Snow Cover Observations from Space Future Perspective Helmut Rott

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Snow Cover Observations from Space Future
PerspectiveHelmut Rott
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Requirements for Improved Snow Information

• Coherent long-term cryosphere observing system
  for climate monitoring
• Hydrology and Land Surface Process Models
• Snow data assimilation and validation in
  mesoscale atmospheric models
• Key missing variable
• Spatially distributed data on snow water
  equivalent various new techniques proposed

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Need for Snow Process Model Input and Validation
Parameterisation of Land Surface Processes in
Climate Models Intercomparison of 21 Snow
Sub-Models at a test site Daily modelled SWE,
mean over 18 years Source Slater et al., 2001
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Need for Improved Snow Data in NWP ECMWF Snow
Depth Jan. 2001 and Difference to USAF
Source ECMWF, Land Surface Assimilation Scheme
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Snow Information NeedsIGOS Cryosphere Theme

• The importance of observing the cryosphere was
  noted at the Earth Observation Summit (July 2003)
• The cryosphere was identified a key missing
  element in the coverage of the planets
  environments by IGOS Themes
• A concept paper was initiated by experts of the
  WCRP Climate and Cryosphere (CliC) Project
• The IGOS-Cryosphere theme is aimed at creating a
  framework for improved coordination of
  cryospheric observations conducted by scientific
  and operational programmes
• The first stream is a comprehensive system of
  validated remote sensing and in-situ observations
  of the land-based cryosphere, capable of
  providing a complete picture of precipitation,
  snow reserves, river and lake ice, permafrost,
  and frozen soil characteristics

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Needs for Advanced Snow Information
Assimilation and Validation of Land Surface
Models

• Applications
• Mesoscale numerical models of atmosphere,
  including surface/atmosphere exchange processes,
  diagnostic and forecasting, typical spatial
  resolution 5 km, being improved to 1 km
• Distributed hydrological models, typical grid
  size ? 1 km
• Mesoscale (nested grid) Model forced by
• GCM (pressure, temperature, precipitation, wind
  etc., typically at 40 km grid)
• Spatially interpolated information from met
  stations (precipitation, temperature, )
  Inadequate, in particular over complex terrain
  and high latitudes !
• Snow component of mesoscale models
• Calculates distributed snow energy and mass
  balance surface/atmosphere exchange

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Concept for Advanced Snow Information System for
Land Surface Process Model Input
Mesoscale Atmospheric Model TT, PP, pp, vv, ...
Snow parametrization at Sub-grid
Topography Land Cover
Snow process model
Pre- processor Downscaling Spatial Interpolation
Satellite Snow Information Snow area, SWE, Vw,
albedo, metamorphic state
Online Meteo and Hydro Stations Temp. Precip, SWE
, Runoff ..

• Gridded Output
• Snow mass
• Snow/atmosphere fluxes

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Plans for Satellite-borne SAR

• Sensor Satellite fGHz/Polar.
  Resolution Swath
• m km
• SAR Radarsat1(1995-) 5.3 VV 10,30,100
  100-500
• ASAR Envisat (2002-) 5.3 HH,VV,HV 30,100
  100-400
• PALSAR ADEOS (2005-) 1.2 PP 15/100
  40-350
• TerraSAR-X TerraSAR(2006-) 9.6 PP 1, 3, 16
  5,30,100
• SAR Radarsat2(2006-) 5.3 PP 3, 10, 30
  ?20
• C-SAR 3-Constellation 5.3 VV 50
  350
• Sentinel-1 GMES, ESA-EC 5.3 PP ?
• PP Polarimetric

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Experiment on SWE Retrieval by InSAR Phase Shifts
E-SAR L-band
Differential displacement Dr of CR
Dr -0.0420 m ? Df -2.3 rad ? SWE 43 mm
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Potential of Repeat-Pass SAR for SWE Retrieval

• The interferometric phase shift of repeat pass
  SAR provides a physically based means for mapping
  the the mass of snow on ground (the SWE)
  (Guneriussen at al., 2001).
• Temporal decorrelation due to differential phase
  delays at sub-pixels scale during snow fall and
  wind drift is the main limiting factor.
  Decorrelation due to refraction in the snow is
  also critical.
• L-band is preferable for interferometric SWE
  retrievals because of better coherence and larger
  measurement range (2 ? ambiguity) than shorter
  wavelength.
• L-band InSAR could be of interest for SWE
  retrieval in experimental basins. Extensive use
  is unlikely because of stringent requirements in
  terms of repeat-pass data.

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CoRe H2O Proposed Mission for SWE Retrieval by SAR
COld REgions Hydrology High-resolution Observatory
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CoRe H2O Product Requirements
CoRe H2O Sensor Specifications

•                           Dual-frequency SAR
  Ku-band (17 GHz) and X-band (9.6 GHz) VV and VH
•         Swath gt 100 km (ScanSAR)
•         Spatial resolution ca. 75 m (gt 8 looks)
•         Orbitpolar dawn/dusk, duty cycle ca.
  25
•         Mission duration 3 years minimum,
  target of 5 years
•         Repeat cycles 3 days (for the first 2
  years), then 15 days.

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Ongoing DevelopmentsSnow in GMES and EOMD
Projects

• GMES - Global Monitoring for Environment and
  Security initiative of ESA and EC
• ESA GMES Services Element
• GSE will deliver policy-relevant services to
  end-users, primarily (but not exclusively) from
  Earth Observation sources
• Services under Consolidation
• Northern View Ice and Arctic Monitoring Services
  
• Prime C-Core (CAN)
• ICEMON Emphasis on Sea Ice services, also Snow
  cover glacier products for climate monitoring.
  Prime NSERC (UK)
• ESA EOMD Earth Observation Market Development
• EO-Hydro Snow Cover Services for Hydropower
  plantsPrime Carlo Gavazzi Space(I)