Sensitivity of land-atmosphere fluxes to biogeophysical and biogeochemical parameters in the Community Land Model

Background/Question/Methods

Knowledge about how parameter sensitivities vary across space, time and model outputs are of key importance to not only the modeling community, but also the measurement community as this knowledge can inform observation strategies targeted at reducing prediction uncertainty. Here we apply the Morris method, a basic but efficient way to perform a parameter sensitivity analysis, on 24 biogeophysical parameters in the Community Land Model (CLM), using 200 offline 1.9x2.5 degree global simulations. Model output variables of interest are photosynthetic fluxes, energy fluxes, and hydrologic variables.

Results/Conclusions

We find that the ranking of parameter importance strongly depends on climate (e.g. mean annual temperature and precipitation), geographical locations and seasons. The parameterization of stomatal conductance is particularly important in most locations. We then present results from a second ensemble simulations (80 members) to investigate in particular the sensitivity of land Evapotranspiration (ET) and Gross Primary Productivity (GPP) to key CLM biogeochemical parameters. The performance of the model ensemble against benchmark datasets for ET and GPP will also be examined.