Soil moisture mapping from SMOS: evaluating the accuracy of the operational product in a Mediterranean setting

ABSTRACT

The present study provides a thorough evaluation of the SMOS surface soil moisture (SSM) product in a typical Mediterranean setting in Greece. For this purpose, a total of 4 agricultural sites were used for which co-orbital in-situ measurements from ground SSM sensors were available for year 2020. In this context, the effect of topographical and geomorphological features, land use/cover and the satellite orbit type and the Radio Frequency Interference (RFI) were also examined. A series of statistical metrics were computed, which allowed evaluating the agreement between the 2 datasets. In overall, results showed a reasonable agreement in specific land use/cover types between the SMOS product and the corresponding in-situ measurements obtained from the 0–5 cm soil moisture layer. In most cases, Root Mean Square Difference (RMSD) was close to 0.15 m³ m⁻³ (minimum 0.126 m³ m⁻³). Tomato and vineyard showed a satisfactory agreement compared to walnut and cotton crops. The autumn period had the highest agreement for tomato crop. The effect of RFI was also quite noticeable, as after the exclusion of pixels with high RFI, statistical agreement was noticeably improved. This study is, to our knowledge, one of the few that investigates in a Greek setting the accuracy of the SMOS product. The study results can contribute to the understanding of the practical value of the SMOS product in agricultural and arid/semi-arid Mediterranean environments while support efforts ongoing globally aiming at improving the SMOS SSM product accuracy.

KEYWORDS:

• Soil moisture
• remote sensing
• SMOS
• validation
• agriculture
• Mediterranean setting

Acknowledgements

The authors wish to thank Neuropublic S.A. for providing the in-situ measurements used in the present study. The participation of George P. Petropoulos was financially supported by the LISTEN-EO project, implemented in the framework of H.F.R.I call “Basic research Financing (Horizontal support of all Sciences)” under the National Recovery and Resilience Plan “Greece 2.0” funded by the European Union –NextGenerationEU (H.F.R.I. Project Number: 15898). Also authors are grateful to the anonymous reviewers for their comments that helped improving the initially submitted manuscript.

Disclosure statement

No potential conflict of interest was reported by the author(s).