Global joint assimilation of GRACE and SMOS for improved estimation of root-zone soil moisture and vegetation response
<p>The lack of direct measurement of root-zone soil moisture poses a challenge to the large-scale prediction of ecosystem response to variation in soil water. Microwave remote sensing capability is limited to measuring moisture content in the uppermost few centimetres of soil. The GRACE (Gravi...
| Main Authors: | , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2019-02-01
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| Series: | Hydrology and Earth System Sciences |
| Online Access: | https://www.hydrol-earth-syst-sci.net/23/1067/2019/hess-23-1067-2019.pdf |
| Summary: | <p>The lack of direct measurement of root-zone soil moisture poses a challenge
to the large-scale prediction of ecosystem response to variation in soil
water. Microwave remote sensing capability is limited to measuring moisture
content in the uppermost few centimetres of soil. The GRACE (Gravity Recovery
and Climate Experiment) mission detected the variability in storage within
the total water column. However, root-zone soil moisture cannot be separated
from GRACE-observed total water storage anomalies without ancillary
information on surface water and groundwater changes. In this study, GRACE
total water storage anomalies and SMOS near-surface soil moisture
observations were jointly assimilated into a hydrological model globally to
better estimate the impact of changes in root-zone soil moisture on
vegetation vigour. Overall, the accuracy of root-zone soil moisture estimates
through the joint assimilation of surface soil moisture and total water
storage retrievals showed improved consistency with ground-based soil
moisture measurements and satellite-observed greenness when compared to
open-loop estimates (i.e. without assimilation). For example, the correlation
between modelled and in situ measurements of root-zone moisture increased
by 0.1 (from 0.48 to 0.58) and 0.12 (from 0.53 to 0.65) on average for
grasslands and croplands, respectively. Improved correlations were found
between vegetation greenness and soil water storage on both seasonal
variability and anomalies over water-limited regions. Joint assimilation
results show a more severe deficit in soil water anomalies in eastern
Australia, southern India and eastern Brazil over the period of 2010 to 2016
than the open-loop, consistent with the satellite-observed vegetation
greenness anomalies. The assimilation of satellite-observed water content
contributes to more accurate knowledge of soil water availability, providing
new insights for monitoring hidden water stress and vegetation conditions.</p> |
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| ISSN: | 1027-5606 1607-7938 |