Long-Term Trends of P-Band Temporal Decorrelation Over a Tropical Dense Forest-Experimental Results for the BIOMASS Mission

• Published in: IEEE transactions on geoscience and remote sensing Vol. 60; pp. 1 - 15
• Main Authors: El Idrissi Essebtey, Salma, Villard, Ludovic, Borderies, Pierre, Koleck, Thierry, Burban, Benoit, Le Toan, Thuy
• Format: Journal Article
• Language: English
• Published: New York IEEE 2022; The Institute of Electrical and Electronics Engineers, Inc. (IEEE); Institute of Electrical and Electronics Engineers
• Subjects: Biomass; BIOMASS mission; Coherence; Dry season; Engineering Sciences; Evolution; Forestry; long-term temporal decorrelation; P-band; P-band scatterometer; Physics; Poles and towers; Rainforests; Rainy season; repeat-pass polarimetric and interferometric synthetic-aperture radar (PolInSAR) and synthetic-aperture radar tomography (TomoSAR); Seasons; Spaceborne radar; Statistical methods; Time series; Time series analysis; Tomography; tower-scat experiment; Trends; Tropical climate; tropical dense forest; Tropical forests; Wet season; P-band; BIOMASS mission; long-term temporal decorrelation; P-band scatterometer; tropical dense forest; tower-scat experiment
• ISSN: 0196-2892; 1558-0644
• DOI: 10.1109/TGRS.2021.3082395

Fostered by the upcoming BIOMASS mission, this article explores long-term trends of P-band temporal decorrelation over a tropical forest due to a time series of 617 days acquired during the TropiScat-2 experiment. The interest in this unique time series is twofold. First, it provides consistent statistics to monitor the yearly evolution of temporal coherences according to specific time scales of the BIOMASS tomographic and interferometric phases. Second, it provides key insights to explore new processing approaches with the combination of data from different orbit directions (ascending/descending) and different mission cycles separated by about seven months according to the current acquisition plan. For the first time, this study shows that 18-day coherences (corresponding to the time interval between the first and last acquisitions of the BIOMASS tomographic processing) can vary significantly according to rainy and dry seasons (medians from 0.3 to 0.9). The extension to time intervals of up to 90 days within both seasons and over two consecutive years puts forward the key role of the typical sporadic rainfalls occurring during dry periods in tropical rainforests, with a stronger impact on temporal coherence evolution compared to the more reproducible rainy seasons. Furthermore, outstanding values significantly above zero have been obtained for the 7- and 14-month coherences (medians of 0.35 and 0.2, respectively), opening the way to new methods of change detection. Overall, this study highlights the role of P-band temporal decorrelation not only as a disturbance factor for coherent applications but also as a relevant indicator of forest changes.