h. rott –coreh2o snow_rs-workshop_boulder_aug-2013 coreh 2 o – preparations for a radar mission...
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H. Rott –CoReH2O Snow_RS-Workshop_Boulder_Aug-2013
CoReH2O – Preparations for a Radar Mission for Snow and Ice Observations
H. RottH. Rott11, D. Cline, D. Cline22, C. Duguay, C. Duguay33, R. Essery, R. Essery44, P. Etchevers, P. Etchevers55, I. Hajnsek, I. Hajnsek66, ,
M. KernM. Kern77, G. Macelloni, G. Macelloni88, E. Malnes, E. Malnes99, J. Pulliainen, J. Pulliainen1010, S. Yueh, S. Yueh1111
1 University of Innsbruck & ENVEO IT, Austria
2 NOAA, NWS, Hydrology Laboratory, USA
3 University of Waterloo, Canada
4 University of Edinburgh, UK
5 Meteo-France, Saint Martin d’Héres, France
6 DLR-HR, Germany & ETH Zürich, Switzerland
7 ESA-ESTEC, Noordwijk, NL
8 IFAC-CNR, Firenze, Italy
9 NORUT IT, Tromsǿ, Norway
10 Finish Meteorological Institute, Helsinki, Finland
11 JPL-Caltech, Pasadena, USA
H. Rott –CoReH2O Snow_RS-Workshop_Boulder_Aug-2013
Background Information
CoReH2O Cold Regions Hydrology –High Resolution Observatory
•Submitted to ESA in response to the 2005 Call for Earth Explorer Core Missions (EE-7)
•Selected as one of 6 missions for Pre-Phase A studies
•In 2009 selected as one of 3 missions for detailed scientific and technical studies, Phase A
•Scientific studies included retrieval algorithm development, SAR image simulator, performance analysis, field campaigns, synergy with other satellites, etc.
•2 parallel contracts on sensor & satellite development
•March 2013: Down-selection to one EE7 mission > Biomass
H. Rott –CoReH2O Snow_RS-Workshop_Boulder_Aug-2013
Scientific Observation Requirements
Primary parametersSpatial scale
Regional/Global
Sampling
(days)
Accuracy
(rms)
Snow water equivalent 200 m / 500 m 3-15 3 cm for SWE 30 cm,
10% for SWE > 30 cm
Snow extent 100 m / 500 m 3-15 5% of area
Glacier snow accumulation
200 m / 500 m 15 10% of winter maximum
Secondary parameters
Diagenetic facies types, glacial lakes
Glaciers
Ice area; freeze up and melt
onset
Lake and river ice
Melting snow area, snow
depth
Snow
Snow on ice (SWE, melt onset and area); type and thickness of
thin ice
Sea ice
H. Rott –CoReH2O Snow_RS-Workshop_Boulder_Aug-2013
Signal as Basis for SWE Retrieval
SnowScat ° (dB) at Ku-band (16.7 GHz) and X-band (10.2 GHz), = 40° winter 2010/11, vs. SWE in snow pits, Sodankylä, Finland (NoSREx-2).
H. Rott –CoReH2O Snow_RS-Workshop_Boulder_Aug-2013
CoReH2O SAR Sensor Requirements
Parameter Ku-band SAR X-band SAR
Frequency 17.2 GHz 9.6 GHz
Polarization VV, VH
Swath width, Inc angle ≥ 100 km; 30° to 45° range
Spatial resolution ≤ 50 m x 50 m (≥ 4 ENL)
NESZ ≤ -25dB VH ≤ -27dB VH
Radiom. Stability / Bias ≤ 0.5 dB / ≤ 1.0 dB
2 Mission concepts
ScanSAR
EADS-Astrium
Thales-Alenia
H. Rott –CoReH2O Snow_RS-Workshop_Boulder_Aug-2013
Cost Function
Iterative SWE Retrieval – Constrained Minimization
(.) backscatter forward model (radiative transfer, RT)
X 2 free model parameters (SWE, eff. grain radius RE)
i ith CoReH2O Band (for i=1,..4: X vv, vh; Ku vv, vh)
j index for free model parameters: SWE
vari variance of measured °
backscatter value in CoReH2O band i
c1,..,cr RT model configuration parameters (Ts, s, as)
io
Regularization
22
12
202121
12 2
1ˆ.....,,;,
2
1
j
jjj
iriiii
n
i i
xxcccxxxJ
Regularization parameters are needed to constrain the inversion: a-priori RE, SWE
t
et
gpq
t
etpqtpqi
aspqi
tpq
SWEkSWEk
cos
'2exp
cos
'2exp1cos75.0 2
Forward model used for iteration:
Forward model - Measurement
H. Rott –CoReH2O Snow_RS-Workshop_Boulder_Aug-2013
Performance Analysis SWE Retrieval – Simulated Data
SWE in open forest 20% fractional cover
Based on backscatter simulations with Synthetic Scene Generator (SSG)
Unbiased regularization
RMSD between retrieved and true SWE
Red grid: observ requirement
Snow on open land
Retrievals with improved algorithm 50 m grid size; speckle filter 7 x 7
H. Rott –CoReH2O Snow_RS-Workshop_Boulder_Aug-2013
Performance Analysis SWE Retrieval – Simulated Data
15% bias for regularization parameter RE (effective grain radius)
Impact of bias in regularization parameters
Snow on open land.
50% bias for regularization parameter SWE
H. Rott –CoReH2O Snow_RS-Workshop_Boulder_Aug-2013
Field Experiments with Airborne Sensor
SnowSAR Field campaigns Sodankylä March 2011, winter 2011/12
AlpSAR 2013 – Austrian Alps
SnowSAR CharacteristicsFrequencies 9.6 GHz, 17.25 GHzPolarization Polarimetric Modulation FMCWBandwidth 150 MHzLook angle 35° to 45°
AlpSAR
Leutasch
23-02-2013
H. Rott –CoReH2O Snow_RS-Workshop_Boulder_Aug-2013
SWE Map from Airborne Backscatter Data
SWE map, derived from SnowSAR data, Sodankylä, 15/03/2011
Performance:
SWEobs– SWEret = -5 mmStand. error : 11 mm
A-priori estimates for retrieval input by CoSDAS snow model driven by HIRLAM forecast data