Effects of Implementing the Simple Biosphere Model in a General Circulation Model

TLDR

The Simple Biosphere Model (SiB) simulates land‑atmosphere interactions by explicitly representing vegetation and incorporating biophysical controls on radiation, momentum, sensible, and latent heat exchanges. This study details the implementation of SiB into a modified National Meteorological Center GCM and examines its effects on land‑surface fluxes and near‑surface meteorological conditions. The coupled SiB‑GCM and a control GCM with a conventional hydrological model were run for summer and winter to generate comparable simulations. SiB‑GCM produced a more realistic land‑surface energy partitioning, with higher sensible and lower latent heat fluxes that deepened the daytime planetary boundary layer, reduced continental precipitation, and slightly weakened the 200 mb jet relative to the control GCM.

Abstract

The Simple Biosphere Model (SiB) of Sellers et al. was designed to simulate the interactions between the Earth's land surface and the atmosphere by treating the vegetation explicitly and realistically, thereby incorporating the biophysical controls on the exchanges of radiation, momentum, sensible and latent heat between the two systems. This paper describes the steps taken to implement SiB in a modified version of the National Meteorological Center's global spectral general circulation model (GCM) and explores the impact of the implementation on the simulated land surface fluxes and near-surface meteorological conditions. The coupled model (SiB-GCM) was used to produce summer and winter simulations. The same GCM was used with a conventional hydrological model (Ctl-GCM) to produce comparable "control" summer and winter simulations for comparison. It was found that SiB-GCM produced a more realistic partitioning of energy at the land surface than Ctl-GCM. Generally, SiB-GCM produced more sensible heat flux and less latent heat flux over vegetated land than did Ctl-GCM and this resulted in a much deeper daytime planetary boundary layer and reduced precipitation rates over the continents in SiB-GCM. In the summer simulation, the 200 mb jet stream was slightly weakened in the SiB-GCM relative to the Ctl-GCM results and analyses made from observations.