A study on the dynamic tie points ASI algorithm in the Arctic Ocean
A study on the dynamic tie points ASI algorithm in the Arctic Ocean
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DOI：
10.1007/s13131-015-0659-y
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发表时间：
2015-11
影响因子：
1.4
通讯作者：
Guanghua Hao;Jie Su
中科院分区：
文献类型：
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作者：
Guanghua Hao;Jie Su
海冰密集度是极地海冰监测的重要参数。基于89 GHz AMSR-E（Advanced Microwave Scanning Radiometer for Earth Observing System）数据，采用ASI（the Arctic Radiation And Turbulence Interaction Study（ARTIST）Sea Ice）反演算法，可以获得网格化的高分辨率被动微波海冰浓度产品。本文提出了一种基于每天变化的连接点的ASI算法，即动态连接点ASI算法。在这里，连接点表示为亮温极化差的开放水域和100%的海冰。2010年，北极开放水域和海冰的年平均连接点估计分别为50.8 K和7.8 K。结果表明，利用动态连接点ASI算法反演的海冰密集度能够增加（减少）低（高）值区的海冰密集度。这在一定程度上改善了现有的微波海冰浓度反演算法。与采用固定连接点的产品相比，采用动态连接点ASI算法从AMSR-E数据反演的海冰浓度更接近于采用中分辨率成像光谱仪（MODIS）数据反演的海冰浓度。在选取的40个无云区域中，95%的结果与固定连接点的结果相比具有较小的平均差，75%的结果具有较小的均方根差。
Sea ice concentration is an important parameter for polar sea ice monitoring. Based on 89 GHz AMSR-E (Advanced Microwave Scanning Radiometer for Earth Observing System) data, a gridded high-resolution passive microwave sea ice concentration product can be obtained using the ASI (the Arctic Radiation And Turbulence Interaction Study (ARTIST) Sea Ice) retrieval algorithm. Instead of using fixed-point values, we developed ASI algorithm based on daily changed tie points, called as the dynamic tie point ASI algorithm in this study. Here the tie points are expressed as the brightness temperature polarization difference of open water and 100% sea ice. In 2010, the yearly-averaged tie points of open water and sea ice in Arctic are estimated to be 50.8 K and 7.8 K, respectively. It is confirmed that the sea ice concentrations retrieved by the dynamic tie point ASI algorithm can increase (decrease) the sea ice concentrations in low-value (high-value) areas. This improved the sea ice concentrations by present retrieval algorithm from microwave data to some extent. Comparing with the products using fixed tie points, the sea ice concentrations retrieved from AMSR-E data by using the dynamic tie point ASI algorithm are closer to those obtained from MODIS (Moderate-resolution Imaging Spectroradiometer) data. In 40 selected cloud-free sample regions, 95% of our results have smaller mean differences and 75% of our results have lower root mean square (RMS) differences compare with those by the fixed tie points.