期刊
IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING
卷 54, 期 6, 页码 3513-3531出版社
IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC
DOI: 10.1109/TGRS.2016.2519842
关键词
Advanced Microwave Scanning Radiometer-Earth Observing System (AMSR-E); Advanced Scatterometer (ASCAT); soil moisture; vegetation optical depth
类别
资金
- Austrian Science Funds (FWF) through the Doctoral Program on Water Resource System of the Vienna University of Technology [DK-plus W1219-N22]
- European Space Agency (ESA) through the Climate Change Initiative for Soil Moisture [4000104814/11/I-NB]
- European Organisation for the Exploitation of Meteorological Satellites (EUMETSAT) through the Satellite Application Facility on Support to Operational Hydrology and Water Management (H-SAF)
In microwave remote sensing of the Earth's surface, the satellite signal holds information on both soil moisture and vegetation. This necessitates a correction for vegetation effects when retrieving soil moisture. This paper assesses the strengths and weaknesses of the existing vegetation correction as part of the Vienna University of Technology (TU-Wien) method for soil moisture retrieval from coarse-scale active microwave observations. In this method, vegetation is based on a multiyear climatology of backscatter variations related to phenology. To assess the plausibility of the correction method, we first convert the correction terms for retrievals from the Advanced Scatterometer (ASCAT) into estimates of vegetation optical depth tau(a) using a water-cloud model. The spatial and temporal behaviors of the newly developed ta are compared with the optical depth retrieved from passive microwave observations with the land parameter retrieval model tau(a). Spatial patterns correspond well, although low values for ta are found over boreal forests. Temporal correlation between the two products is high (R = 0.5), although negative correlations are observed in drylands. This comparison shows that ta and thus the vegetation correction method are sensitive to vegetation dynamics. Effects of the vegetation correction on soil moisture retrievals are investigated by comparing retrieved soil moisture before and after applying the correction term to modeled soil moisture. The vegetation correction increases the quality of the soil moisture product. In areas of high interannual variability in vegetation dynamics, we observed a negative impact of the vegetation correction on the soil moisture, with a decrease in correlation up to 0.4. It emphasizes the need for a dynamic vegetation correction in areas with high interannual variability.
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