References

HESS

Hydrology and Earth System Sciences

HESS

Hydrol. Earth Syst. Sci.

1607-7938

Copernicus Publications

Göttingen, Germany

10.5194/hess-18-4363-2014

Translating aboveground cosmic-ray neutron intensity to high-frequency soil moisture profiles at sub-kilometer scale

Rosolem

https://orcid.org/0000-0002-4914-692X

¹ Hoar

² Arellano

³ Anderson

J. L.

² Shuttleworth

W. J.

⁴ Zeng

https://orcid.org/0000-0001-7352-2764

³ Franz

T. E.

https://orcid.org/0000-0003-2947-0906

⁵

Queens School of Engineering, University of Bristol, Bristol, UK

NCAR Data Assimilation Research Section, Boulder, USA

Department of Atmospheric Sciences, University of Arizona, Tucson, USA

Department of Hydrology and Water Resources, University of Arizona, Tucson, USA

School of Natural Resources, University of Nebraska-Lincoln, Lincoln, USA

04 11 2014

18 11 4363 4379

2014

This work is licensed under the Creative Commons Attribution 3.0 Unported License. To view a copy of this licence, visit https://creativecommons.org/licenses/by/3.0/

This article is available from https://hess.copernicus.org/articles/18/4363/2014/hess-18-4363-2014.html

The full text article is available as a PDF file from https://hess.copernicus.org/articles/18/4363/2014/hess-18-4363-2014.pdf

Above-ground cosmic-ray neutron measurements provide an opportunity to infer soil moisture at the sub-kilometer scale. Initial efforts to assimilate those measurements have shown promise. This study expands such analysis by investigating (1) how the information from aboveground cosmic-ray neutrons can constrain the soil moisture at distinct depths simulated by a land surface model, and (2) how changes in data availability (in terms of retrieval frequency) impact the dynamics of simulated soil moisture profiles. We employ ensemble data assimilation techniques in a "nearly-identical twin" experiment applied at semi-arid shrubland, rainfed agricultural field, and mixed forest biomes in the USA. The performance of the Noah land surface model is compared with and without assimilation of observations at hourly intervals, as well as every 2 days. Synthetic observations of aboveground cosmic-ray neutrons better constrain the soil moisture simulated by Noah in root-zone soil layers (0–100cm), despite the limited measurement depth of the sensor (estimated to be 12–20cm). The ability of Noah to reproduce a "true" soil moisture profile is remarkably good, regardless of the frequency of observations at the semi-arid site. However, soil moisture profiles are better constrained when assimilating synthetic cosmic-ray neutron observations hourly rather than every 2 days at the cropland and mixed forest sites. This indicates potential benefits for hydrometeorological modeling when soil moisture measurements are available at a relatively high frequency. Moreover, differences in summertime meteorological forcing between the semi-arid site and the other two sites may indicate a possible controlling factor to soil moisture dynamics in addition to differences in soil and vegetation properties.

National Science Foundation

ATM-0838491

National Aeronautics and Space Administration

NNX09A021G

National Aeronautics and Space Administration

NNX11A110G

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