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A NETWORK OF SCINTILLOMETERS A NETWORK OF SCINTILLOMETERS FOR GROUND-TRUTHING OF SURFACE FLUXES IN NEW MEXICO Jan Kleissl, J. Gomez, S.-H. Hong, W. Defoor, K. Bandy, J.M.H. Hendrickx New Mexico Tech Outline Outline Ground Truthing for

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SLIDE 1

A NETWORK OF SCINTILLOMETERS A NETWORK OF SCINTILLOMETERS FOR GROUND-TRUTHING OF SURFACE FLUXES IN NEW MEXICO

Jan Kleissl, J. Gomez, S.-H. Hong,

  • W. Defoor, K. Bandy, J.M.H. Hendrickx

New Mexico Tech

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SLIDE 2

Outline Outline

  • Ground Truthing for SEBALNM

Ground Truthing for SEBAL

  • Large Aperture Scintillometer (LAS):

Principle of Operation Principle of Operation

  • LASs for Hydrology: The New Mexico

T h LAS N t k Tech LAS Network

  • Preliminary validation results from SEBAL

applied to MODIS for July 2006

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SLIDE 3

Energy Balance at the Earth’s surface

Rnet = H + LE + G Rsd Rlu H

net

Rnet: net radiation

l: longwave; s: shortwave u: upwelling d: downwelling

Rsu

lu

LE

p g g

G: soil / ground heat flux H: sensible heat flux LE: latent heat flux

G

LE: latent heat flux

E b l b d t ti t LE Energy balance can be used to estimate LE: LE = Rnet – G - H

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SLIDE 4

SEBALNM ET from Landsat

SEBAL: Surface Energy Balance Algorithm for Land

April 07 2000 June 16 2002 September 14 2000

0.0

ET (mm/d)

Rio Grande basin, NM

SEBAL: Surface Energy Balance Algorithm for Land

ET

0.0 < 1.0 < 2.0 < 3.0 < 4.0 < 5.0 6 0

E

< 8.0 < 9.0 < 6.0 < 7.0

ld i l H

Hot pixel: ET = 0 H = Rn - G

cold pixel: H = 0

dT

BUT:

T0 dT T

cold

Thot

/

p ah

H c dT r ρ =

( , )

  • z

f LAI α =

Remote sensing algorithms need to be validated using ground-truth measurements

Hong, Kleissl et al. WRR 2006

*

( , , )

ah

  • r

f u z z =

[s m-1]

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SLIDE 5

The NMT LAS network for SEBALNM The NMT LAS network for SEBAL

  • Validate remote sensing sensible heat

fluxes estimates using ground measurements

– Scintillometer: large constrained fp – Scintillometer: large, constrained fp – EC: smaller variable footprint

  • 7 scintillometers installed over arid

and humid transects in NM

  • Derive and calibrate ET maps:

– Index H to surface temperature – LE = Rn – G – H

Scintillometer

dT

EC

T0 dT T

cold

Thot

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SLIDE 6

Locations

Valles Caldera

  • ca o s

S A i SNWR McKenzie Flats G t

K

San Acacia Riparian San Acacia Alfalfa Grants Sevilleta San Acacia

Key:

arid humid

Sevilleta Magdalena Ridge Socorro San Acacia

humid irrigated lava flow t i

MRO EMRTC

mountain

MRO

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SLIDE 7

Sevilleta National Wildlife Refuge

Dry grassland

Aerial Photos

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SLIDE 8

SNWR Intercomparison Studies

Dry grassland

Good agreement for H measured by different LASs and EC

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SLIDE 9

San Acacia Riparian Area

Other Scintillometer t t i N

Magdalena Ridge Mountainous Grassland

transects in New Mexico

Valle Grande, VCNP Base of M-mountain Mountainous Grassland Desert

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SLIDE 10

Coming soon … g

I-25 S A i Alf lf San Acacia Alfalfa Photograph from Indian Hill facing West El Malpais Lava flows Lava flows

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SLIDE 11

Transect overview Transect overview

  • Transect lengths 1.8 – 3.4 km
  • Effective heights 31 - 63 m
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SLIDE 12

Thanks to the Field Crew! Thanks to the Field Crew!

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SLIDE 13

LAS Operation

Scintillation Setup

f Hot surface

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SLIDE 14

LAS Specs LAS Specs

Large Aperture Scintillometer Transmitter Voltage 12 VDC nominal Power 0.5 A maximum Optical wavelength of LED 880 nm (spectral bandwidth at 50% ~ 80nm) Optical power output of LED Maximum 80 mW (IF = 1A), eye safe Beam width ~1 m at 100 m distance Aperture Diameter .152 m Physical dimensions 0.37 m x 0.23 m x 0.32 m Weight 13.5 kg Path Length 250 m – 4500 m g

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SLIDE 15

Scintillometer Data Processing Scintillometer Data Processing

Scintillations

Monin-Obukhov similarity theory in the surface

T,q n St t

theory in the surface layer, e.g.

Structure parameter

2 2 2

C C σ → →

S ll A t (SAS) L A t (LAS)

n T

C C

χ

σ → → Heat flux H

Small Aperture (SAS) ≤ 250 m pathlength Inner length scale Large Aperture (LAS) ≤ 5000 m pathlength

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SLIDE 16

Footprint

Footprint of LAS measurements Footprint

Wind

measurements

  • Model by Hsieh et al. 2000

F t i t i hti f ti

  • Footprint weighting function

for each pixel

Wind

peak of weighting peak of weighting function is usually within 1km x 1km i l f t t pixel from transect center

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SLIDE 17

SEBAL – LAS Intercomparison SEBAL LAS Intercomparison

  • MODIS images: 1 km x 1 km resolution at

MODIS images: 1 km x 1 km resolution at nadir

  • cloud free images centered over NM
  • cloud-free images centered over NM

– June 18, 1100 MST

  • 3 transects in operation:

– Valles Caldera: mountains, grass – Sevilleta: desert – San Acacia: riparian area

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SLIDE 18

SEBALNM-MODIS sensible heat flux SEBAL MODIS sensible heat flux

Valles Caldera Sevilleta San Acacia

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SLIDE 19

Valles C

Results

Caldera

wind

Sevilleta

H [W m-2] LAS SEBAL

VCNP 222-306 221-278

San Ac

Sevilleta 328-376 286 San Acacia 215 112-167

cacia

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SLIDE 20

Conclusions Conclusions

  • NMT-LASNet nearing completion

NMT LASNet nearing completion

NM ideal for ground truthing

  • Large Aperture Scintillometers provide reliable

Large Aperture Scintillometers provide reliable estimates of H over footprints similar to MODIS pixels

  • Future Research:

– Analyze more images & sites – Include surface temperature, downwelling shortwave radiation measurements Calibrate SEBALNM using LASNet – Calibrate SEBALNM using LASNet

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SLIDE 21

Acknowledgements Acknowledgements

  • NSF-EPSCOR
  • USGS – WRRI
  • Field Assistance: Kathy Fleming, Jack Cheney

Fl T d J Cl l Ji Thib l

  • Flux Tower data: James Cleverly, Jim Thibault
  • Site selection:

– San Acacia: Rob Bowman Korky Herkenhoff David – San Acacia: Rob Bowman, Korky Herkenhoff, David Morris – MRO: Dan Klinglesmith VCNP: Bob Parmenter Johnny Albert & Juglio – VCNP: Bob Parmenter, Johnny, Albert, & Juglio, Karen Montgomery (DGPS) – Sevilleta: Renee Robichaud, Mike Friggens El M l i J ff Alb H h l S h l – El Malpais: Jeff Albers, Herschel Schulz

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SLIDE 22

LAS Sensible Heat Fluxes W m-2 LAS Sensible Heat Fluxes W m

Sev

Sev- EC

San A i Valles C ld

VCNP-EC 30 min

Acacia Caldera

6/6 1030-1040

336*

189

226*

no data no data

6/18 1050 1100

219 210

6/18 1050-1100

328

219

213 306±23

210

6/18 1100-1110

376

234

222 222±16

212

7/16 1120-1130

266* 169* 142 44±4 cloudy

* >30% variation in 10 min prior and/or thereafter

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SLIDE 23

Additional variables

d=

wdir deg wspd m s-1 σθ deg L m Rsd W m-2 T_sfc deg C

6/6 1030-1040

343 1.13* 36*

  • 3.3*
  • Sev

=.02, zo =

6/18 1050-1100

356 1.60

CSAT

39

  • 1.57

1008 52.5

6/18 1100-1110

345 3.04 24

  • 1.47

1018 52.9

villet

.03, zU =

6/18 1100 1110

CSAT

7/16 1120-1130

238 1.23* 13*

  • 1.03*

480* 43.2 di d L R d

a

= 2.85m

wdir deg wspd m s-1 σθ deg L m Rsd W m-2

6/6 1030-1040 No data

V Ca

6/18 1050-1100

173 | 151

EC30 | LAS

2.68 | 4.65*

EC30 | LAS

7.9*

  • 1.3

1000

6/18 1100-1110

144 | 155 4.60 | 3.77 11

  • 8.3

1008

Valles aldera

6/18 1100 1110

|

EC30 | LAS

|

EC30 | LAS

7/16 1120-1130

| 205 | 1.76* 22* 781*

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SLIDE 24

Additional variables

d

wdir deg wspd m s-1 σθ deg L m Rsd W m-2

6/6 1000-1030

205 1.16 50.9*

  • 9.3*

No data

San

= 2, zo =

CSAT

LAS

Rnet=630

6/6 1030-1040

244

CSAT

1.08 33.3* LAS

  • 8.8

No data

Rnet=705

Acac

.52, zU =

6/18 1050-1100

7

CSAT

0.86 20 LAS

  • 12.4*

1018

Rnet=726

6/18 1100-1110

20 0.82 31* LAS

  • 7.5*

1030

R t 747

cia

= 6.53m

CSAT

LAS

Rnet=747

7/16 1120-1130

262* 0.75* 12 LAS

  • 1.4*

960

Rnet = 764