The Noah-MP Land Surface Model

Michael Barlage

Research Applications Laboratory

National Center for Atmospheric Research

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2

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

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

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

Noah-MP: a community land model

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

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

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

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

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

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

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

• 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?

SWdn

shaded fraction

What does that mean visually?SWdn

shaded fraction

Option 1 Option 2

• 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

• 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

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

Datasets: NLCD Land Cover

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

• 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

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

Datasets: 3D Soil Properties

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

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KFLG Forecast Bias (ºC)

Forecast Hour (Initialized at 12Z daily)

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

“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

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