Experimental downscaled TROPOMI SIF dataset for continental Europe

The present dataset represent the attempt done within the Sen4GPP project to produce a prototype downscaled SIF for continental Europe. The objective was to adapt an existing downscaling methodology (Duveiller et al. 2020) and apply it to selected sentinel data in order to downscale TROPOMI SIF data (Guanter et al. 2022) from a 10 km grid to a 1 km grid. The method relies on a locally calibrated model linking fine spatial resolution explanatory variables to the coarse spatial resolution target using a moving window. In this case, the explanatory variables are the Sentinel-3 OLCI green vegetation index (OGVI), and Sentinel-3 SLSTR daytime land surface temperature (LST), which are preprocessed into 8-daily composites by project partner U. of Southampton. For details on the downscaling algorithm, the reader is directed to the ATBD document of the Sen4GPP project.

The dataset covers the TROPOMI period from 2018-05-11 until 2020-12-29 for continental Europe. The data is in provided in sinusoidal projection widely used with the MODIS land products, and it covers the area of the MODIS tiles v2 to v5 and h17 to h20. The dataset is divided in separate NetCDF files, with each file covering the entire spatial domain for a single time slice, and each slice representing a period of 8-days. The main variable of interest in each individual file is the predicted downscaled SIF at 1km (variable name: sif) that is mapped on the main dimensions (easting, northing) that cover 4800 by 4800 pixels of circa 1km in the Sinusoidal projection.

本数据集记录了Sen4GPP项目中针对欧洲大陆制作降尺度日光诱导叶绿素荧光（SIF, Solar-Induced Chlorophyll Fluorescence）原型产品的相关尝试。本项目的目标是对已有的降尺度方法（Duveiller等人，2020）进行适配，并将其应用于选定的哨兵（Sentinel）系列卫星数据，从而将TROPOMI获取的SIF数据（Guanter等人，2022）从10公里网格分辨率降尺度至1公里网格分辨率。该方法依托一种经局部校准的模型，通过移动窗口技术将高空间分辨率的解释变量与低空间分辨率的目标变量建立关联。本研究中，解释变量为哨兵3号（Sentinel-3）OLCI绿色植被指数（OGVI）以及哨兵3号（Sentinel-3）SLSTR日间地表温度（LST, Land Surface Temperature），上述数据已由项目合作方南安普顿大学预处理为8天合成产品。如需了解降尺度算法的详细信息，请参阅Sen4GPP项目的ATBD文档。
本数据集的覆盖时段为2018年5月11日至2020年12月29日，对应TROPOMI的观测周期，研究区域为欧洲大陆。本数据集采用MODIS陆地产品广泛使用的正弦投影（Sinusoidal Projection），覆盖MODIS瓦片v2至v5以及h17至h20对应的区域范围。数据集被划分为多个独立的NetCDF格式文件，每个文件对应单个时间切片的全空间范围，每个时间切片代表8天的合成时段。每个文件中的核心关注变量为1公里分辨率的降尺度预测SIF（变量名：sif），该变量在正弦投影下的东向（easting）和北向（northing）维度上进行映射，对应4800×4800个约1公里分辨率的像素。