10 years of SMOS – Passive Microwave Vegetation Opacity Study

The overall objective of this project is to create two consistent data cubes containing long, consistent, times series of vegetation variables estimated with microwaves and visible observations. The microwave Vegetation Optical Depth (VOD) will be derived from at frequencies from 1.4GHz to 37 GHz. Vegetation variables such as the Fraction of Absorbed Photosynthetically Active Radiation or Leaf Chlorophyll Content will be derived from visible wavelengths. The VOD and visible data will be used to explore a number of applications, in particular to estimate the Above Ground Biomass (AGB). An alternative method using machine learning approaches to estimate AGB directly from the brightness temperatures measured at microwave wavelengths, without estimating VOD, will also be studied.

The two methods to estimate AGB will be evaluated to i) assess the most efficient and appropriate method to estimate AGB ii) improve current AGB estimates from remote sensing observations.

SMOS is the core of this project as it provides 12 years of L-band observations and most importantly, L-band observations are very sensitive to the biomass and its vegetation water content, as shown by recent studies.”

  • J. Rodríguez-Fernández, A. Mialon, S. Mermoz, A. Bouvet, P. Richaume, A. Al Bitar, A. Al-Yaari, M. Brandt, T. Kaminski, T. Le Toan, Y. H. Kerr, and J.-P. Wigneron, “An evaluation of smos l-band vegetation optical depth (l-vod) data sets : high sensitivity of l-vod to above-ground biomass in africa,” Biogeosciences, vol. 15, no. 14, pp. 4627–4645, 2018.
  • Rodríguez-Fernández, N. J., Richaume, P., Bousquet, E., Mialon, A., Al Bitar, A., Saatchi, S., & Kerr, Y. H. (2019, July). Is vegetation optical depth needed to estimate biomass from passive microwave radiometers? A statistical study using neural networks. In IGARSS 2019-2019 IEEE International Geoscience and Remote Sensing Symposium (pp. 5496-5499). IEEE.
  • Emma Bousquet, Arnaud Mialon, Nemesio Rodriguez Fernandez, Stéphane Mermoz, Alexandre Bouvet, Olivier Merlin, Yann Kerr, 2019. Downscaling the Vegetation Optical Depth from SMOS for High Resolution estimation of Biomass, IGARSS August 2019
  • Mialon, N. J. Rodríguez-Fernández, M. Santoro, S. Saatchi, S. Mermoz, E. Bousquet, and Y. H. Kerr, “Evaluation of the sensitivity of smos l-vod to forest above-ground biomass at global scale,” Remote Sensing, vol. 12, no. 9, p. 1450, 2020.
  • Bousquet, A. Mialon, N. Rodriguez-Fernandez, C. Prigent, F. Wagner, and Y. Kerr, “Influence of surface water variations on vod and biomass estimates from passive microwave sensors,” Remote Sensing of Environment, vol. 257, p. 112345, 2021.
  • Schwank, A. Kontu, A. Mialon, R. Naderpour, D. Houtz, J. Lemmetyinen, K. Rautiainen, P. Richaume, and Y. Kerr, “Temperature dependence of l-vod of a boreal forest.” in revision Remote Sensing of Environment, 2021.