Model validation: flux sites

Model validation: flux sites- NOAA/ATDD-Tilden Meyers flux data sets

- Components of the surface energy budget:(incoming/outgoing short/longwave radiation,latent, sensible, ground heat flux), plusmeteorological observations and sub-surfacetemperature and soil mositure

- 11 measurement sites across CONUS

- 2+ years of data available (at NCEP)

NOAA/ATDD Surface Flux Network

FP

BV,BP

AZWB,CH

SFBH

MO

GC

CV

NCEP model vs obsMAY 2007

average fluxes

Ft. Peck, MT

H LE

MAY 2007 avg. H, NCEP model vs obs

MAY 2007 avg. LE, NCEP model vs obs

LST verification 07May2006

300

310

LST verification May2006 Mean

For a fully-vegetated surface:

Ch = exchange coefficient (=1/ra)

rs = canopy resistance (inverse canopy cond.)

Using surface fluxes to evaluateland-surface physics formulations

and parametersSensible heat flux (bulk aerodynamic form):

H = cpCh(Tsfc - Tair)Latent heat flux (i.e. Penman-Monteith form):

_______________________LE = (Rn-G) + cp(esfc - eair)/ra

+ (1+rs/ra)

Transpiration processes/parameters:

...e.g., effect of vapor pressure deficit on canopy conductance:

· Better NLDAS results with new VPD option (next pages)

cano

py c

ondu

ctan

ce (

cm/s

)

Vapor pressure deficit (mb)

soy beans(C3)

corn (C4)

Bondville, Ill. flux siteJULY 2006

T>20C,SWDN>600W/m2

current Noah

test Noah

From Chen et al. 1996

Using a narrow range of this tends to overestimate the evaporation during wet periods (spring) and underestimate the evaporation during dry periods (summer).

SMHIGH and SMLOW

BXEXP

To reduce low LH biases during the SummerVapor pressure deficit function

Experimental Design ARM/CART sites • Oklahoma Mesonet sites

• CONTROL• TEST:Seasonal LAI

Root Fraction

Vapor Pressure Deficit Function

SIMULATION PERIOD: OCT 1996 - SEP 1999

ARM/CART

Averaged over 24 ARM/CART sites CONTROL

TEST