Applied Hydrology (2011/7/6) Modeling of land surface processes Kenji Tanaka Kenji Tanaka Water Resources Research Center, DPRI, Kyoto University [email protected]Land Surface Process “Land surface processes are those associated with the those associated with the exchange of water and energy between the land surface and between the land surface and the atmosphere and are, therefore, integral components of hydrologic and atmospheric sciences.” (by Bill Crosson (NASA MSFC)) (by Bill Crosson (NASA MSFC)) Hydrological Cycle Hydrological Cycle from GEWEX home page
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Applied Hydrology (2011/7/6)
Modeling of land surface processes
Kenji TanakaKenji TanakaWater Resources Research Center,
Land Surface Process“Land surface processes are those associated with thethose associated with the exchange of water and energy between the land surface andbetween the land surface and the atmosphere and are, therefore, integral components of hydrologic and atmospheric sciences.”(by Bill Crosson (NASA MSFC))(by Bill Crosson (NASA MSFC))
Hydrological CycleHydrological Cyclefrom GEWEX home page
LSS (L d S f S h )LSS (Land Surface Scheme)
In general, Land Surface Scheme (LSS) are designed to solve for the interaction of radiation, energy, momentum,
d ( t ) b t th f d thand mass (water vapor) between the surface and the overlying atmosphere.
LSS also have to deal with the large heterogeneity of the earth's surface and this fact creates great complexity in LSS.
In attempt to provide appropriate lower boundaryIn attempt to provide appropriate lower boundary conditions to the atmosphere, several LSS have been developed and coupled into global-scale and regional-scale atmospheric models in the past decade.
i d
i it tiCanopy energy fluxes
wind
precipitation
Interception b
y gySensible Latent
Top of
Radiative Fluxes
Sh Lby canopycanopy Shortwave Longwave
TranspirationEnergy budget
Th hf ll S f ff
Bare soil energy fluxesSensible Latent
Radiation budget
Throughfall
Infiltration
Surface runoffGroundheat flux
W t b d tDiffusion/drainageHeat exchange
Water budget
Baseflow
Radiation budgetRadiation budget• All surfaces receive short-wave radiation during g
daylight and exchange long-wave radiation continuously with the atmosphere. y p
Energy budgetEnergy budget• Rn is partitioned into fluxes of sensible, latent, p , ,
and gound heat.
• This partitioning is strongly dependent on both the land cover characteristics (landuse) and itsthe land cover characteristics (landuse) and its hydrological state (wet/dry).
• Why energy partitioning is important?R H λE GRn = H + λE + G
H heating lower atmosphereλE h ti iddl t hλE heating middle atmosphereG surface (time lag between RB & EB)
Surface energy balance at different landuseSurface energy balance at different landuse
paddy field forestlElE
H
G
GHH
lake cityGGG
lElE
H
H
H
Water budgetWater budget• Water is exchanged between the atmosphere
and the land surface through the processes of precipitation, evaporation, and transpiration.
• Water is exchanged between the land surface d /l k th h ffand ocean/lake through runoff.
∆S P E R• ∆S = P - E - R P : precipitation(rain/snow) input from atmosphereE : water vapor flux by evaporation and transpirationE : water vapor flux by evaporation and transpirationR : runoff flux by river system and ground water system∆S : change in the surface water and soil moisture
InputSurface meteorological variables(Prec, SWdown, LWdown, Tair, Eair, Wind, Psfc, etc.)Surface parameters(V t ti t S il t LAI fl t t )(Vegetation type, Soil type, LAI, reflectance, etc.)
OutputOutputSurface energy balance components (H, λE, G, etc.)Surface water balance components (Evap Qs Qsb etc )Surface water balance components (Evap, Qs, Qsb, etc.)Surface state variables (Tsoil, SoilMois, SWE, etc.)
Land Surface ModelM l i l b d di i (P i i i Meteorological boundary condition (Precipitation, Temperature, Humidity, Radiation, Wind)
Radiation Water budgetRadiation budget
E
Evaporation
Energy budget
Temperature
Soil moistureRun0off
p
Soil moistureRun0off
LSS for what?LSS for what?
• BC of atmospheric model (energy & radiation balance, friction)
• BC of hydrological model(surface runoff, baseflow)
• Analysis/Predictiontime varying parameters for past/futureseasonal variation + inter annual variation+seasonal variation + inter-annual variation+human impact
History of LSS development• Bucket scheme (1969)
A near surface layer of soil is modeled as a bucket that can be filled by
History of LSS development
A near-surface layer of soil is modeled as a bucket that can be filled by precipitation and snowmelt and emptied by evaporation and by runoff (occurs only when the bucket is full). The evaporation efficiency is a linear function of the amount of water in the bucket below some critical value.
• BATS (1986); SiB (1986); ISBA (1989)The vegetation is treated explicitly as two separate layers, scaling fromThe vegetation is treated explicitly as two separate layers, scaling from the size of real leaves up to the size of a grid element of the atmospheric model.
• PLAID (1989); MOSAIC(1992)PLAID (1989); MOSAIC(1992)The heterogeneity of vegetation cover is treated by mosaic-of tiles with each tile consisting of a single land-use. The grid averaged surface fluxes are obtained by averaging the surface fluxes over each land-use
i ht d b it f ti lweighted by its fractional area.
• SiB2 (1996)A more realistic treatment of the response of stomatal conductance to
i t l f i Gl b l d t t f t ti h l denvironmental forcing. Global data sets of vegetation phenology and associated model parameters are derived from satellite observations.
Present ? Future ?1. How the hydrological cycle in watershed will bey g y
affected due to external disturbance such asclimate change?
2. How the hydrological cycle in watershed will bey g yaffected due to the alteration of land surfacecondition such as deforestation, urbanization?
3. What kind of watershed is strong/ feasible/gadaptable/ sustainable under climate change ?
4. Human activity (flood control, irrigation, release of heat) is also an important part of energy andof heat) is also an important part of energy andwater cycle.
Need for the land surface scheme that can express the actual land surface condition and that is physically based (not black box)
Th ti ti f thThe motivation for the development of SiBUCp
• To represent various land surface condition
• Extension of urbanized areaarea
• Agricultural cropland?
W t B d ?• Water Body?
Land use for the Lake Biwa Basin
• Strategy of model developmentStrategy of model development- basic policy:physically consistent- the element which has different major processthe element which has different major process should be treated distinctly
- but not be too complicatedbut not be too complicated(awareness of application)
• Mount human activity to physical modelirrigation anthropogenic heat land use change- irrigation, anthropogenic heat, land-use change
SiBUC (land surface model)
CComponent1.Green area model2 U b d l2.Urban canopy model3.Water body model
INPUTBoundary Conditions
Zm reference height m
Tm air tempreture at Zm K result
INPUT
Culculate
em vapor pressure at Zm mb
um wind speed at Zm m/s
S↓downwward short-wave radiation
W/m2
T surface temperaturecanopy, ground, water body, roof of building, wall of building, road
Tg ground temperature green area, water body, urban
L↓downward long-wave radiation
W/m2
P precipitation m/s
M interrupted precipitationcanopy, ground, roof ofbuilding, wall of building
W soil moisture contentSurface layer, root zone, recharge zone
F ti l A P t i tiFractional Area Parameterization
S ibl h t l t t h t d t fl• Sensible heat, latent heat, and momentum fluxes are calculated separately for each landuse.
• [F]total=[F]iVi=[F]gaVga+[F]uaVua+[F]wbVwb
Land surface model (SiBUC)( )
Grid box is divided into1.Broadleaf-evergreen trees2.Broadleaf-deciduous trees3 Broadleaf and needle leaf trees
three landuse categories1. Green Area
3.Broadleaf and needle leaf trees4.Needle leaf-evergreen trees5.Needle leaf-deciduous trees6 Sh t t ti /C4 l d
2. Urban Area3. Water Body
6.Short vegetation/C4 grassland7.Broadleaf shrubs with bare soil8.Dwarf trees and shrubsy9.Farmland (non-irrigated)10. Paddy field (non-irrigated)11. Paddy field (irrigated)y ( g )12. Spring wheat (irrigated)13. Winter wheat (irrigated)14 Corn (irrigated)14. Corn (irrigated)15. Other crops (irrigated)
Green Area Model (SiB)Green Area Model (SiB)
T d l th t ti it lf d th b• To model the vegetation itself and thereby calculate the radiation, momentum, heat and water vapor transfer properties of the surface in a consistent way.
• The morphological and physiological characteristics of the vegetation are used c a acte st cs o t e egetat o a e usedto derive coefficients and resistances.
Green area model(SiB)( )• Prognostic variables
temperature (canopy, ground, deep soil)p ( py g p )interception water (canopy, ground)soil wetness (surface, root zone, recharge)
• Surface layeracts as a significant source of direct evaporationacts as a s g ca t sou ce o d ect e apo at owhen the soil surface is wet
• Root zone• Root zoneThe roots are assumed to access the soil moisture from the second layermoisture from the second layer
• Recharge layeracts as a source for hydrological baseflow andacts as a source for hydrological baseflow andupward recharge of the root zone.
Physical Processes expressed in SiBy p• the reflection, transmission, absorption and emission of
direct and diffuse radiation in the visible near infrared anddirect and diffuse radiation in the visible, near infrared and thermal wavelength intervals (radiative transfer)
• the interception of rainfall and its evaporation from the leaf p psurfaces (interception loss)
• the infiltration, drainage, and storage of the residual rainfall in the soil (soil hydrology)in the soil (soil hydrology)
• the control by the photosynthetically active radiation (PAR) and the soil moisture potential over the stomataland the soil moisture potential over the stomatalfunctioning (canopy resistance)
• transfer of the soil moisture to the atmosphere through the l f f h ( )root-stem-leaf system of the vegetation (transpiration)
• the aerodynamic transfer of water vapor, sensible heat and momentum from the vegetation and soil to a referencemomentum from the vegetation and soil to a reference level within the ABL (turbulent transfer)
Turbulent transferTurbulent transfer• Vertical profile of wind speed
d dd diff i iand eddy diffusivity are calculated using different regime in each layer.regime in each layer.
Above transition layerwithin transition layerwithin canopy air spacewithin canopy air spacebelow canopy
• Resistances are calculated byResistances are calculated by integrating the inverse of eddy diffusivity along the transfer pathwaytransfer pathway.
Surface resistancesSurface resistances
• Soil surface resistance is a function of surface soil wetness(dry large)of surface soil wetness(dry large)
• Stomatal resistance of single leaf is a function of PAR flux, leaf
d fi itemperature, water vapor deficit, leaf water potential.
• Single leaf stomatal resistances are• Single leaf stomatal resistances are integrated using leaf angle distribution function to produce bulk canopy resistance.
[ ]*
1( ) p c
c c a g a c
C W r W rE e T e V V
ρλ
⎛ ⎞−= − +⎜ ⎟蒸散 [ ]* ( )c c a g a c
c b br r rγ ⎜ ⎟+⎝ ⎠蒸散
抵抗の概念を用いたバルク式
Wrc : 濡れてる面積Vc : 植物キャノピー率Vga : 緑地面積
蒸散抵抗蒸散抵抗Rc
• 気孔の開閉を支配する因子• 気孔の開閉を支配する因子– PAR強度– 葉面温度– 大気の飽差
葉水ポ シ
ストレス項として表現 : f(Σ)– 葉水ポテンシャル
気孔抵抗
OL θθξππ
∫∫∫2 )sin()(1
dLddPARr
ONf
r s
L
cc
tc θξθξκθθξπ
∫∫∫∑=2
0
2
00 ),,,(
)sin(),()(
1
ストレス項 f(Σ)( )
dLddO
NfLtc θξθθξππ
∫∫∫∑2
2)sin(),(
)(1
気孔抵抗 dLddPARr
Nfr s
cc
θξθξκ
ξ∫∫∫∑=
0
2
00 ),,,(
)(),()(
4
( ) ( ) ( , ) ( )
( )( )
a a l
h
f f T f T e f
T T T T
ψ∑ =4
40 0
( )( )( )
( )( )
( )
l hh
l h
T T T Tf T
T T T T
T T
− −=
− − 0 : ( ) 1
:h
T f T
T
=最適温度
最高限界温度
[ ]
04
0
5
( )
( )
( ) 1 ( )
h
l
T Th
T T
f T h T
−=
−5
:
:
:
lT
h
ψ
最低限界温度
種に依存する定数
気孔が閉じ始める時の水分ポテンシャル[ ]5*
2
( , ) 1 ( )
( )
a a a a
ll
f T e h e T e
fψ ψψ
= − −
−=
1
2
:
:
ψψ
気孔が閉じ始める時の水分ポテンシャル
気孔が開き始める時の水分ポテンシャル
1 2ψ ψ−
Sensible and latent heat fluxesSensible and latent heat fluxes
Fl i ti l t• Flux is propotional to potential difference and inversely propotional to (a e se y p opot o a to (aseries of) resistance.
• Total of evaporation from il ti f fsoil, evaporation of surface
water, transpiration from canopy, evaporation ofcanopy, evaporation of intercepted water is equal to the water vapor flux from canopy air space tocanopy air space to reference height.
Prognostic equation of green area modelPrognostic equation of green area model
W: soil moisture contentM:interrupted precipitationQ:discharge E:evaptranspiraionDgPg E
Ed1
1 2tr d c d cE E E= +
E:evaptranspiraion
Surface layerW1
groundDgPg Eg
D1Q12
Edc1
D ’ lSurface layer
Root zoneW2 D2
Q12
Q23
Edc2
1Q Kz
∂Ψ⎡ ⎤= +⎢ ⎥∂⎣ ⎦
Darcy’s low
Recharge zoneW3
D3
Q3
⎣ ⎦
Paddy field modelPaddy field model• Water depth and water temperature
are addedare added
cccc
c lEHRnt
TC −−=
∂∂
)(gwg
w
gwwwww
www
CTT
kT
C
D
TTklEHRn
t
TDC
−∂
−−−−=
∂∂
)(
)(
dgd
dd
dggw
gww
gg
TTCT
C
TTCD
TTk
t
TC
−=∂
−−=∂∂
ω
ω
• Water depth control (irrigation / drainage)
di t th i t
)( gdt∂
according to the growing stage, optimal / minimum water depthare specifiedPonding irrigationPonding irrigationInternal drainIntermittent irrigation
Irrigation scheme
Water control in farmland
Soil moisture
Days
• Basic concept is to maintain water depth / soil moisture within appropriate ranges for optimal crop growthwithin appropriate ranges for optimal crop growth
• New water layer is added to treat paddy field more accurately
• Application to wheat, corn, soy bean and rice (paddy field) etc…
Irrigation scheme
Water control in paddy field
• Basic concept is to maintain water depth / soil moisture within appropriate ranges for optimal crop growthwithin appropriate ranges for optimal crop growth
• New water layer is added to treat paddy field more accurately
• Application to wheat, corn, soy bean and rice (paddy field) etc…