ESTIMATES OF FOREST GROWING STOCK VOLUME OF THE NORTHERN HEMISPHERE FROM ENVISAT ASAR

摘要

This paper presents and assesses a dataset of forest growing stock volume (GSV) above 30°N estimated from multi-temporal backscatter measurements acquired by Envisat Advanced Synthetic Aperture Radar (ASAR) in ScanSAR mode. The retrieval was based on the BIOMASAR algorithm that combines standard SAR processing techniques for multi-temporal SAR data and an automated GSV estimation approach based on a Water Cloud-like model and a weighted combination of GSV estimates from individual measurements of the SAR backscatter. Approximately 70,000 ASAR images were used to estimate GSV at a pixel size of 0.01°. Assessment of the retrieved GSV indicated (ⅰ) the importance of comparing to reference data at the same scale, (ⅱ) moderate agreement with reference datasets at full resolution because of the limited sensitivity of Cband SAR backscatter to GSV, (ⅲ) strong agreement with reference datasets after aggregation at regional and national level, (ⅳ) consistent retrieval results throughout the study area, (ⅴ) saturation at approximately 300 m~3/ha.