Changes between Version 119 and Version 120 of DevelopmentActivities/ORCHIDEE-DOFOCO

Timestamp:

2017-06-20T13:38:46+02:00 (7 years ago)

Author:

luyssaert

Comment:

--

DevelopmentActivities/ORCHIDEE-DOFOCO

@@ -26 +26 @@
 === Allocation ===
 === Diameter classes ===
-Diameter classes were introduced to better simulate the canopy structure. Given that the canopy is the interface between the land and the atmosphere this feature has effects well beyond forest management. Stand structure was observed to affect albedo, transpiration, photosynthesis, soil temperature, roughness length, and recruitment. Using diameter classes adds very little complexity to setting-up the simulations as well as to the output files. The complexity is mostly within the code. 
+Diameter classes were introduced to better simulate the canopy structure, they are a tool to simulate heterogeneity within a single PFT. Given that the canopy is the interface between the land and the atmosphere this feature has effects well beyond forest management. Stand structure was observed to affect albedo, transpiration, photosynthesis, soil temperature, roughness length, and recruitment. Using diameter classes adds very little complexity to setting-up the simulations as well as to the output files. The complexity is mostly within the code. 
 
-The computational cost of using diameter classes is negligible and when a reasonable low number of diameter classes is used, the memory cost remains very small as the dimensions of only two variables are increased. The number of diameter classes is the same for all PFTs and is set by the parameter '''NCIRC'''. ORCHIDEE-CN, ORCHIDEE-CNP, and ORCHIDEE-MICT are all coded and used for NCIRC = 1. ORCHIDEE-DOFOCO and ORCHIDEE-CN-CAN are coded and tested for NCIRC = 3. Until further testing, three diameter classes are considered sufficient.
+The computational cost of using diameter classes is negligible and when a reasonable low number of diameter classes is used, the memory cost remains very small as the dimensions of only two variables are increased. The number of diameter classes is the same for all PFTs and is set by the parameter '''NCIRC'''. ORCHIDEE-CN, ORCHIDEE-CNP, and ORCHIDEE-MICT are all coded and used for NCIRC = 1. ORCHIDEE-CAN and ORCHIDEE-CN-CAN are coded and tested for NCIRC = 3. Until further testing, three diameter classes are considered sufficient.
 
 Given earlier choices in ORCHIDEE, we either need to define the boundaries of each diameter class or the diameter distribution. While developing the code, we considered the second approach the most flexible. To allow maximal flexibility, each diameter class needs to be defined separately by the variable '''CIRC_CLASS_DIST_0000X''', where X is the number of the diameter class. The smallest number presents the smallest diameter class. From literature it is known that a truncated exponential distribution is a good first guess: 
@@ -38 +38 @@
 
 === Age classes ===
+Age classes were introduced to better handle heterogeneity at the landscape level. The feature allows us to distinguish between different successional stages of the same PFT. Age classes are independent of the number of diameter classes. Using age classes adds a lot of details in both the biophysics and the biogeochemistry following natural disturbances, forest management and land cover change. If half of a grassland is afforested with a PFT that already exists in the pixel, previous versions of ORCHIDEE will combine this newly forest land and the existing forest in a single PFT. This will result in a low albedo, a high roughness, ... When age classes are used, the newly afforested and the existing forest will end up in separate PFTs. One will have a high albedo, the other a low, ... 
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+Age classes were defined as separate PFTs and if wanted different age classes of the same PFT could be run with different parameters. This option has not been tested yet because it is expected to result in discontinuities when the biomass is moved from one age class to another. The number of age classes is fixed but for each PFT it can be decided whether age classes are used or not. This adds a lot of flexibility to the model. ORCHIDEE-CAN, for example, has been run with 64 PFTs, using age classes for European forest and using no age classes for all forests outside the domain of interest. Setting-up a simulation with age classes will require some thinking when setting-up the run.def. A python-script was written to create this kind of run.def. Increasing the number of PFTs has important consequences for the speed of the model and the memory use. Because a single run can contain PFTs with and PFTs without age classes, processing of the simulation output needs to account for the relationship between PFTs of the same species but a different age class.
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+The number of age classes is defined by the parameter '''NAGEC'''. Setting this parameter to 1 is a good start unless you have a special interest in using age classes.
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 === CWRR vs Choinell ===