Browsing by Author "Owen D. Howells"

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Examining the variation of soil moisture from cosmic-ray neutron probes footprint: experimental results from a COSMOS-UK site
(Springer Science and Business Media Deutschland GmbH, 2023) Owen D. Howells; George P. Petropoulos; Dimitris Triantakonstantis; Zacharias Ioannou; Prashant K. Srivastava; Spyridon E. Detsikas; George Stavroulakis
Utilising cosmic-ray neutron probes is a relatively new approach in obtaining larger area soil moisture and various operational monitoring networks have been established worldwide utilising this technology to measure operationally this parameter. One such network located in the United Kingdom (UK) is the Cosmic-ray Soil Moisture Observing System, so-called COSMOS-UK, established in 2013. The present study aims at investigating the true footprint and the variations within the footprint detectable area at the COSMOS-UK sites using as a case study one such site located in Riseholme, UK. At the selected experimental site extensive fieldwork was conducted in July 2017 that allowed examining the agreement among the soil moisture data retrieved by the Time Domain Transmissometer (TDT) sensors and the corresponding estimates from the COSMOS-UK network station probe. The COSMOS-UK site footprint was compared using GPS-aided information from ground instrumentation, assisted by drone imagery acquisition and the implementation of geospatial interpolation methods in a Geographical Information System (GIS) environment. Altogether, this information was used for assessing the soil moisture footprint extent from the COSMOS-UK site. The COSMOS-UK station footprint was representative for an area shorter in size than the alleged footprint of 600 m diameter, as generally proposed in various relevant investigations. The COSMOS network slightly overestimated soil moisture content measured by the TDT sensor probes installed in the area. Our study findings although concern specifically the studied experimental site contribute towards efforts aiming at assessing the COSMOS-UK soil moisture measurement footprint showcasing the added value of geospatial analysis in this direction. © 2022, The Author(s).
Exploring the potential of SCAT-SAR SWI for soil moisture retrievals at selected COSMOS-UK sites
(Taylor and Francis Ltd., 2021) Owen D. Howells; George P. Petropoulos; Prashant K. Srivastava; Dimitrios Triantakonstantis; Ionut Sandric
The need for information on soil moisture at large scale to facilitate a sustainable intensification of agricultural land and to ensure food security due to increasing populations cannot be overstated. Remote sensing provides a platform for potential national coverage of soil moisture monitoring. This study explores the potential for using a Synthetic-Aperture-Radar Soil Water Index (SCAT-SAR SWI) product as a method of accurately monitoring soil moisture across the UK by comparing its output with the COSMOS-UK cosmic-ray soil moisture observation network. Using the daily data from these stations, SWI data from SCAT-SAR were compared during 2015 for the UK. Five COSMOS-UK network sites were selected across the UK for assessment, and the respected SCAT-SAR SWI pixels were extracted for their soil moisture values. Statistical test that were computed allowed quantifying the correlation between the truth data of the TDT soil moisture sensors and the COSMOS and SCAT-SAR soil moisture product. It was found that the SCAT-SAR product consistently underestimated the soil moisture with elevation affecting the level of agreement. The COSMOS network slightly overestimated soil moisture but was found, at least in this study, noticeably more accurate than the SCAT-SAR. The RMSD of the SCAT-SAR product was noticeably higher at sites with the highest elevation. © 2021 Informa UK Limited, trading as Taylor & Francis Group.
RETRACTED ARTICLE: Examining the variation of soil moisture from cosmic-ray neutron probes footprint: experimental results from a COSMOS-UK site (Environmental Earth Sciences, (2023), 82, 1, (41), 10.1007/s12665-022-10721-1)
(Springer Science and Business Media Deutschland GmbH, 2025) Owen D. Howells; George P. Petropoulos; Dimitrios P. Triantakonstantis; Z. Ioannou; Prashant Kumar Srivastava; Spyridon E. Detsikas; G. G. Stavroulakis
The Editors have retracted this article. Following the Comment by Scheiffele et al. (2023), errors were found in data interpretation concerning the footprint radius of cosmic-ray neutron sensors. The authors have been offered to submit a revised manuscript for further peer review in future. George P. Petropoulos has stated on behalf of the authors that they disagree to this retraction. © The Author(s) 2024.