Temporal Decorrelation of Tropical Dense Forest at C-Band: First Insights From the TropiScat-2 Experiment

Salma El Idrissi Essebtey (1) , Ludovic Villard (2) , Pierre Borderies (1) , Thierry Koleck (2) , Jean-Pascal Monvoisin (1) , Benoît Burban (3) , Thuy Le Toan (2)

1 DEMR, ONERA, Université de Toulouse [Toulouse]
2 CESBIO - Centre d'études spatiales de la biosphère
3 UMR ECOFOG - Ecologie des forêts de Guyane

Following the past TropiScat and AfriScat tower-based scatterometer experiments conducted as part of the ESA BIOMASS mission preparation activities, a follow-on experiment referred to as TropiScat-2 has been undertaken in French Guiana since March 2018. Based on new capabilities including C-band acquisitions, this paper addresses the question of temporal decorrelation variability at several time scales using a period of 67 days dating back to early August 2018. Overall, C-band coherences have been found very dependent on the reference hour and higher than expected at night (15-min coherences above 0.75 and 1-hour coherences above 0.5 75% of the time). Supported by meteorological data from the flux-tower, clear evidence about diurnal convective effects is shown. For the first time the link with evapotranspiration is pointed out based on a drop of the 15-min coherences going from about 0.8 to 0.2 in less than 1 hour (around 7h30) and before the rise of convective winds. Furthermore, the specific impacts of convective winds during the day have been demonstrated using very short timescales (with the spread of coherences at 1sec from 0 to 0.9), whereas it is more difficult to separate these effects from those of water transfer for longer timescales. In addition to provide new insights for the understanding of microwave interactions with dense vegetation, these results should also contribute to widen the capabilities of future companion or high revisit space-borne missions at C-band.

Mots clés: C-band; Convective Wind; Evapotranspiration; Temporal Decorelation; Time Series; Tower-Based Scatterometer; Tropical Dense Forests

Mots clés: Series Temporelles; Décorrélation Temporelle; Evapotranspiration; Bande C; Vent de convection; Diffusiomètre à tour; Forêt tropicale dense

Domaines: Sciences de l'ingénieur [physics]; Physique [physics]

Salma El Idrissi Essebtey, Ludovic Villard, Pierre Borderies, Thierry Koleck, Jean-Pascal Monvoisin, et al.. Temporal Decorrelation of Tropical Dense Forest at C-Band: First Insights From the TropiScat-2 Experiment. IEEE Geoscience and Remote Sensing Letters, 2019, pp.1-5. ⟨10.1109/LGRS.2019.2937382⟩. ⟨hal-02488980⟩