Validation of Vegetation Biophysical Parameters at the Valencia Anchor Station in the Framework of Copernicus Sentinel-3 OLCI

<p>The <em>Valencia Anchor Station</em> (VAS) is an Earth Observation super site run by the <em>University of Valencia</em>, where a fair number of satellite remote sensing missions are validated. Within the framework of the Joint ESA-EUMETSAT &#8220;<em>OLCI Land Validation</em> (OLCI-Land-Val)&#8221; project, and of the <em>Joint Research Center</em> <em>Ground-Based Observations for Validation (GBOV) of Copernicus Global Land Products</em>, the <em>Climatology from Satellites</em> <em>Group </em>(GCS) has installed a total of 16 FAPAR <em>(Fraction of Absorbed Photosynthetic Active Radiation</em>) stations over a large vineyard area, where the GCS has carried out an extended number of field campaigns following the vine phenological cycle to validate the relevant parameters related to chlorophyll and N₂ content, LAI (<em>Leaf Area Index</em>), surface temperature and soil moisture together with the Sentinel-3-A and -B more OLCI-specific products OLCI FAPAR and OTCI (<em>OLCI Terrestrial Chlorophyll Index</em>).</p><p>This presentation shows the work carried out from the design and assembly of the FAPAR fixed stations, and the data series processed for the entire study period (2016-2021), to the different observations and validations carried out during the intensive observation campaigns. carried out in the area. Specifically, the data collection carried out consists of measurements using the SPAD 502 Plus Chlorophyll Meter which instantly measures the chlorophyll content or &#8220;greenness&#8221; of the plants, and whose calibration is carried out by means of cold extraction in the laboratory. These measurements are also used for the validation of the OTCI product obtained from Sentinel-3, as well as for its correlation with the continuously measured FAPAR and with the corresponding Sentinel-3 OLCI FAPAR product. Additionally, LAI data are included to establish the vegetation cover as well as soil moisture content and radiative surface temperature as a reference for the hydric stress conditions suffered by the vegetation.</p><p>At the same time, a study of the vegetation cover has been carried out on the study area using the products MCD15A3H, MCD12Q1-2 and MOD-MYD13, to establish a soil correction of the data collected at the plant level.</p><p>This leads to results where FAPAR and chlorophyll can be observed at three different levels, namely, in-situ plant, in-situ 300m x 300m with correction for the influence of the soil and satellite data. This research is important as a starting point in the validation of new indices with greater physical foundation and as confirmation of the robustness of the sensors on board the Sentinel 3-A, -B satellites for the continuity of the programme.</p>