Updated Sea Ice Products for the NIMBUS 5 Electrically Scanning Microwave Radiometer data from 1972–1977

The Electrically Scanning Microwave Radiometer (ESMR) instrument onboard the NIMBUS 5 satellite was a one-channel microwave radiometer that measured the 19.35 GHz horizontally polarized brightness temperature (TB) from 11 December 1972 to 16 May 1977.Kolbe et. al. (2024) reprocessed this data in order to derive sea Ice concentration for the period and showed that sea ice extend and concentration was indeed recoverable, but one major challenge was that the implemented one-channel algorithm was unable to distinguish first year ice and multiyear ice, resulting in ambiguity between areas with multi-year ice, and areas with low sea ice concentration. Furthermore, since publishing, we have found the applied filtering to be removing too much data, especially after 1975, and on top of that, we have resolved minor data issues.Two datesets are uploaded here, split in to 4 files ;1) A reprocessed version of the data using the methods of Kolbe et. al. (2024), but with some corrections to the output and a new filtering scheme. This is a direct update to https://doi.org/10.5285/34a15b96f1134d9e95b9e486d74e49cf.2) A post processed dataset (LDTPcorrected) where a local dynamical tie point framework has been applied, which resolves the ambiguity by enforcing stability of tiepoints over time.For each dataset a file for each hemisphere (Northern Hemisphere, NH, and Southern Hemisphere (SH)) can be downloadet.The dataset is created using the code available in the referenced github repository https://github.com/EHTellefsen/N5ESMR-SIC-processing

搭载于NIMBUS 5卫星的电扫描微波辐射计（Electrically Scanning Microwave Radiometer, ESMR）为单通道微波辐射计，工作频段为19.35 GHz，可采集1972年12月11日至1977年5月16日期间的水平极化亮温（brightness temperature, TB）数据。

Kolbe等人（2024）对该数据开展再处理以反演该时段的海冰浓度，证实海冰范围与浓度可通过该数据有效恢复，但该研究存在一项核心局限：所采用的单通道算法无法区分一年冰与多年冰，导致多年冰覆盖区域与低海冰浓度区域的反演结果存在歧义。

此外，该研究发表后，我们发现其应用的滤波方案过滤掉了过多有效数据，尤其在1975年之后；除此之外，我们还修正了部分细微的数据异常问题。

本次共上传两份数据集，分为4个文件：
1. 基于Kolbe等人（2024）的方法进行再处理的版本，但对输出结果进行了修正，并采用了全新的滤波方案。该数据集是对https://doi.org/10.5285/34a15b96f1134d9e95b9e486d74e49cf的直接更新。
2. 经过后处理的数据集（LDTPcorrected），该数据集应用了局地动力学联结点（local dynamical tie point, LDTP）框架，通过强制联结点随时间保持稳定，解决了前述海冰类型反演的歧义问题。

每份数据集均包含对应南北半球（北半球NH、南半球SH）的文件可供下载。

本数据集的生成代码可在参考文献给出的GitHub仓库https://github.com/EHTellefsen/N5ESMR-SIC-processing中获取。