基于Bootstrap算法的FY-3/MWRI北极海冰密集度反演

Arctic sea ice concentration retrieval study of FY-3/MWRI based on the bootstrap algorithm

海冰作为全球气候系统的重要组成部分,不仅影响着大气与海洋环流,也是气候变化的重要指示器。海冰密集度是描述极地海冰极为重要的地球物理参数之一。本文基于风云三号卫星微波成像仪(MWRI)亮温数据开展北极海冰密集度反演研究,采用线性回归和阈值法确定了动态亮温系点值,利用天气滤波器和陆地污染修正法消除了天气和陆地对海冰密集度反演的影响,计算了2019年—2020年海冰范围和海冰面积并与同类产品进行了比对。结果表明,本研究获取的北极海冰密集度产品与NSIDC发布的海冰密集度产品有较高的相关性,海冰密集度的差异在冬季小于3%,夏季小于8%。利用SAR数据进行了不同产品的结果评估,结果表明本文算法的反演结果优于NASA Team算法,在冬季精度约有1%的提升,在夏季精度约有4%左右的提升。动态亮温系点值较好地反映了海冰辐射特性的季节变化。本研究为中国自主卫星的海冰密集度产品的业务化发布奠定了基础。

As an essential part of the global climate system,sea ice affects the atmosphere and ocean circulation.It is also an important indicator of climate change.Sea ice concentration is one of the most important geophysical parameters for describing polar sea ice.We conduct an inversion study of Arctic sea ice concentration based on a Microwave Radiation Imager(MWRI) carried by FY3 series satellites.The daily dynamic tie point of the brightness temperature is determined by linear regression and the threshold method.The influence of weather and land pollution on sea ice concentration retrieval is eliminated using a weather filter and land pollution correction methods.The trend of sea ice extent and sea ice area calculated from 2019 to 2020 has a strong correlation with the sea ice concentration products released by NSIDC.The mean differences in the sea ice extent and sea ice area are-0.052 ± 0.015 × 106 km~2 and-0.401 ± 0.093 × 106 km~2,respectively.The sea ice concentrations have negative differences,approximately-3% in winter with a mean absolute deviation of 2%—4%and negative deviations of approximately-8% in summer with a mean absolute deviation of approximately 10%.The accuracy of sea ice concentration datasets based on different algorithms of MWRI is evaluated using SAR data.Results show that the retrieval result of the bootstrap algorithm is better than that of the NASA team algorithm.The accuracy is improved by approximately 1% in winter and approximately 4% in summer.The dynamic tie points of the brightness temperature effectively reflect the seasonal variation of sea ice radiative characteristics.This research has laid a foundation for the business release of sea ice intensive products of China's autonomous satellites,thereby guaranteeing the continuity of sea ice records in polar regions facing interruptions for more than 40 years.