Documentation of N2O flux service - Description of the N2O inversion production chain

Page created by Ashley Vazquez

Copernicus Atmosphere Monitoring Service

                Documentation of N2O flux service
                Description of the N 2 O inversion production

                Issued by: NILU/Rona Thompson
                Date: 22/06/2021
                Ref: CAMS73_2018SC2_D5.2.3-2021_202106_Documentation N20 flux_v1
This document has been produced in the context of the Copernicus Atmosphere Monitoring Service (CAMS).
The activities leading to these results have been contracted by the European Centre for Medium-Range Weather Forecasts,
operator of CAMS on behalf of the European Union (Delegation Agreement signed on 11/11/2014). All information in this
document is provided "as is" and no guarantee or warranty is given that the information is fit for any particular purpose.
The user thereof uses the information at its sole risk and liability. For the avoidance of all doubts, the European Commission
and the European Centre for Medium-Range Weather Forecasts has no liability in respect of this document, which is merely
representing the authors view.
Copernicus Atmosphere Monitoring Service


                    Rona Thompson

CAMS73_2018SC2 -Documentation of N2O flux service   Page 3 of 20
Copernicus Atmosphere Monitoring Service

Table of Contents

1. Atmospheric observations                                   7
1.1 Atmospheric measurements and locations                    7
1.2 Processing of observations                                7

2. Prior fluxes                                               8

3. Atmospheric transport model and input                      8

4. Uncertainty estimates                                      9
4.1 Uncertainty in the observation space                      9
4.2 Uncertainty in the state space                            9

5. Inversion Methodology                                      9

6. Flux and concentration output                            10

7. References                                               10

CAMS73_2018SC2 -Documentation of N2O flux service   Page 4 of 20
Copernicus Atmosphere Monitoring Service

ECMWF - Shinfield Park, Reading RG2 9AX, UK

Copernicus Atmosphere Monitoring Service

The CAMS N2O fluxes are estimated using the atmospheric inversion framework, PyVAR-N2O.
Atmospheric inversions use observations of atmospheric mixing ratios, in this case, of N2O, and
provide the fluxes that best explain the observations while at the same time being guided by a prior
estimate of the fluxes. In other words, the fluxes are optimized to fit the observations within the limits
of the prior and observation uncertainties. To produce the optimized (a posteriori) fluxes a number
of steps are involved: first, the observations are pre-processed (described in section 1), second, a
prior flux estimate is prepared (described in section 2), third mixing ratios are simulated using the
prior fluxes and are used to estimate the model representation error (described in sections 3 and 4),
and fourth, the inversion is performed (described in section 5).

CAMS73_2018SC2 -Documentation of N2O flux service                                               Page 6 of 20
Copernicus Atmosphere Monitoring Service

1. Atmospheric observations
1.1 Atmospheric measurements and locations
In total 123 ground-based sites, ship transects and aircraft profiles are included in the inversion (see
Table 1 and Fig. 1). The term “site” refers to locations where there is a long-term record of
observations from ground-based measurements, both from discrete samples (or “flasks”) and quasi-
continuous sampling by in-situ instruments. N2O concentrations are measured using Gas
Chromatographs equipped with an Electron Capture Detector (GC-ECD)
Some ground-based sites have measurements made by different laboratories, which provides a
means to check for consistency between them. In addition to the sites, data from aircraft profiles and
ship transects, i.e. the NOAA ESRL programme, are included. Up to now, satellite observations of N2O
have been neither accurate nor precise enough to be used for estimating fluxes, with bias errors of
~7 ppb (parts-per billion) and precisions of ~1% (~3 ppb) (Xiong et al. 2014), compared to the 0.3 ppb
achieved by ground-based observations. Very recently, a new product has become available for
testing from the Infrared Atmospheric Sounding Interferometer (IASI) aboard the MetOp-A satellite.
Tests with this satellite retrieval have been performed as part of the service evolution in 2020.
Observations of N2O with sufficient accuracy for inverse modelling are available from the mid-1990s,
thus the period covered by the inversion is from 1995 to 2019. The data density over time is shown
in Fig. 2.

1.2 Processing of observations
Owing to the small signal to noise ratio of N2O observations, it is critical to pre-process the
observations to remove outliers and to correct for calibration differences between laboratories.
Outliers are determined as observations outside 2-σ standard deviations of the running mean
calculated over time window of 90 days, for flask observations, 0.5 days for continuous and aircraft
observations, and 60 days for ship observations. The removal of outliers is performed iteratively until
no more data are removed. Using this method, in the order of 2% of all observations are classified as
Calibration differences are determined relative to the NOAA-2006A scale maintained by NOAA ESRL
GMD (Hall et al. 2007). A number of other laboratories/networks have their own scale, namely AGAGE
who uses the SIO-1998 scale, NIES who use the NIES-94 scale, and Tohoku University who use the
Tohoku scale. Even different laboratories operating on the same scale have differences between
measurements. For this reason, the calibration differences with respect to NOAA-2006A are
determined and specified by a regression coefficient and bias. These are found by either comparing
the measurements made by a given laboratory with those of NOAA at the same location, where these
both exist, or for laboratories with no sites co-located with a NOAA site, by inter-comparison of gas
standards by the different laboratories. A summary of the calibration differences is given in Fig. 3.
Using the regression coefficient and bias for each laboratory the observations are corrected to the
NOAA-2006A scale. Previous analyses (Thompson et al. 2014), found a drift in the NOAA-2006A with
respect to the SIO-1998 scale. Since then, AGAGE has revised their calibration scale to correct for drift
in the gas references. All observations were transferred to this revised scale (SIO-16) in 2017 and this
revision was included in the inversion. As a result, the correlation coefficient for the AGAGE network
compared to the NOAA-2006A scale is much closer to one than previously (see Fig. 3).

CAMS73_2018SC2 -Documentation of N2O flux service                                              Page 7 of 20
Copernicus Atmosphere Monitoring Service

Data from ground-based in-situ sites are generally assimilated into the inversion as daily afternoon
averages (between 12:00 and 17:00), however, for mountain sites, a night-time average (between
00:00 and 06:00) is used to avoid times with complex circulation patterns, such as upslope winds,
which cannot be reproduced with the current resolution of global atmospheric transport models.
Aircraft and ship data are assimilated as the average of all observations falling in each grid-cell and
time step of the transport model.

2. Prior fluxes
A prior estimate of the total N2O flux with monthly resolution and inter-annually varying fluxes is
prepared from a number of models and inventories (see Table 2). For the natural soil fluxes
(specifically from unmanaged soils) an estimate from the land surface model OCN-v1.2-GCP2019 is
used, which is driven by observation-based climate data, N-fertilizer statistics and modelled N-
deposition (Zaehle et al. 2011). For the ocean fluxes, an estimate from the ocean biogeochemistry
model PlankTOM-v10.2 is used, which is a prognostic model (Buitenhuis et al. 2018). In this model,
the global ocean source is 2.6 TgN y-1 and is lower than the prior estimates used in previous inversions,
of 5 to 6 TgN y-1 but is still in the range of ocean biogeochemistry models used in the GCP N2O Budget,
of 2.3 to 4.5 TgN y-1. The change in ocean source value is due to the change in model, from the
diagnostic to the prognostic version of the PlankTOM model. For biomass burning fluxes, the GFED-
v4.1s data is used, which is based on fire activity data from the MODIS satellite and emission factors
from Akagi et al. (2011). Lastly, for anthropogenic emissions (agriculture, industry, waste and fuel
combustion), the EDGAR inventory data are used. EDGAR-v5 was used for the period 2005-2019, with
2016-2019 using the 2015 estimates as v5 covers only 2005-2015. For the period 1995-2004, EDGAR-
v4.32 was used. All flux data are interpolated/averaged from their original resolution to that of the
atmospheric transport model, i.e., 3.75° × 1.875° (longitude by latitude). The change in the ocean
source means that the prior global total source is lower by about 3 TgN y-1 than in previous inversions.

3. Atmospheric transport model and input
Atmospheric transport is modelled using an offline version of the Laboratoire de Meteorologie
Dynamique model, LMDz5, which computes the evolution of atmospheric compounds using archived
fields of winds, convection mass fluxes and planetary boundary layer (PBL) exchange coefficients that
have been calculated using the online version nudged to ECMWF ERA interim winds. LMDz5 uses a
Eulerian grid of 3.75° × 1.875° (longitude by latitude) and 39 hybrid pressure levels. Stratospheric
losses of N2O through reaction with O(1D) and photolysis are calculated for each time-step and grid-
cell using pre-calculated fields of O(1D) and photolysis rate from the online LMDz5 model.
Initial conditions, in this case, 3D fields of N2O concentration, are taken from forward simulations of
the online model (run for at least 5 years) and are scaled to be consistent with observed
concentrations at background sites.

CAMS73_2018SC2 -Documentation of N2O flux service                                              Page 8 of 20
Copernicus Atmosphere Monitoring Service

4. Uncertainty estimates
4.1 Uncertainty in the observation space
Uncertainty in the observation space is calculated as the quadratic sum of the measurement and
transport uncertainties. The measurement uncertainty is assumed to be 0.3 ppb (approximately 0.1%)
based on the recommendations of data providers. The transport uncertainty includes estimates of
uncertainties in advective transport (based on the method of Rödenbeck et al. (2003)) and from a
lack of subgrid-scale variability (based on the method of Bergamaschi et al. (2010)). The calculated
total model transport uncertainty varied typically between 0.1 and 1.0 ppb, depending on the
synoptic situation and the location, and had a mean of 0.2 ppb. We included an additional uncertainty
on observations from southern mid to high latitudes of 1.0 ppb to account for known errors in
stratosphere-troposphere exchange in the Southern Hemisphere in LMDz5. It is assumed that there
are no cross-correlations between observations (i.e. the observation error covariance matrix is
diagonal), which is a reasonable approximation considering that the observations are assimilated as
afternoon (or night-time) means for ground-based data and at the grid-cell and time-step of the
model for aircraft and ship data.

4.2 Uncertainty in the state space
For the error in each land grid cell, the maximum magnitude of the flux in the cell of interest and its
8 neighbours is used, while for ocean grid cells the magnitude of the cell of interest only is used. This
is done to allow the more degrees of freedom to change the fine spatial patterns of the fluxes on
land, whereas on in the ocean, this method is not used to avoid having too large uncertainties in grid
cells close to coastlines. The covariance was calculated as an exponential decay with distance and
time using correlation scale lengths of 500 km over land and 1000 km over ocean and 3 months. The
prior error covariance matrix is scaled so that the sum of its elements was equal to a global
uncertainty of 2 TgN y-1, which is chosen to reflect an approximate uncertainty of about 12% in the
total source.

5. Inversion Methodology
PyVAR-N2O uses the Bayesian inversion method to find the optimal fluxes of N2O given prior
information about the fluxes and their uncertainty, and observations of atmospheric N2O mole
fractions. The method is the same as that used in Thompson et al. (2014) and the reader is referred
to this paper for full details about the method. In summary, the optimal fluxes are those that minimize
the following cost function (for derivation of the cost function see Rodgers et al. (2000)):

      1                            1
J(x) = (x − x b )T B−1 (x − x b ) + (H (x) − y)T R −1 (H (x) − y)            (1)
      2                            2

where the flux uncertainties are described by the error covariance matrix B, the observation
uncertainties are described by the error covariance matrix R and H is a non-linear operator for
atmospheric transport and chemistry (in Eq. 1, the matrix transpose is indicated by T). We use the
variational approach to solve Eq. 1, which is an iterative process where the gradient of J is calculated

CAMS73_2018SC2 -Documentation of N2O flux service                                              Page 9 of 20
Copernicus Atmosphere Monitoring Service

at each iteration using a conjugate gradient algorithm (Lanczos 1950). This involves using an adjoint
of the chemistry transport model (CTM) (Chevallier et al. 2005).
Posterior flux uncertainties are calculated from a Monte Carlo ensemble of inversions, based on the
method of Chevallier et al. (2005). In each ensemble member, the prior fluxes were randomly
perturbed to introduce errors consistent with those described by the prior error covariance matrix,
B. The standard deviation of the posterior fluxes were assumed to be consistent with the probability
distribution of the true fluxes.

6. Flux and concentration output
The optimized N2O fluxes are saved as NetCDF files, where each file contains fluxes for one year at
monthly temporal, and 3.75° × 1.875° (longitude by latitude) spatial, resolution. In addition, 3D N2O
concentration fields, generated using the optimized fluxes, are saved. These are also NetCDF files
with one file per month containing the N2O concentration every 3 hours for the 39 vertical levels and
3.75° × 1.875° (longitude by latitude) horizontal resolution.

7. References
Akagi, S. K., Yokelson, R. J., Wiedinmyer, C., Alvarado, M. J., Reid, J. S., Karl, T., Crounse, J. D. and
     Wennberg, P. O.: Emission factors for open and domestic biomass burning for use in atmospheric
     models, Atmos. Chem. Phys., 11(9), 4039-4072, doi:10.5194/acp-11-4039-2011, 2011.
Bergamaschi, P., Krol, M., Meirink, J. F., Dentener, F., Segers, A., van Aardenne, J., Monni, S.,
     Vermeulen, A. T., Schmidt, M., Ramonet, M., Yver, C., Meinhardt, F., Nisbet, E. G., Fisher, R. E.,
     O'Doherty, S. and Dlugokencky, E. J.: Inverse modeling of European CH4 emissions 2001-2006, J.
     Geophys. Res, 115(D22), D22309, doi:10.1029/2010jd014180, 2010.
Buitenhuis, E. T., Suntharalingam, P., & Le Quéré, C.: Constraints on global oceanic emissions of N2O
     from observations and models. Biogeosciences, 15(7), 2161–2175, doi:10.5194/bg-15-2161-
     2018, 2018
Chevallier, F., Fisher, M., Peylin, P., Serrar, S., Bousquet, P., Bréon, F. M., Chédin, A. and Ciais, P.:
     Inferring CO2 sources and sinks from satellite observations: Method and application to TOVS data,
     J. Geophys. Res., 110(D24309), doi:10.1029/2005jd006390, 2005.
Dutreuil, S., Bopp, L. and Tagliabue, A.: Impact of enhanced vertical mixing on marine
     biogeochemistry: lessons for geo-engineering and natural variability, Biogeosciences, 6(5), 901-
     912, doi:10.5194/bg-6-901-2009, 2009.
Hall, B. D., Sutton, G. S. and Elkins, J. W.: The NOAA nitrous oxide standard scale for atmospheric
     observations, J. Geophys. Res., 112(D09305), doi:10.1029/2006JD007954, 2007.
Machida, T., Matsueda, H., Sawa, Y., Nakagawa, Y., Hirotani, K., Kondo, N., Goto, K., Nakazawa, T.,
     Ishikawa, K. and Ogawa, T.: Worldwide measurements of Atmospheric CO2 and Other Trace Gas
     Species Using Commercial Airlines, J. Atmos. Ocean. Tech, 25, 1744-1754,
     doi:10.1175/2008JTECHA1082.1, 2008.

CAMS73_2018SC2 -Documentation of N2O flux service                                             Page 10 of 20
Copernicus Atmosphere Monitoring Service

Rödenbeck, C., Houweling, S., Gloor, M. and Heimann, M.: CO2 flux history 1982-2001 inferred from
    atmospheric data using a global inversion of atmospheric transport, Atmos. Chem. Phys, 3, 1919-
    1964, 2003.
Thompson, R. L., Chevallier, F., Crotwell, A. M., Dutton, G., Langenfelds, R. L., Prinn, R. G., Weiss, R.
    F., Tohjima, Y., Nakazawa, T., Krummel, P. B., Steele, L. P., Fraser, P., Ishijima, K. and Aoki, S.:
    Nitrous oxide emissions 1999 - 2009 from a global atmospheric inversion, Atmos. Chem. Phys.,
    14, 1801-1817, doi: 10.5194/acp-14-1801-2014, 2014.
Xiong, X., Maddy, E. S., Barnet, C., Gambacorta, A., Patra, P. K., Sun, F. and Goldberg, M.: Retrieval of
    nitrous oxide from Atmospheric Infrared Sounder: Characterization and validation, J. Geophys.
    Res., 119(14), 9107-9122, doi:10.1002/2013JD021406, 2014.
Zaehle, S., Ciais, P., Friend, A. D. and Prieur, V.: Carbon benefits of anthropogenic reactive nitrogen
    offset by nitrous oxide emissions, Nature Geosci, 4(9), 601-605, 2011.

CAMS73_2018SC2 -Documentation of N2O flux service                                             Page 11 of 20
Copernicus Atmosphere Monitoring Service

Table 1. List of sites and campaigns. The symbol “V” means various locations.

ID          Network      Latitude   Longitude   Altitude   Type   Description
ABP         NOAA         -12.76     -38.16      6          FM     Arembepe, Brazil
AAO         NOAA         40.10      -88.55      V          AM     Airborne Aerosol Observatory, USA
ACG         NOAA         V          V           V          AM     Alaska Coast Guard, USA
ALT         NOAA         82.45      -62.52      205        FM     Alert, Nunavut, Canada
ALT         CSIRO        82.45      -62.52      210        FM     Alert, Nunavut, Canada
ALT         EC           82.45      -62.52      205        FM     Alert, Nunavut, Canada
AMT         NOAA         45.01      -68.66      157        FM     Amsterdam Island, France
AMY         NOAA         36.54      126.33      112        FM     Anmyeon-do, Korea
ASC         NOAA         -7.97      -14.4       90         FM     Ascension Island, UK
ASK         NOAA         23.18      5.42        1847       FM     Asseskrem, Algeria
AZR         NOAA         38.77      -27.38      24         FM     Terceira Island, Azores, Portugal
BAL         NOAA         55.43      16.95       28         FM     Baltic Sea, Poland
BHD         NOAA         -41.41     174.87      90         FM     Baring Head, New Zealand
BKT         NOAA         -0.2       100.32      850        FM     Bukit Kototabang, Indonesia
BME         NOAA         32.37      -64.65      17         FM     St Davids Head, Bermuda, UK
BMW         NOAA         32.26      -64.88      60         FM     Tudor Hill, Bermuda, UK
BNE         NOAA         40.80      -97.18      V          AM     Beaver Crossing, Nebraska, USA
BRW         NOAA         71.32      -156.61     13         FM     Barrow, Alaska, USA
BSC         NOAA         44.18      28.66       5          FM     Black Sea, Constanta, Romania
CAR         NOAA         40.37      -104.30     V          AM     Briggsdale, Colorado, USA
CBA         NOAA         55.21      -162.72     25         FM     Cold Bay, Alaska, USA
CFA         CSIRO        -19.28     147.05      2          FM     Cape Ferguson, Australia
CGO         AGAGE        -40.68     144.68      94         CM     Cape Grim, Tasmania, Australia
CGO         NOAA         -40.68     144.68      164        FM     Cape Grim, Tasmania, Australia
CGO         CSIRO        -40.68     144.68      94         FM     Cape Grim, Tasmania, Australia
CHL         EC           58.75      -94.07      35         FM     Churchill, Canada
CHR         NOAA         1.7        -157.15     2          FM     Christmas Island, Republic of Kiribati
CIB         NOAA         41.81      -4.93       850        FM     CIBA, Spain
CMA         NOAA         38.83      -74.32      V          AM     Cape May, New Jersey, USA
CMN         URB          44.18      10.70       2165       CM     Monte Cimone, Italy
COI         NIES         43.16      145.5       45         CM     Cape Ochi-ishi, Japan
CPT         NOAA         -34.35     18.49       260        FM     Cape Point, South Africa
CRI         CSIRO        15.08      73.83       60         FM     Cape Rama, India
CRV         NOAA         V          V           V          AM     CARVE aircraft campaigns
CRZ         NOAA         -46.43     51.85       202        FM     Crozet Island, France
CYA         CSIRO        -66.28     110.53      55         FM     Casey Station, Australia
DND         NOAA         47.50      -99.24      V          AM     Dahlen, North Carolina, USA
DRP         NOAA         V          V           V          SM     Drake Passage Cruises
DSI         NOAA         20.7       116.73      8          FM     Dongsha Island, Taiwan

CAMS73_2018SC2 -Documentation of N2O flux service                                                          Page 12 of 20
Copernicus Atmosphere Monitoring Service

EIC         NOAA         -27.15    -109.45     55     FM   Easter Island, Chile
ESP         NOAA         49.38     -126.55     V      AM   Estevan Point, Canada
ESP         EC           49.38     -126.55     47     FM   Estevan Point, Canada
ESP         CSIRO        49.38     -126.55     47     FM   Estevan Point, Canada
ETL         NOAA         54.35     -104.98     V      AM   East Trout Lake, Saskatchewan, Canada
GMI         NOAA         13.39     144.66      6      FM   Mariana Islands, Guam
GPA         CSIRO        -12.25    131.05      25     FM   Gunn Point, Australia
HAA         NOAA         21.23     -158.95     V      AM   Molokai Island, Hawaii, USA
HAT         NIES         24.06     123.81      11     CM   Hateruma, Japan
HBA         NOAA         -75.61    -26.21      35     FM   Halley Station, Antarctica
HFM         NOAA         42.54     -72.17      V      AM   Harvard Forest, Massachusetts, USA
HIL         NOAA         40.07     -87.91      V      AM   Homer, Illinois, USA
HPB         NOAA         47.8      11.02       990    FM   Hohenpeissenberg, Germany
HSU         NOAA         41.05     -124.73     8      FM   Humboldt University, USA
HUN         NOAA         46.95     16.65       344    FM   Hegyhatsal, Hungary
ICE         NOAA         63.25     -20.15      120    FM   Storhofdi, Vestmannaeyjar, Iceland
INX         NOAA         39.72     -85.95      V      AM   INFLUX, Indianapolis, USA
IZO         NOAA         28.3      -16.48      2378   FM   Izana, Tenerife, Canary Islands, Spain
IZO         AEM          28.30     -16.48      2397   CM   Izana, Tenerife, Canary Islands, Spain
JFJ         EMPA         46.55     7.99        3580   CM   JungfrauJoch, Switzerland
KEY         NOAA         25.67     -80.2       6      FM   Key Biscayne, Florida, USA
KUM         NOAA         19.52     -154.82     8      FM   Cape Kumukahi, Hawaii, USA
KZD         NOAA         44.08     76.87       600    FM   Sary Taukum, Kazakhstan
KZM         NOAA         43.25     77.88       2524   FM   Plateau Assy, Kazakhstan
LEF         NOAA         45.95     -90.27      V      AM   Park Falls, Wisconsin, USA
LEF         NOAA         45.93     -90.27      868    FM   Park Falls, Wisconsin, USA
LLB         NOAA         54.95     -112.45     546    FM   Lac La Biche, Alberta, Canada
LLN         NOAA         23.46     120.86      2867   FM   Lulin, Taiwan
LMP         NOAA         35.51     12.61       50     FM   Lampedusa, Italy
MAA         CSIRO        -67.62    62.87       32     FM   Mawson, Australia
MEX         NOAA         18.98     -97.31      4469   FM   High-Alt. Glob. Clim. Obs., Mexico
MHD         AGAGE        53.33     -9.9        26     CM   Mace Head, County Galway, Ireland
MHD         NOAA         53.33     -9.9        26     FM   Mace Head, County Galway, Ireland
MID         NOAA         28.22     -177.37     11     FM   Sand Island, Midway, USA
MKN         NOAA         -0.06     37.3        3649   FM   Mt Kenya, Kenya
MLO         NOAA         19.53     -155.58     3402   FM   Mauna Loa, Hawaii, USA
MLO         CSIRO        19.53     -155.58     3397   FM   Mauna Loa, Hawaii, USA
MQA         CSIRO        -54.48    158.97      12     FM   Macquarie Island, Australia
NAT         NOAA         -5.51     -35.26      20     FM   Farol de Mae Luiza Lighthouse, Brazil
NHA         NOAA         42.95     -70.63      V      AM   Worcester, Massachusetts, USA
NMB         NOAA         -23.58    15.03       461    FM   Gobabeb, Namibia
NWR         NOAA         40.05     -105.58     3526   FM   Niwot Ridge, Colorado, USA

CAMS73_2018SC2 -Documentation of N2O flux service                                                   Page 13 of 20
Copernicus Atmosphere Monitoring Service

OXK         NOAA         50.03     11.81       1185   FM   Ochsenkopf, Germany
PAL         NOAA         67.97     24.12       565    FM   Pallas-Sammaltunturi, Finland
PFA         NOAA         65.07     -147.29     V      AM   Poker Flat, Alaska, USA
POC         NOAA         V         V           V      SM   Pacific Ocean Moorings
PSA         NOAA         -64.92    -64         15     FM   Palmer Station, Antarctica
PTA         NOAA         38.95     -123.73     22     FM   Point Arena, California, USA
RGL         UBRIS        52.0      -2.54       294    CM   Ridgehill, UK
RPB         AGAGE        13.17     -59.43      45     CM   Ragged Point, Barbados
RPB         NOAA         13.16     -59.43      20     FM   Ragged Point, Barbados
RTA         NOAA         -21.25    -159.83     V      AM   Rarotonga, Cook Islands
SCA         NOAA         32.77     -79.55      V      AM   Charleston, South Carolina, USA
SDZ         NOAA         40.65     117.12      298    FM   Shangdianzi, China
SEY         NOAA         -4.68     55.53       3      FM   Mahe Island, Seychelles
SGP         NOAA         36.62     -97.48      V      AM   Southern Great Plains, Oklahoma, USA
SGP         NOAA         36.62     -97.48      374    FM   Southern Great Plains, Oklahoma, USA
SHM         NOAA         52.72     174.1       28     FM   Shemya Island, Alaska, USA
SIS         CSIRO        60.08     -1.25       30     FM   Shetland Islands, UK
SMO         AGAGE        -14.23    -170.57     77     CM   Tutuila, America Samoa, USA
SMO         NOAA         -14.25    -170.57     47     FM   Tutuila, America Samoa, USA
SSL         UBA          47.92     7.92        1213   CM   Schauinsland, Germany
SPO         NOAA         -89.98    -24.8       2815   FM   South Pole, Antarctica
SPO         CSIRO        -89.98    -24.8       2810   FM   South Pole, Antarctica
STM         NOAA         66        2           7      FM   Ocean Station M, Norway
SUM         NOAA         72.58     -38.42      3215   FM   Summit, Greenland
SYO         NOAA         -69       39.58       11     FM   Syowa Station, Antarctica
TAC         UBRIS        52.52     1.14        241    CM   Tacolneston Tall Tower, UK
TAC         NOAA         52.52     1.14        241    FM   Tacolneston Tall Tower, UK
TAP         NOAA         36.73     126.13      21     FM   Tae-anh Peninsula, Republic of Korea
TGC         NOAA         27.73     -96.86      V      AM   Sinton, Texas, USA
THD         AGAGE        41.05     -124.15     107    CM   Trinindad Head, California, USA
THD         NOAA         41.05     -124.15     V      AM   Trinindad Head, California, USA
THD         NOAA         41.05     -124.15     112    FM   Trinindad Head, California, USA
UTA         NOAA         39.9      -113.72     1332   FM   Wendover, Utah, USA
UUM         NOAA         44.45     111.1       1012   FM   Ulaan Uul, Mongolia
WBI         NOAA         41.72     -91.35      V      AM   West Branch, Iowa, USA
WIS         NOAA         30.86     34.78       482    FM   Negev Desert, Israel
WKT         NOAA         31.32     -97.33      708    FM   Moody, Texas, USA
WLG         NOAA         36.27     100.92      3815   FM   Mt Waliguan, China
WPC         NOAA         V         V           V      SM   Western Pacific Cruises
WSA         EC           43.93     -60.02      5      FM   Sable Island, Canada
ZEP         NOAA         78.91     11.89       489    FM   Ny-Alesund, Svalbard, Norway
ZSF         UBA          47.42     10.98       2671   CM   Zugspitze, Germany

CAMS73_2018SC2 -Documentation of N2O flux service                                                 Page 14 of 20
Copernicus Atmosphere Monitoring Service

Table 2. Overview of prior fluxes (totals are given for the year 2010).
 Category                         Data source       Resolution            Total (TgN y-1)
 Natural soils                    OCN v1.2          1.0°×1.0°             5.86
 Coastal and open ocean           PlankTOMv10.2     1.0°×1.0°             2.61
 Agriculture                      EDGARv4.32/v5     0.1°×0.1°             3.89
 Other anthropogenic              EDGARv4.32/v5     0.1°×0.1°             1.25
 Biomass burning                  GFED-4.1s         0.25°×0.25°           0.51
 Total                                                                    14.12

CAMS73_2018SC2 -Documentation of N2O flux service                                           Page 15 of 20
Copernicus Atmosphere Monitoring Service

                                     Figure 1: Map of the observation network

    in situ

CAMS73_2018SC2 -Documentation of N2O flux service                               Page 16 of 20
Copernicus Atmosphere Monitoring Service

CAMS73_2018SC2 -Documentation of N2O flux service   Page 17 of 20
Copernicus Atmosphere Monitoring Service

                                                                                                   AAO NOAA
                                                                                                   ACG NOAA
                                                                                                   BGI NOAA
                                                                                                   BNE NOAA
                                                                                                   CAR NOAA
                                                                                                   CMA NOAA
                                                                                                   CRV NOAA
                                                                                                   DND NOAA
                                                                                                   ESP NOAA
                                                                                                   ETL NOAA
                                                                                                   FWI NOAA
                                                                                                   HAA NOAA
                                                                                                   HFM NOAA
                                                                                                   HIL NOAA
                                                                                                   HIP NOAA
                                                                                                   INX NOAA
                                                                                                   LEF NOAA
                                                                                                   NHA NOAA
                                                                                                   OIL NOAA
                                                                                                   PFA NOAA
                                                                                                   RTA NOAA
                                                                                                   SCA NOAA
                                                                                                   SGP NOAA
                                                                                                   TGC NOAA
                                                                                                   THD NOAA

           1995   1997   1999   2001   2003   2005   2007    2009   2011   2013   2015   2017   2019


Figure 2. Availability of ground-based data over time by site and laboratory (number of observation
per month). Shown are the tower and flask sampling sites (top) and aircraft based data (bottom).

CAMS73_2018SC2 -Documentation of N2O flux service                                                             Page 18 of 20
Copernicus Atmosphere Monitoring Service

                                                                                               ABP NOAA
                                                                                               ALT NOAA
                                                                                               ALT CSIRO
                                                                                               ALT EC
                                                                                               AMT NOAA
                                                                                               AMY NOAA
                                                                                               ASC NOAA
                                                                                               ASK NOAA
                                                                                               AZR NOAA
                                                                                               BAL NOAA
                                                                                               BHD NOAA
                                                                                               BKT NOAA
                                                                                               BME NOAA
                                                                                               BMW NOAA
                                                                                               BRW NOAA
                                                                                               BSC NOAA
                                                                                               CBA NOAA
                                                                                               CFA CSIRO
                                                                                               CGO AGAGE
                                                                                               CGO NOAA
                                                                                               CGO CSIRO
                                                                                               CHL EC
                                                                                               CHR NOAA
                                                                                               CIB NOAA
                                                                                               CMN URB
                                                                                               COI NIES
                                                                                               CPT NOAA
                                                                                               CRI CSIRO
                                                                                               CRZ NOAA
                                                                                               CYA CSIRO
                                                                                               DSI NOAA
                                                                                               EIC NOAA
                                                                                               ESP CSIRO
                                                                                               ESP EC
                                                                                               GMI NOAA
                                                                                               GPA CSIRO
                                                                                               HAT NIES
                                                                                               HBA NOAA    30
                                                                                               JFJ EMPA
                                                                                               KEY NOAA
                                                                                               KUM NOAA
                                                                                               KZD NOAA
                                                                                               KZM NOAA
                                                                                               LEF NOAA
                                                                                               LLB NOAA
                                                                                               LLN NOAA
                                                                                               LMP NOAA
                                                                                               MAA CSIRO
                                                                                               MEX NOAA
                                                                                               MHD AGAGE
                                                                                               MHD NOAA
                                                                                               MID NOAA
                                                                                               MKN NOAA
                                                                                               MLO NOAA
                                                                                               MLO CSIRO
                                                                                               MQA CSIRO
                                                                                               NAT NOAA
                                                                                               NMB NOAA
                                                                                               NWR NOAA
                                                                                               OXK NOAA
                                                                                               PAL NOAA
                                                                                               PSA NOAA
                                                                                               PTA NOAA
                                                                                               RGL UBR
                                                                                               RPB AGAGE
                                                                                               RPB NOAA
                                                                                               SDZ NOAA
                                                                                               SEY NOAA
                                                                                               SGP NOAA
                                                                                               SHM NOAA
                                                                                               SIS CSIRO
                                                                                               SMO AGAGE
                                                                                               SMO NOAA
                                                                                               SPO NOAA
                                                                                               SPO CSIRO
                                                                                               SSL UBA
                                                                                               SSL UBA
                                                                                               STM NOAA
                                                                                               SUM NOAA
                                                                                               SYO NOAA
                                                                                               TAC NOAA
                                                                                               TAC UBR
                                                                                               TAP NOAA
                                                                                               THD AGAGE
                                                                                               THD NOAA
                                                                                               UTA NOAA
                                                                                               UUM NOAA
                                                                                               WIS NOAA
                                                                                               WKT NOAA
                                                                                               WLG NOAA
                                                                                               WSA EC
                                                                                               ZEP NOAA
                                                                                               ZSF UBA

    1995   1997   1999   2001   2003   2005   2007   2009   2011   2013   2015   2017   2019


                                                                                               AAO NOAA
                                                                                               ACG NOAA
                                                                                               BNE NOAA
                                                                                               CAR NOAA
                                                                                               CMA NOAA
                                                                                               CRV NOAA
                                                                                               DND NOAA
                                                                                               ESP NOAA
                                                                                               ETL NOAA
                                                                                               HAA NOAA
                                                                                               HFM NOAA
                                                                                               HIL NOAA
                                                                                               INX NOAA
                                                                                               LEF NOAA
                                                                                               NHA NOAA
                                                                                               PFA NOAA
                                                                                               RTA NOAA
                                                                                               SCA NOAA
                                                                                               SGP NOAA
                                                                                               TGC NOAA
                                                                                               THD NOAA

    1995   1997   1999   2001   2003   2005   2007   2009   2011   2013   2015   2017   2019


CAMS73_2018SC2 -Documentation of N2O flux service                                                                 Page 19 of 20
Copernicus Atmosphere Monitoring Service

 Figure 3. Calibration comparison to the NOAA scale (NOAA-2006A). The regression coefficient is shown for
the comparison of the other laboratories scale with that of NOAA. For some laboratories/networks there is
more than one site (i.e. AGAGE and CSIRO) and the comparison for each site where a comparison is possible

                          1.1                                         ECC
 Regression Coefficient





                                                    is shown.

CAMS73_2018SC2 -Documentation of N2O flux service                                             Page 20 of 20
You can also read