 |
| Titel |
Space-based passive microwave soil moisture retrievals and the correction for a dynamic open water fraction |
| VerfasserIn |
B. T. Gouweleeuw, A. I. J. M. Dijk, J. P. Guerschman, P. Dyce, M. Owe |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1027-5606
|
| Digitales Dokument |
URL |
| Erschienen |
In: Hydrology and Earth System Sciences ; 16, no. 6 ; Nr. 16, no. 6 (2012-06-08), S.1635-1645 |
| Datensatznummer |
250013325
|
| Publikation (Nr.) |
 copernicus.org/hess-16-1635-2012.pdf |
|
|
|
|
|
| Zusammenfassung |
| The large observation footprint of low-frequency satellite microwave
emissions complicates the interpretation of near-surface soil moisture
retrievals. While the effect of sub-footprint lateral heterogeneity is
relatively limited under unsaturated conditions, open water bodies (if not
accounted for) cause a strong positive bias in the satellite-derived soil
moisture retrieval. This bias is generally assumed static and associated
with large, continental lakes and coastal areas. Temporal changes in the
extent of smaller water bodies as small as a few percent of the sensor
footprint size, however, can cause significant and dynamic biases. We
analysed the influence of such small open water bodies on near-surface soil
moisture products derived from actual (non-synthetic) data from the Advanced
Microwave Scanning Radiometer for the Earth Observing System (AMSR-E) for
three areas in Oklahoma, USA. Differences between on-ground observations,
model estimates and AMSR-E retrievals were related to dynamic estimates of
open water fraction, one retrieved from a global daily record based on
higher frequency AMSR-E data, a second derived from the Moderate Resolution
Imaging Spectroradiometer (MODIS) and a third through inversion of the
radiative transfer model, used to retrieve soil moisture. The comparison
demonstrates the presence of relatively small areas (<0.05) of open water
in or near the sensor footprint, possibly in combination with increased,
below-critical vegetation density conditions (optical density <0.8), which
contribute to seasonally varying biases in excess of 0.2 (m3 m−3)
soil water content. These errors need to be addressed, either through
elimination or accurate characterisation, if the soil moisture retrievals
are to be used effectively in a data assimilation scheme. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|