Start-of-season date 2017-present (raster 10m and 100m), Europe, yearly, Nov. 2022 - adjusted to the HRL grid

The Start-of-Season Date (SOSD), one of the Vegetation Phenology and Productivity (VPP) parameters, is a product of the pan-European High Resolution Vegetation Phenology and Productivity (HR-VPP) component of the Copernicus Land Monitoring Service (CLMS). The Start-of-Season Date (SOSD) marks the date when the vegetation growing season starts in the time profile of the Plant Phenology Index (PPI). The start-of-season occurs, by definition, when the PPI value reaches 25% of the season amplitude during the green-up period. The Plant Phenology Index (PPI) is a physically based vegetation index, developed for improving the monitoring of the vegetation growth cycle. The PPI index values, with 5-day satellite revisit cycle, are first used in a function fitting to derive the PPI Seasonal Trajectories, which is a filtered time series with regular 10-day time step. From these Seasonal Trajectories, a suite of 13 Vegetation Phenology and Productivity (VPP) parameters are then computed and provided, for up to two seasons each year. The Start-of-Season Date is one of the 13 parameters. The full list is available in the table 3 of the Product User Manual in the below link section. A complementary quality indicator (QFLAG) provides a confidence level, that is described in table 4 of the same manual. The SOSD dataset is made available as raster files with 10 x 10m and 100 x 100m resolutions, in ETRS89-LAEA projection corresponding to the HRL grid, for those tiles that cover the EEA38 countries and the United Kingdom and for two seasons in each year from 2017 onwards. It is updated in the first quarter of each year.季始日期（Start-of-Season Date, SOSD）是植被物候与生产力（Vegetation Phenology and Productivity, VPP）参数之一，隶属于哥白尼陆地监测服务（Copernicus Land Monitoring Service, CLMS）泛欧洲高分辨率植被物候与生产力（High Resolution Vegetation Phenology and Productivity, HR-VPP）组件产出的产品。 季始日期标识了植物物候指数（Plant Phenology Index, PPI）时间剖面中植被生长季启动的节点。根据定义，当植被返青期内植物物候指数达到该季振幅的25%时，即判定为生长季开始。 植物物候指数（Plant Phenology Index, PPI）是一种基于物理机制的植被指数，专为优化植被生长周期监测而研发。该指数的卫星重访周期为5天，其数值首先通过函数拟合得到PPI季节轨迹（PPI Seasonal Trajectories）——这是一种采用10天固定时间步长的滤波时间序列。基于上述季节轨迹，可计算并提供共计13项植被物候与生产力参数，每年最多可输出两个生长季的对应数据，季始日期即为这13项参数之一。完整参数列表可参见下文链接部分的《产品用户手册》表3。 配套的质量标识（QFLAG）可提供数据置信度等级，相关说明见该手册的表4。 季始日期数据集以栅格文件形式发布，分辨率包含10×10米与100×100米两种，投影采用对应高分辨率网格（High Resolution Grid, HRL）的ETRS89-LAEA坐标系，覆盖EEA38成员国与英国的相关分幅数据，自2017年起每年可提供两个生长季的数据，且于每年第一季度完成更新。