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Atmospheric Chemistry, Carbon Cycle and Climate (AC4) logo

Funding Opportunities and Research Priorities

AC4 is a competitive research program, which solicits research proposals typically on an annual basis, starting with the FY2013 announcement released during summer of 2012. In addition, occasionally, the program participates in an interagency call for proposals. Current and past solicitations and research priorities are listed below.

View past AC4 funding opportunities (and those of predecessor programs) below.

In order to continue improving our understanding of urban air composition and to inform mitigation strategies such as in the case of Salt Lake City’s high summer ozone problem, the AC4 program invites proposals for data analysis focused on one or more of the following topics: 

  1. Emission sources and atmospheric processes contributing to urban air quality challenges in Salt Lake City and other urban areas
  2. Influence of NH3 on urban air quality
  3. Regional modeling that improve urban scale processes
  4. Urban monitoring collaboration with local communities with increased risk of the health impacts due to poor air quality on prototyping urban monitoring

Methane Across Scales

In FY23, the AC4 Program is soliciting research proposals focused on methane measurements and modeling across spatial and temporal scales, building on NOAA’s decades long expertise in measuring methane and other greenhouse gases, as well as other AC4 specific investments. Research priorities of this solicitation include urban, regional and global methane concentrations and fluxes, especially as relevant for monitoring, reporting and verification of emissions.

Fire and smoke at the wildland urban interface

In FY22, to build on and expand its previous wildfire investments, the AC4 program invites proposals focused on one or more of the following:

  • Research that puts FIREX-AQ data in a larger, including interannual, context, ideally incorporating data from other field campaigns and measurement networks
  • Applications of JPSS and GOES satellite products to study biomass burning, both within the US and globally
  • Analysis of wildland fire smoke impacts on urban areas and fires at the wildland-urban interface
  • Investigation of emission factors of fires that include household materials

Emissions, Air Quality, and Heat in Urban Areas

In FY21, the AC4 program will focus on a subset of AEROMMA by seeking to support studies of emissions and chemical transformation in the urban atmosphere. Specifically, AC4 plans to support the types of projects that:

  • Determine organics emissions and chemistry, including of understudied VCPs to better understand the impact on ozone and aerosol formation, and to study their relative importance on urban air quality compared to other sources of VOCs such as from energy-related, cooking, and biogenic sources.
  • Determine reactive nitrogen emissions and chemistry in urban corridor(s) (i.e., urban core to suburban and outlying rural areas) to understand the current importance of combustion and non-combustion sources, continue the trend analysis and determine changes in the reactive nitrogen cycle chemistry and its influence on ozone and aerosol formation.
  • Determine the fraction of urban VOC and NOx emissions associated with emissions of CO2 and methane (CH4) from transportation, buildings, industry, and landfills to quantify co-benefits of managing for both air quality and carbon emissions in urban settings.
  • Investigate urban meteorology, to better understand extreme heat on urban air quality, urban heat islands, and the role of long-range transport versus local sources of air pollution.

Atmospheric impacts due to changes in anthropogenic activity during the COVID-19 pandemic

In response to this unique opportunity to study the atmospheric composition effects of the ongoing pandemic in FY21, AC4 and COM programs invite proposals focused on, but not limited to, one or more of the following:

  • Analysis of pandemic-related impacts within individual cities or regions in the United States or impacts of changes in particular anthropogenic activity
  • Comparative studies across different regions or sectors of varying characteristics
  • The use of previously collected and existing in situ measurements
  • Collection of complementary in situ data to fully document atmospheric changes after the pandemic
  • Application of JPSS and GOES satellite products, including identification of best suite of products for assessing and monitoring impacts on national and global scales
  • Development of observational-based datasets (inclusive of satellites, in-situ) or emission inventories, through compilation or integration, that enable analysis of pandemic impacts
  • Identification of atmospheric constituents, which can serve as markers of particular human and/or economic activity – agriculture, shipping, air traffic etc. – as affected by the pandemic disruptions and assessment of its return to previous levels
  • Assessment of the overall magnitude of the event (as measured in changes in emissions and concentrations), and its place in a long term and/or national/global context

Urban atmosphere in a warming climate: chemistry, carbon and composition

In FY20, to continue and expand its investments in the urban atmosphere, the AC4 program invites proposals focused on one or more of the following:

  • Research that builds on previously developed resources, e.g. CO2-USA network, or existing infrastructure to analyze or otherwise explore in depth recently studied cities across the United States
  • Multispecies approach to understanding the urban environment
  • Research with the potential to inform mitigation strategies, especially with regard to co- benefits for air pollution and greenhouse gas reduction
  • Participation in upcoming field efforts in U.S. cities or exploration of novel chemistry and tracers of urban air, although an FY21 solicitation for field efforts is also anticipated
  • Investigation of the evolution of urban air composition in a warming climate

In FY19, the AC4 Program in NOAA’s Climate Program Office solicits proposals that aim to explain various trends, patterns and extremes detectable in the existing long-term observational records.

Features that could be explored include, but are not limited to:

  • Factors influencing gradient of the long-term trends
  • Patterns, anomalies and extremes in long-term trends
  • Intra-and-interannual variability and change
  • Changes in amplitude of seasonal cycle
  • Local or regional changes in the long-term trends

The Role of Reactive Nitrogen in Biogenic VOC Oxidation and Aerosol Formation

In FY18, as part of a continuing interest in the nitrogen cycle, the Atmospheric Chemistry, Carbon Cycle and Climate (AC4) program announcement focuses on laboratory, modeling, and analysis studies (of existing field data) that address one or more of the following priorities:

Features that could be explored include, but are not limited to:

  • Investigate the mechanisms of BVOC oxidation involving reactive nitrogen species in yielding organic nitrogen aerosols and/or their role in NOx removal.
  • Perform complementary chamber and/or laboratory studies to better constrain NO3- BVOC reaction mechanisms and organic aerosol formation.
  • Use relevant satellite products or develop new ones (e.g. formaldehyde), particularly from SNPP/JPSS-1 and their predecessors.

Synthesis Research: Urban Emissions and Emissions from the Oil & Gas Sector

The FY17 AC4 announcement builds on the wealth of collected atmospheric measurements of emissions from oil & gas sector, as well as a number of studies focused on emissions from urban regions to support synthesis efforts, including analysis and modeling of emissions and chemistry. Multi PI projects synthesizing several aspects of a particular geographical region or those which involve a synthesis across several geographical regions with common science objectives are solicited.

Fires in the Western US: Emissions and Chemical Transformations

In FY16, AC4 program solicits proposals focused on Western US fire research relevant to FIREX. Specifically, AC4 plans to support the types of projects that:

  • Collect, analyze and/or model data from FIREX or related field or laboratory experiments
  • Exploit multiple data sets – in situ, remote, and /or satellite, especially from CrIS instrument
  • Focus on the effects of biomass burning on nitrogen cycle
  • Contribute to improving the prediction of smoke from wildfires, especially in NOAA’s Air Quality Forecasting system, via improvements to regional prediction modeling systems that utilize models like CMAQ and WRF-Chem.

Nitrogen cycle improvements in the GFDL Earth System Models

In FY15, AC4 program solicited proposals focused on

  • Improvements to nitrogen cycle representation in GFDL’s Earth System Models.

Observational Constraints on Sources and Sinks of Aerosols and Greenhouse Gases

In FY14, AC4 program solicited proposals targeting research areas including

  • Emissions from Southeast of US
  • Emissions from oil & gas extraction
  • Deposition processes

Interagency carbon cycle call for proposals (under NASA ROSES)

In the carbon cycle interagency call for proposals under NASA/ROSES, NOAA’s participation in (through our AC4 program) focused on “Carbon dynamics within urban-suburban-forested-agricultural landscapes”. The full solicitation included other topics within carbon cycle.

The link to the solicitation is the following:

In FY13, AC4 program solicited proposals targeting research areas including

  • Emissions from urban areas and oil & gas extraction
  • Improvements to CarbonTracker
  • Nitrogen cycle

18 projects were awarded, 40% success rate

(Competition cancelled, no awards were made)


  • Nitrogen cycle


  • Improvements to CarbonTracker
  • Carbon emissions from urban areas
  • Analysis of biogeochemical feedbacks in CMIP5


  • Analysis of CalNex field measurements
  • Formation and transformation of ice nuclei


  • Causes of variability in sources and sinks
  • Future atmospheric carbon dioxide concentrations
  • Ocean carbon cycling, biogeochemical and ecosystem dynamics
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