PhD defence Mr Longhui Li

Department of Water Resources


Title of defence

Simulating energy, water and CO2 fluxes at representative desert ecosystems over Central Asia


Quantifying the exchanges of energy, water and CO2 between the land surface and the atmosphere is the principal objective of Land Surface Models. Despite considerable advances in LSMs during the past few decades, predictive ability of the LSMs in dry environments remains low and unsatisfactory, and hindered our ability to understand the interactions of climate and vegetation. Therefore, this thesis is aiming at evaluating the performance of the Common Land Model (CLM) in simulating energy, water and CO2 at desert sites in Central Asia. By comparing the results from CLM against the eddy covariance measured surface flux variables, we found that, in general, the CLM is able to satisfactorily reproduce the energy fluxes at three desert sites in Central Asia but net radiation during night-time was systematically overestimated. We confirmed that more realistic representation of vertical distribution of root in soil profile and the root water uptake function has significant improvements on the simulation of water and carbon fluxes at desert sites. However, the performance of the CLM for simulating carbon flux was site-dependent and varied greatly with time scales and the simulated ecosystem respiration was poorly correlated to the observed one. Overall, the CLM was proven to simulate energy fluxes better than carbon fluxes. We concluded that there is large potential to improve the land surface model when applied in Central Asian desert ecosystems. Generating accurate input information on vegetation coverage, compositions, and improving the ability in estimating leaf area index and integrating our latest understanding on the morphological functions into the current land surface models may greatly help advancing LSMs in desert ecosystems.


Mr Longhui Li was born in Shangnan, Shaanxi, China. He awarded a PhD degree in July 2008 from Chinese Academy of Sciences. During his PhD study, he was invited to conduct collaborative research in agroecosystem modelling in USDA-ARS from Sep. 2006 to Mar. 2007. In 2007, he commenced his second PhD degree in the Institute of Geo-Information Sciences and Earth Observations (ITC), in the Netherlands. After he graduated with his PhD in China, he commenced his postdoctoral research at Laboratory of Science of Climate and Environment (LSCE), in France in July 2008. In LSCE, he mainly undertook the evaluation and improvement of a process-based ecosystem model named ORCHIDEE-STICS (a hybrid model between vegetation dynamic model and crop growth model), and conduct of the model’s sensitivities to agricultural practice management including crop varieties, irrigation, nitrogen application, planting and harvest dates. In May 2010 he moved to Plant Functional Biology and Climate Change Cluster (C3), University of Technology, Sydney (UTS) as an ecosystem modeller. His main role is to improve the description of ecohydrological processes in CABLE (CSIRO Atmosphere-Biosphere Land Exchange) model to better simulate the carbon and energy fluxes within Australia landscapes. In 2011, he was awarded a highly competitive (success rate of 10%) Australia Research Council (ARC) “Discovery Early Career Researcher Award” (DECRA) grant (valued at AUD375,000). The principle effort of this ARC project is to integrate advanced understanding on root functioning into land surface model (LSM) and enhance the response of LSM to drought, which is an essential factor to constrain ecosystem functioning. He was awarded a “Hundred Talent” project (CNY2,600,000) from Chinese Academy of Sciences in 2011, and the key effort is to quantify the carbon and water fluxes from dryland ecosystems in Central Asia.


Event starts: Thursday 23 April 2015 at 15:45
Venue: ITC Auditorium
City where event takes place: Enschede

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