Abstract
The improvements and validation of several parameterization schemes in the second version of the Beijing Climate Center Atmosphere–Vegetation Interaction Model (BCC_AVIM2.0) are introduced in this study. The main updates include a replacement of the water-only lake module by the common land model lake module (CoLM-lake) with a more realistic snow–ice–water–soil framework, a parameterization scheme for rice paddies added in the vegetation module, renewed parameterizations of snow cover fraction and snow surface albedo to accommodate the varied snow aging effect during different stages of a snow season, a revised parameterization to calculate the threshold temperature to initiate freeze (thaw) of soil water (ice) rather than being fixed at 0°C in BCC_AVIM1.0, a prognostic phenology scheme for vegetation growth instead of empirically prescribed dates for leaf onset/fall, and a renewed scheme to depict solar radiation transfer through the vegetation canopy. The above updates have been implemented in BCC_AVIM2.0 to serve as the land component of the BCC Climate System Model (BCC_CSM). Preliminary results of BCC_AVIM in the ongoing Land Surface, Snow, and Soil Moisture Model Intercomparison Project (LS3MIP) of the Coupled Model Intercomparison Project Phase 6 (CMIP6) show that the overall performance of BCC_AVIM2.0 is better than that of BCC_AVIM1.0 in the simulation of surface energy budgets at the seasonal timescale. Comparing the simulations of annual global land average before and after the updates in BCC_AVIM2.0 reveals that the bias of net surface radiation is reduced from −12.0 to −11.7 W m−2 and the root mean square error (RMSE) is reduced from 20.6 to 19.0 W m−2; the bias and RMSE of latent heat flux are reduced from 2.3 to −0.1 W m−2 and from 15.4 to 14.3 W m−2, respectively; the bias of sensible heat flux is increased from 2.5 to 5.1 W m−2 but the RMSE is reduced from 18.4 to 17.0 W m−2.
Highlights
A land surface model (LSM) is an important tool to simulate the variations of earth surface conditions and to investigate the physical processes involved in land–atmosphere interactions
In BCC_AVIM1.0, the terrestrial carbon cycle was realized via a series of biochemical and physiological processes related to the photosynthesis and respiration of vegetation
Considering the heterogeneous land surface and inhomogeneous precipitation, LSMs should take into account the subgrid variability of topography in a model grid cell to decrease the magnitude of Snow cover fraction (SCF) (Roesch et al, 2001)
Summary
A land surface model (LSM) is an important tool to simulate the variations of earth surface conditions and to investigate the physical processes involved in land–atmosphere interactions. Years to develop a climate system model (CSM) with an integrated LSM to simulate the physical as well as biogeophysical processes of land surfaces. After completion of the CMIP5 experiments, attempts were made to improve the parameterization schemes in BCC_AVIM1.0 related to snow cover, soil freeze/thaw processes, rice paddies, lakes with real depths in a snow–ice–water–soil framework, solar radiation transfer through vegetation canopies, and a prognostic phenology based on the carbon budget of a plant functional type (PFT). The atmospheric forcing to drive BCC_AVIM2.0 in this study for the Great Lakes region and the entire globe is the Princeton global forcing dataset (Sheffield et al, 2006), which was developed for land surface and other terrestrial models, and for analyzing changes in near-surface climate. The ILAMB package was used to evaluate the preliminary performance of BCC_AVIM2.0 in simulating global land surface energy budgets and their seasonal evolutions
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