Input data set: N-Deposition (ISIMIP4)

The nitrogen deposition datasets provide atmospheric inputs of reactive nitrogen for ISIMIP4b impact simulations. They include both wet and dry deposition of reduced nitrogen (NHx) and oxidized nitrogen (NOy), representing the deposition of nitrogen originating from anthropogenic and natural emissions. Nitrogen deposition is required by terrestrial ecosystem, vegetation, and biogeochemical impact models to represent nutrient inputs and associated ecosystem responses. Unlike atmospheric CO₂ concentrations, nitrogen deposition is not diagnosed by emission-driven Earth System Models in CMIP7. Consequently, the same prescribed nitrogen deposition forcing is used for both concentration-driven and emission-driven climate simulations to ensure a consistent representation of atmospheric nitrogen inputs across all ISIMIP4 simulations.

The dataset provides monthly gridded fields of wet and dry deposition for reduced nitrogen (NHx) and oxidized nitrogen (NOy). Variables follow the Input4MIPs conventions and are supplied on a regular global latitude-longitude grid in units of kg N m⁻² s⁻¹. Historical forcing covers the CMIP7 historical period, while corresponding scenario datasets provide future projections consistent with the CMIP7 ScenarioMIP forcing framework. The same deposition fields are applied irrespective of whether the driving climate simulation is concentration-driven or emission-driven.

Nitrogen deposition forcing is taken from the CMIP7 Input4MIPs nitrogen deposition dataset FZJ-CMIP-nitrogen-2-0, developed by Forschungszentrum Jülich and distributed through the Input4MIPs infrastructure. Specifically:

Historical: FZJ-CMIP-nitrogen-2-0 (v20260318)
Future scenarios: FZJ-CMIP-nitrogen-vl-1-0 and FZJ-CMIP-nitrogen-vl-1-0 ( v20260409)

This dataset provides globally gridded monthly fields of wet and dry deposition for NHx and NOy for historical and scenario simulations Documentation is available at:

https://input4mips-cvs.readthedocs.io/en/latest/dataset-overviews/nitrogen-deposition/

The prescribed deposition fields are used unchanged for both concentration-driven and emission-driven CMIP7 simulations because atmospheric nitrogen deposition is an external forcing and may not be interactively calculated by the emission-driven Earth System Models.