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Extreme enhancements in the total columns of carbon monoxide (CO), peroxyacetyl nitrate (PAN), ethylene (C2H4 ), methanol (CH3 OH), and formic acid (HCOOH) were observed over the Canadian high Arctic during the period of 17–22 August 2017 by a ground‐based Fourier transform infrared (FTIR) spectrometer at Eureka, Nunavut (80.05°N, 86.42°W), and by the Infrared Atmospheric Sounding Interferometer (IASI) satellite instruments. These enhancements have been attributed to wildfires in British Columbia (BC) and the Northwest Territories (NWT) of Canada, and represent the largest short‐term perturbations of PAN, C2H4, and HCOOH above ambient concentrations over the 14‐year (2006–2020) Eureka time‐series. Enhancement ratios, emission ratios, and emission factors relative to CO were calculated for all species for both FTIR and IASI observations. The C2H4 and HCOOH emission factors are significantly larger than previous studies, suggesting unusually high emissions from these fires. The wildfire plumes were also simulated using the GEOS‐Chem model. Initial GEOS‐Chem simulations displayed a severe under‐estimation relative to observations for these fire plumes resulting from the injection height scheme of the model. Sensitivity tests highlighted that injection heights of 12.5 km for BC (based on previous studies) and 10 km for the NWT fires yielded the strongest correlations with ground‐based measurements. Applying these injection heights to the model significantly improves the simulated plume transport and agreement with ground‐ and space‐based observations. GEOS‐Chem was also used to estimate the magnitude of secondary in‐plume production of CH3OH and HCOOH; it was found to be an important component (∼18%) of the enhanced HCOOH columns at Eureka., SCOPUS: ar.j, info:eu-repo/semantics/published

Large releases of volatile organic compounds (VOCs) to the atmosphere occur frequently from heavy industries and megacities but these emission fluxes are still poorly constrained in current inventories. Identifying and monitoring such localized sources is therefore key to mitigate air pollution. Using the multi-annual and spatially dense measurements from the Infrared Atmospheric Sounding Interferometer (IASI) on Metop satellites, in combination with an advanced oversampling technique that augments the spatial resolution of averaged satellite data, we explore the potential of spaceborne infrared observations for tracking down anthropogenic emitters of VOCs. We report the detection of worldwide point-sources of several major VOCs, among which ethylene (C2H4) and methanol (CH3OH). Those are found to be mainly associated with heavy industries such as petrochemical hubs, coal-related activities (e.g. coal mining and processing), and megacities. For some point-sources, we provide a first order estimate of their annual VOC emissions based on the IASI measurements. We find an important mismatch between the top-down industrial fluxes and the VOC emissions from the anthropogenic inventory EDGAR, often dominated by non-industrial sectors. This work highlights the importance of current and future infrared satellite measurements to monitor and track industrial air pollution., info:eu-repo/semantics/nonPublished

Nitrous acid (HONO) plays a key role in atmospheric chemistry as a major source – through rapid photolysis – of the hydroxyl radical (OH), the primary oxidant in the Earth's atmosphere. However, significant uncertainties remain on the spatial and temporal variability of HONO, on its formation pathways in the atmosphere, and on the contribution of its primary emissions over its secondary formation. Recently, spaceborne measurements in the UV-Vis spectral domain, taken in the early afternoon with the S5P/TROPOMI instrument, have provided a first global picture of HONO in fresh biomass burning plumes, demonstrating the importance of satellite data for improving our representation of atmospheric HONO. With daily overpass times in the early morning and early evening, the polar-orbiting IASI/Metop instruments and their global measurements of the Earth's radiance in the thermal infrared, have the potential to contribute to tackling remaining uncertainties on HONO and to complement the TROPOMI measurements.So far detected by infrared satellite sounders in the exceptional 2009 and 2019/2020 Australian bushfires only, we use a sensitive detection method to demonstrate that unambiguous HONO enhancements can also be identified in IASI spectra recorded in concentrated fire plumesworldwide. With this method, we analyse the long, unique observational timeseries (2007-2022) of IASI and we report a 15-year record of fire events in which HONO has been detected. This dataset reveals first that HONO is primarily captured by IASI at the Northern Hemisphere mid and high latitudes, and secondly that the IASI evening measurements allow a significantly higher number of HONO detections than during daytime despite the overall weaker thermal contrast and lower measurement sensitivity affecting such night-time observations. We discuss different factors that can explain these features, such as the sharp intra-day variability of HONO, the links with the diurnal variations and intensity of fires, info:eu-repo/semantics/nonPublished

The three Infrared Atmospheric Sounding Interferometer (IASI) instruments on board the Metop family of satellites have been sounding the atmospheric composition since 2006. More than 30 atmospheric gases can be measured from the IASI radiance spectra, allowing the improvement of weather forecasting and the monitoring of atmospheric chemistry and climate variables. The early detection of extreme events such as fires, pollution episodes,volcanic eruptions, or industrial releases is key to take safety measures to protect the inhabitants and the environment in the impacted areas. With its near-real-time observations and good horizontal coverage, IASI can contribute to the series of monitoring systems for the systematic and continuous detection of exceptional atmospheric events in order to support operational decisions. In this paper, we describe a new approach to the near-real-time detectionand characterization of unexpected events, which relies on the principalcomponent analysis (PCA) of IASI radiance spectra. By analyzing both theIASI raw and compressed spectra, we applied a PCA-granule-based method onvarious past, well-documented extreme events such as volcanic eruptions,fires, anthropogenic pollution, and industrial accidents. We demonstratethat the method is well suited to the detection of spectral signatures for reactive and weakly absorbing gases, even for sporadic events. Consistent long-term records are also generated for fire and volcanic events from the available IASI/Metop-B data record. The method is running continuously, delivering email alerts on a routinebasis, using the near-real-time IASI L1C radiance data. It is planned to beused as an online tool for the early and automatic detection of extremeevents, which was not done before., SCOPUS: ar.j, info:eu-repo/semantics/published

Satellite measurements play an increasingly important role in the study of atmospheric ammonia (NH3). Here, we present version 4 of the Artificial Neural Network for IASI (ANNI; IASI: Infrared Atmospheric Sounding Interferometer) retrieval of NH3. The main change is the introduction of total column averaging kernels (AVKs), which can be used to undo the effect of the vertical profile shape assumption of the retrieval. While the main equations can be matched term for term with analogous ones used in UV/Vis retrievals for other minor absorbers, we derive the formalism from the ground up, as its applicability to thermal infrared measurements is non-trivial. A large number of other smaller changes were introduced in ANNI v4, most of which improve the consistency of the measurements across time and across the series of IASI instruments. This includes a more robust way of calculating the hyperspectral range index (HRI), explicitly accounting for long-term changes in CO2 in the HRI calculation and the use of a reprocessed cloud product that was specifically developed for climate applications. The NH3 distributions derived with ANNI v4 are very similar to the ones derived with v3, although values are about 10 %–20 % larger due to the improved setup of the HRI. We exclude further large biases of the same nature by showing the consistency between ANNI v4 derived NH3 columns with columns obtained with an optimal estimation approach. Finally, with v4, we revised the uncertainty budget and now report systematic uncertainty estimates alongside random uncertainties, allowing realistic mean uncertainties to be estimated., SCOPUS: ar.j, info:eu-repo/semantics/published

Wildfires are a common occurrence in many parts of the globe and can emit significant quantities of trace gases and particulate matter, negatively impacting air quality on large spatial scales. Among the various trace gases emitted by wildfires are volatile organic compounds (VOCs). Four VOCs that are of particular importance are methanol (CH3OH), formic acid (HCOOH), peroxyacetyl nitrate (PAN), and ethylene (C2H4). These reactive VOCs can have a variety of negative impacts on the atmospheric chemistry and environment of remote regions including influencing trace gas budgets, impacting atmospheric acidity, and contributing to the ‘Arctic haze’ pollution phenomenon.During August 2017, two independent large-scale wildfires in British Columbia and the Northwest Territories of Canada generated vast smoke plumes that merged and were subsequently transported to the high Arctic. Simultaneous observations by a high-resolution ground-based Fourier transform infrared (FTIR) spectrometer at the Polar Environment Research Laboratory (PEARL) in Eureka, Nunavut (80.05°N, 86.42°W), and the Infrared Atmospheric Sounding Interferometer (IASI) satellite instruments display extreme enhancements in these species relative to background concentrations during the fire-affected period in late August 2017, demonstrating the long-range transport and secondary formation of these typically short-lived species. Comparisons of observations with the GEOS-Chem global chemical transport model illustrate that this exceptional wildfire event contributed to a substantial perturbation to the VOC budget of the high-Arctic atmosphere., info:eu-repo/semantics/nonPublished

Peroxyacetyl nitrate (PAN, CH3COO2NO2) is the main tropospheric reservoir of NOx (NO + NO2). PAN is formed when non-methane volatile organic compounds (NMVOCs) oxidation products react with NOx. Anthropogenic and natural emission sources (fossil fuel combustion, biomassburning, lightning, and processes responsible for NMVOC emissions) contribute to PAN formation (Fischer et al. 2014). Its lifetime can reachseveral months in the upper cold troposphere. This enables the long-range transport of NOx radicals, under the form of PAN, far from the regions of emission (Tereszchuk et al. 2013; Fischer et al. 2014). The subsequent release of NOx through the PAN thermal decomposition leads to the efficient formation of tropospheric ozone (O3), with important consequences for tropospheric oxidative capacity and air quality. PAN total columns have been retrieved from ground-based high-resolution solar absorption Fourier transform infrared (FTIR) spectra. The developed strategy has been applied to observations recorded at remote FTIR stations of the Network for the Detection of Atmospheric Composition Change (NDACC, visit https://www.ndaccdemo.org/). The resulting datasets are compared with a GEOS-Chem (Goddard Earth Observing System) global chemical transport model (CTM) simulation and with total column time series derived from IASI (Infrared Atmospheric Sounding Interferometer) satellite observations., info:eu-repo/semantics/published

Large releases of volatile organic compounds (VOCs) occur frequently in link with human activities, especially in the vicinity of industrial areas and megacities where the potential emitters are numerous. Identifying and monitoring such anthropogenic sources is therefore key to mitigate air pollution. However, these sources are still poorly represented in the current emission databases as they primarily lack constraints from global and consistent measurements. The multi-annual and spatially dense measurements from the Infrared Atmospheric Sounding Interferometer (IASI) offer the opportunity to monitor the atmospheric abundance of VOCs at the global scale. We exploit the extensive IASI dataset in combination with an advanced oversampling technique that allows augmenting the spatial resolution of averaged satellite data beyond what the sounder can initially offers. As it resolves much finer spatial features, such techniques are effective in locating emitter sources of a target pollutant. We demonstrate that, applied to the IASI VOC measurements, this allows the detection from space of anthropogenic point sources of major VOCs, namely ethylene (C2H4), acetylene (C2H2) and methanol (CH3OH). We categorize these point-sources worldwide, which are found to be mainly associated with heavy industries such as petrochemical hubs, coal-related activities, and megacities. This work highlights the importance of spaceborne measurements and the key role that will be played by future satellite missions to tackle the problematic of industrial air pollution., info:eu-repo/semantics/nonPublished

info:eu-repo/semantics/nonPublished

info:eu-repo/semantics/nonPublished

info:eu-repo/semantics/nonPublished