SST CCI Auxiliary Datasets

These auxiliary datasets are used in the generation of SST CCI ATSR and AVHRR products. Each set of files is contained in a separate tar archive and their application is briefly described below. For more information on the SST CCI algorithms please refer to the publicly available Algorithm Theoretical Basis Document. Retrieval coefficients: ATSR_Retrieval_Coeffs.tar These files contain the retrieval coefficients used to retrieve SST for the ATSR instruments. These are banded by total column water vapour and viewing angle. Coefficients are provided for all applicable retrievals - nadir two channel (n2), nadir three channel (n3), dual-view two channel (d2) and dual-view three channel (d3). Spectral response functions: AATSR_SRF.tar, ATSR2_SRF.tar, ATSR1_SRF.tar, AVHRR_SRF.tar These files contain the spectral response functions for each channel of each ATSR and AVHRR instrument. Note that all the AVHRR instruments are bundled in a single tar file including NOAA6 - NOAA19 and MetopA. All files are in plain text format containing two columns, the first is the wavelength and the second the filter response at that wavelength. Probability Density Functions: ATSR_PDFs.tar, AVHRR_PDFs.tar These are netCDF format files which include spectral and textural PDFs for cloudy conditions and textural PDFs only for clear-sky conditions. Dimensions are defined also as variables which give metadata describing their bounds and bin widths. The PDFs themselves are multi-dimensional variables constrained by the definitions of their given dimensions. Sea Surface Emissivity: ATSR_sse.tar, AVHRR_sse.tar Within SST CCI, the sea surface emissivity is calculated offline, and then passed to RTTOV for use within the radiative transfer calculation (by-passing the internal RTTOV surface emissivity model). These files are in ascii format and constructed in such a way as to be readable by RTTOV. Level 4 Land/Sea Mask mask_ostia20Tnolakes.nc This is a netCDF format file containing the land/sea mask used when generating Level 4 data on the OSTIA grid.

本辅助数据集用于生成海表温度气候变化倡议（SST CCI）的沿轨扫描辐射计（ATSR）与先进甚高分辨率辐射计（AVHRR）产品。每组文件均存储于独立的tar归档文件中，其应用场景下文将简要说明。如需了解SST CCI算法的更多细节，请参阅公开可用的《算法理论基础文档》（Algorithm Theoretical Basis Document）。

反演系数（Retrieval coefficients）：ATSR_Retrieval_Coeffs.tar
该归档文件包含用于ATSR仪器反演海表温度的反演系数。这些系数按总柱水汽与观测视角进行分组。所有适用的反演场景均提供了对应系数——包括天底双通道（n2）、天底三通道（n3）、双视角双通道（d2）以及双视角三通道（d3）。

光谱响应函数（Spectral response functions）：AATSR_SRF.tar、ATSR2_SRF.tar、ATSR1_SRF.tar、AVHRR_SRF.tar
这些归档文件包含各ATSR与AVHRR仪器各通道的光谱响应函数。请注意，所有AVHRR仪器（涵盖NOAA 6至NOAA 19以及MetopA）的光谱响应函数均打包至单个tar归档文件中。所有文件均为纯文本格式，包含两列数据：第一列为波长，第二列为该波长下的滤光片响应值。

概率密度函数（Probability Density Functions，PDFs）：ATSR_PDFs.tar、AVHRR_PDFs.tar
这些文件为网络通用数据格式（netCDF）文件，包含云况下的光谱与纹理概率密度函数，以及晴空下仅有的纹理概率密度函数。维度同样以变量形式定义，用于提供描述其边界与分箱宽度的元数据。概率密度函数本身为受给定维度定义约束的多维变量。

海表发射率（Sea Surface Emissivity）：ATSR_sse.tar、AVHRR_sse.tar
在SST CCI项目中，海表发射率先通过离线方式计算，随后传入RTTOV用于辐射传输计算（绕过RTTOV内置的海表发射率模型）。这些文件为美国信息交换标准代码（ASCII）格式，其结构可被RTTOV直接读取。

四级海陆掩膜（Level 4 Land/Sea Mask）：mask_ostia20Tnolakes.nc
该文件为网络通用数据格式（netCDF）文件，包含在OSTIA网格上生成四级数据时所用的海陆掩膜数据。