Nitrogen Cycle improvements in the GFDL Earth System Models

  • 7 October 2015
  • Number of views: 2948

In FY 2015, CPO’s Atmospheric Chemistry, Carbon Cycle and Climate (AC4) program funded one new multi-institutional award totaling $1.45 million, which consisted of $400,000 in Grants to universities, $974,874 in other awards to universities, and $95,000 in internal NOAA funding to advance Earth System Models. AC4 solicited proposals for a research team focused on improving the representation of the nitrogen cycle in GFDL’s Earth System Models. Proposals were expected to address processes associated with one or more of the following: Improved characterization of reactive nitrogen (Nr) cycling between the atmosphere and the land and/or ocean on diurnal to decadal timescales (particularly focusing on the impacts of agricultural activities); the role of biomass and fossil fuel burning in reactive nitrogen cycling; or the formation of nitrate aerosols.

Anthropogenic activities have profoundly perturbed the natural nitrogen cycle. Present‐day anthropogenic sources of reactive nitrogen (Nr) exceed natural terrestrial production. Major sources of anthropogenic Nr to the atmosphere result from fertilizer use and other agricultural activities, fossil fuel combustion, and biomass burning. Emissions of nitrogen oxides (NOx), ammonia (NH3) and nitrous oxide (N2O) have increased by factors of two to three since 1850. NOx is an important precursor for tropospheric ozone and, together with ammonia (NH3), leads to the production of aerosol particles. These aerosols impact climate by scattering solar radiation, modifying cloud microphysics, and perturbing photochemical oxidant production. Nitrous oxide (N2O) is a potent greenhouse gas and is currently the leading stratospheric ozone depleting substance. Anthropogenic activities have also increased the source of Nr to estuarine and marine systems, both directly and through the deposition of nitrogen‐containing gases, with large consequences for water quality, eutrophication and the carbon cycle.

Modeling and model development is crucial to NOAA’s mission to respond to the societal needs to better predict and project future climate change. Recognizing the substantial effects of nitrogen cycle perturbation on climate, NOAA’s Geophysical Fluid Dynamics Laboratory’s (GFDL) has been working to evolve global climate models into Earth System Models to account for interactions (e.g. land use, emissions, fire, chemistry, ocean acidification) between human activities, ecosystems and climate. This comprehensive examination of the nitrogen cycle representation offers an opportunity for research to guide future development of Earth System models. Past efforts have demonstrated that the most persistent and vexing problems in how global models represent key processes are best tackled by bringing together field experimentalists and remote sensing experts, process modelers, and global-scale modelers together in research teams.

The new competitively selected project to be funded by the AC4 program in 2015 is:

“Reactive Nitrogen Biogeochemical Cycling in the GFDL Earth System Models: Advancing Understanding Atmosphere-Land Interactions Under Change Climate and Land Use,” PI: Larry Horowitz (NOAA Geophysical Fluid Dynamics Laboratory), co-PI: Elena Shevliakova, (Princeton University), co-Is: Duncan Menge (Columbia University), Richard Conant (Colorado State University), Donald Zak (University of Michigan), Jennifer Murphy (University of Toronto).  

AC4 is a program in the Climate Program Office, within NOAA’s Office of Oceanic and Atmospheric Research that supports research on the processes governing atmospheric concentrations of greenhouse gases and aerosols in the context of the Earth System and Climate. To learn more about AC4’s funding opportunities and supported projects, visit:

For a full list of CPO’s grants and awards for 2015, visit:

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