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INTERNATIONAL INSTITUTE FOR GEO-INFORMATION SCIENCE AND EARTH OBSERVATION
SEBS for ILWIS OPEN 3.4
An interface for Surface Energy Balance in ILWIS Open Source (Jul 2007)
Gabriel ParodiWRS - ITC
S. E. B. Models of Agricultural Areas from Earth Observation Data”, Lima, Perú, 13 March 2008
Environment for a SEB operation
Work area and sensor/s definition.
(frequency defines volume of operation)
Requires ground and satellite pre- and post-processing near-real time.
pre-processing:
Satellite : download, calibration, geo-location, atm. Correction + extras
Ground data: meteorological and land properties (depending on adopted SEB)
processing:
Calibration, validation?
Running the selected SEB model and archiving (simplified).
Post-processing
Linking outputs to routines for information distribution in PLEIADeS.
Assisting in reports and eventual performance
From the operational point of view the algorithm itself is a “minor”problem.
S. E. B. Models of Agricultural Areas from Earth Observation Data”, Lima, Perú, 13 March 2008
What we have and can offer to PLEIADeS
Today: SEBS (Beta vesion) Interface in ILWIS Open
source.
When required: Software algorithms adaptations,
interface customization and complementary software
requirements.
Educational and transfer efforts if required.
S. E. B. Models of Agricultural Areas from Earth Observation Data”, Lima, Perú, 13 March 2008
ILWIS 3.4 open
1 July 2007, ILWIS is free of charge ('as-it-is‘) as open source software (binaries and source code) under the 52°North initiative (GPL license). This software version is called ILWIS 3.4 Open.Since then, independent work is carried out to add methods and models in ILWIS.
New release with updates (SEBS included): End March 2008.
http://52north.org/index.php?option=com_content&task=view&id=131&Itemid=155
S. E. B. Models of Agricultural Areas from Earth Observation Data”, Lima, Perú, 13 March 2008
ILWIS 3.4 Open
ILWIS is a remote sensing and GIS software.
Integrates image, vector and thematic data in one unique and powerful package.
ILWIS delivers a wide range of features including:import/export, digitizing, editing, analysis and display of data
production of quality maps.
functional, user-friendly
has established a wide user community over the years of its development.
It remains active after the open source release, both within and outside ITC.
S. E. B. Models of Agricultural Areas from Earth Observation Data”, Lima, Perú, 13 March 2008
What is SEBS4ILWIS now?
Adapted from SEBS in BEAM.
Interface done for educational purposes.
Limited volume of data and no customization.
SEBS module is documented in many articles
Additional methods are selected from simplicity but they can be customized
according to needs.
Preprocess only MODIS
This version was recently developed and testing was limited to WRS
testing cases. It is in the final debugging state. Deadline (End of March)
S. E. B. Models of Agricultural Areas from Earth Observation Data”, Lima, Perú, 13 March 2008
Pre-processing (optional) – 1 -
S. E. B. Models of Agricultural Areas from Earth Observation Data”, Lima, Perú, 13 March 2008
Pre-processing (optional) – 2 -
CharacteristicsInterface and models fully customizable (methods + Sensors)Today is customized for teaching and research purposes:
MODIS pre-processing:Raw – radiances – reflectance.Raw – radiances – brightness temperature.Atmospheric correction visible (several sensors SMAC algorithm implemented in ILWIS)Land surface albedoLand surface emissivityLand surface temperature
S. E. B. Models of Agricultural Areas from Earth Observation Data”, Lima, Perú, 13 March 2008
Pre-processing (optional) – 3 -
S. E. B. Models of Agricultural Areas from Earth Observation Data”, Lima, Perú, 13 March 2008
Pre-processing (optional) – 4 -
S. E. B. Models of Agricultural Areas from Earth Observation Data”, Lima, Perú, 13 March 2008
Summary: pre-processing for MODIS
Calibration: It works fine but requires 3 softwares: RAW image - HEG: conversion to GEO TIFF of all necessary bands + angles - Importing to ILWIS - Resampling the files - Get calibration coefficients with HDF explorer - to finally convert raw into radiance or reflectance. It was programmed for teaching purposes. For daily routinely tasks requires adaptation.
Brightness temperature: Inversion of Planck equation (standard).
SMAC: very convenient, easy, many sensors supported (thanks to authors). Only 2 atmospheric types. Actual limitation: it is band by band.
Land Surface albedo: weight method based on Liang, 2000.
Land surface emissivity: based on PV-NDVI following Sobrino, et. al (2003) and Carlson and Ripley (1997).
Land surface temperature: based on previous emissivity and Sobrino and Raissouni, 2000.
Improvements, more methods/sensors can be customized.
S. E. B. Models of Agricultural Areas from Earth Observation Data”, Lima, Perú, 13 March 2008
wetdry
wetr HH
HH−−
−=Λ 1
GRE
GRE
n
wetr
n −⋅Λ
=−
=Λλλ
( ) ⎟⎟⎠
⎞⎜⎜⎝
⎛ ∆+⎟⎟
⎠
⎞⎜⎜⎝
⎛ −⋅−−=
γγρ
10ee
rC
GRH s
ew
pnwet
0
0 ,0
GRH
orHGRE
ndry
dryndry
−=
≡−−=λ
wetnwet
wetnwet
EGRHorHGRE
λλ
−−=−−=
0
0 ,
wet
wet
wetr E
EEEE
λλλ
λλ −
−==Λ 1
EHGRn λ++= 0
( ) ( )( )GRE
GRH
n
n
−⋅Λ=−⋅Λ−=
λ1
SEBS Basic Equations Su, 2002, HESS, 6(1),85-99
S. E. B. Models of Agricultural Areas from Earth Observation Data”, Lima, Perú, 13 March 2008
Adopted/distinctive SEBS concepts
1. To evaluate evaporative fraction the energy balance is calculated at limiting wet & dry cases (used in SEBI).
H, u*, L calculated using set of non-linear equations F(u_ref, Ta_ref, To)
H is constrained between Hwet and HdryHdry= Rn-G
Hwet=Rn-G-λEwet and λEwet obtained from Penman Monteith (meteorology!!)
No user interaction or decision affecting the results (Fc required!!).
2. Roughness for heat transfer is calculated instead of being a “fixed”value with respect to roughness for momentum
kB-1= F(weighted with fc of a canopy, a soil and an interaction function)
3. Algorithms for upscaling ASL -> PBL and downscaling PBL-> ASLUses Monin-Obukhov Similarity (MOS) for ASL
Uses Bulk atmospheric Boundary Layer (ABL) Similarity (BAS) for PBL scaling
Criteria for using MOS or BAS follows (Brutsaert, 1999). Valid for unstable conditions.
Stable and unstable situations MOS & BAS considered.
wetdry
wetr HH
HH−−
−=Λ 1GR
EGR
E
n
wetr
n −⋅Λ
=−
=Λλλ
S. E. B. Models of Agricultural Areas from Earth Observation Data”, Lima, Perú, 13 March 2008
Relative evaporation
The relative evaporation is given as
S. E. B. Models of Agricultural Areas from Earth Observation Data”, Lima, Perú, 13 March 2008
Surface air potentials
S. E. B. Models of Agricultural Areas from Earth Observation Data”, Lima, Perú, 13 March 2008
Normalized temperature difference versus albedo
S. E. B. Models of Agricultural Areas from Earth Observation Data”, Lima, Perú, 13 March 2008
The scalar roughness height for heat transfer
The within-canopy wind speed profile extinction coefficient,
( )22*2 huu
LAICn dec
⋅=
( ) ( )( ) 21
*2
2*
10*
214
sst
hz
huu
sccn
t
d fkBC
kfff
ehu
uC
kCkBm
ec
−
−
− +⋅⋅
+−
=
( ) [ ]4.7lnRe46.2 41*
1 −=−skB
( )100 exp/ −= kBzz mh
S. E. B. Models of Agricultural Areas from Earth Observation Data”, Lima, Perú, 13 March 2008
Wind, air temperature, humidity(aerodynamic roughness,
thermal dynamic roughness)H
G0
LERn
⎥⎦
⎤⎢⎣
⎡⎟⎠⎞
⎜⎝⎛Ψ+⎟
⎠⎞
⎜⎝⎛ −
Ψ−⎟⎟⎠
⎞⎜⎜⎝
⎛ −=
Lz
Ldz
zdz
kuu m
mmm
00
0
0* ln
( )1
00
0
00* ln
−
⎥⎦
⎤⎢⎣
⎡⎟⎠⎞
⎜⎝⎛Ψ+⎟
⎠⎞
⎜⎝⎛ −
Ψ−⎟⎟⎠
⎞⎜⎜⎝
⎛ −−=
Lz
Ldz
zdzCkuH h
hhh
ap θθρ
kgHuC
L vp θρ 3*−=
[ ]?,, 000 hm zdz
Energy Balance Residual Method - Turbulent Heat Fluxes
[ ]?,, quTa
S. E. B. Models of Agricultural Areas from Earth Observation Data”, Lima, Perú, 13 March 2008
SEBS Interface
Originally developed in Beam and converted to ILWIS
last year.
Require both maps and ground data. All input is
delivered in one interface.
There are mandatory inputs, optional inputs and
alternative or subrogate inputs to compensate
mandatory's.
No interaction after the process is initiated, calculation
time depends on number of pixels in the map and, of
course, processor speed.
Mandatory map
Mandatory Map or Modeled map
Mandatory value: manual or modeled
Mandatory value
Mandatory map or mandatory value
Surrogate value
S. E. B. Models of Agricultural Areas from Earth Observation Data”, Lima, Perú, 13 March 2008
SEBS sequence
SW↓, To, ro, Ta, εa → Rn
Pv, Rn → G
Rn, G → Hdry
Based on PBL height and Reference height: MOS or BAS
U, To, Ta, LAI, Zom, PV →u*, L, H, kB-1, Zoh
RH, Rn, G, u*, Zoh → Lwet, Hwet
Hdry, Hwet, H → Λr
Hwet, Rn, G → λEwet
λEwet, Λr , Rn, G → Λ
Λ, Rn, G → λEwet
Λ, Rn24, G24 → Edaily
S. E. B. Models of Agricultural Areas from Earth Observation Data”, Lima, Perú, 13 March 2008
SEBS Input: Mandatory maps
± 0.01± 0.01± 0.01± 0.1Precision:
FcG
RnRnRnGH, L, u*
Used for:
Units [-]AC
Units [-]AC, broadband
Units [-]broadband
Units [K]AC
Pre-processing:
NDVIAlbedoSurf. EmissivitySurface Temp.
AC: atmospherically correctedRn: net radiationFc: fractional canopy coverage
G: soil heat fluxRn: net radiationFc: fractional canopy coverage
S. E. B. Models of Agricultural Areas from Earth Observation Data”, Lima, Perú, 13 March 2008
SEBS Input: Mandatory or modeled maps
± 0.01± 0.01± 0.1Precision:
Zom (attribute table)GkB-1
kB-1Used for:
Equations!
Land UsePvLAI
( )2minmax
min
NDVINDVINDVINDVI−
−NDVI
NDVINDVI−
+⋅1
)1(
S. E. B. Models of Agricultural Areas from Earth Observation Data”, Lima, Perú, 13 March 2008
Mandatory value when modeled
τ⋅−⋅⋅⋅↓= )cos(
1
)cos(1367 SZAo eSZAeSW
)5.51/exp(042.0
)5.5(105.05.5)0(10
)5.5(/)0(ln(5.51
0030765.0)5.5(0116.0)0(
)0()50log()0(
aHHDEMaHaHaH
aHaHaaH
ar
rVis
a
ββτ
ββββ
ββ
ββ
ββ
+⋅=
⋅−=⋅=
=
==
−=
S. E. B. Models of Agricultural Areas from Earth Observation Data”, Lima, Perú, 13 March 2008
OTHER equations in the program
( )26 15.273102.9 +⋅⋅= −aatm Tε
( )28 15.27310678.5 +⋅⋅⋅↓= −aatm TLW ε
S. E. B. Models of Agricultural Areas from Earth Observation Data”, Lima, Perú, 13 March 2008
Outputs from SEBS as Maps in ILWIS
Instantaneous actual evaporationDaily evaporationSoil heat fluxSensible heat flux at dry limitSensible heat flux at wet limitSensible heat fluxNet radiationLatent heat fluxUpdates are possible after feedback.