time scale, the red line is 4-week moving average, the dark shaded band is the one-sigma uncertainty after the assimilation. All units are PgC/yr. The red line is a 4-week running average of the weekly CarbonTracker estimate introduced to remove the short-term variability in our a-priori guess. The shaded areas denote one-sigma (68% confidence) intervals calculated from the posterior covariance matrixes, disregarding its temporal structure. This figure includes biological and fire fluxes, no fossil fuels.

The table summarizes averages with uncertainty of the data displayed in the figure. The total flux is the sum of the components in the table. Note that fossil fuel emissions can occur over regions characterized as ocean. This is partly due to real emissions from international shipping, and partly due to emissions occurring in coastal land regions that are assigned to the ocean in our coarse 1x1 degree division scheme. The same is true for fossil fuel emissions over non-optimized regions such as ice, polar deserts, and inland seas.

Time series of CO2 mole fractions, both simulated and observed, at this CarbonTracker observation site. In the top panel, measured mole fractions (open black circles) are plotted along with CarbonTracker simulated values (light blue open circles). At some sites, there are observations that CarbonTracker can not simulate successfully; these are shown as filled red circles. The observations corresponding to these rejected simulated values are shown with open red circles. The bottom panel shows a time series of residuals--the difference between the simulated and measured mole fractions--shown with dark green open circles. These residuals should be uncorrelated in time, unbiased (i.e., have a mean of zero), and distributed normally. Also shown in the lower panel is the imposed model-data mismatch (orange lines), which in part defines the rejection criterion (see documentation). Any model first guess value which is more than three times the MDM away from zero, after accounting for potential adjustments to the simulated value due to optimizing fluxes, is rejected by the optimization system. Rejected values, if there are any, are shown with filled red circles.

Seasonal histograms of the residuals at this site. 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. The assumed model-data mismatch 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.