SICEv3.0 Iceland snow and ice broadband albedo and surface optical properties from Sentinel-3’s OLCI at 500 m resolution, Near Real Time (NRT)

SICE v3.0. 0.5 km Arctic land ice SSA, broadband albedo and spectral reflectance for 2017 to 2023 Timespan 1 April, to 31 September for each year 2017 to 2023 and is being updated starting ~April each year Description For Greenland, 0.5km daily data (Table 1) from the pySICE v2.1 algorithm, see Bahbah et al (2023) and Kokhanovsky et al (2023) for details. Broadband albedo \"albedo_bb_planar_sw\" is after Kokhanovsky et al (2019). \"BBA_combination\" is albedo_bb_planar_sw for albedo_bb_planar_sw values above 0.565 and is combined with an ampirical albedo for albedo_bb_planar_sw below or equal to 0.565, see Wehrlé et al (2021). Data format is GeoTiff in the EPSG:3413 - WGS 84 / NSIDC Sea Ice Polar Stereographic North. We suggest using rasterio to read the data files. The data are also available from https://thredds.geus.dk/ Data Format Data format is GeoTiff in the EPSG:3413 - WGS 84 / NSIDC Sea Ice Polar Stereographic North projection.   Table 1, SICE v3.0 data, alphabetical name, description ANG, Angström parameter for atmospheric aerosol correction AOD_550, aerosol optical depth at 550 nm from CAMS, m units al, effective absorption length, mm units albedo_bb_spherical_sw, albedo under isotropic radiation albedo_bb_planar_sw, broadband albedo albedo_spectral_planar_NN, multispectral albedo_spectral_planar, where NN is a number for bands 01-21 diagnostic_retrieval, per pixel diagnostic info cloud_mask,SCDA cloud mask cloud_mask, SCDA cloud mask cv1, quality check 1 (see ATBD) cv2, quality check 2 (see ATBD) factor<,snow covered fraction within mixed pixels grain_diameter, effective optical snow grain diameter isnow, See Table 2 lat, decimal latitude lon, decimal longitude O3_SICE, OLCI total ozone retrieval corrected for ozone scattering after Kokhanovsky et al 2020 r0, reflectance of a semi-infinite non-absorbing snow layer r_TOA_NN, multispectral TOA reflectance, where NN is a number for bands 01-21 r_BRR_NN, multispectral botttom of atmosphere reflectance, where NN is a number for bands 01-21 snow_specific_surface_area, SSA saa, solar azimuth angle sza, solar zenith angle vaa, viewing azimuth angle vza, viewing zenith angle Table 2, Diagnostic codes Diagnostic Code, Description 0, clean snow 1, polluted snow 6, polluted snow for which r0 was calculated and not derived from observations 7, polluted snow of calculated spherical albedo in bands 1 and 2 greater than 0.98 reprocessed as clean snow 100, sza exceeding 75, no retrival albedo 102, TOA reflectance at band 21 less than 0.1, no retrieval 104, grain_diameter less than 0.1, no retrieval, potential cloud flag -N, impossible to solve polluted snow albedo equation at band N See also related information below Reference Publications Kokhanovsky, A., Vandecrux, B., Wehrlé, A., Danne, O., Brockmann, C., and Box, J. E.: An improved retrieval of snow and Ice properties using spaceborne OLCI/S-3 spectral reflectance measurements: Updated atmospheric correction and snow impurity load estimation, Remote Sens. (Basel), 15, 77, https://doi.org/10.3390/rs15010077, 2022 Kokhanovsky A.A., Lamare, M. and Rozanov, V. (2020) Retrieval of the total ozone over Antarctica using Sentinel-3 ocean and land colour instrument. Journal of Quantitative Spectroscopy and Radiative Transfer 251, 107045 https://doi.org/10.1016/j.jqsrt.2020.107045 Code Bahbah, R., Wehrlé, A., Mankoff, K., Vandecrux, B., and Box, J. E.: Sentinel-3 snow and ice optical properties retrieval (SICE) version 3.0, https://doi.org/10.5281/zenodo.10058790, 2023. How to gather and read the data see https://github.com/GEUS-SICE/SICE_gather and raise any issues there. Acknowledgements SICE has been supported by the following contracts to the European Space Agency (ESA): Dec. 2016 – Jan. 2019 SEOM S34Sci Land Study 1: Snow, ESRIN Contract 4000118926/16/I-NB Dec. 2018 – Jul. 2020 EO Science For Society, ESA/Contract 4000125043/18/I-NB – ESA/AO/1-9101/17/I-NB EO SCIENCE FOR SOCIETY, Pre-operational Sentinel-3 Snow and Ice Products (SICE) Jan. 2019 – Dec. 2020 ESA PRODEX, An operational service of new Sentinel-3 algorithms for climate monitoring of the Greenland Cryosphere within the CryoClim network May 2021 – June 2023 ESA PRODEX, Seamless Integration of Sentinel-3 Albedos in a Weather-modelling System (SISAWS) Feb 2022 – Oct. 2023 ESA EO Science For Society, Snow and ICE optical and physical properties from Sentinel-3 (SICE), ESA CCN contract 4000125043/18/I-NB and the ESA Network of Resources, Related Information description of variables, inputs and outputs https://github.com/GEUS-SICE/pySICE/tree/pySICEv2.1 https://snow.geus.dk/ Questions? contact Jason Box, [e-mail]

SICE v3.0 数据集包含2017至2023年北极陆地冰的0.5千米分辨率比表面积（Specific Surface Area, SSA）、宽带反照率与光谱反射率数据，时间跨度为每年4月1日至9月30日，且自每年4月起持续更新。

### 数据集说明
针对格陵兰地区，数据采用pySICE v2.1算法生成0.5千米日尺度数据集（见表1），详细方法可参考Bahbah等（2023）与Kokhanovsky等（2023）的研究。其中"albedo_bb_planar_sw"（宽带平面短波反照率）的反演方法源自Kokhanovsky等（2019）的研究。"BBA_combination"组合反照率规则如下：当"albedo_bb_planar_sw"值大于0.565时，直接采用该值；当该值小于等于0.565时，则结合经验反照率模型进行融合，具体方法可参考Wehrlé等（2021）的研究。
数据格式为采用EPSG:3413坐标系（WGS 84 / NSIDC海冰北极极射投影）的GeoTiff文件，建议使用rasterio库读取数据。数据集也可通过https://thredds.geus.dk/获取。

### 数据格式
数据采用EPSG:3413坐标系（WGS 84 / NSIDC海冰北极极射投影）的GeoTiff格式存储。

### 表1 SICE v3.0数据集变量（按字母排序）及说明
1. ANG：用于大气气溶胶校正的安斯特朗参数（Angström parameter）
2. AOD_550：来自CAMS的550 nm波段气溶胶光学厚度（Aerosol Optical Depth, AOD），单位为m
3. al：有效吸收长度，单位为mm
4. albedo_bb_spherical_sw：各向同性辐射下的宽带反照率
5. albedo_bb_planar_sw：宽带平面短波反照率
6. albedo_spectral_planar_NN：多光谱平面反照率，其中NN代表01-21波段编号
7. diagnostic_retrieval：逐像素反演诊断信息
8. cloud_mask,SCDA cloud mask：SCDA云掩膜
9. cv1：质量检查1（详见算法理论基础文档ATBD）
10. cv2：质量检查2（详见算法理论基础文档ATBD）
11. factor<：混合像元内的积雪覆盖占比
12. grain_diameter：有效光学雪粒直径
13. isnow：详见表2
14. lat：十进制纬度
15. lon：十进制经度
16. O3_SICE：经Kokhanovsky等（2020）臭氧散射校正后的OLCI总臭氧反演结果
17. r0：半无限非吸收积雪层的反射率
18. r_TOA_NN：多光谱大气层顶（Top of Atmosphere, TOA）反射率，其中NN代表01-21波段编号
19. r_BRR_NN：多光谱大气底界面反射率（Bottom of Reflectance, BRR），其中NN代表01-21波段编号
20. snow_specific_surface_area, SSA：积雪比表面积
21. saa：太阳方位角
22. sza：太阳天顶角
23. vaa：观测方位角
24. vza：观测天顶角

### 表2 诊断代码及说明
| 诊断代码 | 说明 |
| --- | --- |
| 0 | 洁净积雪 |
| 1 | 污染积雪 |
| 6 | 已计算r0且未通过观测推导的污染积雪 |
| 7 | 波段1、2的计算球面反照率大于0.98的污染积雪，已重新处理为洁净积雪 |
| 100 | 太阳天顶角超过75°，无反演反照率结果 |
| 102 | 波段21的大气层顶反射率小于0.1，无反演结果 |
| 104 | 雪粒直径小于0.1，无反演结果，疑似云标记 |
| -N | 波段N处无法求解污染积雪反照率方程 |

### 参考文献
1. Kokhanovsky, A., Vandecrux, B., Wehrlé, A., Danne, O., Brockmann, C., and Box, J. E.: 利用星载OLCI/S-3光谱反射率测量数据改进雪与冰属性反演：更新的大气校正与积雪杂质负荷估算方法，《Remote Sens. (Basel)》，15, 77, https://doi.org/10.3390/rs15010077, 2022
2. Kokhanovsky A.A., Lamare, M. and Rozanov, V. (2020) 利用Sentinel-3海洋与陆地彩色仪器反演南极地区总臭氧，《Journal of Quantitative Spectroscopy and Radiative Transfer》251, 107045, https://doi.org/10.1016/j.jqsrt.2020.107045

### 代码与数据获取
Bahbah, R., Wehrlé, A., Mankoff, K., Vandecrux, B., and Box, J. E.: Sentinel-3雪冰光学属性反演（SICE）v3.0版本，https://doi.org/10.5281/zenodo.10058790, 2023。数据获取与读取方法可参考https://github.com/GEUS-SICE/SICE_gather，相关问题可在此仓库提交。

### 致谢
本数据集由以下欧洲空间局（ESA）合同项目资助：
- 2016年12月 – 2019年1月：SEOM S34Sci陆地研究1：积雪，ESRIN合同4000118926/16/I-NB
- 2018年12月 – 2020年7月：EO科学赋能社会，ESA/合同4000125043/18/I-NB – ESA/AO/1-9101/17/I-NB EO科学赋能社会，预运行Sentinel-3雪冰产品（SICE）
- 2019年1月 – 2020年12月：ESA PRODEX，格陵兰冰冻圈气候监测用新型Sentinel-3算法业务化服务（CryoClim网络内项目）
- 2021年5月 – 2023年6月：ESA PRODEX，天气模式系统中Sentinel-3反照率的无缝集成（SISAWS）
- 2022年2月 – 2023年10月：ESA EO科学赋能社会，基于Sentinel-3的雪冰光学与物理属性研究（SICE），ESA CCN合同4000125043/18/I-NB，以及ESA资源网络。

### 相关信息
变量、输入与输出参数说明：https://github.com/GEUS-SICE/pySICE/tree/pySICEv2.1；https://snow.geus.dk/

问题咨询请联系Jason Box，邮箱：[e-mail]