search

metno / emep-ctm

Open Source EMEP/MSC-W model
GNU General Public License v3.0
27 stars 18 forks source link

Expected dynamic range of stomatal resistance (gsto) within Rsurface_mod #91

Closed PaulHamer closed 2 years ago

PaulHamer commented 2 years ago

This might be a difficult question to answer, but I was wondering if anyone knows what the calculated dynamic range of gsto is within Rsurface_mod? I assume that it can be as low as zero during winter, but what are the expected maximum values for forest, grassland, and crop land surface types when in a state of maximum growth?

mifads commented 2 years ago

Hi Paul, Sorry for a late reply; I don't check this webpage so often and just saw this. Anyway, first we need to be careful to distinguish the leaf-level gsto from the big-leaf Gsto, but the relation is smple Gsto = LAI*gsto.

In the file Inputs_DO3SE.csv you can see that gmax is given as 150 mmole (O3)/m2 (PLA) for deciduous forests (DF), and 270 for grass (GR). The LAImax values can be found in Inputs_LandDefs.csv, and are 4 m2(PLA)/m2 for DF and 3.5 for GR (the PLA signifies that we use projected leaf area for LAI).

gmax represents the maximum possible conductance. The values given can be converted to m/s with a factor of ca. 41000 (it is T and P dependent), or cm/s with 4.1e6, so we get:

DF:  gsto = 0.366 cm/s, Gsto = 1.46 cm/s
GR: gsto = 0.659 cm/s, Gsto = 2.3 cm/s

Deposition velocities will be lower than Gsto of course, modified by Ra, Rb, and Gns : see Sect. 8 of the 2012 ACP document. The lowest value of gsto is zero, and occurs at night when we assume the stomata close.

mifads commented 2 years ago

Hopefully this is answered now, so I just close. Re-open if needed.