Ecosystem and climate variability in West Africa – a study using the SSiB4/TRIFFID biophysical/dynamic vegetation model
Yongkang
Xue, University of California, Los Angeles, yxue@geog.ucla.edu
(Presenting)
Guoqiong
Song, University of California, Los Angeles, songhappy@hotmail.com
(Presenting)
Peter
Cox, University of Exeter, UK, p.m.cox@exeter.ac.uk
Steve
Prince, University of Maryland, College Park, MD, sprince@umd.edu
West Africa is a diverse climatic and ecosystem region and suffered the most severe and longest drought in the world during the Twentieth Century since the later 1960s. We apply SSiB4/TRIFFID over West Africa for this study. The TRIFFID is a dynamic vegetation model, in which the relevant land-surface characteristics of vegetation cover and structure are modeled based on the surface carbon balance and the vegetation variables are updates, driven by carbon assimilation, allocation, and accumulation, as well as competition between plant functional types (PFT). SSiB4 is a biophysical model based on surface water and energy balance, with a parameterization scheme to directly relate surface albedo and surface aero dynamic resistances to TRIFFID-updated surface variables, such as LAI, for different PFTs.
The offline SSiB4/TRIFFID is tested using the observed precipitation and reanalysis-based meteorological forcing from 1948 to 2000 with 1 degree horizontal resolution. The results indicate that the simulated spatial distributions of dominator types are generally consistent with the satellite-derived vegetation map, with deficiency in the C3-grass distribution. The simulated LAIs are also compared with satellite derived products. The simulated LAI over the Sahel region exhibits decadal variability very well, consistent with the Sahel drought in the 1970s and the 1980s and partial recovery in the 1990s and the 2000s.
To investigate the mechanism of ecosystem, water, carbon, and radiation interactions, the analysis is conducted to find relationships between simulated LAI and environmental conditions. It is found that the vegetation characteristics simulated by SSiB4/TRIFFID responds primarily to four factors: air temperature, soil moisture, solar short wave and long wave radiation (CO2 is fixed in simulation). Different factors play dominant role for different PFTs over different regions.
Presentation Type: Poster
Poster Session: Ecosystems Science
NASA TE Funded Awards Represented:
Prince, Stephen
Vegetation dynamics in drylands and implications for regional climate: analysis of two decades of observations in the African Sahel