Coupled PPE model output - land parameter impacts on the mean climate state

Terrestrial processes influence the atmosphere by controlling land-to-atmosphere fluxes of energy, water, and carbon. Prior research has demonstrated that parameter uncertainty drives uncertainty in land surface fluxes. However, the influence of land process uncertainty on the climate system remains underexplored. Here, we quantify how assumptions about land processes impact climate using a perturbed parameter ensemble for 18 land parameters in the Community Earth System Model (CESM2) under preindustrial conditions. We find that an observationally-informed range of land parameters generate biogeophysical feedbacks that significantly influence the mean climate state, largely by modifying evapotranspiration. Global mean land surface temperature ranges by 2.2°C across our ensemble (standard deviation = 0.5°C) and precipitation changes were significant and spatially variable. Our analysis demonstrates that the impacts of land parameter uncertainty on surface fluxes propagates to the entire ..., We ran PPEs under preindustrial conditions using two configurations of CESM2: a partially coupled configuration (“coupled”) and an uncoupled, land only configuration (“land-only”). In both the coupled and land-only PPE, the land model (CLM5) was run with prognostic leaf area. The land was initialized with the spun-up land state from the default model parameterization which includes the carbon content of soil and vegetation pools.  In the coupled ensemble, we ran preindustrial simulations with constant greenhouse gas concentrations using an active atmosphere (CAM6) and a slab ocean which is based on q-fluxes from preindustrial simulations of the full dynamic ocean model. Because these simulations have fixed concentrations of greenhouse gasses including CO2, they capture the biogeophysical impacts of land parameters which is the focus of this project, but they do not capture biogeochemical feedbacks.  The land-only simulations used a custom atmospheric forcing, which was generated by CAM6..., , # Coupled PPE model output - land parameter impacts on the mean climate state

## Description of the data and file structure

This dataset is organized into three folders: `coupled_PPE`, `landonly_PPE`, and `doubling_CO2`. `coupled_PPE` and`landonly_PPE` contain monthly model output from the coupled and land only PPEs, respectively, for all output variables used in our analysis. These output variables are land surface temperature (TSKIN), land precipitation (PREC_FROM_ATM), latent heat flux (EFLX_LH_TOT), sensible heat flux (FSH), downwelling shortwave radiation (FSDS), and reflected shortwave radiation (FSR). Data filenames for the PPE are formatted as `VARIABLENAME_timeseries_PPETYPE.nc` (e.g. for the TSKIN data from the coupled PPE, the filename is `TSKIN_timeseries_coupled.nc`). PPE data has dimensions of [time, lat, lon, ensemble_key]. The ensemble keys correspond to different parameter perturbation ensemble members, which are described at . Data from the reference simulation ar...