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AQMEII-NA_N2O / N2O_emission_inventories_over_AQMEII-NA_2008

table of contents

global atmospheric N,,2,,O (source=European Environmental Agency, http://www.eea.europa.eu/data-and-maps/figures/atmospheric-concentration-of-n2o-ppb-1)

N2O sources and sinks

In order to model tropospheric N2O over {AQMEII-NA, 2008}, we need to understand the processes that produce and consume tropospheric N2O, and to identify available emissions inventories (EIs) that best reflect those sources and sinks. Thomson et al 2012, Figure 1 illustrates current understanding (at a high and global level, and to a first approximation) of the sources of N2O production and their relative magnitudes:

Thomson et al 2012, Figure 1

Tropospheric N2O sink and source processes must necessarily be either stratospheric, tropospheric, or earth-surface. Current work on global atmospheric N2O production, transport, and fate seems to agree that

  1. Sinks for atmospheric N2O are (approximately) entirely stratospheric. Tropospheric N2O is converted into stratospheric NOx, for which it is the dominant source (Ravishankara et al. (2009)). Unfortunately, CMAQ is currently a troposphere-only model (plans for adding a stratosphere is currently informal).
  2. Atmospheric N2O has only small tropospheric sources, and no significant sinks. 2-3% of total global atmospheric N2O is produced tropospherically (Thomson et al. (2012)): mechanisms include NH3 oxidation and NH4NO3 decomposition (Rubasinghege et al. (2011)). This should be process-modeled in CMAQ, but CMAQ chemical mechanisms currently lack N2O. Fortunately, this tropospheric N2O production appears to be captured by EDGAR-4.2 categories 7B+7C.
  3. Atmospheric N2O is overwhelmingly sourced from, but only slightly sunk to, earth-surface processes. While there are significant anthropogenic sources, most surface sources (and sinks) are microbial, which "can be considered either anthropogenic or natural, depending on the setting. Anthropogenic sources of N2O largely relate to agricultural soils, especially production of nitrogen-fixing crops and forages, the use of synthetic and manure fertilizers, and manure deposition by livestock. Natural sources reflect microbial processes in uncultivated soils, oceans and other aquatic systems, and possibly wetlands." (US EPA, "Methane and Nitrous Oxide Emissions From Natural Sources," p1-4)

CMAQ's current lack of all stratospheric processes has an important consequence for this research at this time: we can currently model N2O loss only via advection out of the domain, and by the extent to which our EIs capture (net out) N2O loss.

EPA N2O estimates

(Note that, in this section, the spatial extent of all estimates is either the surface of the entire globe or that of the full US (not CONUS). This complicates use of the following data to check estimates over the AQMEII-NA spatial domain, which includes non-CONUS parts (but not all) of North America, but not the non-contiguous parts of the US.)

US EPA estimates that net total global annual N2O emission is 18.8 TgN (6.89e+11 molN2O), with a range of 8.5-27.7 TgN (3.03e+11-9.89e+11 molN2O) (US EPA, "Methane and Nitrous Oxide Emissions From Natural Sources," Table ES-1). (The range estimate cites "Denman et al., 2007, and references therein." Denman et al. (2007) is perhaps better known as IPCC AR4 WG1 chapter 7.) EPA further estimates natural sources produce 64% of total N2O (US EPA, "Methane and Nitrous Oxide Emissions From Natural Sources," Table ES-1), and therefore 36% are anthropogenic. (It acknowledges difficulties in attribution, particularly regarding fire and riverine/estuarine emissions.)

EPA estimates of US anthropogenic N2O

US EPA further finds that, in the US, managed soils dominate other anthropogenic sources by better than 2-to-1:

"U.S. Nitrous Oxide Emissions, By Source" from http://epa.gov/climatechange/ghgemissions/gases/n2o.html retrieved 29 May 2013, indirectly from "Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2011" http://epa.gov/climatechange/Downloads/ghgemissions/US-GHG-Inventory-2013-Main-Text.pdf

Specifically, for 2008, US EPA estimated total "U.S. [Anthropogenic N2O] Emissions and Sinks" at 349.7 TgCO2e, and quantified individual source sectors as (in descending quantitative order)

source
activity
2008 US emission
(TgCO2e)
2008 emission fraction of
US anthropogenic total
Agricultural Soil Management2.45e+27.02e-1
Mobile Combustion2.55e+17.29e-2
Stationary Combustion2.11e+16.03e-2
Manure Management1.78e+15.09e-2
Nitric Acid Production1.69e+14.83e-2
Forest Land Remaining Forest Land7.40e+02.12e-2
Wastewater Treatment4.90e+01.40e-2
N2O from Product Uses4.40e+01.26e-2
Adipic Acid Production2.60e+07.43e-3
Composting1.90e+05.43e-3
Settlements Remaining Settlements1.50e+04.29e-3
International Bunker Fuels1.00e+02.86e-3
Incineration of Waste4.00e-11.14e-3
Field Burning of Agricultural Residues1.00e-12.86e-4
Wetlands Remaining Wetlandsn/an/a
total US anthropogenic349.71

(from "Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2011," Executive Summary, Table ES-2, retrieved 29 May 2013)

EPA estimates of global natural N2O

"Currently" (as of 2010), and globally (not for US), US EPA estimates net total global annual N2O emission from natural sources at 12.1 TgN (4.32e+11 molN2O): 64% of total global N2O emission, no range cited (US EPA, "Methane and Nitrous Oxide Emissions From Natural Sources," Table ES-1). It acknowledges difficulties in attribution, particularly regarding fire and riverine/estuarine emissions."Methane and Nitrous Oxide Emissions From Natural Sources" quantified individual natural source sectors as (for no single year, in descending quantitative order):

source
sector
annual global emission
(TgN)
emission fraction of
global natural total
annual emission range
(TgN)
notes
Upland soils and riparian areas6.60e+05.45e-13.3-9.0table ES-1
Open ocean3.20e+02.64e-1table ES-3
Continental shelves1.50e+01.24e-1table ES-3
Upwelling zones4.00e-13.31e-2table ES-3
Estuaries2.00e-11.65e-2table ES-3
Rivers1.00e-18.26e-3table ES-3
Wildfires1.00e-18.26e-3n/atable ES-1
Lakesnegligible0.004-0.04table ES-1
Permafrostnegligibletable ES-1
Wetlandsnegligibletable ES-1
global natural total1.21e+1table ES-1
estimated global total1.89e+1table ES-1

EPA N2O estimates in CMAQ units

CMAQ wants concentrations of species in mol/s, so for reference purposes I can convert both of EPA's units (TgN and TgCO2e to molN2O. (See work done in my inventory-analysis spreadsheet, sheet=EPA.)

activity
or sector
emission
(molN2O)
fraction of
category
emissions
fraction of
total global
emissions
natural
Upland soils and riparian areas2.36e+115.45e-13.49e-1
Open ocean1.14e+112.64e-11.69e-1
Continental shelves5.35e+101.24e-17.93e-2
Upwelling zones1.43e+103.31e-22.12e-2
Estuaries7.14e+91.65e-21.06e-2
Rivers3.57e+98.26e-35.29e-3
Wildfires3.57e+98.26e-35.29e-3
Lakesnegligible
Permafrostnegligible
Wetlandsnegligible
total natural4.32e+119.99e-16.27e-1
total all (estimated)6.89e+111.00e+0
anthropogenicemission
(molN2O)
fraction of
category
emissions
fraction of
total global
emissions
Agricultural Soil Management1.80e+106.99e-12.66e-02
Mobile Combustion1.87e+97.28e-22.77e-03
Stationary Combustion1.55e+96.02e-22.29e-03
Manure Management1.30e+95.08e-21.93e-03
Nitric Acid Production1.24e+94.82e-21.84e-03
Forest Land Remaining Forest Land5.42e+82.11e-28.04e-04
Wastewater Treatment3.59e+81.40e-25.32e-04
N2O from Product Uses3.22e+81.26e-24.78e-04
Adipic Acid Production1.91e+82.82e-04
Composting1.39e+85.42e-32.06e-04
Settlements Remaining Settlements1.10e+84.28e-31.63e-04
International Bunker Fuels7.33e+72.85e-31.09e-04
Incineration of Waste2.93e+71.14e-34.34e-05
Field Burning of Agricultural Residues7.33e+62.85e-41.09e-05
Wetlands Remaining Wetlandsn/a
total anthropogenic2.57e+111.00e+03.81e-02

constants and calculations used

  • molar mass N2O (molN2O)=44.013 g
  • molar mass N2 (molN2)= 28.013 g
  • molar mass N (molN)=14.007 g (aka atomic weight)
  • 1 gN → 3.5700e-2 molN2O (inverse of molar mass N2)
  • global warming potential over 100 years N2O (GWPN2O100)=310, per "Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2011," Table ES-1. Note that currently estimated GWPN2O100=298 (per IPCC AR4 WG1, Table 2.14), but the convention is to use the value from IPCC SAR (aka AR2).
  • 1 gCO2e → 7.62e-5 molN2O (inverse of (GWPN2O100 * molar mass N2O))
    • for EPA, 1 gCO2e → 7.33e-5 molN2O (inverse of (GWPN2O100 * molar mass N2O))
  • total global natural N2O emission → 0.64 total global N2O emission (see EPA estimate above)

currently available N2O inventories

IPCC codes

Note on "IPCC codes": these are more properly referred to as "categories of [anthropogenic] emissions and removals." They appear to be most recently defined in Table 8.2 in Chapter 8 of the 2006 IPCC Guidelines for National Greenhouse Gas Inventories, Volume 1 (General Guidance and Reporting). EDGAR also documents how it uses IPCC codes.

timesteps

Note on timesteps: CMAQ (at least, for the PHASE run), runs hourly. None of the EIs mentioned have that temporal fineness, though

  • EPIC may soon be available daily (though not currently)
  • GFED can be resolved to 3-hourly intervals

I would like to impose diurnality on the daily and monthly emissions (CLMCN-N2O and eventually EPIC). I would like to impose seasonality on the annual inputs (EDGAR and GEIA, and currently EPIC).

gridcells

Note on gridcells: CMAQ (at least, for AQMEII), wants 12 km x 12 km LCC (Lambert conformal conic). The non-projected global datasets must be regridded to that.

units

Note on units: excepting GEIA, all of the above are mass fluxes. By contrast, CMAQ requires mol/s (implicitly per-gridcell), so I'll need to compute total mass emitted over the area of each gridcell (which varies, but can be computed, or looked up in the case of EDGAR-4.2).

CLMCN-N2O

units=mgN/m2/mo. CLMCN-N2O is a DNDC-based global process model. References:

Data locally retrieved @ infinity:/project/inf14w/roche/CLM-CN_4.2_N2O_20120701.

CLMCN-N2O header

dimensions:
    lat = 96 ;
    lon = 144 ;
    time = 14 ;
variables:
    double lat(lat) ;
        lat:long_name = "latitude" ;
        lat:units = "degrees_north" ;
    double lon(lon) ;
        lon:long_name = "longitude" ;
        lon:units = "degrees_east" ;
    float time(time) ;
        time:long_name = "time" ;
        time:units = "decimal year" ;
    float n2oemissions(time, lat, lon) ;
        n2oemissions:long_name = "N2O emissions" ;
        n2oemissions:units = "mgN/m2/month" ;

Note in email from Eri Saikawa:

> there are 14 times recorded in this netcdf file but
> the time 0 and 1 are the same (January) and
> time 12 and 13 are the same (December).

CLMCN-N2O domain

horizontal
domainglobal
quanta1.875° lat x 2.5° lon
coordinates
point to
center of cell
temporal
domain2008 (et al)
quantamonthly

EDGAR-4.2

units=kgN20/m2/s. References:

Data locally retrieved @ infinity:/project/inf14w/roche/EDGAR_4.2_N2O_20120701. Note that areas of EDGAR-4.2 gridcells are available here per this webpage.

EDGAR-4.2 header

dimensions:
    lat = 1800 ;
    lon = 3600 ;
variables:
    float lat(lat) ;
        lat:standard_name = "latitude" ;
        lat:long_name = "latitude" ;
        lat:units = "degrees_north" ;
        lat:comment = "center_of_cell" ;
    float lon(lon) ;
        lon:standard_name = "longitude" ;
        lon:long_name = "longitude" ;
        lon:units = "degrees_east" ;
        lon:comment = "center_of_cell" ;
    float emi_n2o(lat, lon) ;
        emi_n2o:standard_name = "tendency_of_atmosphere_mass_content_of_nitrous_oxide_due_to_emission" ;
        emi_n2o:long_name = "Emissions of N2O - " ;
        emi_n2o:units = "kg m-2 s-1" ;
        emi_n2o:cell_method = "time: mean (interval: 1 year, 366 days)" ;
        emi_n2o:total_emi_n2o = "   3.23908e+008 kg/year" ;
        emi_n2o:comment = " (see http://edgar.jrc.ec.europa.eu/methodology.php#12sou for the definitions of the single sources)" ;

// global attributes:
        :Conventions = "CF-1.0" ;
        :title = "Annual Mean Emissions of N2O - " ;
        :institution = "European Commission, Joint Research Centre" ;
        :source = "http://edgar.jrc.ec.europa.eu/" ;
        :history = "Created from original data (0.1x0.1 degrees) using IDL program (edgar_ascii_to_ncdf.pro) on Mon Dec 12 16:11:36 2011" ;
        :references = "European Commission, Joint Research Centre (JRC)/Netherlands Environmental Assessment Agency (PBL). Emission Database for Global Atmospheric Research (EDGAR),http://edgar.jrc.ec.europe.eu" ;
        :copyright_notice = "Reproduction of the data is authorized, except for commercial purposes, provided the source is fully acknowledged in the from\"Source: European Commission, Joint Research Centre (JRC)/Netherlands Environmental Assessment Agency (PBL). Emission Databasefor Global Atmospheric Research (EDGAR), http://edgar.jrc.ec.europe.eu\". Where reproduction is on a web-site,at least one link to http://edgar.jrc.ec.europa.eu, should be provided and maintained. Where prior permission must be obtained for thereproduction or use of textual and multimedia information (sound, images, software, etc.), such permission shall cancel the above-mentionedgeneral permission and shall clearly indicate any restrictions on use." ;
        :contact = "edgar-info@jrc.ec.europa.eu" ;

EDGAR-4.2 domain

horizontal
domainglobal
quanta0.1° x 0.1°
coordinates
point to
center of cell
temporal
domaineach of 1970-2008
quantaannual

EDGAR-4.2 categories

While EDGAR publishes individual estimates for each {IPCC code, nation/sector} tuple, it bundles IPCC codes for gridded emissions (as available for, e.g., EDGAR-4.2 here). The bundles are visible in the download pages's sector dropdown after selecting compound=N2O, e.g.,

Agricultural waste burning (4F)
Energy manufacturing transformation (1A1+1A2)
Industrial process and product use (2)
Manure management (4B)
Oil production and refineries (1B2)
Residential (1A4)
Road transportation (1A3b)
Agricultural soils (4C+4D)
Non-road transportation (1A3a+c+d+e)
Fossil Fuel Fires (7A)
Large Scale Biomass Burning (5A+C+D+F+4E)
=> Totals
Indirect emissions from NOx and NH3 (7B+7C)
Indirect N2O emissions from agriculture (4D3)
Waste solid and wastewater (6)

From that, and with reference to EDGAR-4.2's spreadsheet of N2O emissions by nation/sector and IPCC code, we can determine the IPCC codes used for each set of gridded emissions:

N2O emission source
descriptionIPCC
code(s)
potential alternative(s)used here for
Combustion in energy transformation, manufacturing, and construction1A1+1A2GEIA fosf (fossil fuel burning)
GEIA biof (biofuel burning)
anthropogenic sources other than biomass burning, oceans, and soils
Non-road transportation1A3a+c+d+eGEIA fosf (fossil fuel burning)
GEIA biof (biofuel burning)
anthropogenic sources other than biomass burning, oceans, and soils
Road transportation1A3bGEIA fosf (fossil fuel burning)
GEIA biof (biofuel burning)
anthropogenic sources other than biomass burning, oceans, and soils
Residential1A4GEIA fosf (fossil fuel burning)
GEIA biof (biofuel burning)
anthropogenic sources other than biomass burning, oceans, and soils
Oil production and refining1B2?anthropogenic sources other than biomass burning, oceans, and soils
Non-combustion industrial processes and product uses2GEIA indu "industrial sources (adipic + nitric acid production)"anthropogenic sources other than biomass burning, oceans, and soils
Manure management4BGEIA anexanthropogenic sources other than biomass burning, oceans, and soils
Agricultural soils4C+
4D1+4D2+4D4
GEIA soil
includes "soils under natural vegetation and fertilized agricultural fields"
non-{CONUS, EPIC} agricultural soils
Indirect N2O from leaching/runoff in agriculture4D3?anthropogenic sources other than biomass burning, oceans, and soils
Waste: solid disposal, wastewater, other6?anthropogenic sources other than biomass burning, oceans, and soils
Fossil fuel fires (e.g., coal mines, oil wells)7A?anthropogenic sources other than biomass burning, oceans, and soils
Indirect emissions from non-agricultural NOx and NH3
(tropospheric chemistry?)
7B+7C?anthropogenic sources other than biomass burning, oceans, and soils
descriptionIPCC
code(s)
potential alternative(s)replaced here by
Agricultural waste burning4FGEIA agwb,
GFED
biomass burning
Savanna and non-agricultural biomass burning4E+5A+5C+5D+5FGEIA biob ("deforestation + savanna burning"),
GFED
biomass burning

EPIC-0509

units=kg/ha (implicitly per timestep). References:

EPIC 0509 is the version of EPIC from which Ellen Cooter is currently getting output from Cesar Izaurralde, but we may soon get in-house @ EPA.

EPIC-0509 domain

horizontal
domainCONUS
quanta12 km x 12 km (LCC)
coordinates
point to
center of cell
temporal
domaina 5-year average including 2008
quantadaily

GEIA

units="ton N2O-N/year". References:

Data locally retrieved @ infinity:/project/inf14w/roche/GEIA_N2O_oceanic. Note GEIA data is not natively netCDF! See GEIA data format or my README.txt.

GEIA domain

horizontal
domainglobal
quanta1° x 1°
coordinates
point to
center of cell
temporal
domainno particular year
quantaannual

GEIA categories

N2O emission source
descriptionGEIA suffixpotential alternative(s)
soils under natural vegetation and fertilized agricultural fieldssoilfor agricultural soils only (includes non-fertilized?):
EDGAR 4C+4D1+4D2+4D4
animal excretaanexEDGAR 4B
post-forest clearing enhanced soil N2O emissiondefo?
biomass burning (including deforestation + savanna burning)biobGFED, EDGAR 4E+5A+5C+5D+5F
agricultural waste burningagwbGFED, EDGAR 4F
biofuel burningbiof?
fossil fuel burningfosfEDGAR 1A1, 1A2, 1A3a, 1A3b, 1A3c, 1A3d+1A3e, 1A4
industrial sources (adipic + nitric acid production)induEDGAR 2
oceansocea?

GFED-3.1

units=gN2O/m2 (implicitly per temporal interval, which may be month, day, or 3 hours). References:

Data locally retrieved @ infinity:/project/inf14w/roche/GFED-3.1_N2O_2008 and terrae:/work/MOD3APP/rtd/GFED-3.1_N2O_2008.

GFED-3.1 header

Note monthly emissions are in text format; daily and 3-hourly fire fraction datasets are in netCDF. Instructions for generating daily and 3-hourly from the above, as well as significant metadata, are here.

dimensions:
# for 3-hourly emissions
#     time = UNLIMITED ; // (8 currently)
    lat = 360 ;
    lon = 720 ;
variables:
# for 3-hourly emissions
#     int time(time) ;
#         time:long_name = "time" ;
#         time:units = "The hour on the date" ;
    float lat(lat) ;
        lat:long_name = "latitude" ;
        lat:units = "degrees_north" ;
    float lon(lon) ;
        lon:long_name = "longitude" ;
        lon:units = "degrees_east" ;
    float Fraction_of_Emissions(lat, lon) ;
        Fraction_of_Emissions:_FillValue = -999.f ;
        Fraction_of_Emissions:units = "unitless" ;
        Fraction_of_Emissions:long_name = "Fraction of Emissions" ;
    float DataSources(lat, lon) ;
        DataSources:_FillValue = -999.f ;
        DataSources:Atts = "1: Aqua only, 2: Terra only, 3: Aqua+Terra, 4: uniform distribution-No active fire, 0: outside of GFED regions" ;
        DataSources:units = "unitless" ;
        DataSources:long_name = "Data Sources" ;

// global attributes:
        :creation_date = "Wed Sep 22 10:41:16 PDT 2010" ;
        :Conventions = "Please contact Prof. James Randerson (Email: jranders@uci.edu) or Dr. Mingquan Mu (mmu@uci.edu) for any question" ;
        :source_file = "This file is generated by Global Fire Emission Database (GFED) TEAM" ;
        :title = "Fraction of  Emissions calculated from MODIS AQUA and TERRA active fire data (MCD14ML)" ;

GFED-3.1 domain

horizontal
domainglobal
quanta0.5° x 0.5°
coordinates
point to
center of cell
temporal
domain1997-2010
quantamonthly, from which can generate daily, 3-hourly

GFED-3.1 categories

N2O emission source
descriptionpotential alternative(s)
biomass burning (including agricultural, deforestation, savanna burning)EDGAR: 4E+5A+5C+5D+5F + 4F
GEIA: agwb + biob

my N2O inventory choices

My uncitable sense from the folks with whom I've discussed N2O inventories (notably at AGU 2012, and with Greg Frost) is that

  • EDGAR is best-of-breed for anthropogenic emissions (plus it's now available for 2008)
  • EPA wants to use EPIC for managed soils, but it's currently available only for CONUS
  • GEIA is the default for natural emissions (particularly oceanic)
  • GFED-3.1 is best for biomass burning

Unfortunately,

Fortunately, MIT CGCS has developed a process model for natural soil N2O for CLM. How do these inventories fit together?

sourcequanta provideddetails
typeIPCC code(s)publisherhorizontaltemporalunitsdescription,
questions/problems,
to-do list
Combustion in energy transformation, manufacturing, and construction1A1+1A2EDGAR-4.20.1°x0.1°annualkgN20/m2/s
Non-road transportation1A3a+c+d+eEDGAR-4.20.1°x0.1°annualkgN20/m2/s
Road transportation1A3bEDGAR-4.20.1°x0.1°annualkgN20/m2/s
Residential1A4EDGAR-4.20.1°x0.1°annualkgN20/m2/s
Oil production and refining1B2EDGAR-4.20.1°x0.1°annualkgN20/m2/s
Non-combustion industrial processes and product uses2EDGAR-4.20.1°x0.1°annualkgN20/m2/s
Manure management4BEDGAR-4.20.1°x0.1°annualkgN20/m2/s
Agricultural soils4C+
4D1+4D2+4D4
+ southern CanadaEDGAR-4.20.1°x0.1°annualkgN20/m2/s
+ contiguous USEPIC12 km x 12 kmpotentially daily,
currently annual
kg/ha
+ northern MexicoEDGAR-4.20.1°x0.1°annualkgN20/m2/s
+ rest of earthEDGAR-4.20.1°x0.1°annualkgN20/m2/s
Indirect N2O from leaching/runoff in agriculture4D3EDGAR-4.20.1°x0.1°annualkgN20/m2/s
Agricultural waste burning4FGFED0.5°x0.5°3-hourlygN20/m2/(3*hr)I have R scripts that replicate the computation of the 3-hourly emissions (as illustrated in GFED's IDL scripts) from the monthly emissions and daily and 3-hourly fractions supplied by GFED.
Savanna and non-agricultural biomass burning4E+
5A+5C+5D+5F
GFED0.5°x0.5°3-hourlygN20/m2/(3*hr)
Waste: solid disposal, wastewater, other6EDGAR-4.20.1°x0.1°annualkgN20/m2/s
Fossil fuel fires (e.g., coal mines, oil wells)7AEDGAR-4.20.1°x0.1°annualkgN20/m2/s
Oceanicn/aGEIA ocea1°x1°annual, no particular year"ton N2O-N/year"Note GEIA data is not netCDF, requiring additional processing.
Natural soilsn/aCLMCN-N2O DNDC-based process model1.875° lat x 2.5° lonmonthlymgN/m2/mo

N2O inventory assimilation

I assimilate the above inventories in 5 chunks, which I process {with 5 projects, in 5 repositories}:

project/repositoryIPCC codesEPA categoriesnotes
AQMEII_ag_soil4C+
4D1+4D2+4D4
(antUSA)1Agricultural Soil Managementoverlays EPIC for CONUS onto ag-soils portion of EDGAR-4.2 regridded to AQMEII-NA
CLM_CN_global_to_AQMEII-NA(natglo)1Upland soils and riparian areasglobal natural-soils inventory regridded to AQMEII-NA
GEIA_regrid(natglo)Open ocean
(natglo)Continental shelves
(natglo)Upwelling zones
global marine inventory regridded to AQMEII-NA
GFED-3.1_global_to_AQMEII-NA4E+4F+
5A+5C+5D+5F
(natglo)Wildfiresglobal fire inventory regridded to AQMEII-NA
EDGAR-4.2_minus_soil_and_biomass_to_AQMEII-NA1A1+1A2
1A3a+b+c+d+e
1A4+
1B2+
2+
4B+4D3+
6a+b+c+d+
7A
(antUSA)Mobile Combustion
(antUSA)Stationary Combustion
(antUSA)Manure Management
(antUSA)Nitric Acid Production
(antUSA)Wastewater Treatment
(antUSA)N2O from Product Uses
(antUSA)Adipic Acid Production
(antUSA)Composting
(antUSA)Settlements Remaining Settlements
(antUSA)International Bunker Fuels
(antUSA)Incineration of Waste
"none of the above" parts of EDGAR-4.2 combined and regridded to AQMEII-NA
missing
(natglo)Estuaries
(natglo)Rivers
(natglo)Lakes
(natglo)Permafrost
(natglo)Wetlands
(antUSA)Forest Land Remaining Forest Land
(antUSA)Wetlands Remaining Wetlands

Notes:

[1] (antUSA) refers to EPA's estimates of anthropogenic US N2O emissions, while (natglo) refers to EPA's estimates of natural global N2O emissions.

AQMEII_ag_soil

For details on how this project assimilates data from EPIC and part of EDGAR-4.2, see the project's README at either the project link or the file link. Note its current analytic output includes

EDGAR global emissions (mol/s) from ./v42_N2O_2008_IPCC_4C_4D.0.1x0.1_reunit.nc
|cells|=6.48e+06
|obs|  =6.48e+06
min    =0
q1     =0
med    =0
mean   =5.177e-04
q3     =0
max    =1.003e+00
sum    =3.352e+03

EDGAR emissions (mol/s) over [[AQMEII-NA_spatial_domain|AQMEII-NA]] from ./v42_N2O_2008_IPCC_4C_4D.0.1x0.1_reunit_regrid.nc
|cells|=137241
|obs|  =137241
min    =0
q1     =0
med    =1.575e-04
mean   =1.890e-03
q3     =3.121e-03
max    =8.609e-02
sum    =2.593e+02

EPIC emissions (mol/s) over CONUS from ./5yravg_20111219_pure_emis.nc
|cells|=137241
|obs|  =40763
min    =0
q1     =1.021e-05
med    =1.714e-04
mean   =1.373e-03
q3     =1.112e-03
max    =7.571e-02
sum    =5.596e+01

EDGAR+EPIC emissions (mol/s) over [[AQMEII-NA_spatial_domain|AQMEII-NA]] from ./emis_mole_N2O_2008_12US1_cmaq_cb05_soa_2008ab_08c.nc
|cells|=137241
|obs|  =137241
min    =0
q1     =0
med    =1.600e-04
mean   =1.986e-03
q3     =3.198e-03
max    =8.609e-02
sum    =2.725e+02

Comparison of EDGAR emissions
(units=molN2O/s)

    EDGAR     global      EDGAR  AQMEII-NA  AQMEII-NA/
   global        NAs  AQMEII-NA        NAs     global
 3.35e+03          0   2.59e+02          0   7.74e-02

EPIC vs EDGAR emissions over [[AQMEII-NA_spatial_domain|AQMEII-NA]]
(units=molN2O/s)

     EPIC       EPIC      EDGAR      EDGAR      EPIC/
  (CONUS)        NAs  AQMEII-NA        NAs      EDGAR
 5.60e+01      96478   2.59e+02          0   2.16e-01

EDGAR vs EPIC+EDGAR emissions (both over [[AQMEII-NA_spatial_domain|AQMEII-NA]])
(units=molN2O/s)

    EDGAR      EDGAR   combined   combined     EDGAR/
AQMEII-NA        NAs  AQMEII-NA        NAs   combined
 2.59e+02          0   2.72e+02          0   9.52e-01

EPIC+EDGAR [[AQMEII-NA_spatial_domain|AQMEII-NA]] vs EDGAR global emissions
(units=molN2O/s)

 combined   combined      EDGAR      EDGAR  combined/
AQMEII-NA        NAs     global        NAs      EDGAR
 2.72e+02          0   3.35e+03          0   8.13e-02

EDGAR-4.2 also provides ungridded N2O emissions for 2008 as a CSV spreadsheet. The data's rows are nation/sector (mostly national, plus international aviation, international shipping, and total), its columns are IPCC codes (plus total), and the data is in GgN2O. I can't give you their URI for the CSV, because they don't expose one (ya hafta twiddle their web UI), but I have saved their CSV, with added metadata, as an OpenDocument spreadsheet.

We know that the EDGAR-4.2 ag-soil grid aggregates IPCC codes {4C, 4D1, 4D2, 4D4}. When I sum the EDGAR-4.2 spreadsheet's totals for those columns, I get 4.67e+03 GgN2O, which equals 1.06e+11 molN2O (presuming 1 molN2O=44.013 gN2O). The good news is, this matches my sum of the input/global EDGAR-4.2 ag-soil grid. The bad news are summarized in the following table:

horizontal domain
source/
activity
globalAQMEII-NAUS
EPA Agricultural
Soil Management
n/an/a1.80e+101
EDGAR Agricultural
soils
1.06e+118.19e+091.06e+102
EPICn/an/a1.77e+091
AQMEII_ag_soiln/a8.60e+09not3
processed

notes:

[1] The EPA estimate (from "Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2011," Executive Summary, Table ES-2, retrieved 29 May 2013) is for the full US, while the EPIC estimate is CONUS-only. That being said, I don't suspect too much agriculture is happening (relatively) in the non-CONUS US (ICBW).

[2] See EDGAR-4.2 national and regional estimates for 2008

[3] If necessary I could almost certainly generate a CONUS-only AQMEII_ag_soil estimate (by masking), but not a full-US estimate (since Alaska, Hawaii, et al are not in the spatial domain).

The bad news unpacked:

  • when I sum the values in the row for country=United States for the columns {4C, 4D1, 4D2, 4D4} and convert to molN2O, I get total US ag-soil N2O emission=1.06e+10 molN2O. I realize that looks like exactly 10% of global, but the addends are different, so I don't believe this is an artifact.
  • in summing the EPIC grid, I got total N2O emission=1.77e+09 molN2O. So EPIC's 5-year annual average of N2O for CONUS is about 1/6 EDGAR-4.2's estimate for US for 2008 :-(
  • when I summed my gridded ag-soil output (which is the AQMEII-NA-regridded EDGAR-4.2 data combined with EPIC data where the latter is larger), I got 8.60e+09 mol ... which is 81% of what the EDGAR-4.2 breakdown sheet quotes for just the US :-( Unless Alaska and Hawaii are putting out hellacious N2O, I'm wrong.
  • EPA's recently "released for printing: April 15, 2013" estimates of anthropogenic N2O emitted from various US sources for 2008 (and officially submitted to the UNFCCC/IPCC) in the "Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2011," Executive Summary, Table ES-2 estimates 2008 N2O for the US from "Agricultural Soil Management"=2.45e+2 TgCO2e. In Table ES-1 they quote GWP100y for N2O=310 (probably high, but the convention is to use the IPCC SAR GWPs), from which I calculate 1.80e+10 molN2O.

So for 2008 US N2O, EDGAR-4.2's US estimate is only 59% of EPA's, and EPIC is less than 10% of EPA's US estimate ... but the worst part is, my AQMEII-NA estimate (which is largely a regridding of the global EDGAR-4.2 EI to AQMEII-NA) is smaller than EDGAR-4.2's ungridded US estimate. Is this caused by a defect in my regridding, or by a problem with EDGAR-4.2? I don't know. However, note below that

Finally, Canada and Mexico are issues. Horizontally, AQMEII-NA includes the bulk of Canadian agriculture, which is both globally significant and similar to US agriculture in technology (e.g., in fertilizer application), though smaller in scale. If my AQMEII-NA estimate is low relative to US agriculture (as the ungridded EPA estimate claims), it must be lower relative to US and Canadian agriculture. Furthermore, AQMEII-NA includes northwest Mexico, which is (IIUC) also a significant grain-producing area.

CLM_CN_global_to_AQMEII-NA

For details on how this project assimilates data from CLMCN-N2O, see the project's README at either the project link or the file link. Note its current analytic output includes

Is N2O conserved from input to output? units=mgN
(note (US land area)/(earth land area) ~= 6.15e-02)
           input      input     output     output           
month     global        NAs  AQMEII-NA        NAs     out/in
    1   3.83e+14          0   2.22e+12          0   5.78e-03
    2   4.24e+14          0   2.33e+12          0   5.49e-03
    3   4.67e+14          0   3.46e+12          0   7.41e-03
    4   4.94e+14          0   6.60e+12          0   1.34e-02
    5   4.94e+14          0   1.02e+13          0   2.06e-02
    6   6.95e+14          0   1.77e+13          0   2.54e-02
    7   8.61e+14          0   1.84e+13          0   2.14e-02
    8   1.01e+15          0   1.74e+13          0   1.73e-02
    9   8.08e+14          0   1.64e+13          0   2.03e-02
   10   6.02e+14          0   1.04e+13          0   1.73e-02
   11   4.72e+14          0   5.01e+12          0   1.06e-02
   12   4.49e+14          0   3.67e+12          0   8.18e-03

How does output of 4.06e+09 molN2O for AQMEII-NA compare to EPA estimates? EPA only estimates this source globally, but for that domain, CLMCN-N2O's estimate is within 8%:

horizontal domain
source/
activity
globalAQMEII-NAUS
EPA Upland soils
and riparian areas
2.36e+11n/an/a
CLM_CN_global_to_AQMEII-NA2.56e+114.06e+09n/a

EDGAR-4.2_minus_soil_and_biomass_to_AQMEII-NA

For details on how this project assimilates data from parts of EDGAR-4.2, see the project's README at either the project link or the file link. Note its current analytic output includes

Compare annual emissions reported by EDGAR to our calculated annual emissions:
           raw input    sum 
EDGAR      annual sum   calculated
sector     (kgN2O)      from output   EDGAR/calc
--------   ----------   -----------   ----------
combust     3.24e+08     3.23e+08      1.00e+00 
nonroad     7.79e+07     7.76e+07      1.00e+00 
road        2.23e+08     2.23e+08      1.00e+00 
resid       2.85e+08     2.84e+08      1.00e+00 
petro       6.52e+06     6.52e+06      1.00e+00 
ind         1.33e+09     1.33e+09      1.00e+00 
manure      3.36e+08     3.35e+08      1.00e+00 
runoff      8.94e+08     8.92e+08      1.00e+00 
waste       3.75e+08     3.74e+08      1.00e+00 
fff         7.53e+05     7.53e+05      1.00e+00 
tropo       7.11e+08     6.99e+08      1.02e+00

Is N2O conserved from input to output? units=kg N2O
(note (US land area)/(earth land area) ~= 6.15e-02)
    input      input     output     output           
   global        NAs  AQMEII-NA        NAs     out/in
 4.55e+09          0   4.38e+08          0   9.64e-02

How does output of 9.95e+09 molN2O for AQMEII-NA compare to EPA estimates? The bad news is that, in this case, we're comparing sets of categories that are only roughly similar: "everything anthropogenic EDGAR-4.2 estimates that is not soils or burning or marine" vs "everything anthropogenic EPA estimates that is not soils or burning or marine." Worse yet, EDGAR-4.2 estimates globally, while EPA estimates (anthropogenic) emissions for the US only. But the really bad news is, as with my EDGAR-4.2-derived managed-soil project (but not my GFED-derived biomass-burning project), our estimate for AQMEII-NA is less than that of EDGAR-4.2 for the US alone:

horizontal domain
source/
activity
globalAQMEII-NAUS
EPA anthropogenic
composite
n/an/a7.18e+09
EDGAR anthropogenic
composite
1.04e+119.95e+091.25e+10

GEIA_regrid

For details on how this project assimilates data from GEIA, see the project's README at either the project link or the file link. Note its current analytic output includes

Is N2O conserved from input to output? units=ton-N
(TODO: compare global ocean area to AQMEII-NA ocean area)
    input      input     output     output           
   global        NAs  AQMEII-NA        NAs     out/in
 3.60e+06      28657   1.06e+06      90768   2.96e-01

How does output of 3.78e+10 molN2O for AQMEII-NA compare to EPA estimates? The good news is that, in this case, we seem to have a relatively "apples-to-apples" comparison: GEIA estimates global marine emissions for an unspecified year, while EPA sub-estimates for "open ocean," "continental shelves," and "upwelling zones" for an unspecified year over the globe. (Whether/how to attribute the EPA sub-estimate for "estuaries" to this marine category remains an open question.) The bad news is, the GEIA global estimate is only 70% of that of EPA (and this is believed to be a major fraction of N2O emissions):

horizontal domain
source/
activity
globalAQMEII-NA
EPA open ocean1.14e+11n/a
EPA
continental
shelves
5.35e+10n/a
EPA
upwelling zones
1.43e+10n/a
EPA marine sum11.82e+11n/a
GEIA1.29e+113.78e+10

GFED-3.1_global_to_AQMEII-NA

For details on how this project assimilates data from GEIA, see the project's README at either the project link or the file link. Note its current analytic output includes

GFED monthly N2O (mol) over globe from ./GFED-3.1_2008_N2O_monthly_emissions.nc:
|cells|=3.1104e+06
|obs|  =3.1104e+06
min    =0
q1     =0
med    =0
mean   =5.443e+03
q3     =0
max    =4.440e+07
sum    =1.693e+10

GFED monthly N2O (mol) over AQMEII-NA from ./GFED-3.1_2008_N2O_monthly_emissions_regrid.nc:
|cells|=1.64689e+06
|obs|  =1.64689e+06
min    =0
q1     =0
med    =0
mean   =2.337e+03
q3     =0
max    =1.797e+07
sum    =3.848e+09

AQMEII-NA monthly N2O/global monthly N2O==2.273e-01

[aggregating hourly emissions]
Is N2O conserved from input to output? units=mol N2O
(note (US land area)/(earth land area) ~= 6.15e-02)
    input      input     output     output           
   global        NAs  AQMEII-NA        NAs     out/in
 1.69e+10          0   3.53e+09          0   2.09e-01

How does output of 3.53e+09 molN2O for AQMEII-NA compare to EPA estimates? Differing categories and spatial domains make the comparison difficult. GFED-3.1 includes N2O estimates for

  • "natural" fires in grasslands/savannas, woodlands, and peat
  • deforestation/degradation fires
  • agricultural waste burning

and does so both globally and for CONUS. We can therefore calculate the CONUS fraction of N2O for each source (by dividing the CONUS estimate by the global estimate). EPA estimates (anthropogenic) agricultural waste burning only for the US (and not CONUS) and (natural) "wildfires" only globally, but if we are willing to apply the relevant GFED fraction (and assume rough equality between CONUS and US production), we can attribute the missing quantities. This allows very rough comparisons between the relevant categories and domains (all units=molN2O), particularly that

  • GFED's total global emission is 4.17 times greater than that which can be attributed to EPA.
  • The total GFED emission that I attribute to AQMEII-NA (via regridding) is 2.5 times greater than GFED's explicit total CONUS emission. This seems reasonable in that the AQMEII-NA plot shows significant burning in Canada.
  • GFED's explicit total global emission is 4.81 times greater than that the total I attribute to AQMEII-NA. This seems reasonable in that most global burning is tropical.
horizontal domain
source/
activity
globalAQMEII-NAUS1
EPA field burning4.95e+082n/a7.33e+061
GFED agricultural
waste burning
3.07e+08not3
processed
4.54e+061
EPA wildfires3.57e+09n/a2.92e+071
GFED other fires1.67e+10not3
processed
1.36e+081
EPA total4.06e+095n/a3.65e+076
GFED total1.70e+103.53e+091.41e+081

Notes:

[1] EPA "US" estimates are for the full US, while GFED "US" estimates are for CONUS.

[2] This "EPA estimate" for global agricultural burning is made by multiplying the explicit EPA US field burning estimate by the quotient GFED global agricultural waste burning / GFED CONUS agricultural waste burning.

[3] I did not regrid the GFED "subfields" for its categories (e.g., agricultural waste burning), only its global total.

[4] This "EPA estimate" for US wildfires is made by

  1. summing the GFED estimates (for both the global and CONUS spatial domains) for all categories other than agricultural waste burning
  2. computing the quotient GFED CONUS other fires / GFED global other fires
  3. multiplying the explicit EPA global wildfires estimate by that quotient

[5] This "EPA estimate" for global burning is made by summing the explicit EPA global wildfire estimate and the computed "EPA estimate" for global field burning.

[6] This "EPA estimate" for US burning is made by summing the explicit EPA US field burning estimate and the computed "EPA estimate" for US wildfires.

aggregate analysis

In aggregate, the current assimilations trouble me:

  1. its absolute size seems low
  2. the relative sizes of its components seem implausible

absolute size of aggregate emissions

Summing all gridded components, I get 6.34e+10 molN2O/yr over AQMEII-NA for 2008. By contrast, EPA estimates 2.57e+10 molN2O/yr for only anthropogenic US N2O emissions for 2008, which is 40% of my total. Given that EPA estimates that, globally, anthropogenic N2O ≅ 36% of total N2O emissions, that doesn't seem too low ... except that, as noted above, AQMEII-NA includes the bulk of Canadian agriculture (and, for that matter, Canadian settlement and industry) as well as a significant share of Mexican agriculture and industry. Hence I suspect that EPA's anthropogenic US estimate should be significantly less than 36% of my total AQMEII-NA estimate, not slightly more (as it currently is).

relative size of components

IPCC AR4 WG1 estimates

Thomson et al 2012, Figure 1

just over half (eyeballing, say 55%) of global N2O emissions to source from managed and natural soils (the red zone), with the remainder divided into approximately equal thirds (i.e., 15% each) by source: ocean, cattle and feedlots, and everything else. This seems reasonable, given current knowledge regarding N2O production. By contrast,

shares of subproject emissions

nearly 60% of my AQMEII-NA emissions are marine, while only 19% are from soils (natural+ag)! Even if one overlooks the disparities in inventory schema, this seems quite implausible given the strong continentality of the spatial domain:

horizontal extent of AQMEII-NA spatial domain

Even if I set my AQMEII-NA ag-soil estimate to equal that of EPA's US ag-soil estimate (1.80e+10 molN2O), that would only raise the all-soils fraction of the total to 29%, and lower the marine fraction only to 52%. Hence I suspect my marine estimate (from the rather-old GEIA study) is too high, and my ag-soil estimate (from EDGAR-4.2 and EPIC) is much too low.

Another reason to suspect my ag-soil estimate is too low: its relation to my non-ag-soil anthropogenic emissions. EPA estimates that US agricultural soil management contributes 69% of US anthropogenic N2O; alternatively, that ag-soil N2O emissions are 232% of the sum of all other anthropogenic N2O. Conveniently for this analysis, my assimilation partitions anthropogenic N2O into 2 subprojects, AQMEII_ag_soil (i.e., ag-soil emissions) and EDGAR-4.2_minus_soil_and_biomass_to_AQMEII-NA (i.e., non-ag-soil anthropogenic emissions). Unfortunately, my ag-soil emissions are only 86% of my non-ag-soil anthropogenic emissions, and only 46% of my total anthropogenic emissions.

Updated