to Regional Scales

New Developments in Scintillometry:
Direct Measurement of ET at Field- to Regional Scales
Oscar Hartogensis
EURO-AGRIWAT – March 2016 - Wageningen
Scintillometer measures path-integrated turbulence intensity
Receiver
intensitity
intensitity
Transmitter
time
time
Intensity Fluctuations,
2ln(I)
• Heat Flux, H
• H2O Flux, FH2O
What is a Scintillometer?
Regional (km scale)
Measure H + LvE at Regional-scale
with a bi-Chromatic Scintillometer System or
Optical/Microwave Scintillometer (OMS)
km-scale
Optical part: Large Aperture Scintillometer (LAS)
2
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


n
r
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n
r
1
2
C2 
n
r122 3
I
II
III
From H to ET
H is nice,
but we need
ET !
Water management,
Hydrologists, Farmers,...
H is nice,
but we need
ET !
Colleagues – modeling community
Microwave part: new instrument developed with commercial follow up
RPG: H. Czekala, M. Philipp,
G. Maschwitz, T. Rose
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Frequency: 160.8 GHz (λ=1.86 mm)
Transmitted power: 30 mW
Optics: 300 mm cassegrain (51 dB gain)
Weight: 10kg per unit
Power consumption: ~20W
OMS System Description
OMS method
Ludi et al (2005) BLM117
km-scale
Litfass2013: At regional scale  Ag-landscape (nearly) always heterogeneous
L vE H
L vE 3 H3
LvE 2 H2
L vE 4 H4
L vE 1 H1
L = 4800 m - z = ~50 m
km spatial scale
Litfass2013: Footprint
Scintillometer:
Footprint:
source area of turbulent flux
Eddy Covariance:
km-scale
Litfass2013: H + LvE (ET)
Sensible Heat-flux
Latent Heat-flux (ET)
km-scale
Applications
Urban ET:
Irrigated agriculture;
installation at field edges
Yaqui Valley, Mexico,
C.Watts, JC Rodriguez
Ground truth satellite RS algorithms
km-scale
Field-scale
Measure 1-min H + LvE at field-scale
with a dual-beam Laser Scintillometer and
scalar turbulence measurements
field-scale
Structure Parameter Method (SPM)
𝐹𝑥 =
𝜌𝐾𝐶𝑥2 𝑧1/3
𝐶𝑥2
H2O/CO2 sensor (Licor7500):
 𝐶𝑥2, Structure parameter qx
Laser Scintillometer:
 𝐾𝐶𝑥2 ,
Turbulence exchange
with 𝐾𝐶𝑥2  H & u*
(van Kesteren, 2013)
TransRegio32 – 1min LvE – Response to change in Radiation
LvE: Evapotransipration
Fluxes respond fast (faster than EC can resolve) and with a
delay of ~2min
field-scale
Applications
Light Response Curves based on
6 hours of data :
ET reference for high-res RS:
(1-min scale fits with snap-shot ET estimate RS)
(van Kesteren, 2013)
field-scale
Conclusions:
regional-scale scintillometers:
• Evapotranspiration at large (km2) spatial scales
field-scale scintillometers:
• Evapotranspiration at short (<1-min) temporal scales
Thank you