Decorrelation rate and daily cycle in sub-daily time series of SAR coherence amplitude

Abstract

A dataset of sub-daily C-band data, acquired with a ground-based synthetic aperture radar, has been used to study soil and vegetation dynamics during a complete growing season in a controlled agricultural test site. The data have been exploited to analyse the rate and sources of decorrelation in the scene, as well as the consequences of the observation conditions of a sub-daily satellite (with either low, medium or geosynchronous orbit): short revisit times, availability of multiple acquisitions during a single day, and shallow observations at some incidence angles. Repeat-pass coherence is found to be less affected by temporal decorrelation when the primary image is acquired during nighttime or the last hours predawn. Regarding the incidence angle, VV has increased sensitivity to certain phenological stages as the incidence angle increases. Additionally, a periodic oscillation on a sub-daily scale is observed when creating coherence time series with increasing temporal baseline. Factors which strongly contribute to these oscillations are the daily cycles of temperature, soil moisture and vegetation water dynamics.

This work was funded by the European Space Agency (ESA Contract No. 4000132509/20/NL/FF/ab with UPC), supported by the Spanish MCINN funds Unidad de Excelencia Maria de Maeztu MDM-20160600 and Spanish MCINN AEI under projects PID2020-117303GBC21/AEI/10.13039/501100011033 and PID2020-117303GB-C22/AEI/ 10.13039/501100011033. Arturo Villarroya-Carpio enjoyed a 3-month stay at TU Delft under financial support from Banco Santander and the University of Alicante (Code: 70304B0001, Funding Line: 2023LS0048). Susan C. Steele-Dunne was supported by the Netherlands Organisation for Scientific Research (NWO) and Netherlands Space Office (NSO) under Grant NSOKNW.2019.001.

Peer Reviewed

Postprint (published version)