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ARS Home » Northeast Area » Beltsville, Maryland (BARC) » Beltsville Agricultural Research Center » Hydrology and Remote Sensing Laboratory » Research » Publications at this Location » Publication #304562
Title: Field-scale moisture estimates using COSMOS sensors: a validation study with temporary networks and leaf-area-indices

Author
item Coopersmith, Evan
item Cosh, Michael
item Daughtry, Craig

Submitted to: Journal of Hydrology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/18/2014
Publication Date: 11/27/2014
Publication URL: http://handle.nal.usda.gov/10113/60398
Citation: Coopersmith, E.J., Cosh, M.H., Daughtry, C.S. 2014. Field-scale moisture estimates using COSMOS sensors: A validation study with temporary networks and leaf-area-indices. Journal of Hydrology. 519:637-643.

Interpretive Summary: The Cosmic-ray Soil Moisture Observing System (COSMOS) is a new and innovative method for estimating surface and near surface soil moisture at large (~700 m) scales. However, this systems is susceptible to water molecules in the sensing region. Thererfore, not only soil water, but water within vegetation contributes to the soil moisture estimate. For agricultural domains, this effect may be significant. A study was developed near a COSMOS station in Beltsville, MD, to determine the magnitude of this influence. Routine soil moisture and vegetation water content samples were collected and using a simple linear regression equation, the error associated with vegetation is reduced. The results of this study demonstrate the impact of vegetation water content on the COSMOS estimates and will enable the COSMOS network to improve their calibrations for agricultural domains.

Technical Abstract: The Cosmic-ray Soil Moisture Observing System (COSMOS) is a new and innovative method for estimating surface and near surface soil moisture at large (~700 m) scales. This system accounts for liquid water within its measurement volume. Many of the sites used in the early validation of the system had low and stable vegetation water content. It is necessary to perform validation of COSMOS in a landscape with a significant change in vegetation water content to estimate its impact on the COSMOS estimate, and potentially correct the estimate to account for the dynamic vegetation cover. A COSMOS station was installed in Beltsville, MD in the spring of 2012, within the domain of a long term experimental station on USDA property. This station has a large array of soil moisture sensors in profile across the field, which is approximately 700 meters in diameter. Frequent estimates of Leaf Area Index (LAI) were made throughout the 2012 and 2013 growing seasons (May through September). COSMOS readings, with a simple linear adjustment, were able to produce estimates of area-weighted averages of the existing in situ network with root-mean-squared-errors (RMSE) of soil-water content well below 0.04 m3/m3 and with additional modeling to account for leaf area index values, RMSE values 0.03 m3/m3 were achieved.