the noah-mp land surface model · noah-mp physical processes noah-mp is a land surface model that...
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The Noah-MP Land Surface Model
Michael Barlage
Research Applications Laboratory
National Center for Atmospheric Research
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Conceptual Land Surface Processes
Gravitational Flow
Internal Soil
Moisture Flux
Internal Soil
Heat Flux
Soil Heat Flux
Precipitation
Condensation
on
bare
soil
on
vegetation
Soil Moisture
Flux
Runoff
Transpiration
Interflow
Canopy Water
Evaporation
Direct Soil
Evaporation
Turbulent Heat Flux to/from
Snowpack/Soil/Plant Canopy
Evaporation
from Open Water
Deposition/
Sublimation
to/from
snowpack
D Z = 10 cm
D Z = 30 cm
D Z = 60 cm
D Z = 100 cm
Snowmelt
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Land Surface Models: Summary
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• Land surface models have been used as stand-alone eco-hydrology
models or as boundary conditions for atmospheric and hydrology
models
• Land surface models exist within a wide spectrum of complexity
• Land surface models can be broken down into two parts:
• Physics: approximating the complex real world by a set of
physically-based (hopefully) equations
• Parameters: adapts the approximated physics to work for
heterogeneous surfaces (vegetation/soil/etc.)
• More complex physics tends to produce more parameters
• Current generation LSMs aim to
• improve surface representation especially when significant
heterogeneities exist
• provide land surface process-level information (e.g., multiple surface
temperatures) to an expanding user base
• test multiple process representations in one model
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Noah LSM in NCEP NAM/GFS/CFS, NCAR MM5/WRF Models
Also operational models in Korea, China, Taiwan
Noah-MP LSM in WRF and NCEP CFS and WRF/Hydro
Snow (x,y,z)
Reality
Tcan(x,y,z)
Tsnow(x,y,z)
Model Structural Differences
Tg(x,y)Tbc(x,y,z)
Snow
Noah
Snow
Noah-MP
Tcan
Tsnow(z)Tbc Tg
Tskin
Single surface
temperature
Multiple surface temperatures
and distinct canopy
Tleaf
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Absorbed SW Sensible Heat
• Comparison of observed (O), Noah (N), and Noah-MP (M).
• Noah has less absorbed solar radiation resulting in colder surface and lower
(or negative) sensible heat flux
Noah and Noah-MP LSM Structure Comparison
O
N
M
Jan 2007
O
N
M
Chen, et al. 2014
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Noah-MP: a community land model
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Noah-MP is a land surface model
that allows a user to choose
multiple options for several
physical processes
• Canopy radiative transfer with shading geometry
• Separate vegetation canopy
• Dynamic vegetation
• Vegetation canopy resistance
• Multi-layer snowpack
• Snowpack liquid water retention
• Simple groundwater options
• Snow albedo treatment
• New frozen soil scheme
• New snow cover
SHbare
θgbθgv
θcanopyθleaf
θatmθatm
SHveg
Noah-MP Physical Processes
Vegetated Unvegetated
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LH
Tg
Tcanopy
Noah-MP: Surface Energy Budget
SWdn – SWup + LWdn – LWup (Tsfc)
= SH(Tsfc) + LH(Tsfc) + G(Tsfc)
SWdn,LWdn: input shortwave and longwave
radiation (external to LSM)
SWup : reflected shortwave (albedo)
LWup : upward thermal radiation
SH : sensible heat flux
LH : latent heat flux (soil/canopy
evaporation, transpiration)
G : heat flux into the soil
SH
G
SWdn SWup
LWdn LWup
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Noah-MP is a land surface model
that allows a user to choose
multiple options for several
physical processes
• Canopy radiative transfer with shading geometry
• Separate vegetation canopy
• Dynamic vegetation
• Vegetation canopy resistance
• Multi-layer snowpack
• Snowpack liquid water retention
• Simple groundwater options
• Snow albedo treatment
• New frozen soil scheme
• New snow cover
aquifer
4-layer soil
3-layer snow
snow oncanopy
Noah-MP Physical Processes
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KD F
t z z zq
q q¶ ¶ ¶ ¶æ ö= + +ç ÷
¶ ¶ ¶ ¶è ø
( ) ( )t
T TC K
t z zq q
¶ ¶ ¶æ ö= ç ÷
¶ ¶ ¶è ø
Soil Moisture
- Richards Equation for soil water movement
- D, K functions (soil texture, soil moisture)
Fq- represents sources (rainfall) and sinks (evaporation)
Soil/Snow Temperature
- C, tK functions (soil texture, soil moisture)
- Soil temperature information used to compute ground heat flux
Noah-MP: Soil Water/Energy Transfer
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Noah-MP Physical ProcessesNoah-MP is a land surface model
that allows a user to choose
multiple options for several
physical processes
• Canopy radiative transfer with shading geometry
• Separate vegetation canopy
• Dynamic vegetation
• Vegetation canopy resistance
• Multi-layer snowpack
• Snowpack liquid water retention
• Simple groundwater options
• Snow albedo treatment
• New frozen soil scheme
• New snow cover
SWdn
shaded fraction
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Noah-MP has a separate canopy and uses a two-stream radiative
transfer treatment through the canopy
• Canopy parameters:– Canopy top and bottom
– Crown radius, vertical and horizontal
– Vegetation element density, i.e., trees/grass leaves per unit area
– Leaf and stem area per unit area
– Leaf orientation
– Leaf reflectance and transmittance for direct/diffuse and visible/NIR radiation
• Multiple options for spatial distribution– Full grid coverage
– Vegetation cover equals prescribed fractional vegetation
– Random distribution with slant shading
SWdn
shaded fraction
Noah-MP: more physics, more parameters
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More modelistic view of Noah-MP
LAI
SAI
Direct (visible,NIR)
Diffuse (visible,NIR)
ρL (VIS/NIR)
τL (VIS/NIR)
Reflectance and transmittance
of individual leaf elements
defined by vegetation typeθz
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• Over a Noah-
MP grid,
individual tree
elements can
be randomly
distributed and
have
overlapping
shadows
SE Minnesota in Google Maps
What interesting things can we do?
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SWdn
shaded fraction
What does that mean visually?SWdn
shaded fraction
Option 1 Option 2
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• Using prescribed vegetation fraction
varying from 5% to 100% as radiation
fraction
• Increasing vegetation fraction
increases snow, decreases albedo
SWdn
shaded fraction
Option 1
Noah-MP LSM Options
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• Using randomly distributed shadows as radiation-active fraction using sun angle
• Complex interaction between vegetated and shadowed fraction and canopy/snow radiation absorption
Noah-MP LSM OptionsSWdn
shaded fraction
Option 2
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Key Input to the Noah-MP LSM
• Land-cover/vegetation classification
– Many sources, generally satellite-based and general
• Soil texture class
– Also general with large consolidations
• Many secondary parameters that can be specified as function of the above
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Datasets: NLCD Land Cover
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Parameters: Land Cover
MPTABLE.TBL
contains a look-up
table for vegetation
classes
Limitations:
All pixels with the
same vegetation
have the same
parameters
Modifying
parameters affects
all vegetation of the
same type
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• Vegetation varying in time and space
• Comparison of MODIS LAI to default table-based LAI
MODIS 1km Leaf Area Index Climatology
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Datasets: Soil Texture
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Parameters: Soil Texture
SOILPARM.TBL contains a look-up table for soil texture classes
Limitations:
All pixels with the same soil type have the same parameters
Modifying parameters affects all soil of the same type
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Datasets: 3D Soil Properties
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Conclusions
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• Land surface models are evolving to address
structural deficiencies and to expand user bases
• Evolving land surface model structure is leading to
new challenges, e.g., parameters, parameters!
• Knowledge of both model structure and parameter
assumptions is useful to properly use an LSM
• Continued progress is being made on extensions to
Noah-MP: crop and dynamic vegetation modules,
urban coupling, parameter estimation
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Flagstaff WRF/Noah
v3.2 T2m simulation
(red) compared to
METAR
observations(black)
• Cold bias during the day results
from capped surface temperature
at freezing
• Bias recovers during the night
• When snow is gone, bias is low
Challenges for Noah LSM StructureD
ays in F
eb
FE
B1
FE
B1
3
F
EB
20
FE
B2
7
KFLG Forecast Bias (ºC)
Forecast Hour (Initialized at 12Z daily)
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1. Leaf area index (prescribed; predicted)
2. Turbulent transfer (Noah; NCAR LSM)
3. Soil moisture stress factor for transpiration (Noah; SSiB; CLM)
4. Canopy stomatal resistance (Jarvis; Ball-Berry)
5. Snow surface albedo (BATS; CLASS)
6. Frozen soil permeability (Noah; Niu and Yang, 2006)
7. Supercooled liquid water (Noah; Niu and Yang, 2006)
8. Radiation transfer:
Modified two-stream: Gap = f(3D structure; solar zenith angle; ...) ≤ 1-GVF
Two-stream applied to the entire grid cell: Gap = 0
Two-stream applied to fractional vegetated area: Gap = 1-GVF
9. Partitioning of precipitation to snowfall and rainfall (CLM; Noah)
10. Runoff and groundwater:
TOPMODEL with groundwater
TOPMODEL with an equilibrium water table (Chen&Kumar,2001)
Original Noah scheme
BATS surface runoff and free drainage
More to be added
Total of ~50,000 permutations can be used as multi-physics ensemble members
Noah-MP: a community land modelNoah-MP is an extended version of the Noah LSM with enhanced
Multi-Physics options to address critical shortcomings in Noah
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“Sides of the Box”• A land – atmosphere model (e.g., WRF) is like a box
• Energy, mass, and water flow through the sides of the box
• Must provide this flow to the model running inside the box
• A land surface model (LSM) sits at the bottom of the box
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Noah-MP Calling Structure
Noah-MP
ENERGY
WATER
CARBON
Canopy resistence
- Jarvis
- Ball-Berry
Radiative Transfer
- Two-stream
- Geometric shade
Runoff Options
- Free Drainage
- 2D Aquifer
Vegetation Growth
- Prescribed phen.
- Dynamic Veg.
Example Process Options