The recent availability of freely and openly available satellite remote sensing products has enabled the implementation of global surface water monitoring at a level not previously possible. Here we present a global set of satellite-derived time series of surface water storage variations for lakes and reservoirs for a period that covers the satellite altimetry era. Our goals are to promote the use of satellite-derived products for the study of large inland water bodies and to set the stage for the expected availability of products from the Surface Water and Ocean Topography (SWOT) mission, which will vastly expand the spatial coverage of such products, expected from 2021 on. Our general strategy is to estimate global surface water storage changes (1V ) in large lakes and reservoirs using a combination of paired water surface elevation (WSE) and water surface area (WSA) extent products. Specifically, we use data produced by multiple satellite altimetry missions (TOPEX/Poseidon, Jason-1, Jason-2, Jason-3, and Envisat) from 1992 on, with surface extent estimated from Terra/Aqua Moderate Resolution Imaging Spectroradiometer (MODIS) from 2000 on. We leverage relationships between elevation and surface area (i.e., hypsometry) to produce estimates of 1V even during periods when either of the variables was not available. This approach is successful provided that there are strong relationships between the two variables during an overlapping period. Our target is to produce time series of 1V as well as of WSE and WSA for a set of 347 lakes and reservoirs globally for the 1992-2018 period. The data sets presented and their respective algorithm theoretical basis documents are publicly available and distributed via the Physical Oceanography Distributed Active Archive Center (PO DAAC; https://podaac.jpl.nasa.gov/, last access: 13 May 2020) of NASA s Jet Propulsion Laboratory. Specifically, the WSE data set is available at https://doi.org/10.5067/UCLRS-GREV2 (Birkett et al., 2019), the WSA data set is available at https://doi.org/10.5067/UCLRS-AREV2 (Khandelwal and Kumar, 2019), and the 1V data set is available at https://doi.org/10.5067/UCLRS-STOV2 (Tortini et al., 2019). The records we describe represent the most complete global surface water time series available from the launch of TOPEX/Poseidon in 1992 (beginning of the satellite altimetry era) to the near present. The production of long-term, consistent, and calibrated records of surface water cycle variables such as in the data set presented here is of fundamental importance to baseline future SWOT products.
Bibliographical noteFunding Information:
Financial support. This research has been supported by the NASA Making Earth System Data Records for Use in Research Environments (MEaSUREs) program (grant no. NNX13AK45A to UCLA) and the National Science Foundation (grant nos. 1029711 and 1838159 to UMN).
The data sets presented are available as additional material to this paper and distributed via NASA s PO DAAC (https://podaac-tools.jpl.nasa.gov/drive/files/allData/ preswot_hydrology/, last access: 13 May 2020) as L2 (level variation), L3 (surface area), and L4 (storage change) products. We would like to thank Jessica Hausman (NASA JPL) for comments on the content and format of the records produced in this work and Jongyoun Kim for her work on earlier versions of the data set. We acknowledge that Lake Sakakawea lies on the traditional territory of the Mandan, Hidatsa, and Arikara, who still walk the land today. This research has been supported by the NASA Making Earth System Data Records for Use in Research Environments (MEaSUREs) program (grant no. NNX13AK45A to UCLA) and the National Science Foundation (grant nos. 1029711 and 1838159 to UMN).
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