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Andes-Amazon Project:Hydrology Model-Data Intercomparison
Brad Christoffersen
Nov. 08, 2010Moore Foundation
Key Questions
Water budget partitioning The case of CLM & modifying hydrology structure Was soil physics standardization across models
effective? Do models capture observed ET, runoff partitioning
(Manaus site)? Soil moisture dynamics across models
Are remaining model differences due to physics, or biology?
Are vertical gradients & seasonal variability corroborated by observations?
Hydrology in CLM3.5
Oleson et al., 2008, JGR
water table depth
dW a
dt=qrech arg e−qdrai
q rechaarg e=- k ay zÑ− y10z Ñ− z10
qdrai= 1− f imp qdrai,max exp −2.5zÑ z Ñ= zh ,1025−
W a
0 .2
When Wa = Wa,max = 5000 mm,water table depth = depth of the bottomsoil layer
When water table is below the soil column
One additional water storage variable: Wa
Modified CLM3.5 per Site Simulation Protocol
Oleson et al., 2008, JGR
water table depth
–> Aquifer storage held const = 0
Modified CLM3.5 per Site Simulation Protocol
Oleson et al., 2008, JGR
water table depth
–> Aquifer storage held const = 0
--> Water table depth const > 10 m
Zwt = constant
Modified CLM3.5 per Site Simulation Protocol
Oleson et al., 2008, JGR
water table depth
–> Aquifer storage held const = 0
--> Water table depth const > 10 m
--> Drainage out bottom layer = hydraulic conductivity of bottom layer
Free drainage (= kbot)
Zwt = constant
Modified CLM3.5 per Site Simulation Protocol
Oleson et al., 2008, JGR
water table depth
–> Aquifer storage held const = 0
--> Water table depth const > 10 m
--> Drainage out bottom layer = hydraulic conductivity of bottom layer
--> Soil depth set from 3.5 m to site soil depth
Free drainage (= kbot)
Zwt = constant
Differences in ET seasonality
Subsurface runoffSurface runoff
Soil evapInterception evapTranspiration
Mo
de
l-mo
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J F M A M J J A S O N D
Site PrecipObserved ET
All y-
axis
units a
re m
m/m
onth
J F M A M J J A S O N D J F M A M J J A S O N D J F M A M J J A S O N D
J F M A M J J A S O N D J F M A M J J A S O N D
CLM3 CLM3GW CLM3.5
NOAH IBIS
∑Fluxes + ∆SoilMoisture
J F M A M J J A S O N D
Fluxes:
Modifying hydrology: The case of CLM
Differences in ET seasonality
Subsurface runoffSurface runoff
Soil evapInterception evapTranspiration
Mo
de
l-mo
de
l Inte
rco
mp
ari
so
n
Da
ta-M
od
el In
terc
om
pa
ris
on
J F M A M J J A S O N D
Site PrecipObserved ET
All y-
axis
units a
re m
m/m
onth
J F M A M J J A S O N D J F M A M J J A S O N D J F M A M J J A S O N D
J F M A M J J A S O N D J F M A M J J A S O N D
CLM3 CLM3GW CLM3.5
NOAH IBIS
∑Fluxes + ∆SoilMoisture
J F M A M J J A S O N D
Fluxes:
CLM3.5Aquifer
3.5 m soil depth
0
100
200
300
400
Correct ET seasonality(wrong reason?)
Modifying hydrology: The case of CLM
Surface RunoffSubsurface Runoff
Differences in ET seasonality
Subsurface runoffSurface runoff
Soil evapInterception evapTranspiration
Mo
de
l-mo
de
l Inte
rco
mp
ari
so
n
Da
ta-M
od
el In
terc
om
pa
ris
on
J F M A M J J A S O N D
Site PrecipObserved ET
All y-
axis
units a
re m
m/m
onth
J F M A M J J A S O N D J F M A M J J A S O N D J F M A M J J A S O N D
J F M A M J J A S O N D J F M A M J J A S O N D
CLM3 CLM3GW CLM3.5
NOAH IBIS
∑Fluxes + ∆SoilMoisture
J F M A M J J A S O N D
Fluxes:
CLM3.5Free drainage
3.5 m soil depth
CLM3.5Aquifer
3.5 m soil depth
0
100
200
300
400
Incorrect ET seasonality(what's missing?)
Correct ET seasonality(wrong reason?)
Modifying hydrology: The case of CLM
Surface RunoffSubsurface Runoff
Differences in ET seasonality
Subsurface runoffSurface runoff
Soil evapInterception evapTranspiration
Mo
de
l-mo
de
l Inte
rco
mp
ari
so
n
Da
ta-M
od
el In
terc
om
pa
ris
on
J F M A M J J A S O N D
Site PrecipObserved ET
All y-
axis
units a
re m
m/m
onth
J F M A M J J A S O N D J F M A M J J A S O N D J F M A M J J A S O N D
J F M A M J J A S O N D J F M A M J J A S O N D
CLM3 CLM3GW CLM3.5
NOAH IBIS
∑Fluxes + ∆SoilMoisture
J F M A M J J A S O N D
Fluxes:
CLM3.5Free drainage8m soil depth
CLM3.5Free drainage
3.5 m soil depth
CLM3.5Aquifer
3.5 m soil depth
0
100
200
300
400
Correct ET seasonality(right reason?)
Incorrect ET seasonality(what's missing?)
Correct ET seasonality(wrong reason?)
Modifying hydrology: The case of CLM
Surface RunoffSubsurface Runoff
Was soil physics standardization effective?
JULES ED2 IBIS CLM
Similar pattern & magnitude of water budgets JULES, IBIS, CLM potentially overestimate ET
Manaus K34 - Yes!
Surface RunoffSubsurface Runoff
JULES ED2 IBIS CLM
Evergreen Tapajos K67
JULES ED2 IBIS CLM
Evergreen Tapajos K67
Transitional/Semideciduous Reserva Jaru
JULES ED2 IBIS CLM
Evergreen Tapajos K67
Transitional/Semideciduous Reserva Jaru
Savanna Pe de Gigante
OBS Data from Tomasella & Hodnett 2008
JULES ED2 IBIS CLM OBS
Are predicted budgets consistent with observations? (Manaus K34)
Interlude: Model structure I Infiltration/Surface Runoff:
JULES: Infiltration excess + PFT-dependent infiltration “enhancement factor”
ED2: Infiltration excess + Surface water storage (8-hour lifetime)
IBIS: Green-Ampt wetting front CLM: Infiltration excess + Maximum ponding depth
(10 mm H2O)
Interlude: Model structure I Infiltration/Surface Runoff:
JULES: Infiltration excess + PFT-dependent infiltration “enhancement factor”
ED2: Infiltration excess + Surface water storage (8-hour lifetime)
IBIS: Green-Ampt wetting front CLM: Infiltration excess + Maximum ponding depth
(10 mm H2O)
theta.i theta.swater
soilwetting front
psi = H
z = 0
z = f
Green-Ampt Standard Darcy
ponding depththeta.1, theta.1.sat 1
2
3
Interlude: Model structure II
Rooting dynamics and water extraction: JULES, CLM (& IBIS?): proportional to water
availability & root fraction in each soil layer ED2: proportional to water availability and
maximum rooting depth (by veg. cohort) Consider special case: Homogeneous soil water
profile, (& for ED); mid- to late-successional forest:
Interlude: Model structure II
Rooting dynamics and water extraction: JULES, CLM (& IBIS?): proportional to water
availability & root fraction in each soil layer ED2: proportional to water availability and
maximum rooting depth (by veg. cohort) Consider special case: Homogeneous soil water
profile, (& for ED); mid- to late-successional forest:Fraction of transpiration Fraction of transpiration
Depth (m)
JULES,CLM (& IBIS?)
ED2
0 1 0 1
Soil Moisture Dynamics: Are remaining differences due to
physics or biology?
JULES ED2 IBIS CLM
Green-Ampt Darcy's LawDarcy's LawDarcy's Law
Free drainage Free drainageOther mechanisms?
Free drainage Free drainage
INFILTRATION
BOTTOM BOUNDARY
0.33 0.450.39 0.33 0.450.39 0.33 0.450.39 0.33 0.450.39
Manaus K34
JULES ED2 IBIS CLM
K67
RJA
PDG
0.35 0.45 0.35 0.45 0.35 0.45 0.35 0.45
0.10 0.30
0.05 0.30 0.05 0.30 0.05 0.30 0.05 0.30
0.10 0.30 0.10 0.30 0.10 0.30
What happens in CLM when we implement an ED-like root water uptake scheme?
Free drainagesoil depth 8 m
Root distribution-dependent water stress
Free drainagesoil depth 8 m
Root distribution-independent water stress
Summary & Conclusions
Overall water balance: Encouraging. (Standardization of surface runoff necessary?)
ET Seasonality: All models predict peak of transpiration in dry season; some (ED) predict constant ET year-round.
Soil moisture dynamics: Interesting, important differences among models. IBIS has much higher surface water content ED develops wet season pool near bottom boundary
Discriminating among model mechanisms: Vertical profiles of root water uptake needed (esp. under drought!) Existing soil moisture datasets: Potentially a powerful tool to
discriminate among model mechanisms of root water uptake.
