Mark W. Shephard
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View article: Development and validation of satellite-derived surface NO <sub>2</sub> estimates using machine learning versus traditional approaches in North America
Development and validation of satellite-derived surface NO <sub>2</sub> estimates using machine learning versus traditional approaches in North America Open
Nitrogen dioxide (NO2) is one of the key pollutants with profound implications for air quality, and human health, and is needed to establish the air quality health index (AQHI). Currently, over 600 surface air monitoring stations are distr…
View article: Decadal changes in atmospheric ammonia and dry deposition across China inferred from space-ground measurements and model simulations
Decadal changes in atmospheric ammonia and dry deposition across China inferred from space-ground measurements and model simulations Open
Ammonia (NH3), a key alkaline gas in the atmosphere, significantly influences ecosystem nitrogen cycling and the formation of fine particulate matter (PM2.5). However, limited ground-based monitoring hinders understanding of NH3's spatial …
View article: Geostationary observations of atmospheric ammonia over East Asia: spatio-temporal variations revealed by three years of FY-4B/GIIRS measurements
Geostationary observations of atmospheric ammonia over East Asia: spatio-temporal variations revealed by three years of FY-4B/GIIRS measurements Open
Satellite observations play a crucial role in quantifying ammonia sources by capturing large-scale variations of atmospheric NH3 concentrations. As the world's first geostationary hyperspectral infrared sounder, the Geostationary Interfero…
View article: Ammonia Bidirectional Flux Model Tailored for Satellite Retrieval Parameter Inversions
Ammonia Bidirectional Flux Model Tailored for Satellite Retrieval Parameter Inversions Open
Atmospheric ammonia is an important chemical species for air quality and ecosystem health, and has levels that have been either growing or stagnant in many regions, in contrast to many other pollutants that have been on the decline in rece…
View article: Using multi-satellite observations to constrain ammonia emissions and unlock their potential over open water
Using multi-satellite observations to constrain ammonia emissions and unlock their potential over open water Open
Reducing uncertainty in ammonia ([Formula: see text]) emissions, particularly those over open water, which have largely been unexplored, remains a key challenge. This study refines 2019 [Formula: see text] emissions over the south-central …
View article: Development and validation of satellite-derived surface NO <sub>2</sub> estimates using machine learning versus traditional approaches in North America
Development and validation of satellite-derived surface NO <sub>2</sub> estimates using machine learning versus traditional approaches in North America Open
Nitrogen dioxide (NO2) is one of the key pollutants with profound implications for air quality, and human health, and is needed to establish the air quality health index (AQHI). Currently, over 600 surface air monitoring stations are distr…
View article: Geographic and Temporal Variability of atmospheric surface Ammonia (NH3) in France, Belgium, and the Netherlands (2015 &#8211; 2023) across different land-use types: Insights from Ground-Based and combined Satellite Observations.
Geographic and Temporal Variability of atmospheric surface Ammonia (NH3) in France, Belgium, and the Netherlands (2015 – 2023) across different land-use types: Insights from Ground-Based and combined Satellite Observations. Open
This research study analyzes atmospheric ammonia (NH₃) surface concentrations in France, Belgium (Flanders region), and the Netherlands, highlighting their geographic, temporal, and diel variability from 2015 to 2023 using ground-bas…
View article: Ammonia emission estimates using CrIS satellite observations over Europe
Ammonia emission estimates using CrIS satellite observations over Europe Open
Over the past century, ammonia (NH3) emissions have increased with the growth of livestock and fertilizer usage. The abundant NH3 emissions lead to secondary fine particulate matter (PM2.5) pollution, climate change, and a reduction in bio…
View article: Critical load exceedances for North America and Europe using an ensemble of models and an investigation of causes of environmental impact estimate variability: an AQMEII4 study
Critical load exceedances for North America and Europe using an ensemble of models and an investigation of causes of environmental impact estimate variability: an AQMEII4 study Open
Exceedances of critical loads for deposition of sulfur (S) and nitrogen (N) in different ecosystems were estimated using European and North American ensembles of air quality models, under the Air Quality Model Evaluation International Init…
View article: Ammonia emissions and depositions over the contiguous United States derived from IASI and CrIS using the directional derivative approach
Ammonia emissions and depositions over the contiguous United States derived from IASI and CrIS using the directional derivative approach Open
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…
View article: Infrared Satellite Detection Limits for Monitoring Atmospheric Ammonia
Infrared Satellite Detection Limits for Monitoring Atmospheric Ammonia Open
This study investigates single pixel nadir viewing detection limit of atmospheric ammonia for a range of area flux mapping satellite infrared sensor spectral resolutions (0.05–2.0 cm−1) and measurement noise levels. The detection level of …
View article: Critical Load Exceedances for North America and Europe using an Ensemble of Models and an Investigation of Causes for Environmental Impact Estimate Variability: An AQMEII4 Study
Critical Load Exceedances for North America and Europe using an Ensemble of Models and an Investigation of Causes for Environmental Impact Estimate Variability: An AQMEII4 Study Open
Exceedances of critical loads for deposition of sulphur (S) and nitrogen (N) to different ecosystems were estimated using European and North American ensembles of air quality models, under Phase 4 of the Air Quality Model Evaluation Intern…
View article: Ammonia emission estimates using CrIS satellite observations over Europe
Ammonia emission estimates using CrIS satellite observations over Europe Open
Over the past century ammonia (NH3) emissions have increased with the growth of livestock and fertilizer usage. The abundant NH3 emissions lead to secondary fine particulate matter (PM2.5) pollution, climate change, reduction in biodiversi…
View article: Sensitivity of air quality to vehicle ammonia emissions in the United States
Sensitivity of air quality to vehicle ammonia emissions in the United States Open
The US Environmental Protection Agency (EPA) estimates on-road vehicles emissions using the Motor Vehicle Emission Simulator (MOVES). We developed updated ammonia emission rates for MOVES based on road-side exhaust emission measurements of…
View article: Constraining East Asia ammonia emissions through satellite observations and iterative Finite Difference Mass Balance (iFDMB) and investigating its impact on inorganic fine particulate matter
Constraining East Asia ammonia emissions through satellite observations and iterative Finite Difference Mass Balance (iFDMB) and investigating its impact on inorganic fine particulate matter Open
Uncertainty in ammonia (NH3) emissions causes the inaccuracy of fine particulate matter simulations, which is associated with human health. To address this uncertainty, in this work, we employ the iterative finite difference mass balance (…
View article: Validation of MUSES NH <sub>3</sub> observations from AIRS and CrIS against aircraft measurements from DISCOVER-AQ and a surface network in the Magic Valley
Validation of MUSES NH <sub>3</sub> observations from AIRS and CrIS against aircraft measurements from DISCOVER-AQ and a surface network in the Magic Valley Open
Ammonia is a significant precursor of PM2.5 particles and thus contributes to poor air quality in many regions. Furthermore, ammonia concentrations are rising due to the increase of large-scale, intensive agricultural activities, which are…
View article: Numerical model generation of test frames for pre-launch studies of EarthCARE's retrieval algorithms and data management system
Numerical model generation of test frames for pre-launch studies of EarthCARE's retrieval algorithms and data management system Open
The Earth Cloud, Aerosol and Radiation Explorer (EarthCARE) satellite consists of active and passive sensors whose observations will be acted on by an array of retrieval algorithms. EarthCARE's retrieval algorithms have undergone pre-launc…
View article: Broadband radiative quantities for the EarthCARE mission: the ACM-COM and ACM-RT products
Broadband radiative quantities for the EarthCARE mission: the ACM-COM and ACM-RT products Open
The EarthCARE satellite mission's objective is to retrieve profiles of aerosol and water cloud physical properties from measurements made by its cloud-profiling radar, backscattering lidar, and passive multi-spectral imager. These retrieva…
View article: Cloud-based data mapper (CDM): application for monitoring dry deposition of reactive nitrogen
Cloud-based data mapper (CDM): application for monitoring dry deposition of reactive nitrogen Open
Spatiotemporal monitoring of reactive nitrogen atmospheric deposition is essential for understanding its impact on sensitive ecosystems and quantifying cumulative effects. However, the sparsity of direct surface flux measurements combined …
View article: Accounting for Non-Detects: Application to Satellite Ammonia Observations
Accounting for Non-Detects: Application to Satellite Ammonia Observations Open
Presented is a methodology to explicitly identify and account for cloud-free satellite measurements below a sensor’s measurement detection level. These low signals can often be found in satellite observations of minor atmospheric species w…
View article: Across-track extension of retrieved cloud and aerosol properties for the EarthCARE mission: the ACMB-3D product
Across-track extension of retrieved cloud and aerosol properties for the EarthCARE mission: the ACMB-3D product Open
The narrow cross section of cloud and aerosol properties retrieved by L2 algorithms that operate on data from EarthCARE's nadir-pointing sensors is broadened across-track by an algorithm that is described and demonstrated here. This scene …
View article: Comment on amt-2022-336
Comment on amt-2022-336 Open
Abstract. Ammonia is a significant precursor of PM2.5 particles and thus contributes to poor air quality in many regions. Furthermore, ammonia concentrations are rising due to the increase of large scale, intensive agricultural activities,…
View article: EarthCARE level-2 demonstration products from simulated scenes
EarthCARE level-2 demonstration products from simulated scenes Open
Overview The EarthCARE satellite combines four instruments, a Cloud Profiling Radar (CPR), an Atmospheric Lidar (ATLID), a Multispectral Imager (MSI) and a Broadband Radiometer (BBR), from which many products will be generated on the prope…
View article: EarthCARE level-2 demonstration products from simulated scenes
EarthCARE level-2 demonstration products from simulated scenes Open
Overview The EarthCARE satellite combines four instruments, a Cloud Profiling Radar (CPR), an Atmospheric Lidar (ATLID), a Multispectral Imager (MSI) and a Broadband Radiometer (BBR), from which many products will be generated on the prope…