Changes between Version 1 and Version 2 of DevelopmentActivities/CMIP6/DevelopmentsCMIP6/albedo

Timestamp:

2016-02-07T12:01:41+01:00 (8 years ago)

Author:

peylin

Comment:

--

DevelopmentActivities/CMIP6/DevelopmentsCMIP6/albedo

@@ -1 @@
-= Optimization of the ORCHIDEE albedo =
+= Optimization of the albedo and Updated formulation for Bare soil fraction =
+
+== New albedo scheme and parameter optimization ==
 
 Main actors: Philippe Peylin, Vladislav Bastrikov
 
-Objectives: 
+'''Objectives:''' 
  - Use observed satellite albedo to calibrate the current albedo scheme (MODIS albedo will be used first)
  - First change the bare soil albedo (currently a function of soil color following a color map from FAO and fixed albedo values for each color type (13))
@@ -13 +15 @@
 http://orchidas.lsce.ipsl.fr/dev/albedo2.php
 
+
+== Potential new calculation of the bare soil fraction (under vegetated areas) ==
+
+Main actors: Nicolas Vuichard, Philippe Peylin, Catherine Ottle, Agnes Ducharne, ...
+
+
+'''Problem:'''
+
+ - Current formulation is f_bs = exp(-LAI/2) 
+ - This formulation lead to a fraction of the vegetmax that is considered (treated) as bare soil being roughly 30% for a LAI=2
+ - We believe it is too much and may have strong consequences (for the albedo, but also the partition transpiration / evaporation)
+
+
+'''Proposed solutions:'''
+
+ - Initially after a round table and investigation of how it is done in other models, Philippe P. proposed to use the same approach but with a coefficient different than 2 (like exp(-LAI/1.))
+ - Nicolas Vuichard pointed that this is rather non physical and that we should seek for something more "physicaly based"
+ - NV proposed to use the approach in the PhD of Goudrian: (equation); Few people need to investigate the approach so that we have a concensus on this solution. 
+
+=> work in progress 
+
+