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 microw...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.展开更多
近年来,由于“北极放大”的气候效应,使得北极海冰变化受到了越来越多的关注。而作为海冰被动微波遥感的主要参数,海冰密集度SIC(Sea Ice Concentration)能够表征海冰的主要状态,可用于指导极区走航以及进行不同尺度的海冰变化研究。通...近年来,由于“北极放大”的气候效应,使得北极海冰变化受到了越来越多的关注。而作为海冰被动微波遥感的主要参数,海冰密集度SIC(Sea Ice Concentration)能够表征海冰的主要状态,可用于指导极区走航以及进行不同尺度的海冰变化研究。通过该参数还可以计算出海冰面积、海冰范围等信息,对极区冰情预测以及气候变化研究具有重要意义。本研究探讨了如何利用FY-3B/MWRI(FY-3B/MicroWave Radiometer Imager)较高分辨率通道数据来反演北极地区海冰密集度。基于ASI(ARTIST(Arctic Radiation and Turbulence Interaction STudy)Sea Ice)算法,本研究通过改进算法系点值的方法反演了北极地区海冰密集度,并将反演结果与MWRI海冰密集度产品进行了对比。首先利用Aqua/MODIS(Moderate Resolution Imaging Spectroradiometer)反射率数据获得的海冰密集度对二者进行了验证。结果表明,本研究选用的新系点值ASI算法在全部数据集范围内的平均偏差与MWRI海冰密集度产品相当,但标准偏差和均方根误差均较之明显降低,且在海冰密集度低于95%时精度远高于MWRI产品;然后将二者与不莱梅大学的SIC_UB(Sea Ice Concentration from University of Bremen)海冰密集度产品进行了对比,其中本研究反演海冰密集度与SIC_UB产品的平均偏差和标准偏差分别为3.3%和10.6%,低于MWRI产品与SIC_UB产品之间的5.9%和16.4%;最后,对本研究反演结果、MWRI产品、NSIDC/AMSR-E(National Snow and Ice Data Center/Advanced Microwave Scanning Radiometer-EOS)产品以及SIC_UB产品的日均海冰密集度和海冰面积、海冰范围进行了时间序列对比,结果表明本研究反演海冰密集度的数值在3种统计方式下均显著低于MWRI产品,且较之更接近NSIDC/AMSR-E和SIC_UB产品。本研究利用国产卫星亮温数据反演的北极地区海冰密集度具有较高空间分辨率和较高精度,有利于北极地区气候变化的长时间序列研究。展开更多
An enhanced ARTSIST Sea Ice(ASI)algorithm is presented based on a data fusion method of calculating total sea ice concentration from high-frequency microwave data.Algorithms that use low-frequency data to calculate to...An enhanced ARTSIST Sea Ice(ASI)algorithm is presented based on a data fusion method of calculating total sea ice concentration from high-frequency microwave data.Algorithms that use low-frequency data to calculate total sea ice concentration are less affected by atmosphere,but their spatial resolutions tend to be lower.In contrast,algorithms using high-frequency data have higher spatial resolution but are significantly influenced by atmosphere.Although errors can be eliminated using weather filters,the concentration of mixed pixels cannot be modified.Here,an enhanced ASI algorithm uses the 19 GHz polarization difference to modify the 91 GHz polarization difference,which is substituted into the ASI algorithm to calculate total sea ice concentration.Arctic total sea ice concentration results are obtained based on Special Sensor Microwave Imager Sounder(SSMIS)data on January 3,from 2008 to 2017.Total sea ice area and average concentration using the enhanced ASI algorithm are compared to traditional ASI and NASA Team results.In the Marginal Ice Zone,there is a considerable difference between the enhanced and traditional ASI algorithm results,with the former much closer to the NASA Team results.The proposed algorithm effectively modifies the concentration of the mixed pixels in the marginal zone.展开更多
基金The Global Change Research Program of China under contract No.2015CB953901the National Natural Science Foundation of China under contract Nos 41330960 and 41276193
文摘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.
文摘近年来,由于“北极放大”的气候效应,使得北极海冰变化受到了越来越多的关注。而作为海冰被动微波遥感的主要参数,海冰密集度SIC(Sea Ice Concentration)能够表征海冰的主要状态,可用于指导极区走航以及进行不同尺度的海冰变化研究。通过该参数还可以计算出海冰面积、海冰范围等信息,对极区冰情预测以及气候变化研究具有重要意义。本研究探讨了如何利用FY-3B/MWRI(FY-3B/MicroWave Radiometer Imager)较高分辨率通道数据来反演北极地区海冰密集度。基于ASI(ARTIST(Arctic Radiation and Turbulence Interaction STudy)Sea Ice)算法,本研究通过改进算法系点值的方法反演了北极地区海冰密集度,并将反演结果与MWRI海冰密集度产品进行了对比。首先利用Aqua/MODIS(Moderate Resolution Imaging Spectroradiometer)反射率数据获得的海冰密集度对二者进行了验证。结果表明,本研究选用的新系点值ASI算法在全部数据集范围内的平均偏差与MWRI海冰密集度产品相当,但标准偏差和均方根误差均较之明显降低,且在海冰密集度低于95%时精度远高于MWRI产品;然后将二者与不莱梅大学的SIC_UB(Sea Ice Concentration from University of Bremen)海冰密集度产品进行了对比,其中本研究反演海冰密集度与SIC_UB产品的平均偏差和标准偏差分别为3.3%和10.6%,低于MWRI产品与SIC_UB产品之间的5.9%和16.4%;最后,对本研究反演结果、MWRI产品、NSIDC/AMSR-E(National Snow and Ice Data Center/Advanced Microwave Scanning Radiometer-EOS)产品以及SIC_UB产品的日均海冰密集度和海冰面积、海冰范围进行了时间序列对比,结果表明本研究反演海冰密集度的数值在3种统计方式下均显著低于MWRI产品,且较之更接近NSIDC/AMSR-E和SIC_UB产品。本研究利用国产卫星亮温数据反演的北极地区海冰密集度具有较高空间分辨率和较高精度,有利于北极地区气候变化的长时间序列研究。
基金The National Natural Science Foundation of China under contract No.41606209the Open Fund from Key Laboratory of Global Change and Marine-Atmospheric Chemistry under contract No.GCMAC1605+1 种基金the Natural Science Project of Henan Education Department under contract No.15A120007the Key Laboratory of Ocean Circulation and Waves,Institute of Oceanology,Chinese Academy of Sciences under contract No.KLOCW1805
文摘An enhanced ARTSIST Sea Ice(ASI)algorithm is presented based on a data fusion method of calculating total sea ice concentration from high-frequency microwave data.Algorithms that use low-frequency data to calculate total sea ice concentration are less affected by atmosphere,but their spatial resolutions tend to be lower.In contrast,algorithms using high-frequency data have higher spatial resolution but are significantly influenced by atmosphere.Although errors can be eliminated using weather filters,the concentration of mixed pixels cannot be modified.Here,an enhanced ASI algorithm uses the 19 GHz polarization difference to modify the 91 GHz polarization difference,which is substituted into the ASI algorithm to calculate total sea ice concentration.Arctic total sea ice concentration results are obtained based on Special Sensor Microwave Imager Sounder(SSMIS)data on January 3,from 2008 to 2017.Total sea ice area and average concentration using the enhanced ASI algorithm are compared to traditional ASI and NASA Team results.In the Marginal Ice Zone,there is a considerable difference between the enhanced and traditional ASI algorithm results,with the former much closer to the NASA Team results.The proposed algorithm effectively modifies the concentration of the mixed pixels in the marginal zone.
