Air Quality and Greenhouse Gases

AER scientists perform cutting-edge research on atmospheric chemistry, pollutant dispersion, and meteorology for a variety of agencies (e.g. NSF, NASA, NOAA), and they regularly collaborate with scientists at top research universities and federal laboratories. AER’s Air Quality and Atmospheric Composition group is at the forefront of the development, application, and evaluation of air quality models to study the sources and impacts of air pollution, both for basic research and to support government decision making. AER scientists have also pioneered the coupling of Lagrangian particle dispersion models (LPDMs) to customized meteorological fields generated by the WRF model, with an emphasis on the use of the AER-developed WRF-STILT model for the monitoring, reporting, and verification (MRV) of emissions of greenhouse gases at global to urban (~1 km resolution) scales. In addition, AER’s Data Assimilation and Modeling group performs high-resolution meteorological modeling to support numerous air quality and greenhouse gas studies, and AER’s Radiative Transfer group develops and validates satellite retrievals of greenhouse gases and other air pollutants, such as ozone, carbon monoxide, and ammonia.

Our Air Quality and Greenhouse Gas research expertise includes:

  • Photochemical and Air Quality Modeling at Urban to Global Scales
  • High-Resolution and Ensemble Meteorological Modeling
  • Air Quality and Meteorological Data Analysis
  • Lagrangian and Eulerian Dispersion Modeling
  • Emission Modeling
  • Inverse Modeling to Improve Emission Inventories at Urban to Global Scales
  • Chemistry and Impacts of Biomass Burning Smoke
  • Meteorological and Chemical Data Assimilation

Selected Projects

Questions? To discuss your Air Quality challenges, please contact Matthew Alvarado and Thomas Nehrkorn using the Contact Us page.

Selected Projects Details

Identifying and Quantifying Natural Gas Leaks in Boston

AER participated in a Harvard-led study of the contribution of natural gas leaks to emissions of methane in the Boston area. The study, titled "Methane emissions from natural gas infrastructure and use in the urban region of Boston, Massachusetts", was partially funded by the non-profit Environmental Defense Fund (EDF) and published in the prestigious journal Proceedings of the National Academy of Sciences, found that about 2.7% of all natural gas delivered to the region was being lost to leaks from homes, businesses, and electricity generation facilities, substantially more than estimated  by government authorities (1.1%).

The WRF-STILT model used in this project was developed at AER and is the linchpin of multiple GHG-related efforts worldwide. On-going applications of WRF-STILT include studies of methane emissions over the Arctic and of carbon dioxide emissions over the Northeast corridor of the US.

Air Quality Model Evaluation with Surface, Aircraft, and Satellite Data

AER is leading two research projects funded by the NOAA Climate Program Office to investigate the emissions and impacts of the aerosol precursors NH3, NOx, and SO2. These projects use data from NOAA field campaigns, satellite retrievals of NH3, NO2, and SO2, and the recently updated adjoint of the Community Multi-scale Air Quality (CMAQ) model to improve estimates of the emissions of these gases. Our preliminary results, "Evaluating CMAQ Simulations of Ammonia Sources and Impacts using Surface, Aircraft, and Satellite Data", presented at the EPA’s 21st International Emission Inventory Conference, show that correctly specifying the diurnal cycle of agricultural NH3 emissions is critical to the modeling of atmospheric NH3.

Chemistry and Impacts of Smoke from Wildfires and Agricultural Burns

AER’s Aerosol Simulation Program (ASP) has been developed to study the formation of OH, ozone (O3), and secondary organic aerosols (SOA) within young biomass burning smoke plumes. As part of an NSF-funded project, AER has substantially updated the gas-phase chemistry and the SOA formation module in ASP. Comparisons with in situ aircraft observations have shown good agreement with ASP and have provided information on the chemical behavior of the unidentified organic compounds in smoke plumes. Under a NASA-funded project, this modeling is being extended to the fires sampled during the Studies of Emissions and Atmospheric Composition, Clouds and Climate Coupling by Regional Surveys (SEAC4RS) campaign.

Arctic Greenhouse Gas Inventory Verification

AER is leading the meteorological and atmospheric transport modeling for the NASA Carbon in Arctic Reservoirs Vulnerability Experiment (CARVE), which aims to quantify the fluxes of the greenhouse gases carbon dioxide (CO2) and methane (CH4) between the Alaskan terrestrial ecosystems and the atmosphere. Using a polar variant of WRF-STILT, AER produced high quality meteorological fields and surface influences ("footprints") at a horizontal resolution of 3.3 km over Alaska. These fine-resolution meteorological fields and footprints will support accurate estimates of CO2 and CH4 surface–atmosphere fluxes using CARVE observations.

Studying the Planetary Boundary Layer to Improve Air Quality and GHG Modeling

AER is leading a study of the spatio-temporal variability of the planetary boundary layer (PBL) in the Washington DC – Baltimore, MD urban corridor using ground-based, aircraft, and satellite observations to improve the simulation of the PBL height in the WRF meteorological model. Because the PBL governs the depth to which surface emissions are vertically mixed and transported downstream, observations of its structure and depiction in models are critical to quantifying the sources of pollutants.  Our investigation focuses on the DISCOVER-AQ Washington – Baltimore campaign of July 2011 for which a large suite of ground based micro-pulse lidar (MPL), aircraft High Spectral Resolution Lidar (HSRL), and Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) satellite observations are available to analyze the spatial variability of the PBL height and evaluate the WRF simulations.  The investigation will also include a multi-year assessment of the PBL height variability primarily using measurements from NASA MPLNET.

Advancing the Use of Satellite Observations to Study Air Quality

AER is a leader in the development, validation, and use of satellite retrievals for air quality and atmospheric chemistry studies. AER has worked on the development of trace gas retrievals from NASA’s Tropospheric Emission Spectrometer (TES) for species such as methane, ammonia, formic acid, and methanol. AER has worked closely with scientists at leading research universities to apply these satellite observations to the improvement of atmospheric chemistry models.  AER is also currently leading the development of ammonia and carbon monoxide retrievals from CrIS and their application to NOAA’s CalNex and SENEX air quality studies.

Landmark Study on Earth’s Greenhouse Effect

AER participated in a study, published in Nature, that provided the first direct observation at the surface of the Earth’s increased greenhouse effect due to rising CO2 levels. In this study, an analysis of thermal radiation measurements at two surface locations, one in Oklahoma and one on the North Slope of Alaska, determined that increases in CO2 between 2000 and 2010 led to a rise in the observed thermal radiation, as expected. As each gas in the atmosphere has a particular “fingerprint” with regards to its absorption and emission of different wavelengths of thermal radiation, we were able to distinguish the impact of changes in CO2 from other effects. This study confirms that climate scientists have an excellent understanding of the direct impact of rising greenhouse gases like CO2 on Earth’s radiation energy.