Center for Satellite Applications and Research (STAR) Review 09 – 11 March Arctic Aircraft Altimeter (AAA) Experiment Envisat and ICESat underflights over sea ice Instrumentation Airborne Topographic Mapper (ATM - laser altimeter) D2P Radar Altimeter (ku-band) Photo-Imaging System Airborne and in situ validation of satellite altimetry measurements over sea ice. Laurence N. Connor 1(Government Principal Investigator), Sinead Farrell 2, Dave McAdoo 1 Requirement: Climate - Initiate a competitive program on Loss of Sea Ice in the Arctic. (3-5 year milestone) Science: How precisely can we track thickness and volume change of Arctic sea ice with satellite altimetry? Benefit: -Global Climate Modeling and Climate Change Indicator -US Naval Operations -Commercial Shipping Science Challenges: Develop robust methods for measuring and monitoring sea ice thickness using multiple satellite altimeter data sets. Next Steps: Analyze 2009 CBSIT ATM and Snow Radar data as a step toward developing satellite sea ice thickness and snow depth products. Prepare for and conduct BEaufort Sea Ice Experiment (BESIE) in 2011 to include Envisat and CryoSat-2 underflights and ice camp overflights. Exploit data acquired during BESIE 2011 to validate and analyze sea ice data from ESA’s CryoSat-2. Prepare for ICESat-2 via membership on the Science Definition Team. Transition Path: Sea ice thickness and volume products will be provided to the National Ice Center (NIC) and the National Snow and Ice Data Center (NSIDC) for distribution. Outbound Swath Inbound Swath Ice Drift Outbound Swath Inbound Swath Ice Drift AAA Envisat/RA-2 Sea Ice Validation AAA ICESat/GLAS Sea Ice Validation AAA 2006 Flight Line Envisat ICESat Canada Basin Study Area Simple spatial averaging revealed good agreement between ATM and Envisat/RA-2 derived sea ice elevations, particularly over refrozen leads. The elevation difference observed between ATM and RA- 2 over floe ice (mean of 34 cm) is likely due to snow cover. Refrozen lead “snagging” was identified in some areas whereby the Envisat/RA-2 return signal is dominated by the specular reflection of a refrozen lead. This contributed to differences between the Envisat/RA-2 and ATM elevation measurements when such surfaces fell outside the ATM swath. When the effects of “snagging” were removed, ATM and Envisat sea ice elevation comparisons over leads yielded a residual mean of only 1 cm and a residual standard deviation of 8 cm. Connor et al., RSE, 2009 Overlapping outbound and inbound flight paths enabled measurement of the ice field drift and correction for temporal delay between satellite and aircraft measurements. Derived sea ice velocity field revealed drift surges between large open leads. Typical drift rate of 1-3 cm/sec was observed. Using derived sea ice drift velocities, ICESat footprint locations were shifted to account for temporal delay between satellite and aircraft measurement acquisition Canada Basin Sea Ice Thickness (CBSIT) Experiment Part of NASA’s Operation Ice Bridge (OIB) Envisat underflight over sea ice GreenArc/Danish Ice Camp overflight Airborne Instrumentation ATM - Laser Altimeter Snow Radar (Kansas University) Enhanced Photo Imagery System* (*for example see poster background image) In addition to an Envisat underflight similar to the 2006 AAA experiment, CBSIT included a multiple pass overflight of the GreenArc/Danish Ice Camp in the Lincoln Sea. NOAA scientists coordinated with CRREL researchers at the ice camp to overfly a 2km survey line where direct measurements of snow and ice thickness were acquired. These will be used to validate ATM sea ice elevation measurements and snow depth measurements from the Kansas University Snow Radar. Original Overlaps Shifted/matched Overlaps Original Drift Corrected Leads Original ICESat Footprint Drift Corrected Footprint Example of Original and Drift Corrected Footprints over ATM Swath ATM - GLAS ATM elevations corresponding to drift-corrected footprints show improved agreement between ATM and ICESat/GLAS with a residual mean of 0.25 cm and standard deviation of 17.6 cm. Runway Survey Line Markers Camp GreenArc Ice Camp Selected Publications: Connor, L.N., S.W. Laxon, A.L. Ridout, W.B. Krabill, and D.C. McAdoo. Comparison of Envisat radar and airborne laser altimeter measurements over Arctic sea ice. Remote Sensing of Environment, Volume 113, Issue 3, 16 March 2009, Pages , doi: /j.rse Farrell, S. L., S. W. Laxon, D. C. McAdoo, D. Yi, and H. J. Zwally (2009), Five years of Arctic sea ice freeboard measurements from the Ice, Cloud and land elevation Satellite, J. Geophys. Res., 114, C04008, doi: /2008JC Satellite (ICESat) and airborne (ATM) laser altimetry inter-comparison I 1 NOAA/NESDIS/STAR/SOCD, 2 CICS/ESSIC/University of Maryland Center for Satellite Applications and Research (STAR) Review 09 – 11 March 2010 Lead within ATM swath Lead outside ATM swath MODIS Visible Imagery