Research on Distribution Characteristics of Polar Sea Ice by ENVISAT Altimetry Backscatter Coefficient
YANG Lei;CHANG Xiaotao;GUO Jinyun;KE Baogui;HUANG Kunxue;LIU Xiaohui;First Institute of Oceanography,State Oceanic Administration;College of Geodesy and Geomatics,Shandong University of Science and Technology;Satellite Surveying and Mapping Application Center of NASMG;Chinese Academy of Surveying and Mapping;Key Laboratory of Surveying and Mapping on Island and Reef of NASMG;School of Geodesy and Geomatics,Wuhan University;
The tracks of ENVISAT RA-2 altimeter can reach up to the high latitude of 81.4° of north and south,which provides a way of active microwave sensing to monitor sea ice.A method is developed using backscatter coefficients(σ0)based on the ENVISAT satellite radar altimeter RA-2 to detect the monthly changes of polar sea ice extent and surface properties.Considering the variations of scattering characteristics of the sea water and ice surface,it is proved that a threshold of 13 dB for σ0 can distinguish the sea ice cover from sea.Except for summer times,a highly correspondence between sea ice boundaries from altimeter and from radiometer released by NSIDC is presented.For lacking of satellite tracks on the central areas of Arctic,it is only can estimated the sea ice extent of Antarctic zones.And the ENVASAT altimeter gives a greater value in summer months compared to the radiometer result from NSIDC,which relates to the excellent capacity of altimeter to sensing the dispersed thin ice.In other seasons with high sea ice concentration,the difference of sea ice extent is pretty small as the mean difference of winter is just 0.17 Mkm2.The discrepancy of sea ice properties over two polar zones is also researched,and the result shows that in Arctic the sea ice surface is more rough and dry in in the winter and more wet in the summer than Antarctica.Based on this research,the ENVISAT radar altimeter can precisely detect seasonal evolution of sea ice cover and surface properties and is proved to be a useful tool in sea ice monitoring and polar exploration.
【Fund】： 国家自然科学基金(40974016;40974004);; 地理空间信息工程国家测绘地理信息局重点实验室开放研究基金课题(201306)
【CateGory Index】： P229
【CateGory Index】： P229