A new method for estimating of evapotranspiration and surface soil moisture from optical and thermal infrared measurements: the simplified triangle

ABSTRACT

Earth Observation (EO) provides a promising approach towards deriving accurate spatiotemporal estimates of key parameters characterizing land surface interactions, such as latent (LE) and sensible (H) heat fluxes as well as soil moisture content. This paper proposes a very simple method to implement, yet reliable to calculate evapotranspiration fraction (EF) and surface moisture availability (M_o) from remotely sensed imagery of Normalized Difference Vegetation Index (NDVI) and surface radiometric temperature (T_ir). The method is unique in that it derives all of its information solely from these two images. As such, it does not depend on knowing ancillary surface or atmospheric parameters, nor does it require the use of a land surface model. The procedure for computing spatiotemporal estimates of these important land surface parameters is outlined herein stepwise for practical application by the user. Moreover, as the newly developed scheme is not tied to any particular sensor, it can also be implemented with technologically advanced EO sensors launched recently or planned to be launched such as Landsat 8 and Sentinel 3. The latter offers a number of key advantages in terms of future implementation of the method and wider use for research and practical applications alike.

Acknowledgments

Dr Petropoulos contribution has been supported by the European Union’s Horizon 2020 Marie Skłodowska-Curie project ENViSIoN-EO (project reference number 752094) and the author is grateful to the funding body for the financial support provided. Sincere thanks also go to Erin Grebb helped with the figures’ improvement in the manuscript. Authors wish to also thank the anonymous reviewers and the handling editor for their useful comments, which resulted to improving the initially submitted manuscript.

Disclosure statement

No potential conflict of interest was reported by the authors.

Correction Statement

This article has been republished with minor changes. These changes do not impact the academic content of the article.