Ent: A global dynamic terrestrial ecosystem model for climate interactions at seasonal to century time scales through coupled water, carbon, and nitrogen dynamics

Ent is a dynamic global terrestrial ecosystem model (DGTEM) under development at the NASA GISS for coupling with atmospheric general circulation models (GCMs). Ent will be capable of predicting the fast time scale fluxes of water, carbon, nitrogen and energy between the land-surface and the atmosphere and the resulting diurnal surface fluxes, seasonal and inter-annual vegetation growth, and decadal to century scale alterations in vegetation structure and soil carbon and nitrogen. Canopy radiative transfer, biophysics, biogeochemistry, and ecological dynamics will be integrated in a consistent, prognostic, process-based manner, in a way that is both biologically realistic and computationally efficient, and suitable for two-way coupling and parallel computing in GCMs. Canopy radiative transfer is derived from the Geometric-Optical Radiative Transfer (GORT) model (Ni, et al., JGR, 102(D24): 9,555-29,566, 1997); biophysics combines the dynamic construction/destruction of the photosynthetic apparatus of Kull and Kruijt (Adv. Water Resources Res, 24:745-762, 1998) with stomatal conductance of Ball and Berry (Plant Phys., 77(Suppl. 4):91, 1985); dynamic allocation of plant carbon and nitrogen; CASA soil biogeochemistry with extended soil depth (Potter, et al., GBC, 7(4):811-841); and community dynamics of Moorcroft, et al. (Ecol. Monographs, 71(4):557-586, 2001). The model can be used for both assimilation of satellite data and with the GISS GCM for long-term climate studies. Ent will be a standalone set of modules that can be used by the climate modeling community to couple with land surface models and atmospheric GCMs for studies on seasonal weather evolution, vegetation phenology, the carbon budget, climate variability, paleoclimate, global change, vegetation-climate feedbacks, and astronomical biosignatures. Ent is envisioned as a tool for understanding the conditions and signatures of habitability of the Earth, ancient, modern, and future.