Earth observation method for an operational assessment of crop phenology metric “start of the season”

Abstract

Vegetation phenology is one of the key indicators for assessing inter annual changes of ecosystems while crop phenology has crucial and practical importance for precise timing of farming practices of today’s smart agriculture. The aim of this study is to develop and implement a procedure for filtering and processing daily satellite signals from Moderate Resolution Imaging Spectroradiometer (MODIS) satellites for the operational derivation of vegetation indices and land surface phenology (LSP) metrics. Second, this work investigates and selects precisely adjusted parameters for the calculation of a specific LSP metric – the SOS (start of the season). The SOS obtained from the satellite data was compared with available in situ ground measurements at 80 sites with records from 2000-2012 across the Czech Republic. The coefficients of determination, R2, for the land surface phenology based on Earth observation and traditional ground phenology indicated differences between the two methods. However, the average R2 at all sites for agricultural land was 0.31 for winter wheat onset of leaf sheath elongation; the R2 exceeded 0.5 at 21 sites and was approximately 0.7 at some sites. The developed procedure proved suitable for operational monitoring of actual crop conditions and other influence factors that are important for drought monitoring.