Abstract
Abstract. Canopy structure is one of the most important vegetation characteristics for land–atmosphere interactions, as it determines the energy and scalar exchanges between the land surface and the overlying air mass. In this study we evaluated the performance of a newly developed multi-layer energy budget in the ORCHIDEE-CAN v1.0 land surface model (Organising Carbon and Hydrology In Dynamic Ecosystems – CANopy), which simulates canopy structure and can be coupled to an atmospheric model using an implicit coupling procedure. We aim to provide a set of acceptable parameter values for a range of forest types. Top-canopy and sub-canopy flux observations from eight sites were collected in order to conduct this evaluation. The sites crossed climate zones from temperate to boreal and the vegetation types included deciduous, evergreen broad-leaved and evergreen needle-leaved forest with a maximum leaf area index (LAI; all-sided) ranging from 3.5 to 7.0. The parametrization approach proposed in this study was based on three selected physical processes – namely the diffusion, advection, and turbulent mixing within the canopy. Short-term sub-canopy observations and long-term surface fluxes were used to calibrate the parameters in the sub-canopy radiation, turbulence, and resistance modules with an automatic tuning process. The multi-layer model was found to capture the dynamics of sub-canopy turbulence, temperature, and energy fluxes. The performance of the new multi-layer model was further compared against the existing single-layer model. Although the multi-layer model simulation results showed few or no improvements to both the nighttime energy balance and energy partitioning during winter compared with a single-layer model simulation, the increased model complexity does provide a more detailed description of the canopy micrometeorology of various forest types. The multi-layer model links to potential future environmental and ecological studies such as the assessment of in-canopy species vulnerability to climate change, the climate effects of disturbance intensities and frequencies, and the consequences of biogenic volatile organic compound (BVOC) emissions from the terrestrial ecosystem.
Highlights
Today’s Earth system models (ESMs) integrate ocean, ice sheet, atmosphere, and land surface in order to provide a powerful tool to simulate the Earth’s past, present, and future climates (Drobinski et al, 2012)
The dynamics of the simulated surface fluxes rely on the land surface sub-model that, over the past 40 years, has evolved from a simple bucket model approach towards sophisticated soil–vegetation–atmosphere transfer (SVAT) schemes (Pitman, 2003; Stöckli and Vidale, 2005)
The new scheme calculates the following: (a) within-canopy longwave and shortwave radiation based on a vertical leaf area index (LAI; m2 m−2) profile, (b) a within-canopy and belowcanopy wind profile based on the vertical LAI profile, and (c) the dependency of stomatal resistance and aerodynamic resistance based on the microclimatological conditions along
Summary
Today’s Earth system models (ESMs) integrate ocean, ice sheet, atmosphere, and land surface in order to provide a powerful tool to simulate the Earth’s past, present, and future climates (Drobinski et al, 2012). Several multi-layer SVAT schemes have been proposed and validated with site-level observations (Ogée et al, 2003; Staudt et al, 2011; Haverd et al, 2012; Launiainen et al, 2015) These studies demonstrated that both top-canopy and within-canopy fluxes and micrometeorological profiles could be captured by means of a sophisticated parametrization scheme to describe the vegetation dynamics and the coupling between the atmosphere and the canopy
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