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| Titel |
Investigating temporal field sampling strategies for site-specific calibration of three soil moisture–neutron intensity parameterisation methods |
| VerfasserIn |
J. Iwema, R. Rosolem, R. Baatz, T. Wagener, H. R. Bogena |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1027-5606
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| Digitales Dokument |
URL |
| Erschienen |
In: Hydrology and Earth System Sciences ; 19, no. 7 ; Nr. 19, no. 7 (2015-07-24), S.3203-3216 |
| Datensatznummer |
250120767
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| Publikation (Nr.) |
 copernicus.org/hess-19-3203-2015.pdf |
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| Zusammenfassung |
| The Cosmic-Ray Neutron Sensor (CRNS) can provide soil moisture
information at scales relevant to hydrometeorological modelling
applications. Site-specific calibration is needed to translate CRNS
neutron intensities into sensor footprint average soil moisture
contents. We investigated temporal sampling strategies for
calibration of three CRNS parameterisations (modified N0, HMF,
and COSMIC) by assessing the effects of the number of sampling days
and soil wetness conditions on the performance of the calibration
results while investigating actual neutron intensity measurements,
for three sites with distinct climate and land use: a semi-arid
site, a temperate grassland, and a temperate forest. When calibrated
with 1 year of data, both COSMIC and the modified N0 method
performed better than HMF. The performance of COSMIC was remarkably
good at the semi-arid site in the USA, while the N0mod
performed best at the two temperate sites in Germany. The successful
performance of COSMIC at all three sites can be attributed to the
benefits of explicitly resolving individual soil layers (which is
not accounted for in the other two parameterisations). To better
calibrate these parameterisations, we recommend in situ soil sampled
to be collected on more than a single day. However, little
improvement is observed for sampling on more than 6 days. At the
semi-arid site, the N0mod method was calibrated better
under site-specific average wetness conditions, whereas HMF and
COSMIC were calibrated better under drier conditions. Average soil
wetness condition gave better calibration results at the two humid
sites. The calibration results for the HMF method were better when
calibrated with combinations of days with similar soil wetness
conditions, opposed to N0mod and COSMIC, which profited
from using days with distinct wetness conditions. Errors in actual
neutron intensities were translated to average errors specifically
to each site. At the semi-arid site, these errors were below the
typical measurement uncertainties from in situ point-scale sensors
and satellite remote sensing products. Nevertheless, at the two
humid sites, reduction in uncertainty with increasing sampling days
only reached typical errors associated with satellite remote sensing
products. The outcomes of this study can be used by researchers as a
CRNS calibration strategy guideline. |
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