Lieven Clarisse

• Université Libre de Bruxelles

Atmosphere ammonia (NH3), primarily emitted from agriculture, poses significant threats to ecosystems, climate, and human health through nitrogen deposition and secondary aerosol formation. NH3 flux estimates remain highly uncertain due to limited direct observations and complex emission–deposition processes. Here, we estimated NH3 fluxes over the...

Agricultural practices are a major source of ammonia (NH3) in the atmosphere, which has implications for air quality, climate, and ecosystems. Due to the rising demand for food and feed production, ammonia emissions are expected to increase significantly by 2100 and would therefore impact atmospheric composition such as nitrate (NO3-) or sulfate (S...

Ammonia is a chemical commonly found in fertilizers, cleaning products, and even animal waste. While this substance does have some important uses, rising emissions of ammonia in the atmosphere can pose serious risks to human health, plant and animal health, and the environment. Therefore, measuring and tracking ammonia levels in the air is crucial,...

Ammonia (NH3) emissions have continuously increased due to extensive fertilizer usage in agriculture and increasing production of manure and livestock. However, the current NH3 emission inventories exhibit large uncertainties at all the spatiotemporal scales. We provide atmospheric inversion estimates of the global NH3 emissions over 2019–2022 at 1...

Plain Language Summary Human activities release various gases into the atmosphere, including organic (carbon‐based) gases, which contribute to the creation of pollutants that can be harmful to both the environment and public health. While satellite measurements increasingly monitor gas emissions from specific human‐related sources, they have predom...

Particulate nitrate is a major component of fine particulate matter (PM2.5) and a key target for improving air quality. Its formation is varyingly sensitive to emissions of nitrogen oxides (NOx ≡ NO + NO2), ammonia (NH3), and volatile organic compounds (VOCs). Diagnosing the dominant sensitivity is critical for effective pollution control. Here, we...

Nitrogen oxides (NOx = NO + NO2) are of great concern due to their impact on human health and the environment. In recent years, machine learning (ML) techniques have been widely used for surface NO2 estimation with rapid developments in computational power and big data. However, the uncertainties inherent to such retrievals are rarely studied. In t...

Plain Language Summary Satellite observations play an indispensable role in improving our understanding of the global sources and sinks of HCOOH, an important volatile organic compound in the atmosphere. However, existing polar‐orbiting satellites that are sensitive to tropospheric HCOOH typically provide up to two overpasses per day over the same...

Agricultural practices are responsible for a major source of ammonia (NH3) to the atmosphere which has implications for air quality, climate and ecosystems. Due to the intensification of food and feed production, ammonia emissions are expected to increase significantly by 2100 and would therefore affect atmospheric composition such as nitrate (NO−3...

To mitigate the impact of greenhouse gas (GHG) and air pollutant emissions, it is of utmost importance to understand where emissions occur. In the real world, atmospheric pollutants are produced by various human activities from point sources (e.g. power plants and industrial facilities) but also from diffuse sources (e.g. residential activities and...

Peroxyacetyl nitrate (PAN) is produced in the atmosphere by photochemical oxidation of non-methane volatile organic compounds in the presence of nitrogen oxides (NOx), and it can be transported over long distances at cold temperatures before decomposing thermally to release NOx in the remote troposphere. It is both a tracer and a precursor for tran...

High-spectral resolution infrared sounders on board satellites can measure atmospheric trace gases confined to the planetary boundary layer (PBL). However, their sensitivity to the PBL depends on the temperature difference between the surface and the atmosphere, the so-called thermal contrast (TC). After reviewing the physical aspects of TC and how...

The 21 June 2019 Raikoke eruption (48° N, 153° E) generated one of the largest amounts of sulfur emission to the stratosphere since the 1991 Mt. Pinatubo eruption. Satellite measurements indicate a consensus best estimate of 1.5 Tg for the sulfur dioxide (SO2) injected at an altitude of around 14–15 km. The peak Northern Hemisphere (NH) mean 525 nm...

Nitrous acid (HONO) is a key atmospheric component, acting as a major source of the hydroxyl radical (OH), the primary oxidant in the Earth's atmosphere. However, understanding its spatial and temporal variability remains a significant challenge. Recent TROPOspheric Monitoring Instrument (TROPOMI)/Sentinel-5 Precursor (S5P) ultraviolet–visible (UV–...

Formic acid (HCOOH) is one of the most abundant volatile organic compounds (VOCs) in the Earth’s atmosphere and an important source of atmospheric acidity. Here we present the first retrieval of HCOOH from a geostationary orbit using observations from the Geostationary Interferometric Infrared Sounder (GIIRS) on board FengYun-4B. The results from J...

Plain Language Summary We present a novel application of satellite remote sensing to better understand the causes of particulate nitrate pollution. Particulate nitrate is a major air pollutant throughout the urbanized world. It is produced by atmospheric oxidation of emitted nitrogen oxides (NOx) but may be more sensitive to emissions of ammonia (N...

Ammonia (NH3) is an important air pollutant which, as a precursor of fine particulate matter, raises public health concerns. This study analyzes 2.5 years of NH3 observations derived from ground-based (miniDOAS; differential optical absorption spectroscopy) and satellite (IASI; Infrared Atmospheric Sounding Interferometer) remote sensing instrument...

Knowing where emissions occur is essential for planning effective emission reduction measures and for atmospheric modelling. Emission inventories are typically compiled at national level and provide sector-specific emission estimates. Disaggregating national emissions on high-resolution grids requires spatial proxies that contain information on the...

Nitrous acid (HONO) is a key atmospheric component, acting as a major source of the hydroxyl radical (OH), the primary oxidant in the Earth's atmosphere. However, understanding its spatial and temporal variability remains a significant challenge. Recent TROPOMI/S5P UV-Vis measurements of fresh fire plumes shed light on the impact of global pyrogeni...

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 und...

Ammonia (NH3) is a key precursor to fine particulate matter (PM2.5) and a primary form of reactive nitrogen. The limited number of NH3 observations hinders the further understanding of its impacts on air quality, climate, and biodiversity. Currently, NH3 ground monitoring networks are few and sparse across most of the globe, and even in the most es...

Ammonia (NH3) is one of the most important gases emitted from agricultural practices. It affects air quality and the overall climate and is in turn influenced by long-term climate trends as well as by short-term fluctuations in local and regional meteorology. Previous studies have established the capability of the Infrared Atmospheric Sounding Inte...

Ammonia (NH3) is the most abundant alkaline component in the atmosphere. Changes in NH3 concentrations have important implications for atmospheric chemistry, air quality, and ecosystem integrity. We present a long-term ammonia (NH3) assessment in the western and central African regions within the framework of the International Network to study Depo...

Atmospheric ammonia (NH3) is a reactive nitrogen compound that pollutes our environment and threatens public health. Monitoring the spatial and temporal variations is important for quantifying its emissions and depositions and evaluating the strategies for managing anthropogenic sources of NH3. In this study, we present an NH3 retrieval algorithm b...

The 21st June 2019 Raikoke eruption (48° N,153° E) generated one of the largest amounts of sulfur emission to the stratosphere since the 1991 Mt Pinatubo eruption. Satellite measurements indicate a consensus best estimate of 1.5 Tg for the sulfur dioxide (SO2) injected at an altitude of around 14–15 km. The peak northern hemisphere mean 525 nm Stra...

Ammonia (NH3) is an important air pollutant which, as precursor of fine particulate matter, raises public health issues. This study analyzes 2.5-years of NH3 observations derived from ground-based (miniDOAS) and satellite (IASI) remote sensing instruments to quantify, for the first time, temporal variabilities (from interannual to diurnal) of NH3 c...

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) 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 assumptio...

Extreme enhancements in the total columns of carbon monoxide (CO), peroxyacetyl nitrate (PAN), ethylene (C2H4), methanol (CH3OH), 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 th...

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 cl...

Ammonia (NH3) is a key precursor to fine particulate matter (PM2.5) and a primary form of reactive nitrogen. The limited observations of NH3 hinders further understanding of its impacts on air quality, climate, and biodiversity. Currently, NH3 ground monitoring networks are limited in number across the globe, and even in the most established networ...

Ammonia (NH3) is an important atmospheric constituent. It plays a role in air quality and climate through the formation of ammonium sulfate and ammonium nitrate particles. It has also an impact on ecosystems through deposition processes. About 85 % of NH3 global anthropogenic emissions are related to food and feed production and, in particular, to...

Ammonia (NH3) is the most abundant alkaline component in the atmosphere. Changes in NH3 concentrations have important implications for atmospheric chemistry, air quality, and ecosystem integrity. We present a long-term ammonia (NH3) assessment in the Western and Central Africa region within the framework of the International Network to study Deposi...

Airborne volcanic ash can be observed and quantified from hyperspectral infrared sounders. The retrieval process of physical quantities like particle radius and mass depends critically on the assumed spectrally dependent complex refractive indices that are used. Traditionally, he Pollack et al. (1973) dataset were used almost exclusively. These ind...

The three 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 extrem...

With more than 15 years of continuous and consistent measurements, the Infrared Atmospheric Sounding Interferometer (IASI) radiance dataset is becoming a reference climate data record. To be exploited to its full potential, it requires a cloud filter that is accurate, unbiased over the full IASI life span and strict enough to be used in satellite d...

Ammonia (NH3) is the most abundant alkaline compound in the atmosphere, with consequences for the environment, human health, and radiative forcing. In urban environments, it is known to play a key role in the formation of secondary aerosols through its reactions with nitric and sulfuric acids. However, there are only a few studies about NH3 in Mexi...

Ammonia (NH3) is one of the most important gases emitted from agricultural practices. It affects air quality and the overall climate, and in turn influenced by long term climate trends as well as by short term fluctuations in local and regional meteorology. Previous studies have established the capability of the Infrared Atmospheric Sounding Interf...

Volcanic eruptions can emit large amounts of ash into the atmosphere, which can have significant impacts on infrastructure, human health, agriculture and air traffic. Remote sensing instruments can efficiently detect airborne ash plumes, and the measured spectra can be exploited to obtain information on the physical characteristics of ash (grain si...

Volatile organic compounds are emitted abundantly from a variety of natural and anthropogenic sources. However, in excess, they can severely degrade air quality. Their fluxes are currently poorly represented in inventories due to a lack of constraints from global measurements. Here, we track from space over 300 worldwide hotspots of ethylene, the m...

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 fro...

Atmospheric ammonia (NH3) plays an important role in the formation of fine particulate matter, leading to severe environmental degradation and human health issues. In this work, ground-based Fourier transform infrared spectrometry (FTIR) observations are used to obtain the total columns of atmospheric NH3 at Hefei, China, from December 2016 to Dece...

Ammonia (NH 3 ) is a key precursor of haze particles and fine particulate matter (PM 2.5 ) and its spatiotemporal variabilities are poorly constrained. In this study, we present measurements of NH 3 over the Indian subcontinent region from the IASI and CrIS satellite instruments. This region exhibits a complex emission profile due to the number of...

Ammonia (NH3) is an important atmospheric constituent. It plays a role in air quality and climate through the formation of ammonium sulfate and ammonium nitrate particles. It has also an impact on ecosystems through deposition processes. About 85 % of NH3 global anthropogenic emissions are related to food and feed production and, in particular, to...

In this paper, we exploit the first 10-year data record (2008–2017) of nitric acid (HNO3) total columns measured by the IASI-A/MetOp infrared sounder, characterized by an exceptional daily sampling and a good vertical sensitivity in the lower-to-mid stratosphere (around 50 hPa), to monitor the relationship between the temperature decrease and the o...

Knowledge of sulfur dioxide layer height (SO2 LH) is important to understand volcanic eruption processes, the climate impact of SO2 emissions and to mitigate volcanic risk for civil aviation. However, the estimation of SO2 LH from ground-based instruments is challenging in particular for rapidly evolving and sustained eruptions. Satellite wide-swat...

Emissions of ammonia (NH3) to the atmosphere impact human health, climate, and ecosystems via their critical contributions to secondary aerosol formation. However, the estimation of NH3 emissions is associated with large uncertainties because of inadequate knowledge about agricultural sources. Here, we use satellite observations from the Infrared A...

The presence of a weekly cycle in the abundance of an atmospheric constituent is a typical fingerprint for the anthropogenic nature of its emission sources. However, while ammonia is mainly emitted as a consequence of human activities, a weekly cycle has never been detected in its abundances at large scale. We expose here for the first time the pre...

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 h...

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...

Knowledge of sulfur dioxide layer height (SO2 LH) is important to understand volcanic eruption processes, the climate impact of SO2 emissions and to mitigate volcanic risk for civil aviation. However, the estimation of SO2 LH from ground-based instruments is challenging in particular for rapidly evolving and sustained eruptions. Satellite wide-swat...

With more than 15 years of continuous and consistent measurements, the Infrared Atmospheric Sounding Interferometer (IASI) radiance dataset is becoming a reference climate data record. To be exploited to its full potential, it requires a cloud filter that is both accurate, unbiased over the full IASI lifespan, and strict enough to be used in satell...

Ammonia (NH3) is the most abundant alkaline compound in the atmosphere, with consequences for the environment, human health, and radiative forcing. In urban environments, it is known to play a key role in the formation of secondary aerosols through its reactions with nitric and sulphuric acids. However, there are only a few studies about NH3 in Mex...

Volcanic eruptions eject large amounts of ash and trace gases such as sulfur dioxide (SO2) into the atmosphere. A significant difficulty in mitigating the impact of volcanic SO2 clouds on air traffic safety is that these gas emissions can be rapidly transported over long distances. The use of space-borne instruments enables the global monitoring of...

Tropical cities are experiencing rapid growth but lack routine air pollution monitoring to develop prescient air quality policies. Here, we conduct targeted sampling of recent (2000s to 2010s) observations of air pollutants from space-based instruments over 46 fast-growing tropical cities. We quantify significant annual increases in nitrogen dioxid...

The Arabian Peninsula exhibits extreme hot summers and has one of the world's largest population growth. We use satellite observations and reanalysis as well as climate model projections to analyze morning and evening land surface temperatures (LST), to refer to processes at the surface, and wet bulb temperatures (WBT) to measure human heat stress....

An updated and expanded representation of organics in the chemistry general circulation model EMAC (ECHAM5/MESSy for Atmospheric Chemistry) has been evaluated. First, the comprehensive Mainz Organic Mechanism (MOM) in the submodel MECCA (Module Efficiently Calculating the Chemistry of the Atmosphere) was activated with explicit degradation of organ...

Emissions of ammonia (NH3) to the atmosphere impact human health, climate, and ecosystems through their critical contributions to secondary aerosol formation. Estimation of NH3 emissions is associated with large uncertainties because of inadequate knowledge about agricultural sources. Here, we use satellite observations from the Infrared Atmospheri...

The three infrared atmospheric sounding interferometers (IASIs), launched in 2006, 2012, and 2018, are key instruments to weather forecasting, and most meteorological centres assimilate IASI nadir radiance data into atmospheric models to feed their forecasts. The European Organisation for the Exploitation of Meteorological Satellites (EUMETSAT) rec...

This paper quantifies the tropical stratospheric aerosol content as impacted by volcanic events over the 2013–2019 period. We use global model simulations by the Whole Atmosphere Community Climate Model (WACCM) which is part of the Community Earth System Model version 1.0 (CESM1). WACCM is associated with the Community Aerosol and Radiation Model f...

Volcanic eruptions eject large amounts of ash and trace gases such as sulphur dioxide (SO2) into the atmosphere. A significant difficulty in mitigating the impact of volcanic SO2 clouds on air traffic safety is that these gas emissions can be rapidly transported over long distances. The use of space-borne instruments enables the global monitoring o...

Sensitive and accurate detection of sulfur dioxide (SO2) from space is important for monitoring and estimating global sulfur emissions. Inspired by detection methods applied in the thermal infrared, we present here a new scheme to retrieve SO2 columns from satellite observations of ultraviolet back-scattered radiances. The retrieval is based on a m...

Atmospheric ammonia (NH3) is a precursor to fine particulate matter and a source of nitrogen (N) deposition that can adversely affect ecosystem health. The main sources of NH3 – agriculture and biomass burning – are undergoing are or expected to undergo substantial changes in Africa. Although evidence of increasing NH3 over parts of Africa has been...

The purpose of the EUNADICS-AV (European Natural Airborne Disaster Information and Coordination System for Aviation) prototype early warning system (EWS) is to develop the combined use of harmonised data products from satellite, ground-based and in situ instruments to produce alerts of airborne hazards (volcanic, dust, smoke and radionuclide clouds...

The agricultural sector in Syria was heavily affected by the civil war that started in 2011. We investigate the war’s impact on the country’s atmospheric ammonia (NH3) from 2008 to 2019, using measurements from the infrared atmospheric sounding interferometer instrument on board the Metop satellites. We examine the changes in NH3 close to a fertili...

The three IASI instruments, launched in 2006, 2012, and 2018, are key instruments to weather forecasting, and most meteorological centers assimilate IASI nadir radiance data into atmospheric models to feed their forecasts. The EUropean organisation for the exploitation of METeorological SATellites (EUMETSAT) recently released a reprocessed homogene...

In recent years, the interest has grown in satellite-derived hyperspectral radiance measurements for assessing the individual impact of climate drivers and their cascade of feedbacks on the outgoing longwave radiation (OLR). In this paper, we use 10 years (2008–2017) of reprocessed radiances from the infrared atmospheric sounding interferometer (IA...

An updated and expanded representation of organics in the chemistry general circulation model EMAC (ECHAM5/MESSy for Atmospheric Chemistry) has been evaluated. First, the comprehensive Mainz Organic Mechanism (MOM) in the submodel MECCA (Module Efficiently Calculating the Chemistry of the Atmosphere) was activated with explicit degradation of organ...

Peroxyacetyl nitrate (PAN) is the main tropospheric reservoir of NOx (NO + NO2). Its lifetime can reach several 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. The subsequent release of NOx through the PAN thermal decomposition leads to the efficie...