NH3 spatiotemporal variability over Paris, Mexico City, and Toronto, and its link to PM2.5 during pollution events

Megacities can experience high levels of fine particulate matter (PM2.5) pollution linked to ammonia (NH3) mainly emitted from agricultural activities. Here, we investigate such pollution in the cities of Paris, Mexico, and Toronto, each of which have distinct emission sources, agricultural regulations, and topography. Ten years of measurements from the infrared atmospheric sounding interferometer (IASI) are used to assess the spatiotemporal NH3 variability over and around the three cities. In Europe and North America, we determine that temperature is associated with the increase in NH3 atmospheric concentrations with a coefficient of determination (r2) of 0.8 over agricultural areas. The variety of the NH3 sources (industry and agricultural) and the weaker temperature seasonal cycle in southern North America induce a lower correlation factor (r2=0.5). The three regions are subject to long-range transport of NH3, as shown using HYSPLIT cluster back trajectories. The highest NH3 concentrations measured at the city scale are associated with air masses coming from the surrounding and north/northeast regions of Paris, the south/southwest areas of Toronto, and the southeast/southwest zones of Mexico City. Using NH3 and PM2.5 measurements derived from IASI and surface observations from 2008 to 2017, annually frequent pollution events are identified in the three cities. Wind roses reveal statistical patterns during these pollution events with dominant northeast/southwest directions in Paris and Mexico City, and the transboundary transport of pollutants from the United States in Toronto. To check how well chemistry transport models perform during pollution events, we evaluate simulations made using the GEOS-Chem model for March 2011. In these simulations we find that NH3 concentrations are underestimated overall, though day-to-day variability is well represented. PM2.5 is generally underestimated over Paris and Mexico City, but overestimated over Toronto.</p

Ammonia emissions may be substantially underestimated in China

China is a global hotspot of atmospheric ammonia (NH3) emissions and, as a consequence, very high nitrogen (N) deposition levels are documented. However, previous estimates of total NH3 emissions in China were much lower than inference from observed deposition values would suggest, highlighting the need for further investigation. Here, we reevaluated NH3 emissions based on a mass balance approach, validated by N deposition monitoring and satellite observations, for China for the period of 2000 to 2015. Total NH3 emissions in China increased from 12.1±0.8 Tg N yr-1 in 2000 to 15.6±0.9 Tg N yr-1 in 2015 at an annual rate of 1.9%, which is approximately 40% higher than existing studies suggested. This difference is mainly due to more emission sources now having been included and NH3 emission rates from mineral fertilizer application and livestock having been underestimated previously. Our estimated NH3 emission levels are consistent with the measured deposition of NHx (including NH4+ and NH3) on land (11-14 Tg N yr-1) and the substantial increases in NH3 concentrations observed by satellite measurements over China. These findings substantially improve our understanding on NH3 emissions, implying that future air pollution control strategies have to consider the potentials of reducing NH3 emission in China

Unprecedented atmospheric ammonia concentrations detected in the high Arctic from the 2017 Canadian wildfires

Abstract From 17-22 August 2017 simultaneous enhancements of ammonia (NH3), carbon monoxide (CO), hydrogen cyanide (HCN), and ethane (C2H6) were detected from ground-based solar absorption Fourier transform infrared (FTIR) spectroscopic measurements at two high-Arctic sites: Eureka (80.05°N, 86.42°W) Nunavut, Canada and Thule (76.53°N, 68.74°W), Greenland. These enhancements were attributed to wildfires in British Columbia and the Northwest Territories of Canada using FLEXPART back-trajectories and fire locations from Moderate Resolution Imaging Spectroradiometer (MODIS) and found to be the greatest observed enhancements in more than a decade of measurements at Eureka (2006-2017) and Thule (1999-2017). Observations of gas-phase NH3 from these wildfires illustrates that boreal wildfires may be a considerable episodic source of NH3 in the summertime high Arctic. Comparisons of GEOS-Chem model simulations using the Global Fire Assimilation System (GFASv1.2) biomass burning emissions to FTIR measurements and Infrared Atmospheric Sounding Interferometer (IASI) measurements showed that the transport of wildfire emissions to the Arctic was underestimated in GEOS-Chem. However, GEOS-Chem simulations showed that these wildfires contributed to surface-layer NH3 and enhancements of 0.01-0.11 ppbv and 0.05-1.07 ppbv, respectively, over the Canadian Archipelago from 15-23 August 2017

Global Ammonia Distribution Derived from Infrared Satellite Observations

Over the past century there has been a steady increase in the global emission of ammonia entailing a host of environ-mental problems. There are large un-certainties in our understanding of ammonia levels on both temporal and spatial scales. Part of this is due to the dearth of ground based observations, their representativeness for larger scales, and virtual absence of meas-urements aloft. In this work we present the first local and global daily ammo-nia concentrations measured from the space borne thermal infrared spec-trometer IASI/MetOp. From the 2008 yearly average we identify high ammo-nia hotspots over the world¿s agricul-tural and biomass burning regions. We find an overall good qualitative agree-ment with a global model of the am-monia cycle. On average the measured concentrations are found to be lower than the modeled. However, large un-derestimations in the model fields are found at mid-latitudes in the Northern hemisphere.JRC.H.2-Climate chang

Improving the global tropospheric methanol budget through inverse modelling of spaceborne IASI methanol columns and in situ data

International audienceNew insights into our understanding of methanol sources and sinks in the global troposphere are brought forward by recent measurements of tropospheric columns of methanol retrieved from the IASI satellite sensor. These data are expected to reduce the uncertainties in the knowledge of the methanol distribution in the troposphere, thanks to the unprecedented global spatiotemporal coverage offered by the IASI instrument. According to current estimates, the ocean biosphere and the terrestrial growth source represent two thirds of the total methanol source, whereas plant decay, atmospheric production, anthropogenic and biomass burning sources account for the remainder. In this study we use the IMAGESv2 global chemical transport model and its adjoint module, in order to interpret the new dataset and derive updated methanol source strengths which bring the model predictions closer to the observed abundances. The resulting fluxes are evaluated against an extensive compilation of air- and ground-based methanol measurements, and the implications for the atmospheric chemistry are discussed

Improving the global tropospheric methanol budget through inverse modelling of spaceborne IASI methanol columns and in situ data

International audienceNew insights into our understanding of methanol sources and sinks in the global troposphere are brought forward by recent measurements of tropospheric columns of methanol retrieved from the IASI satellite sensor. These data are expected to reduce the uncertainties in the knowledge of the methanol distribution in the troposphere, thanks to the unprecedented global spatiotemporal coverage offered by the IASI instrument. According to current estimates, the ocean biosphere and the terrestrial growth source represent two thirds of the total methanol source, whereas plant decay, atmospheric production, anthropogenic and biomass burning sources account for the remainder. In this study we use the IMAGESv2 global chemical transport model and its adjoint module, in order to interpret the new dataset and derive updated methanol source strengths which bring the model predictions closer to the observed abundances. The resulting fluxes are evaluated against an extensive compilation of air- and ground-based methanol measurements, and the implications for the atmospheric chemistry are discussed

Observation of tropospheric δD by IASI and comparison with LMDZiso over the Western Siberia

International audienceWestern Siberia has undergone a sharp increase in temperature during the last decades, modifying the biogeochemical and the hydrological cycles. Water vapor plays an important role in the atmosphere including in the radiative transfer, cloud formation and precipitation. Information about evaporation/condensation processes of water vapor can be provided by water stable isotopologues such as H216O and HDO. This study presents the joint H216O and HDO retrievals from Infrared Atmospheric Sounding Interferometer (IASI) spectra over Siberia. IASI is an instrument on board the MetOp-A European satellite launched in October 2006. The global coverage of this instrument and the good signal-to-noise ratio allow us to provide information on δD over this region. IASI measurements may be used to estimate integrated δD between the surface and 3 km altitude or from 1 to 5 km depending on the thermal contrast between the surface and the low troposphere. The retrieved data are compared to simulations from an isotopic GCM, LMDZiso, for 2011. The data show variations that are well correlated with the model at seasonal (r up to 0.8) and day-to-day (r≡0.6) time scales. The IASI-based retrievals and the model capture also well the seasonal variation of the specific humidity in the [0-3km] and the [1-5km] altitude ranges

NH₃ spatio-temporal variability over Paris, Mexico and Toronto and its link to PM_2.5 during pollution events

International audienceMegacities can experience high levels of fine particulate matter (PM2.5) pollution linked to ammonia (NH3) mainly emitted from agricultural activities. Here, we investigate such pollution in the cities of Paris, Mexico and Toronto, each of which have distinct emission sources, agricultural regulations, and topography. Ten years of measurements from the Infrared Atmospheric Sounding Interferometer (IASI) are used to assess the spatio-temporal NH3 variability over and around the three cities.In Europe and North America, we determine that temperature is associated with the increase in NH3 atmospheric concentrations with coefficient of determination (r2) of 0.8 over agricultural areas. The variety of the NH3 sources (industry and agricultural) and the weaker temperature seasonal cycle in southern North America induce a lower correlation factor (r2 = 0.5). The three regions are subject to long range transport of NH3, as shown using HYSPLIT cluster back-trajectories. The highest NH3 concentrations measured at the city scales are associated with air masses coming from the surrounding and north-northeast regions of Paris, the south-southwest areas of Toronto, and the southeast/southwest zones of Mexico City.Using NH3 and PM2.5 measurements derived from IASI and surface observations from 2008 to 2017, annually frequent pollution events are identified in the 3 cities. Wind roses reveal statistical patterns during these pollution events with dominant northeast-southwest directions in Paris and Mexico cities, and the transboundary transport of pollutants from the United-States in Toronto. To check how well chemistry transport models perform during pollution events, we evaluate simulations made using the GEOS-Chem model for March 2011. In these simulations we find that NH3 concentrations are overall underestimated, though day-to-day variability is well represented. PM2.5 is generally underestimated over Paris and Mexico, but overestimated over Toronto

UK Ammonia Emissions Estimated With Satellite Observations and GEOS‐Chem

Agricultural emissions of ammonia (NH 3) impact air quality, human health, and the vitality of aquatic and terrestrial ecosystems. In the UK, there are few direct policies regulating anthropogenic NH 3 emissions and development of sustainable mitigation measures necessitates reliable emissions estimates. Here, we use observations of column densities of NH 3 from two space-based sensors (IASI and CrIS) with the GEOS-Chem model to derive top-down NH 3 emissions for the UK at fine spatial (∼10 km) and time (monthly) scales. We focus on March-September when there is adequate spectral signal to reliably retrieve NH 3. We estimate total emissions of 272 Gg from IASI and 389 Gg from CrIS. Bottom-up emissions are 27% less than IASI and 49% less than CrIS. There are also differences in seasonality. Top-down and bottom-up emissions agree on a spring April peak due to fertilizer and manure application, but there is also a comparable summer July peak in the top-down emissions that is not in the bottom-up emissions and appears to be associated with dairy cattle farming. We estimate relative errors in the top-down emissions of 11%–36% for IASI and 9%–27% for CrIS, dominated by column density retrieval errors. The bottom-up versus top-down emissions discrepancies estimated in this work impact model predictions of the environmental damage caused by NH 3 emissions and warrant further investigation