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Title:   Author  item
                                            DONG, GEANO - Oklahoma State Universityitem
                                            OCHSNER, TYSON - Oklahoma State Universityitem
                                            ZREDA, MAREK - University Of Arizonaitem
                                            Cosh, Michaelitem
                                            ZOU, C.B. - Oklahoma State University
  Submitted to: Vadose Zone Journal
                                    Publication Type: Peer Reviewed Journal
                                    Publication Acceptance Date: 3/15/2014
                                    Publication  Date: 4/17/2014
                                    Publication URL: http://handle.nal.usda.gov/10113/59812Citation: Dong, G., Ochsner, T., Zreda, M., Cosh, M.H., Zou, C. 2014. Calibration and validation of the COSMOS rover for surface soil moisture. Vadose Zone Journal.13:4. doi: 10.2136/vzj2013.08.0148.    Interpretive Summary: A new and innovative device for monitoring large scale soil moisture through the root zone (0-30 cm from the soil surface) has been deployed on a national scale to observe large scale trends in moisture availability.  This Cosmic-ray Soil Moisture Observing System (COSMOS) can detect soil moisture on a scale of up to a 350 m radius from the instrument.  This technology has been applied to a mobile land based platform called the COSMOS Rover, which can be moved across the land surface creating a spatial map of root zone soil moisture across a large domain, at a resolution higher than that available from satellite remote sensing.  This technology is ideal for rapid collection of land surface data for remote sensing validation campaigns.  The errors associated with this instrument are comparable to current in situ instruments and meet the criteria established by many space agencies for their satellite calibration/validation programs.  Users of this technology can also include rangeland managers and county agents, who could collect large scale soil moisture information, rapidly, with high accuracy.
                                Technical Abstract: The mobile COsmic-ray Soil Moisture Observing System (COSMOS) rover may be useful for validating satellite-based estimates of near surface soil moisture, but the accuracy with which the rover can measure 0-5 cm soil moisture has not been previously determined. Our objectives were to calibrate and validate a COSMOS rover for mapping 0-5 cm soil moisture at spatial scales suitable for evaluating satellite-based soil moisture estimates. The COSMOS rover was calibrated to field-average soil moisture measured with impedance probes. The resulting calibration was applied to map soil moisture on two dates for a 16 km × 10 km region around the Marena, Oklahoma, In Situ Sensor Testbed (MOISST) in north central Oklahoma and one date for a 34 km × 14 km region in the Little Washita River watershed in southwestern Oklahoma, USA. The mapped soil moisture patterns were consistent with regional spatial variability of surface soil texture and with soil wetting by an intervening rainfall. The rover measured field-average soil moisture with a RMSD = 0.03 cm3 cm-3 relative to impedance probes. Likewise, the regional-average 0-5 cm soil moisture determined by the rover was within ± 0.03 cm3 cm-3 of the best available independent estimates for each region. These results demonstrate that a COSMOS rover can be used effectively for 0-5 cm soil moisture mapping and for determining average soil moisture at spatial scales suitable for satellite calibration and validation.


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