Impact of spin-up forcing on vegetation states simulated by a dynamic global vegetation model coupled with a land surface model

Authors:

LI Fang ^*1 (李 芳), ZENG Xiaodong ¹ (曾晓东), SONG Xiang ^1;2 (宋 翔),
TIAN Dongxiao ^1;2 (田东晓), SHAO Pu ^1;2 (邵 璞), and ZHANG Dongling¹ (张东凌)
¹ Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029
² Graduate University of Chinese Academy of Sciences, Beijing 100049 

Abstract： 

A dynamic global vegetation model (DGVM) coupled with a land surface model (LSM) is generally initialized using a spin-up process to derive a physically-consistent initial condition. Spin-up forcing, which is the atmospheric forcing used to drive the coupled model to equilibrium solutions in the spin-up process, varies across earlier studies. In the present study, the impact of the spin-up forcing in the initialization stage on the fractional coverages (FCs) of plant functional type (PFT) in the subsequent simulation stage are assessed in seven classic climate regions by a modified Community Land Model’s Dynamic Global Vegetation Model (CLM-DGVM). Results show that the impact of spin-up forcing is considerable in all regions except the tropical rainforest climate region (TR) and the wet temperate climate region (WM). In the tropical monsoon climate region (TM), the TR and TM transition region (TR-TM), the dry temperate climate region (DM), the highland climate region (H), and the boreal forest climate region (BF), where FCs are affected by climate non-negligibly, the discrepancies in initial FCs, which represent long-term cumulative response of vegetation to different climate anomalies, are large. Moreover, the large discrepancies in initial FCs usually decay slowly because there are trees or shrubs in the five regions. The intrinsic growth timescales of FCs for tree PFTs and shrub PFTs are long, and the variation of FCs of tree PFTs or shrub PFTs can affect that of grass PFTs.

Keywords：

Spin-up, vegetation, initial condition, DGVM

Citation:

Li, F., X. D. Zeng, X. Song, D. X. Tian, P. Shao, and D. L. Zhang, 2011: Impact of spin-up forcing on vegetation states simulated by a dynamic global vegetation model coupled with a land surface model. Adv. Atmos. Sci., 28(4), 775{788, doi: 10.1007/s00376-010-0009-0.