Development of the GCOM-C/SGLI Global Land Surface Phenology Product

Abstract:

Vegetation phenology describes not only the life cycle events of periodic plants during the growing season, but also acts as an indicator of biological responses to climate change. The Global Change Observation Mission–Climate (GCOM-C) is a newly launched satellite mission of JAXA (Japan Aerospace Exploration Agency) for understanding global climate change. It carries an optical sensor, Second Generation Global Imager (SGLI), with 250 m spatial resolution. In this study, we proposed a new method to generate Global Land Surface Phenology (GLSP) product based on the GCOM-C/SGLI data. This algorithm uses GCOM-C atmospheric corrected land reflectance data as the input to calculate a semi-analytical snow-free vegetation index, NDGI (Normalized Difference Greenness Index). The NDGI temporal trajectory is then reconstructed using an iterative Savitzky-Golay filter and modeled using a double-logistic function to retrieve the state of seasonal vegetation development. Last, the phenological transition dates were detected correspondingly, and the confidence of phenology detections was characterized based on the satellite data quality. The GCOM-C GLSP algorithm has been verified by the field phenology observations of specific species at multiple observation sites (i.e., Penological Eye Network, PhenoCam Network), and compared with the VIIRS and MODIS GLSP products to evaluate the resulting phenological metrics. The evaluation results demonstrated satisfactory agreements between the satellite-estimated and field-observed phenological metrics, indicating that the GCOM-C/SGLI data can be applied to yield a new generation of GLSP product at 250 m resolution.