A5019950252- Atmospheric chemistry and aerosols
- Atmospheric and Environmental Gas Dynamics
- Atmospheric Ozone and Climate
- Air Quality Monitoring and Forecasting
- Air Quality and Health Impacts
- Cardiac, Anesthesia and Surgical Outcomes
- Aortic aneurysm repair treatments
- Climate variability and models
- Atmospheric aerosols and clouds
- Vehicle emissions and performance
- Synthetic Aperture Radar (SAR) Applications and Techniques
- Maritime Transport Emissions and Efficiency
- Climate Change and Health Impacts
- Calibration and Measurement Techniques
- Geophysics and Gravity Measurements
- Remote-Sensing Image Classification
- Hydrocarbon exploration and reservoir analysis
- Aeolian processes and effects
- Clinical Nutrition and Gastroenterology
- Methane Hydrates and Related Phenomena
- Environmental Justice and Health Disparities
- Vascular Procedures and Complications
- Radiative Heat Transfer Studies
- Remote Sensing and LiDAR Applications
- Global Health Workforce Issues
Dalhousie University
2012-2023
Washington University in St. Louis
2020-2022
Environment and Climate Change Canada
2022
University of British Columbia
2022
University of Southampton
2022
Ambient fine particulate matter (PM2.5) is a leading environmental risk factor for premature mortality. We use aerosol optical depth (AOD) retrieved from two satellite instruments, MISR and SeaWiFS, to produce unified 15-year global time series (1998–2012) of ground-level PM2.5 concentration at resolution 1° x 1°. The GEOS-Chem chemical transport model (CTM) used relate each individual AOD retrieval PM2.5. Four broad areas showing significant, spatially coherent, annual trends are examined...
Abstract Nitrogen dioxide (NO 2 ) is an important contributor to air pollution and can adversely affect human health 1–9 . A decrease in NO concentrations has been reported as a result of lockdown measures reduce the spread COVID-19 10–20 Questions remain, however, regarding relationship satellite-derived atmospheric column data with health-relevant ambient ground-level concentrations, representativeness limited ground-based monitoring for global assessment. Here we derive spatially...
Abstract Satellite-based estimates of ground-level nitrogen dioxide (NO 2 ) concentrations are useful for understanding links between air quality and health. A longstanding question has been why prior satellite-derived surface NO biased low with respect to ground-based measurements. In this work we demonstrate that these biases due both the coarse resolution previous satellite products inaccuracies in vertical mixing assumptions used convert satellite-observed tropospheric columns...
Abstract Satellite observations offer information applicable to top‐down constraints on emission inventories through inverse modeling. Here we compare two methods of modeling for emissions nitrogen oxides (NO x ) from dioxide 2 columns using the GEOS‐Chem chemical transport model and its adjoint. We treat adjoint‐based 4D‐Var approach estimating as a benchmark against which evaluate variations mass balance method. use synthetic NO generated known serve “truth.” find that error in inversions...
Abstract We evaluate two inverse modeling methods by conducting inversion experiments using the GEOS‐Chem chemical transport model and its adjoint. simulate synthetic NH 3 column density as observed Cross‐track Infrared Sounder over North America to test ability of iterative finite difference mass balance (IFDMB) four‐dimensional variational assimilation (4D‐Var) recover known emissions. Comparing more rigorous 4D‐Var method, IFDMB approach requires 3–4 times lower computational cost yields...
Abstract. Modeling atmospheric chemistry at fine resolution globally is computationally expensive; the capability to focus on specific geographic regions using a multiscale grid desirable. Here, we develop, validate, and demonstrate stretched grids in GEOS-Chem model its high-performance implementation (GCHP). These are specified runtime by four parameters that offer users nimble control of region refined refinement. We validate stretched-grid simulation versus global cubed-sphere...
We investigate socioeconomic disparities in air quality at public schools the contiguous US using high resolution estimates of fine particulate matter (PM
On 20 February 2001, a converted Russian ICBM delivered Odin, small Swedish satellite, into low Earth orbit. One of the sensors onboard is Canadian spectrometer called OSIRIS. By measuring scattered sunlight from Earth's horizon, or limb, OSIRIS able to deduce abundance trace gases and particles upper troposphere lower thermosphere. Designed built on modest budget, has exceeded not only its 2-yr lifetime but also all expectations. With more than decade continuous data, recorded over 1.8...
Abstract. A critical step in satellite retrievals of trace gas columns is the calculation air mass factor (AMF) used to convert observed slant vertical columns. This requires a priori information on shape profile. As result, comparisons between satellite-retrieved and model-simulated column abundances are influenced by profile shape. We examine how differences simulated profiles can impact interpretation performing an adjoint-based four-dimensional variational (4D-Var) assimilation synthetic...
Abstract. Accurate representation of surface reflectivity is essential to tropospheric trace gas retrievals from solar backscatter observations. Surface snow cover presents a significant challenge due its variability and thus snow-covered scenes are often omitted retrieval data sets; however, the high reflectance potentially advantageous for retrievals. We first examine implications on upcoming TEMPO geostationary instrument North America. use radiative transfer model how an increase in...
[1] We evaluate climatologies of upper tropospheric ozone and nitric acid retrieved from two satellite instruments (ACE-FTS OSIRIS) with long-term in situ measurements aircraft (MOZAIC, CR-AVE, PRE-AVE, PEM Tropics, TC4) ozonesondes. A global chemical transport model (GEOS-Chem) is used to guide the evaluation relate sparse retrievals. Both retrievals generally reproduce broad features troposphere such as summer enhancements northern subtropics larger concentrations over tropical Atlantic...
ADVERTISEMENT RETURN TO ISSUEViewpointNEXTA Satellite-Based Multi-Pollutant Index of Global Air QualityMatthew J. Cooper*†, Randall V. Martin†‡, Aaron van Donkelaar†, Lok Lamsal§∥, Michael Brauer⊥, and Jeffrey R. Brook‡View Author Information† Dalhousie University, Halifax Nova Scotia, Canada. B3H 3J5‡ Harvard-Smithsonian Center for Astrophysics, Cambridge, Massachusetts, 02138, United States§ Universities Space Research Association, Columbia, Maryland 21044, States ∥ Atmospheric Chemistry...
Abstract This paper interprets tropical tropospheric nitric acid columns from the Infrared Atmospheric Sounding Interferometer (IASI) satellite instrument with a global chemical transport model (GEOS‐Chem). GEOS‐Chem and IASI generally agree over ocean to within 10%. However, simulation underestimates Southeast Asia by factor of 2. The regional bias is confirmed comparing additional (High Resolution Dynamics Limb Sounder, Chemistry Experiment Fourier Transform Spectrometer) aircraft (Pacific...
Abstract Satellite observations from three instruments (Microwave Limb Sounder, Optical Spectrograph and Infrared Imaging System, Atmospheric Chemistry Experiment Fourier Transform Spectrometer) reveal coherent patterns of low ozone events (<20 ppb) in the tropical upper troposphere. Using a chemical transport model (GEOS‐Chem), we find that these result deep convective processes rapidly air with concentrations marine boundary layer. These occur greater frequency over South Pacific warm...
Abstract Retrievals of nitrogen dioxide (NO 2 ) and other trace gases from satellite measurements rely on accurate calculation an air mass factor (AMF) to account for the atmospheric light path. Scattering absorption sunlight by aerosols affects AMFs impacting sensitivity satellite‐observed radiances NO at different altitudes. Current retrievals either do not explicitly these effects or aerosol information external source. Here we investigate a method quantifying impact using Absorbing...
High rain events in the western tropical Pacific were identified using Tropical Rainfall Measuring Mission (TRMM) 3B42 gridded rainfall data set. Horizontal wind measurements from radiosonde arrays, cloud top frequency CALIPSO, and ozonesonde SHADOZ used to construct anomaly patterns of divergence, frequency, ozone mixing ratio about high events. The observed divergence pattern was compared with produced by Goddard Earth Observing System version 4 (GEOS‐4) GEOS‐5 assimilated meteorological...
Abstract. Modeling atmospheric chemistry at fine resolution globally is computationally expensive; the capability to focus on specific geographic regions using a multiscale grid desirable. Here, we develop, validate, and demonstrate stretched-grids in GEOS-Chem model its high performance implementation (GCHP). These grids are specified runtime by four parameters that offer users nimble control of region refined refinement. We validate stretched-grid simulation versus global cubed-sphere...
<h3>Background:</h3> The association between socioeconomic status (SES) and outcomes after abdominal aortic aneurysm (AAA) repair in publicly funded health care systems is poorly described. purpose of this study was to determine the effect SES on postoperative patients who underwent AAA Nova Scotia, Canada. <h3>Methods:</h3> We performed a retrospective analysis all elective repairs Scotia November 2005 March 2015 using administrative data sources. compared 30-day long-term survival across...
Abstract. Accurate representation of surface reflectivity is essential to tropospheric trace gas retrievals from solar backscatter observations. Surface snow cover presents a significant challenge due its variability; however, the high reflectance advantageous for retrievals. We first examine implications on upcoming TEMPO geostationary instrument North America. use radiative transfer model how an increase in changes sensitivity satellite NO2 lower troposphere. find that substantial fraction...