noah land surface model working group meeting, boulder, 15 july 2007 planned noah changes in wrf...

Noah land surface model working group meeting, Boulder, 15 July 2007

Planned Noah Changes in WRF

• Changes in model physics

• Changes in land surface fields (time-fixed and time-varying)


Unified Noah Land Surface Model in WRF

• Goal: to have one single Noah code in both ARW and NMM WRF codes (to eliminate the option 99 in WRF/NMM code)

• Unify or set options for different treatments of physics/parameters in two Noah codes used in ARW and NMM

• The unified Noah for both ARW and NMM is almost ready to be implemented in the NCAR repository

• Will it be the unified Noah V1.0?

• Most likely ready in coupled WRF for the next major release (March 2008?)


Future Development of Noah Land Surface Model

Subsurface Flow Routing Noah-RouterSubsurface Flow Routing Noah-Router (NCAR Tech Note: Gochis and Chen, 2003)(NCAR Tech Note: Gochis and Chen, 2003)

Saturated Subsurface RoutingSaturated Subsurface RoutingWigmosta et. al, 1994Wigmosta et. al, 1994

Surface Exfiltration fromSurface Exfiltration fromSaturated Soil ColumnsSaturated Soil Columns

Lateral Flow fromLateral Flow fromSaturated Soil LayersSaturated Soil Layers

• New Parameters: Lateral KNew Parameters: Lateral Ksatsat, n – , n –

exponential decay coefficientexponential decay coefficient

• Critical initialization value: water table Critical initialization value: water table depthdepth

• 8-layer soil model (2m – depth)8-layer soil model (2m – depth)

• Quasi steady-state saturated flow model, Quasi steady-state saturated flow model, 2-d (x-,y-configuration)2-d (x-,y-configuration)

• Exfiltration from fully-saturated soil Exfiltration from fully-saturated soil columnscolumns

, 1 30i jSOX dzdx Eβ = − + −1

nz

hhSOLDEP

⎛ ⎞= −⎜ ⎟⎝ ⎠

( )tan

gsize LKSAT SOLDEP

nγ β× ×= xqsub hhγ= ∗


Ball-Berry Scheme in GEM

Jarvis scheme

LAI – Leaf Area Index, F1 ~ f (amount of PAR)F2 ~ f(air temperature: heat stress)F3 ~ f(air humidity: dry air stress)F4 ~ f(soil moisture: dry soil stress)

Ball-Berry scheme in GEM (Gas Exchange Model)

hs – relative humidity at leaf surface ps – Surface atmospheric pressure An – net CO2 assimilation or photosynthesis rateCs – CO2 concentration at leaf surfacem and b are linear coeff based on gas exchange consideration

ns s s

s

Ag m h p b

C= +

sc g

R1

=

€

Rc =Rc _ min

LAI × F1× F2 × F3 × F4

Fundamental difference: evapotranspiration as an ‘inevitable cost’ the foliage incurs during photosynthesis or carbon assimilation

An: three potentially limiting factors: 1. efficiency of the photosynthetic enzyme system2. amount of PAR absorbed by leaf chlorophyll3. capacity of the C3 and C4 vegetation to utilize the photosynthesis products



• Ball-Berry photosynthesis-based canopy resistance (Niyogi, Kumar, Ball-Berry photosynthesis-based canopy resistance (Niyogi, Kumar, Purdue U.) Purdue U.)

• Test in HRLDAS for 2001-2002 is nearly finished Test in HRLDAS for 2001-2002 is nearly finished • Responses of canopy resistance to environmental and soil conditions are fairly different in Jarvis and GEM/photosynthesis formulations.• That leads to large differences in soil moisture and latent heat fluxes.• Incorporation of GEM in Noah is sensitive to description of land use (C3, C4 grass) and vegetation phenology (LAI, vegetation fraction, etc).

GEM model reference: Niyogi, Alapaty, Raman, Chen, 2007: JAMC, in revision.



• Multi-layer urban canopy model (Taha, Multi-layer urban canopy model (Taha, Altostratus Inc; Borenstein, SJSU; Ching, EPA)

• Has not yet started

T int

Q wall

Ts roof

Drainage outside the system

Sensible heat flux

Latent heat flux

Net radiation

Storage heat flux

Anthropogenic heat flux

Precipitation

Roughness approach

Root zone layer

Infiltration

Diffusion

Deep soil layer

Drainage

Drainage network

natural soil

roof

water

Paved surface

bare soil

Surface layer

Drag-Force approach

Rn pav Hsens pav LEpav

Gs pav Ts pav

Noah land surface model working group meeting, Boulder, 15 July 2007 Locations of 68 SCAN sites

The HRLDAS-simulated 2006 soil temperature and moisture were verified against Soil Climate Analysis Network (SCAN) data

Averaged diurnal cycle over 6 SCAN stations in northeast domain

obs6-layers

Using 1-deg2-m air T


MODIS Land-use and other land/vegetation products

USGS land-use MODIS

Data Collection Instrument

AVHRR (Advanced Very High Resolution Radiometer)

MODIS (MODerate resolution Imaging

Spectroradiometer)

Channels 5 channels 15 land surface/vegetation dedicated channels

Data Collection Dates April 1992 – March 1993 January 2001 – December 2001

Reflecting recent land-use change

Data Provider USGS/ORNL Boston University

Classification Scheme Modified USGS Modified IGBP

IGBP used in NPOESS and next-generation NWP models

# of Categories 25* 19*


MODIS vs AVHRR

Red: urban areas in the Pearl River Delta, China

1993 USGS data2001 MODIS data

AVHRR MODIS

Water boundary mapping is different

Pearl River Delta, China

Houston


New land/vegetation Products

• NESDIS 20-year climatology NDVI based products:

– Monthly green vegetation fraction (GVF)

– Monthly albedo

• MODIS land products – 8-day and monthly LAI, GVF,

emissivity, albedo

– Monthly products

• Real-time vegetation products

• We are changing WRF Pre-prosessing System (WPS) infrastructures to handle these and future (realtime) land/vegetation data.

WRF-Noah land-use based LAI, 1 July 2006

MODIS based LAI, 1 July 2006

Fine-scale Urban Data Sets

• Goal: Accommodate more complex urban models

• National Urban Database with Access Portal Tool (NUDAPT) project led by Jason Ching of EPA

• Plan

– Consider these types of data are user specific and not to be included in WRF core data set?

– However, WPS should enable an easy integration of these data.

– change in WPS?


Link between land surface and atmospheric surface layer

• Coupling between skin layer and first model level (depends on roughness lengths and wind speed)

• Surface fluxes are more sensitive to the treatment of roughness length for heat/moisture than to M-O based surface layer schemes themselves

Surface sensible heat flux

Surface latent heat flux

Surface exchange coefficient:


Link between land surface and atmospheric surface layer

• WRF surface layer schemes– MM5 similarity: Based on Monin-Obukhov with Carslon-Boland viscous

sub-layer and standard similarity functions from look-up tables.

– Eta similarity: Used in Eta model. Based on Monin-Obukhov with Zilitinkevich thermal roughness length and standard similarity functions from look-up tables.

– Need to evaluate these surface layer schemes, particularly WRT to nocturnal stable regime. Data sets for such evaluation?

– Other schemes in consideration?

€

Zom

Z ot

= exp(k C R e* )

C = 0.1 (Chen et al.1997, BLM)

€

Zot =Cs /ρCpku*

Cs = 5.97 ×10−5 cal cm−1s−1 (Boland and Carlson,1978, JAM)

noah land surface model working group meeting, boulder, 15 july 2007 planned noah changes in wrf...

Documents