Estimating Annual Water Storage Variations Using Microwave-based Soil Moisture Retrievals
Wade T. Crow1, Eunjin Han2, Dongryeol Ryu3, Christopher R. Hain4, and Martha C. Anderson11USDA Hydrology and Remote Sensing Laboratory, Beltsville MD, USA 2International Research Institute for Climate and Society, Columbia University, NY, USA 3University of Melbourne, Melbourne, Victoria, Australia 4Earth System Science Interdisciplinary Center, University of Maryland, College Park MD, USA
Received: 03 Nov 2016 – Accepted for review: 17 Nov 2016 – Discussion started: 21 Nov 2016
Abstract. Due to their shallow vertical support, remotely-sensed surface soil moisture retrievals are commonly regarded as being of limited value for water budget applications requiring the characterization of temporal variations in total terrestrial water storage (S). However, advances in our ability to estimate evapotranspiration remotely now allow for the direct evaluation of approaches for quantifying annual variations in S via water budget closure considerations. By applying an annual water budget analysis within a series of medium-scale (2,000–10,000 km2) basins within the United States, we demonstrate that, despite their clear theoretical limitations, surface soil moisture retrievals derived from passive microwave remote sensing contain significant information concerning relative inter-annual variations in S. This suggests the possibility of using (relatively) higher-resolution microwave remote sensing to enhance the spatial resolution of S estimates acquired from gravity remote sensing. However, challenging calibration issues regarding the relationship between S and surface soil moisture must be resolved before the approach can be used for absolute water budget closure.
Crow, W. T., Han, E., Ryu, D., Hain, C. R., and Anderson, M. C.: Estimating Annual Water Storage Variations Using Microwave-based Soil Moisture Retrievals, Hydrol. Earth Syst. Sci. Discuss., doi:10.5194/hess-2016-572, in review, 2016.