h. rott –coreh2o snow_rs-workshop_boulder_aug-2013 coreh 2 o – preparations for a radar mission...

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


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


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


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).


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


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


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


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


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


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

h. rott –coreh2o snow_rs-workshop_boulder_aug-2013 coreh 2 o – preparations for a radar mission...

Documents