 |
| Titel |
A new perspective on the spatio-temporal variability of soil moisture: temporal dynamics versus time-invariant contributions |
| VerfasserIn |
H. Mittelbach, S. I. Seneviratne |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1027-5606
|
| Digitales Dokument |
URL |
| Erschienen |
In: Hydrology and Earth System Sciences ; 16, no. 7 ; Nr. 16, no. 7 (2012-07-20), S.2169-2179 |
| Datensatznummer |
250013372
|
| Publikation (Nr.) |
 copernicus.org/hess-16-2169-2012.pdf |
|
|
|
|
|
| Zusammenfassung |
| Knowledge about the spatio-temporal variability of soil moisture is essential
to understand and predict processes in climate science and hydrology. A
significant body of literature exists on the characterization of the spatial
variability and the rank stability (also called temporal stability) of
absolute soil moisture. Yet previous studies were generally based on
short-term measurement campaigns and did not distinguish the respective
contributions of time-varying and time-invariant components to these
quantities. In this study, we investigate this issue using measurements from
14 grassland sites of the SwissSMEX soil moisture network (spatial extent of
approx. 150 × 210 km) over the time period May 2010 to July 2011.
We thereby decompose the spatial variance of absolute soil moisture over time
in contributions from the spatial variance of the mean soil moisture at all
sites (which is time-invariant), and components that vary over time and are
related to soil moisture dynamics. These include the spatial variance of the
temporal soil moisture anomalies at all sites and the covariance between the
site anomalies to the spatial mean at a given time step and those for the
temporal mean values. The analysis demonstrates that the time-invariant term
contributes 50–160% (on average 94%) of the spatial soil moisture variance
at any point in time, while the covariance term generally contributes
negatively to the spatial variance. On the other hand, the spatial variance of
the temporal anomalies, which is overall most relevant for climate and
hydrological applications because it is related to soil moisture dynamics, is
relatively limited and constitutes at most 2–30% (on average 9%) of the
total variance. Nonetheless, this term is not negligible compared to the
temporal anomalies of the spatial mean. These results suggest that a large
fraction of the spatial variability of soil moisture assessed from short-term
campaign may be time-invariant if other regions present a similar behavior.
Moreover, we find that the rank (or temporal) stability concept, when
applied to absolute soil moisture at the sites, mostly characterizes the
time-invariant patterns. Indeed, sites that best represent the mean soil
moisture dynamics of the network are not the same as those that best reflect
mean soil moisture at any point in time. Overall, this study shows that
conclusions derived from the analysis of the spatio-temporal variability of
absolute soil moisture need not generally apply to temporal soil moisture
anomalies, and hence to soil moisture dynamics. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|