Changes between Version 116 and Version 117 of DevelopmentActivities/ORCHIDEE-DOFOCO

Timestamp:

2017-06-20T13:01:16+02:00 (7 years ago)

Author:

luyssaert

Comment:

--

DevelopmentActivities/ORCHIDEE-DOFOCO

@@ -29 +29 @@
 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 affects albedo, transpiration, photosynthesis, soil temperature, roughness length, and recruitment. The computational cost of using diameter classes is negligible and when a reasonable low number of diameter classes is used, the memory cost is also very small. 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.
 
+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. From literature it is known that a truncated exponential distribution is a good first guess: 
+CIRC_CLASS_DIST__00001=9
+CIRC_CLASS_DIST__00002=3
+CIRC_CLASS_DIST__00003=1 
 
-CIRC_CLASS_DIST__00001=1
-#CIRC_CLASS_DIST__00002=3
-#CIRC_CLASS_DIST__00003=1 
+The above declaration implies that 9/13th of the trees will always be in the smallest diameter class, 3/13th will be in the medium class and 1 tree out of 13 will be in the largest diameter class. These ratios are kept throughout the simulations and boundaries of the diameter classes are adjusted to respect this constraint. Consequently, an even-aged stand will be simulated with 3 diameter classes where the diameter of the first class may be, for example, 20.3 cm, the diameter of the second class 20.4 cm and the diameter of the third class 20.5 cm. The same code and set-up allows to simulate, in the same simulation, an uneven-aged stand for the same PFT but in a different pixel with, for example, the smallest diameter 7 cm, the medium diameter 25 cm and the largest diameter 45 cm.
  
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 === CWRR vs Choinell ===