PROGRESS IN ADDRESSING SCIENCE GOALS FOR GLACIER OBSERVATIONS BY MEANS OF SAR. Frank Paul & Thomas Nagler

Transcription

1 PROGRESS IN ADDRESSING SCIENCE GOALS FOR GLACIER OBSERVATIONS BY MEANS OF SAR Frank Paul & Thomas Nagler SAR Coordination Working Group Meeting, 13/11/2016

2 Observed glacier products and sensors Product Area Facies Elev. change (ALT) Elev. change (DEM) Velocity Sensor Optical (Radar) Optical Altimeter (opt./radar) Optical / Radar Optical / Radar Format Shape file (vector) Shape (line) Shapefile (csv) Geotiff (raster) Shapefile (csv) Sources GLIMS/RGI raw data ask scientist ask scientist (WGMS) ask scientist (GLIMS) Correction/ Validation Validation datasets Manual editing (visual) High resolution data (Google Earth), coherence images Manual editing (visual) WGMS observations Filtering (slope, outlier) IceBridge / Cryovex co-registration, stable ground differences ICESat, LIDAR & national DEMs Filtering, stable ground, in-situ Automatic GNSS Challenges Global consistency, debris, snow, clouds, shadow, water contrast, Aufeis, precise DEMs for topogr. correction clouds / footprint size, interpolation, short time series Co-registration, data voids, penetration, cell size, projection, sensor biases (jitter) orthorectification of input data (DEM accuracy), lack of contrast (optical) Archived datasets Corona, Hexagon Landsat MSS / TM / ETM+ (SLC on) Landsat MSS / TM / ETM+ (SLC on) ICESat GLAS EnviSat RA 2 SRTM, GDEM2, RAMP, NED / CDED, GIMP, SPOT SPIRIT ERS 1/2, PALSAR Envisat ASAR, Landsat TM / ETM+ (SLC on) Ongoing missions Landsat ETM+/OLI Terra ASTER, SPOT, Sentinel 2A Landsat ETM+ /OLI, Sentinel 2, SPOT, ASTER Cryosat 2 ASTER14 DMO, TanDEM X PALSAR 2, TerraSAR X, Cosmo Skymed, ASTER, Landsat OLI, Sentinel 2A Forthcoming Sentinel 2B Sentinel 2B Sentinel 3, ICESat 2 GDEM3, ALOS DEM, World DEM Sentinel 2B

3 Requirements for glaciers (technical) Satellite-derived products are complementary to field observ. in Glaciers_cci: Area (outlines/inventory), elevation change (alt/ddem), velocity (opt. / MW) not yet (but soon in Option 3): Facies (snow mapping on glaciers) Glaciers are globally distributed (200000) & require high res. Area/inventory creation is organized within GLIMS, but region selection is science based Elev. change / velocity: driven by data availability, science agenda, special events Techniniques are mature but some require manual editing velocity: ~ automatical, elev. change: pre-processing manual, area: post-processing manual accuracy assement difficult (lack of reference data) but not impossible (precision more easy) Processing lines require a precise DEM as a key input either for pre-processing (orthorectification) or deriving products (divides, topo parameters) current spatial resolution and accuracy of DEMs is not sufficient in steep mountain terrain glacier surface elevations change quickly (100 m / decade), causing orthorectification errors the DEMs used for orthorectification (PlanetDEM) need to be freely available as well Systematic acquisitions of time series of DEMs for estimation of ice volume changes highly needed (exploit TDX archive)

4 Requirements for glaciers (observation) Observation requirements are different for each product Optical sensors: must be cloud free Area: only end of ablation period in specific years, facies (EOSS): dto. but in all years, velocity: during ablation season (each year), elevation change: as area but less critical Microwave: winter preferred for velocity/dems, summer for coherence images (area), short repeat intervals, C or X-band work but for elevation change snow penetration is important Timing for outlines dependes on latitude and climate Different in tropical and monsoon regions (end of dry period) Often seasonal snow in maritime climates and clouds in mid-latitudes (=> try each year) Global coverage ok (optical) but limited impact on acquisition Archive consolidation at USGS is highly appreciated, reprocessing of GLS1990 is encoraged reprocessing of ASTER archive to L1T is also appreciated, VIS is still fine for DEM & velocity Access data from other space agencies (Brasil/China/India)? not easy to find and even more difficult to get...

5 Svalbard Ice Cap Monitoring by Sentinel-1 Time Series of Ice velocity Of major outlet glaciers

6 Svalbard Ice Cap Time series of Ice velocity - KRONEBREEN GLACIER Monitoring by Sentinel-1 Time Series of Ice velocity Of major outlet glaciers

7 South Georgia PALSAR 2010 TSX 2013 South Georgia Track Number of pixels Mean dif [m d -1 ] RMSE dif [m d -1 ] , , , Mean over all products

8 Ice Velocity maps Karakoram,TSX/TDX

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10 Covered Glacier area, and fraction of valid IV estimates Glacier Dates Coverage (GLIMS) 1. Yinsugaiti 9/9/12-25/11/ % 2. Musita 9/9/12-25/11/ % 3. Qiaogeli 9/9/12-25/11/ % 4. Baltoro 9/9/12-25/11/ % 4

11 TSX Ice Velocity for FEDCHENKO Glacier, PAMIR

12 Ice Velocity Maps for Novaya Zemlya PALSAR Semzinel

13 Elevation change: DEM Differencing

14 Glaciers_cci Recommendations to Space Agencies

15 Glaciers_cci Recommendations to Space Agencies