Direct Download (Raster Data Gateway)

Objective: Evaluate the impact of atmospheric nitrogen deposition on various ecosystem components including lichens, tree species (both growth and mortality), mycorrhizal communities, herbaceous plant species (changes in species richness), and leaching.

Data: Deposition data is the 3-year average output from the Total Deposition (TDep) modeling system (https://nadp.slh.wisc.edu/committees/tdep/). TDep uses measurement-model fusion to bias correct modelled estimates (Tdep Program, https://nadp.slh.wisc.edu/committees/tdep/). TDep uses observations of air concentrations from the Clean Air Status and Trends Network (CASTNET) for measurements of dry deposition and observations of precipitation and precipitation chemistry from various National Atmospheric Deposition Program (NADP) networks. These observations are interpolated and used to create seasonal bias surfaces for results generated from CMAQ. Bias-adjusted CMAQ results are then merged with observations to create a set of deposition estimates that better align with measurements than model results alone. The full description of this methodology is available in: Schwede et al., 2014. There is a two year lag between the source data and the TCA Assessment year, so source data 3-year ranges with assessment year in parentheses are: 2016-2018 (2020 assessment), 2017-2019 (2021 assessment), 2018-2020 (2022 assessment), 2019-2021 (2023 assessment), 2020-2022* (2024 assessment) ), 2021-2023* (2025 assessment). *The data used in the 2024 and 2025 assessments had a small gap in western North and South Dakota, which was filled with data from the 2019-2021 product due to the small amount of interannual variability in the region.

Data Format: Raster data are continuous

Units: kg/ha/yr

Spatial Resolution: 400m (resampled from 4km)

Source data: Total Deposition Science Committee (TDep)

Additional Resources:

Details on Method Changes and Source Data Versions

Overview of the Terrestrial Condition Assessment: TCA Hubsite or Landfire Office Hour Presentation

Explore the results of the most recent assessment: TCA Interactive Data Viewer

Learn more about the TCA KPI: TCA Dashboard