Changes between Version 128 and Version 129 of DevelopmentActivities/ORCHIDEE-DOFOCO

Timestamp:

2017-06-21T09:23:39+02:00 (7 years ago)

Author:

luyssaert

Comment:

--

DevelopmentActivities/ORCHIDEE-DOFOCO

@@ -109 +109 @@
 === CWRR vs Choinell ===
 === Albedo ===
+ORCHIDEE-CN-CAN makes use of a two stream radiative transfer scheme through the canopy. The scheme is based on Pinty et al 2006. This approach accounts not only for the leaf mass but also for the vertical and horizontal distribution of the leaf mass (=canopy structure). In ORCHIDEE-CN-CAN the same scheme is used to simulate the reflected, transmitted and absorbed light. This implies that albedo and photosynthesis are now fully consistent as well as the light reaching the forest floor (the latter is used in for example recruitment). ORCHIDEE-CN-CAN cannot revert to previous approaches for calculating albedo.
+ 
+The radiative transfer through the canopy is controlled by 3 parameters for each wavelength/band: single leaf scattering '''leaf_ssa_xxx''', forward scattering '''leaf_psd_xxx''' and background reflectance '''bgrd_ref_xxx'''. At present VIS and NIR have been parameterized. Parameterization is based on running an inverse radiation scheme on the MODIS albedo product while accounting for the different land cover types. The inverted parameters are provided by the JRC as the JRC TIP product.
+
 === Background albedo ===
+If covered by snow, the background albedo is calculated by the snow module and accounts for snow age and snow density (needs to be checked – last time snow did not account for NIR). If not covered by snow the background albedo is not simulated but prescribed by the parameters '''bgrd_ref_vis''' and '''bgrd_ref_nir'''. In deciduous forest, grasslands and croplands, the background albedo is known to be strongly affected by the phenology and senescence of the understory vegetation. ORCHIDEE-CN-CAN has two options to prescribe the background albedo:
+
+1 - The background albedo is prescribed per PFT but is constant throughout the year. This is the option that has been used in ORCHIDEE-CAN and is the option that has been validated over Europe.
+
+2 - The background albedo varies with time but is constant across PFTs. This option reads background maps. Given that those maps are based on the JRC TIP product, they should be compatible with the new albedo scheme. This option, however, has not been validated yet.
+
 === Single layer vs multi layer energy budget ===