wiki:Documentation/EvolutionOfFunctionality

Version 3 (modified by luyssaert, 4 years ago) (diff)

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Evolution of the Functionality of the ORCHIDEE model

Table 1. Concise description of processes (in alphabetical order) simulated in subsequent model versions

Process ORCHIDEE Krinner et al 2005 ORCHIDEE v2.1 ORCHIDEE v3.0 ORCHIDEE v4.0
Albedo For each PFT the total albedo for the grid square is computed as a weighted average of the vegetation albedo and the background albedo. The background albedo is composed by a snow and soil albedo. The soil albedo depends on the soil properties. Rather than using soil properties, ORCHIDEE v2.1 uses spatially explicit observation-derived estimates for its background albedo in the absence of snow. Not changed Describe Pinty et al.

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Biogeography & Describe what was done in Krinner et al 2005. & Motivate the changes. Which changes were made?

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Biological volatile emissions & Not applicable & Why was it added? What is added?

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Carbon allocation & Carbon is allocated to the plant following resource limitations (Friedlingstein et al 1999). Plants allocate carbon to their different tissues in response to external limitations of water, light and nitrogen availability. When the ratios of these limitations are out of bounds, prescribed allocation factors are used. & No change

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Energy budget & The coupled energy balance scheme, and its exchange with the atmosphere, is based on that of Dufresne and Ghattas (2009). The surface is described as a single layer that includes both the soil surface and any vegetation. The energy budget is solved with an implicit numerical scheme that couples the lower atmosphere to the surface, in order to increase numerical stability. & No change

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Grass and crop harvest & Describe what was done in Krinner et al 2005. & No change

\bottomhline \end{tabular} \end{table} %\end{sidewaystable*} \normalsize

% Continuation of table 1 \addtocounter{table}{-1} %\begin{sidewaystable} \begin{table} \caption{Continuation of Table 1.} %\begin{tabular}{p{2.5cm} p{7.9cm} p{7.8cm} } \begin{tabular}{p{2.2cm} p{7.6cm} p{7.6cm} } \tophline \bf {Process} & \bf {Description} & \bf {Motivation for change}
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Growth respiration & A prescribed fraction of 28\% of the photosynthates allocated to growth is used in growth respiration (McCree?, 1974). The remaining assimilates are distributed among the various plant organs using an allocation scheme based on resource limitations (see allocation). & No change

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Land cover change & not applicable & Describe why it was added? how is it implemented? Mention it is net land cover change we calculate.

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Maintenance respiration & Maintenance respiration contributes together with growth respiration to the autotrophic respiration. Maintenance respiration occurs in living plant compartments and is a function of temperature, biomass and, the prescribed carbon/nitrogen ratio of each tissue (Ruimy et al., 1996). & No change

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Mortality and turnover & All biomass pools have a turnover time. Living biomass is transferred to the litter pool, litter is decomposed or transferred to the soil pool. & No change.

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Phenology & At the end of each day, the model checks whether the conditions for leaf onset are satisfied. The PFT-specific conditions are based on long and short term warmth and/or moisture conditions (Botta et al., 2000). & No change

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Photosynthesis & C3 and C4 photosynthesis is calculated following Farquhar et al. (1980) and Collatz et al. (1992), respectively. A semi-analytical approach (REF) is used to solve the set of equations for photosynthesis (\hl{units}), stomatal conductivity (\hl{units}) and internal \co2 concentration in the leaf (ppm) at the PFT level. & The semi-analytical solution was replaced by an analytical solution \citep{yin2009}. The Vcmax parameter was redefined as. The analytical solution is faster than the semi-analytical solution and by redefining vcmax, large observational database could be used to parameterize the model.

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Product use & Not applicable & Why was this added? How is it calculated?

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% Continuation of table 1 \addtocounter{table}{-1} %\begin{sidewaystable} \begin{table} \caption{Continuation of Table 1.} %\begin{tabular}{p{2.5cm} p{7.9cm} p{7.8cm} } \begin{tabular}{p{2.2cm} p{7.6cm} p{7.6cm} } \tophline \bf {Process} & \bf {Description} & \bf {Motivation for change}
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Roughness & [COMMENT: It is calculated every half-hour but none of its drivers varies within a day. Should we leave it here or move it up to table 1?] & Rougness is observed to be different for heat and momentum. Also the roughness is driven by the leaf area. The formulation of Shu et al.is now used to account for the leaf area when calculating a separate roughness length for heat and momentum.

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Routing & Not applicable & Why was it added? How is it calculated in ORCHIDEE \vv. \citep{NgoDuc2007}? What is the spatial scale?

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Senescence & Describe how senescence is calculated in Krinner et al 2005. & No change

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Snow temperature and dynamics & Describe snow energy budget in Krinner et al 2005.? & Why was this changed? How is it calculated now? The snow dynamics and its temperature are calculated at the pixel level?. See Tao
\middlehline Soil hydrology & Describe bucket model. Calculated for X soil columns. & ?Motivation? Vertical water flow in the soil is based on the Fokker \textendash Planck equation that resolves water diffusion in non \textendash saturated conditions from the Richards equation (Richards, 1931). The 4\,m soil column consists of eleven moisture layers with an exponentially increasing depth (D'Orgeval et al., 2008). Bare soil, short vegetation, and tall vegetation each have their own water column.

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Soil and litter carbon and heterotrophic respiration & Following Parton et al. (1988), prescribed fractions of the different plant components go to the metabolic and structural litter pools following senescence, turnover or mortality. The decay of metabolic and structural litter is controlled by temperature and soil or litter humidity. For structural litter, its lignin content also influences the decay rate. & No change

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% Continuation of table 1 \addtocounter{table}{-1} %\begin{sidewaystable} \begin{table} \caption{Continuation of Table 1.} %\begin{tabular}{p{2.5cm} p{7.9cm} p{7.8cm} } \begin{tabular}{p{2.2cm} p{7.6cm} p{7.6cm} } \tophline \bf {Process} & \bf {Description} & \bf {Motivation for change}
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Soil temperature & The soil temperature is computed according to the Fourier equation using a finite difference implicit scheme with seven numerical nodes unevenly distributed between 0 and 5.5\,m (Hourdin, 1992).? How many soil temperature columns did we have before? & The differences in the vertical discretisation between the soil hydrology and soil temperature resulted in difficulties to conserve energy. The soil hydrology and temperature are now calculated on a single vertical discretisation. A separate soil temperature is calculated for the bare soil, short vegetation, and tall vegetation.

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Vegetation distribution & \cite{krinner2005} describes global vegetation by 13 meta-classes (MTCs) with a specific parameter set (one for bare soil, eight for forests, two for grasslands and two for crop-lands) & The implementation of the MTC was generalized such that more than one PFT can be used to represent an MTC. ORCHIDEE \vv uses 13 MTCs to define 15 PFTs.

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Wood harvest & Not applicable & Wood harvest following LUHv2 maps. Wood harvest is accounted for at the PFT level.

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