Transcript 4_IGARSS11
MONITORING THICKNESS CHANGES OF MOUNTAIN GLACIER BY DIFFERENTIAL INTERFEROMETRY OF ALOS PALSAR DATA Jianmin Zhou, Zhen Li, Qiang Xing Key Laboratory of Digital Earth, Center for Earth Observation and Digital Earth, Chinese Academy of Sciences 2011.07.28 Vancouver Outline Research background Study Area and Datasets Methodology Experimental Study Conclusions Future Work Research background Why study glacier? • Important archives of past climatic information • Important water source in dry areas (e.g. prairies) • Indicators of climate fluctuations at local and global scale (IPCC) • Important for climate change studies • They contribute to sea level rise Research background Space-borne techniques have been developed and successfully applied for detecting glacier area change and glacier movement. The major current gap in glacier monitoring from space lies in the measurement of glacier thickness or volume change for their contribution to sea-level change and as sensitive indicators of local climate. Mass loss of mountain glaciers, ice caps and ice sheets are estimated to account for one third of the current 3 mm/yr of sea level rise( Cazenave, 2006, Science) Monitoring the response of land ice to climate change requires accurate and multi-temporal topographic data. Research background Source: Dyurgerov and Meier 2005 Research background Problems: Two DEMS Low precision Field GPS measurement costly and laborious The current methods Not enough field measurements to do qualified validation, need of extra data DInSAR Monitoring technique: providing real-time deformation information avoiding costly and laborious with sparse observing locations and unavailable in some inaccessible regions DInSAR has demonstrated the capability of measuring displacement with mm accuracy over wide areas. ur eG la cie r Study Area and Datasets K an gw N 0 1 km This glacier belongs to a subcontinent high mountain glacier in low altitude. The accumulation season for this glacier starts from the end of spring and the beginning of summer and ends in the end of autumn. The ablation season is in the summer. Local circulation is weak and mass balance is controlled by Indian Ocean monsoon circulation in the Kangwure Glacier region. It was a flat-top glacier, inclining to northeast with flat surface, and there was no debris on the glacier surface. Kangwure Glacier (28°27′N, 85°45′E) is situated on the north side of Mt. Xixiabangma, which is in the middle part of the Himalayas. The glacier terminus reaches to an altitude of 5680 m a.s.l. with an altitudinal difference of 476 m to the summit and the glacier exposes to the north in the upper area, then north-east. Study Area and Datasets Datasets: Two winter ALOS/PALSAR orbits acquired on Jan. 21, 2010 and Mar. 8, 2010 with HH polarization covering Kangwure Glacier was exploited. The images were taken under favorable weather conditions and were selected in order to compute an interferogram with acquisition time intervals of 46 days and short baselines (132 m). Acquisition Date Satellites Orbit type Seasons 2007-12-10 ALOS/PALSAR Ascending Winter 2008-01-25 ALOS/PALSAR Ascending Winter Methodology INSAR GEOMETRY AND PHASE A2 A1 r2 r1 Methodology PHASE CALCULATION E1 e E2 e j scatterer j sca tterer E1E e * 2 e j j e 4 r1 j 4 r2 4 (r1 r2 ) or, simply, 4 (r1 r2 ) Methodology INSAR GEOMETRY - DEFORMATION Methodology INSAR DEFORMATION PHASE Phase similar to before but now has displacement term (def ) 2 1 4 R To infer deformation, get difference and compensate for topo term, leaving only deformation signal in LOS direction. Methodology METHOD IN THIS STUDY Methodology InSAR pairs data (here, ALOS/PALSAR) Glacier topography InSAR processing Component decomposition Thickness changes of the glacier Experimental Study (a) The interferogram image at the Kangwure glacier area; (b): differential interferogram image at the Kangwure glacier area for ALOS/PALSAR pair between Jan. 21 and Mar. 8, 2010. Experimental Study N High:3.464 cm 0 1 km Low:-1.793 cm Thickness changes distribution map. Conclusions In conclusion, the results imply that this method, compared to conventional method, has advantage to derive the glacier’s thickness changes in high-accuracy. According to the historical measurement data of the Kangwure glacier, our test study shows that the result is reasonable. The method developed in this study can be used to accurately extract glacier thickness changes. Future Work Need More InSAR Data Thanks！