Scale factors for anthropogenic emissions

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This page describes the methodology of the interannual scaling factors used for anthropogenic emissions in GEOS-Chem.


Philippe Le Sager / Aaron van Donkelaar wrote:

Global annual scaling factors are available for NOx, CO, and SOx from 1985-2006. The approach, as implemented by van Donkelaar et al. (ACP, 2008) builds upon the work of Bey et al. (2001) and Park et al. (2004). Scale factors are automatically applied to any inventory, if needed, to get as close as possible to simulated year conditions. This behavior can be overwritten. Scale factors have been derived from numerous sources and directly use government statistics, where available.
Trend data for the following regions is derived from:
Canada – Environment Canada National Pollutant Release Inventory Trends (
United States – Industrial emissions are scaled according to reported trends from the EPA Acid Rain Program ( Other emissions are scaled according to National Emissions Inventory (NEI) Air Pollutant Emissions Trends Data (
Europe – European Monitoring and Evaluation Program (EMEP; UNECE (2009) Present state of emission data, ECE/EB.AIR/97,
Asia – Regional Emission inventory in Asia (REAS; Ohara et al., ACP, 2007;
Beyond these regions, NOx, SOx and CO are scaled according to CO2 trends available from the Carbon Dioxide Information Analysis Center ( NOx, SOx and CO are scaled according to trends in total, solid and liquid CO2, respectively.

From van Donkelaar et al., [2008]:

We scale all regional and global inventories from their respective base year to 2003, the last year of available statistics, unless its base year is after 2003. Our approach follows Bey et al. (2001) and Park et al. (2004). Emissions are scaled according to estimates provided by individual countries, where available. These countries/regions include the United States, Canada, Japan and Europe. NOx emissions of remaining countries are scaled proportional to changes in total CO2 emissions. SOx emissions are similarly scaled to solid fuel CO2 emissions and CO emissions to liquid fuel CO2 emissions. CO2 emission data are obtained from the Carbon Dioxide Information Analysis Center (CDIAC).

Extension of scale factors to 2010

This update was tested in the 1-month benchmark simulation v9-02m and approved on 30 Jul 2013. This update is included in Adjoint v35d.

Annual anthropogenic scale factors will be extended to 2010 for U.S.A. and Canada in v9-02. Note that these factors remain fixed past 2006 for other regions unless overwritten by other emission inventory data (e.g. EMEP and Streets).

Seasonal Scale Factors

Seasonal scale factors are also applied to many anthropogenic emissions:
Europe – When using EMEP, European monthly variation of NOx, SOx, CO and NH3 is based upon input into the Open Source Unified EMEP model (, that was produced by the GENEMIS project, coordinated by the Institute of Energy Economics and the Rational Use of Energy (IER) at the University of Stuttgart. These source-specific, country-level variations are combined with sector-level gridded EMEP emissions ( to estimate an overall species specific variation.
North America – Regional NA emission monthly variation of NOx is based upon the VISTAS inventory. All other species, with the exception of NH3, are based upon NEI99 seasonality. For NEI2005, NH3 seasonality is based upon Park et al., JGR, 2004. When using VISTAS or NEI2005, a year-varying scalar in additionally included to account for recent ozone regulations. These are based upon reported trends from the EPA Acid Rain Program (
Asia – When using the Streets inventory, monthly variation is present for NOx and CO only. As of v9-01-02, there is also seasonality in Asian NH3 emissions (described here).
Canada – There is currently no seasonal variation in the CAC inventory, other than ammonia emission which has monthly emissions data.
Mexico – There is currently no seasonal variation in the BRAVO inventory.
Global – The seasonal variation of both EDGAR (Olivier and Berdowski, 2001) and GEIA is derived from the seasonality of GEIA.

Comparison of Emission Configurations

The overall impact of the anthropogenic scale factors upon total emissions of NOx, SOx and CO can be greatly affected by the choice of base emission inventory. The following figures below illustrate the possible range of annual equivalent global and North American emissions for 6 different emission setups, based upon GEOS-Chem v8-02-03 run at 4 x 5 degrees. Not all setups affects all species (see table), and lines of equivalent emissions are coloured to match. Note the large impact of switching between Streets 2000 and Streets 2006 from 2000 to 2001 upon global NOx and CO (see discussion below).
An additional factor causing this jump is the inclusion of biofuel CO from Streets 2006 in the fossil fuel CO emission diagnostics (ND29). This inventory does not separate fossil fuel from biofuel emissions and therefore cannot by separated by source. This should not effect CO concentrations, but has impacted the CO emission diagnositic over the Asian region.
Global NOx Comparison
Global SO2 Comparison
Global CO Comparison
NA NOx Comparison
NA SO2 Comparison
NA CO Comparison
Emission within these figures are configured as:
Descriptor Global Inventory CAC NEI VISTAS ICARTT EMEP BRAVO Streets

Diurnal Variation

A diurnal variation is applied to all NOx. It is derived from EDGAR hourly variations sc(k,H) for each source k and hour H, spatially weighted by the sources. In other words:
                            Σ sc(k,H) * NOx(I,J,k)
     ScaleFactor(H,I,J) = --------------------------
                                 Σ NOx(I,J,k)

Philippe Le Sager wrote:

Note that the scale factors in van Donkelaar et al, 2008] have been updated to go up to 2005, and are based on REAS data now for South East Asia: Relative changes in the REAS inventory (Ohara et al., ACP, [2007]) over East Asia have been used.
This should be a good improvement as REAS emissions are gridded, rather than national scale emissions, giving us much better spatial detail. Also, these scalars are now based on actual NOx, SOx and CO emission estimates, not strictly an assumed proportionality between total, solid and liquid CO2 emissions.


  1. Anthropogenic emissions wiki page
  2. Bey, I., D. J. Jacob, R. M. Yantosca, J. A. Logan, B. Field, A. M. Fiore, Q. Li, H. Liu, L. J. Mickley, and M. Schultz, Global modeling of tropospheric chemistry with assimilated meteorology: Model description and evaluation, J. Geophys. Res., 106, 23,073–23,096, 2001. PDF
  3. Ohara, T., H. Akimoto, J. Kurokawa, N. Horii, K. Yamaji, X. Yan, and T. Hayasaka, An Asian emission inventory of anthropogenic emission sources for the period 1980–2020, Atmos. Chem. Phys.,, 7, 4419-4444, 2007. ACP site
  4. Park, R. J., D. J. Jacob, B. D. Field, R. M. Yantosca, and M. Chin, Natural and transboundary pollution influences on sulfate-nitrate-ammonium aerosols in the United States: implications for policy, J. Geophys. Res., 109, D15204, 10.1029/2003JD004473, 2004. PDF
  5. van Donkelaar, A., R. V. Martin, W. R. Leaitch, A.M. Macdonald, T. W. Walker, D. G. Streets, Q. Zhang, E. J. Dunlea, J. L. Jimenez, J. E. Dibb, L. G. Huey, R. Weber, and M. O. Andreae, Analysis of Aircraft and Satellite Measurements from the Intercontinental Chemical Transport Experiment (INTEX-B) to Quantify Long-Range Transport of East Asian Sulfur to Canada, Atmos. Chem. Phys., 8, 2999-3014, 2008. PDF

--Bob Y. 09:41, 23 February 2010 (EST)