Atmospheric carbon monoxide (CO) concentrations have been
decreasing since 2000, as observed by both satellite- and ground-based
instruments, but global bottom-up emission inventories estimate ...increasing
anthropogenic CO emissions concurrently. In this study, we use a
multi-species atmospheric Bayesian inversion approach to attribute
satellite-observed atmospheric CO variations to its sources and sinks in
order to achieve a full closure of the global CO budget during 2000–2017.
Our observation constraints include satellite retrievals of the total column
mole fraction of CO, formaldehyde (HCHO), and methane (CH4) that are
all major components of the atmospheric CO cycle. Three inversions (i.e.,
2000–2017, 2005–2017, and 2010–2017) are performed to use the observation
data to the maximum extent possible as they become available and assess the
consistency of inversion results to the assimilation of more trace gas
species. We identify a declining trend in the global CO budget since 2000
(three inversions are broadly consistent during overlapping periods), driven
by reduced anthropogenic emissions in the US and Europe (both likely from
the transport sector), and in China (likely from industry and residential
sectors), as well as by reduced biomass burning emissions globally,
especially in equatorial Africa (associated with reduced burned areas). We
show that the trends and drivers of the inversion-based CO budget are not
affected by the inter-annual variation assumed for prior CO fluxes. All
three inversions contradict the global
bottom-up inventories in the world's top two emitters: for the sign of
anthropogenic emission trends in China (e.g., here -0.8±0.5 % yr−1 since 2000, while the prior gives 1.3±0.4 % yr−1)
and for the rate of anthropogenic emission increase in South Asia (e.g.,
here 1.0±0.6 % yr−1 since 2000, smaller than 3.5±0.4 % yr−1 in the prior inventory). The posterior model CO
concentrations and trends agree well with independent ground-based
observations and correct the prior model bias. The comparison of the three
inversions with different observation constraints further suggests that the
most complete constrained inversion that assimilates CO, HCHO, and CH4
has a good representation of the global CO budget, and therefore matches best
with independent observations, while the inversion only assimilating CO
tends to underestimate both the decrease in anthropogenic CO emissions and
the increase in the CO chemical production. The global CO budget data from
all three inversions in this study can be accessed from
https://doi.org/10.6084/m9.figshare.c.4454453.v1 (Zheng et al., 2019).
Air pollution reaching hazardous levels in many Chinese cities has been a major concern in China over the past decades. New policies have been applied to regulate anthropogenic pollutant emissions, ...leading to changes in atmospheric composition and in particulate matter (PM) production. Increasing levels of atmospheric ammonia columns have been observed by satellite during recent years. In particular, observations from the Infrared Atmospheric Sounding Interferometer (IASI) reveal an increase of these columns by 15 % and 65 % from 2011 to 2013 and 2015, respectively, over eastern China. In this paper we performed model simulations for 2011, 2013 and 2015 in order to understand the origin of this increase and to quantify the link between ammonia and the inorganic components of particles: NH4(p)+/SO4(p)2-/NO3(p)-. Interannual change of meteorology can be excluded as a reason: year 2015 meteorology leads to enhanced sulfate production over eastern China, which increases the ammonium and decreases the ammonia content, which is contrary to satellite observations. Reductions in SO2 and NOx emissions from 2011 to 2015 of 37.5 % and 21 % respectively, as constrained from satellite data, lead to decreased inorganic matter (by 14 % for NH4(p)++SO4(p)2-+NO3(p)-). This in turn leads to increased gaseous NH3(g) tropospheric columns by as much as 24 % and 49 % (sampled corresponding to IASI data availability) from 2011 to 2013 and 2015 respectively and thus can explain most of the observed increase.
We have used the variational inversion drivers of the recent Community Inversion Framework (CIF), coupled to a European configuration of the CHIMERE regional chemistry transport model and its ...adjoint to derive carbon monoxide (CO) emissions from Measurement of Pollution in the Troposphere (MOPITT) TIR-NIR (thermal-infrared near-infrared) observations, for a period of over 10 years from 2011 to 2021. The analysis of the inversion results reveals the challenges associated with the inversion of CO emissions at the regional scale over Europe. Annual budgets of national emissions have decreased by about 1 %–11 % over the decade and across Europe. These decreases are mainly due to negative corrections during autumn and winter. The posterior CO emissions follow a decreasing trend over the European Union and United Kingdom area of about −2.2 % yr−1, slightly lower than in the prior emissions. The assimilation of the MOPITT observation in the inversions indeed attenuates the decreasing trend of the CO emissions in the TNO inventory over areas benefiting from the highest number of MOPITT super-observations (particularly over Italy and over the Balkans), and particularly in autumn and winter. The small corrections of the CO emissions at national scales by the inversion can be attributed, first, to the general consistency between the TNO-GHGco-v3 inventory and the satellite data. Analysis of specific patterns such as the impact of the Covid-19 crisis reveals that it can also be seen as a lack of observation constraints to adjust the prior estimate of the emissions. The large errors associated with the observations in our inversion framework and the lack of data over large parts of Europe are sources of limitation on the observational constraint. Emission hotspots generate a relatively strong local signal, which is much better caught and exploited by the inversions than the larger-scale signals, despite the moderate spatial resolution of the MOPITT data. This is why the corrections of these hotspot emissions are stronger and more convincing than the corrections of the national- and continental-scale emissions. Accurate monitoring of the CO national anthropogenic emissions may thus require modelling and inversion systems at spatial resolutions finer than those used here as well as satellite images at high spatial resolution. The CO data of the TROPOMI instrument on board the Sentinel-5P mission should be well suited for such a perspective.
The Monitoring Nitrous Oxide Sources (MIN2OS) satellite project aims at monitoring global-scale nitrous oxide (N2O) sources by retrieving N2O surface fluxes from the inversion of space-borne N2O ...measurements that are sensitive to the lowermost atmospheric layers under favorable conditions. MIN2OS will provide emission estimates of N2O at a horizontal resolution of 1° × 1° on the global scale and 10 × 10 km2 on the regional scale on a weekly to monthly basis depending on the application (e.g., agriculture, national inventories, policy, scientific research). Our novel approach is based on the development of: 1) a space-borne instrument operating in the Thermal InfraRed domain providing, in clear sky conditions, N2O mixing ratio in the lowermost atmosphere (900 hPa) under favorable conditions (summer daytime) over land and under favorable and unfavorable (winter nighttime) conditions over the ocean and 2) an atmospheric inversion framework to estimate N2O surface fluxes from the atmospheric satellite observations. After studying three N2O spectral bands (B1 at 1240–1350 cm−1, B2 at 2150–2260 cm−1 and B3 at 2400–2600 cm−1), a new TIR instrument will be developed, centered at 1250–1330 cm−1, with a resolution of 0.125 cm−1, a Full Width at Half Maximum of 0.25 cm−1 and a swath of 300 km. To optimally constrain the retrieval of N2O vertical profiles, the instrument will be on-board a platform at ~830 km altitude in a sun-synchronous orbit crossing the Equator in descending node at 09:30 local time in synergy with two other platforms (Metop-SG and Sentinel-2 NG) expected to fly in 2031–32 aiming at detecting surface properties, agricultural information on the field scale and vertical profiles of atmospheric constituents and temperature. The lifetime of the MIN2OS project would be 4–5 years to study the interannual variability of N2O surface fluxes. The spectral noise can be decreased by at least a factor of 5 compared to the lowest noise accessible to date with the Infrared Atmospheric Sounding Interferometer-New Generation (IASI-NG) mission. The N2O total error is expected to be less than ~1% (~3 ppbv) along the vertical. The preliminary design of the MIN2OS project results in a small instrument (payload of 90 kg, volume of 1200 × 600 × 300 mm3) with, in addition to the spectrometer, a wide field and 1-km resolution imager for cloud detection. The instruments could be hosted on a small platform, the whole satellite being largely compatible with a dual launch on VEGA-C. The MIN2OS project has been submitted to the European Space Agency Earth Explorer 11 mission ideas.
•The MIN2OS satellite project aims at retrieving global-scale N2O sources.•MIN2OS is an IR spectrometer (1250–1330 cm-1) dedicated to N2O measurements.•MIN2OS will observe N2O in the lowermost troposphere at 10x10 km2 resolution.•A source inversion tool will estimate N2O surface fluxes from MIN2OS observations.•The MIN2OS project has been submitted to the ESA EE11 mission ideas.
China is a highly polluted region, particularly the North China Plain (NCP).
However, emission reductions have been occurring in China for about the last
10 years; these reduction measures have been ...in effect since 2006 for SO2 emissions and
since 2010 for NOx emissions. Recent studies have shown a
decrease in the NO2 tropospheric column since 2013 that has been attributed to
the reduction in NOx emissions. Quantifying how these emission
reductions translate regarding ozone concentrations remains unclear due to
apparent inconsistencies between surface and satellite observations. In this
study, we use the lower tropospheric (LT) columns (surface – 6 km a.s.l. – above sea level)
derived from the IASI-A satellite instrument to describe the variability and
trend in LT ozone over the NCP for the 2008–2016 period. First, we investigate the IASI
retrieval stability and robustness based on the influence of atmospheric
conditions (thermal conditions and aerosol loading) and retrieval sensitivity
changes. We compare IASI-A observations with the independent IASI-B
instrument aboard the Metop-B satellite as well as comparing them with surface and ozonesonde
measurements. The conclusion from this evaluation is that the LT ozone columns
retrieved from IASI-A are reliable for deriving a trend representative of the
lower/free troposphere (3–5 km). Deseasonalized monthly time series of LT
ozone show two distinct periods: the first period (2008–2012) with no
significant trend (<−0.1 % yr−1) and a second period (2013–2016) with a
highly significant negative trend of −1.2 % yr−1, which leads to an
overall significant trend of −0.77 % yr−1 for the 2008–2016 period. We
explore the dynamical and chemical factors that could explain these negative
trends using a multivariate linear regression model and chemistry transport
model simulations to evaluate the sensitivity of ozone to the reduction in
NOx emissions. The results show that the negative
trend observed from IASI for the 2013–2016 period is almost equally attributed to
large-scale dynamical processes and emissions reduction, with the large El Niño
event in 2015–2016 and the reduction of NOx emissions being
the main contributors. For the entire 2008–2016 period, large-scale
dynamical processes explain more than half of the observed trend, with a
possible reduction of the stratosphere–troposphere exchanges being the
main contributor. Large-scale transport and advection, evaluated using CO as
a proxy, only contributes to a small part of the trends (∼10 %). However,
a residual significant negative trend remains; this shows the limitation of
linear regression models regarding their ability to account for nonlinear processes such as ozone
chemistry and stresses the need for a detailed evaluation of changes in chemical
regimes with the altitude.
Agriculture is the main source of ammonia (NH3) in France, an important gaseous precursor of atmospheric particulate matter (PM). National
and global emission inventories are known to have difficulty ...representing the large spatial and temporal variability inherent to
atmospheric NH3. In this study, we compare NH3 emissions in France during spring 2011 from one reference inventory, the TNO
inventory, and two alternative inventories that account in different manners for both the spatial and temporal variabilities of the emissions:
(i) the NH3SAT satellite-derived inventory based on IASI NH3 columns and (ii) the CADASTRE-CIT inventory that combines
NH3 emissions due to nitrogen fertilization calculated with the mechanistic model VOLT'AIR on the database of the CADASTRE_NH3
framework and other source emissions from the CITEPA. The total spring budgets, from March to May 2011, at the national level are higher when
calculated with both alternative inventories than with the reference, the difference being more marked with CADASTRE-CIT. NH3SAT and
CADASTRE-CIT inventories both yield to large NH3 spring emissions due to fertilization on soils with high pH in the northeastern part of
France (65 and 135 kt NH3, respectively, vs. 48 kt NH3 for TNO-GEN), while soil properties are not accounted for by the
TNO-GEN methodology. For the other parts of France, the differences are smaller. The timing of fertilization and associated ammonia emissions is
closely related to the nitrogen requirements and hence the phenological stage of the crops, and therefore to the crop year's specific weather
conditions. Maximum emissions are observed in March for 2011 for some regions for both alternative inventories, while April is the period with
maximum emissions for the reference inventory regardless of the region or the year. Comparing the inventories at finer temporal resolutions, typically at
daily scale, large differences are found. The convergence of alternative, independent and complementary methods on the spatiotemporal representation
of the spring NH3 emissions, particularly over areas where the contribution of mineral fertilizer spreading to the spring budget is strong,
encourages further developments in both prospective complementary directions, as this will help improve national NH3 emission inventories.
Up-to-date and accurate emission inventories for air pollutants are
essential for understanding their role in the formation of tropospheric
ozone and particulate matter at various temporal scales, ...for anticipating
pollution peaks and for identifying the key drivers that could help mitigate
their concentrations. This paper describes the Bayesian variational inverse
system PYVAR-CHIMERE, which is now adapted to the inversion of reactive
species. Complementarily with bottom-up inventories, this system aims at
updating and improving the knowledge on the high spatiotemporal variability
of emissions of air pollutants and their precursors. The system is designed
to use any type of observations, such as satellite observations or surface
station measurements. The potential of PYVAR-CHIMERE is illustrated with
inversions of both carbon monoxide (CO) and nitrogen oxides (NOx) emissions in Europe, using the MOPITT and
OMI satellite observations, respectively. In these cases, local increments
on CO emissions can reach more than +50 %, with increases located mainly
over central and eastern Europe, except in the south of Poland, and
decreases located over Spain and Portugal. The illustrative cases for
NOx emissions also lead to large local increments (> 50 %), for example over industrial areas (e.g., over the Po Valley) and
over the Netherlands. The good behavior of the inversion is shown through
statistics on the concentrations: the mean bias, RMSE, standard deviation,
and correlation between the simulated and observed concentrations. For CO,
the mean bias is reduced by about 27 % when using the posterior emissions,
the RMSE and the standard deviation are reduced by about 50 %, and the
correlation is strongly improved (0.74 when using the posterior emissions
against 0.02); for NOx, the mean bias is reduced by about 24 % and the
RMSE and the standard deviation are reduced by about 7 %, but the
correlation is not improved. We reported strong non-linear relationships
between NOx emissions and satellite NO2 columns, now requiring a
fully comprehensive scientific study.
The Chinese government introduced regulations to control emissions and reduce the level of NOx pollutants for the first time with the 12th Five-Year Plan in 2011. Since then, the changes in NOx ...emissions have been assessed using various approaches to evaluate the impact of the regulations. Complementary to the previous studies, this study estimates anthropogenic NOx emissions in 2015 and 2019 over Eastern China using as a reference the Hemispheric Transport of Air Pollution (HTAP) v2.2 emission inventory for 2010 and the new variational inversion system the Community Inversion Framework (CIF) interfaced with the CHIMERE regional chemistry transport model and OMI satellite observations. We also compared the estimated NOx emissions with the independent Multi-resolution Emission Inventory for China (MEIC) v1.3, from 2015. The inversions show a slight global decrease in NOx emissions (in 2015 and 2019 compared to 2010), mainly limited to the most urbanized and industrialized locations. In the locations such as Baotou, Pearl River Delta, and Wuhan, the estimations in 2015 compared to 2010 are consistent with the target reduction (10%) of the 12th Five-Year Plan. Comparisons between our emission estimates and MEIC emissions in 2015 suggest that our estimates likely underestimate the emission reductions between 2010 and 2015 in the most polluted locations of Eastern China. However, our estimates suggest that the MEIC inventory overestimates emissions in regions where MEIC indicates an increase of the emissions compared to 2010.
The objective of this study is to assess and understand the NH3 recent trends and to identify the key components driving its concentrations. We have simulated the seasonal cycle, the interannual ...variability, and the trends in NH3 vertical column densities (VCD) from 2008 to 2015 over Europe, with the CHIMERE regional chemistry–transport model. We have also confronted the simulations against the Infrared Atmospheric Sounding Interferometer (IASI) satellite observations. IASI often shows a strong maximum in summer in addition to the spring peak, whereas CHIMERE only shows a slight peak in summer some years. This result could point to a misrepresentation of the temporal profile of the NH3 emissions, i.e., to missing emission sources during summertime either due to more than expected fertilizer use or to increased volatilization under warmer conditions. The simulated NH3 VCDs present an increasing trend over continental Europe (+2.7 ± 1.0 %/yr) but also at the national scale for Spain, Germany, UK, France, and Poland. Sensitivity tests indicate that these simulated positive trends are mainly due to (i) the trends in NH3 emissions, found heterogeneous in the EMEP NH3 emissions with strong disparities depending on the country, and (ii) the negative trends in NOx and SOx emissions. The impact of reductions in NO2 and SO2 emissions on NH3 concentrations should therefore be taken into account in future policies. This simulated NH3 VCD increase at the European scale is confirmed by IASI-v3R satellite observations in spring and summer, when ammonia emissions strongly contribute to the annual budget in accordance with crop requirements. Nevertheless, there are remaining differences about the significance and magnitude between the simulated and observed trends at the national scale, and it warrants further investigation.
In this paper, we present the first multiyear time
series of atmospheric ammonia (NH3) ground-based measurements in the Paris region
(Créteil, 48.79∘ N, 2.44∘ E, France) retrieved with
the ...midresolution “Observations of the Atmosphere by Solar absorption
Infrared Spectroscopy” (OASIS) ground-based Fourier transform infrared
solar observatory. Located in an urban region, OASIS has previously been
used for monitoring air quality (tropospheric ozone and carbon monoxide)
thanks to its specific column sensitivity across the whole troposphere down
to the atmospheric boundary layer. A total of 4920 measurements of
atmospheric total columns of ammonia have been obtained from 2009 to 2017,
with uncertainties ranging from 20 % to 35 %, and have been compared with
NH3 concentrations derived from the Infrared Atmospheric Sounding
Interferometer (IASI). OASIS ground-based measurements show significant
interannual and seasonal variabilities of atmospheric ammonia. NH3
total columns over the Paris megacity (12 million people) vary seasonally by 2 orders of magnitude from approximately 0.1×1016 molec. cm−2
in winter to 10×1016 molec. cm−2 for spring peaks, probably due
to springtime spreading of fertilizers on surrounding croplands.
PDF
