Post on 07-Jul-2022
Preliminary studies towards a more
realistic root parameterisation
G. Vogel
Lindenberg Meteorological Observatory – Richard Aßmann Observatory G. Vogel September 2012
Current parameterisation
COSMO-DE domain
Lindenberg Meteorological Observatory – Richard Aßmann Observatory G. Vogel September 2012
Percental land use in the COSMO-DE domain
(645 x 645 grid boxes) based on SEAWIFS data
January July
Lindenberg Meteorological Observatory – Richard Aßmann Observatory G. Vogel September 2012
Lindenberg Meteorological Observatory – Richard Aßmann Observatory G. Vogel September 2012
plant cover > 0.85 (forest)
Plant cover > 0.99 (low vegetation) ≥
≥
Lindenberg Meteorological Observatory – Richard Aßmann Observatory G. Vogel September 2012
plant cover > 0.85 (forest)
Plant cover > 0.99 (low vegetation) ≥
≥
Lindenberg Meteorological Observatory – Richard Aßmann Observatory G. Vogel September 2012
Canadell, J. et al. (1996)
Basis representation of root distribution
za
i
z
iiiietAtAtz
,
iia ln
Root biomass za
i
izaz
iiii e
a
tAdzetAtzB
1,
0
Root density
i
ii
a
tAtB ,
A(t): surface root
density of a specific
kind of vegetation
parameter values
known from literature
for a lot of biomes
za
i
ii
ietB
tzBzf
1)(
),()(
,
ii
ii
a
zfzd
ln
3)(1ln)(
(Jackson et al., 1996)
(Arora and Boer, 2003)
Lindenberg Meteorological Observatory – Richard Aßmann Observatory G. Vogel September 2012
ztB
btBbetBtatz zta
exp, 1
ztB
betzf zta
exp11,
b
tB
tatd
33
density profile [kg/m²]
rooting depth [m] (comprising 95% of root biomass)
cumulative root fraction
new structure parameters tB
bta
tB
tAta
B, a ,al: determined
from field measure-
ments for relevant
biomes
Extended formulation (Arora and Boer, 2003)
Lindenberg Meteorological Observatory – Richard Aßmann Observatory G. Vogel September 2012
3/4
LR MM
Science 22 (2002), Vol. 295 no. 5559 pp. 1517-1520
Lindenberg Meteorological Observatory – Richard Aßmann Observatory G. Vogel September 2012
b
Bd
3rooting depth [m]
Use of SEAWIFS based NDVI-ratio for time-scaling
Btrb
td ndvi
3
vvbab vva v
vBaB
B : gridbox-averaged total root biomass
: SAEWIFS-based NDVI-ratio ndvir
: gridbox-averaged vegetation parameters b,: area percentage of vegetation kind
va
Lindenberg Meteorological Observatory – Richard Aßmann Observatory G. Vogel September 2012
Lindenberg Meteorological Observatory – Richard Aßmann Observatory G. Vogel September 2012
plant cover > 0.85 (forest)
Plant cover > 0.99 (low vegetation) ≥
≥
15 May
15 April
15 March
COSMO-DE domain
LAI Rooting depth (old) Rooting depth (new)
Lindenberg Meteorological Observatory – Richard Aßmann Observatory G. Vogel September 2012
Lindenberg Meteorological Observatory – Richard Aßmann Observatory G. Vogel September 2012
Seasonal variation of root biomass
Conclusions and future works
Lindenberg Meteorological Observatory – Richard Aßmann Observatory G. Vogel September 2012
The use of SEAWIFS-based LAI and plant cover values leads to a serious incon-
sistency among the external parameters describing the structural vegetation pro-
perties if the parameterization of the rooting depth is not likewise updated.
Based on an approach by Arora and Boer (2003) the annual cycle of the rooting
depth is made consistent to LAI and plant cover by scaling the total root biomass
with the ndvi-ratio.
Moreover, the approach opens the way for a more plant-specific parameterization
being of interest for the coming TILE-approach.
The current transpiration scheme of the TERRA module should be adapted to the
presented root parameterization. This way, its reliability and usefulness can be
verified in more detail.
Lindenberg Meteorological Observatory – Richard Aßmann Observatory G. Vogel September 2012
Many thanks for your attention!