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| Titel |
Influence of cracking clays on satellite estimated and model simulated soil moisture |
| VerfasserIn |
Y. Y. Liu, J. P. Evans, M. F. McCabe, R. A. M. Jeu, A. I. J. M. Dijk, H. Su |
| 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 ; 14, no. 6 ; Nr. 14, no. 6 (2010-06-18), S.979-990 |
| Datensatznummer |
250012337
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| Publikation (Nr.) |
 copernicus.org/hess-14-979-2010.pdf |
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| Zusammenfassung |
| Vertisols are clay soils that are common in the monsoonal and dry warm
regions of the world. One of the characteristics of these soil types is to
form deep cracks during periods of extended dry, resulting in significant
variation of the soil and hydrologic properties. Understanding the influence
of these varying soil properties on the hydrological behavior of the system
is of considerable interest, particularly in the retrieval or simulation of
soil moisture. In this study we compare surface soil moisture (θ in m3 m−3)
retrievals from AMSR-E using the VUA-NASA (Vrije Universiteit
Amsterdam in collaboration with NASA) algorithm with simulations from the
Community Land Model (CLM) over vertisol regions of mainland Australia. For
the three-year period examined here (2003–2005), both products display
reasonable agreement during wet periods. During dry periods however, AMSR-E
retrieved near surface soil moisture falls below values for surrounding
non-clay soils, while CLM simulations are higher. CLM θ are also higher than
AMSR-E and their difference keeps increasing throughout these dry periods.
To identify the possible causes for these discrepancies, the impacts of land
use, topography, soil properties and surface temperature used in the AMSR-E
algorithm, together with vegetation density and rainfall patterns, were
investigated. However these do not explain the observed θ responses.
Qualitative analysis of the retrieval model suggests that the most likely
reason for the low AMSR-E θ is the increase in soil porosity and surface
roughness resulting from cracking of the soil. To quantitatively identify
the role of each factor, more in situ measurements of soil properties that
can represent different stages of cracking need to be collected. CLM does
not simulate the behavior of cracking soils, including the additional loss
of moisture from the soil continuum during drying and the infiltration into
cracks during rainfall events, which results in overestimated θ when cracks
are present. The hydrological influence of soil physical changes are
expected to propagate through the modeled system, such that modeled
infiltration, evaporation, surface temperature, surface runoff and
groundwater recharge should be interpreted with caution over these soil
types when cracks might be present. Introducing temporally dynamic roughness
and soil porosity into retrieval algorithms and adding a "cracking clay"
module into models are expected to improve the representation of vertisol
hydrology. |
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