Publication Date:
2013-07-16
Description:
Soil moisture (SM) can be retrieved from active microwave (AM)-, passive microwave (PM)- and thermal infrared (TIR)-observations, each having unique spatial and temporal coverage. A limitation of TIR-based retrievals is a dependency on cloud-free conditions, while microwave retrievals are almost all weather proof. A downside of SM retrievals from PM is the coarse spatial resolution. While SM retrievals at coarse spatial resolution proved to be valuable for global- and continental-scale studies, their value for regional-scale studies remains limited. To increase the use of SM retrievals from PM observations, an existing method to enhance their spatial resolution was applied. We present an inter-comparison study over the Iberian Peninsula for three SM products on two different spatial sampling grids. The remotely sensed soil moisture products were also compared to in situ observations from the Remedhus network. Variations between ground data and satellite-based SM are observed; all three remotely sensed SM products show good agreement to the ground observations. The comparison shows that these ground observations and satellite data are consistent, based on the correlation coefficient ( R ) and Root Mean Square Error ( RMSE ). The remotely sensed products were inter-compared after sampling at 25x25 km 2 , and after applying the Smoothing Filter based Intensity Modulation (SFIM) downscaling technique at 10x10 km 2 grids. After the application of the SFIM technique, the SM retrievals from PM observations show better agreement with the other remotely sensed SM products for approximately 40% of the study area. For another 40% of the study area we found similar agreement between these product combinations, while in extreme environments, both arid and densely vegetated regions, the agreement decreases after the application of the SFIM technique. Agreement between retrievals of absolute SM content from PM and TIR-observations is generally high ( R = 0.77 for semi-arid areas). This study enhances our understanding of the remotely sensed SM products for improvements of SM retrieval- and merging strategies. This article is protected by copyright. All rights reserved.
Print ISSN:
0885-6087
Electronic ISSN:
1099-1085
Topics:
Architecture, Civil Engineering, Surveying
,
Geography
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