Global Surface Water Index

Project Summary

Extreme hydrologic events include droughts and floods, which adversely affect the economy, environment, and society. However, capabilities for detection and monitoring of these events is limited, in part, due to their complex multi-component nature and the lack of reliable methods for global monitoring. To address the need for better global monitoring, we used satellite multi-frequency microwave remote sensing observations from the Advanced Microwave Scanning Radiometer (AMSR) sensors to develop a new operational surface wetness index (SWI), which quantifies integrated moisture anomalies in near-surface atmospheric vapor pressure deficit (VPD), volumetric soil moisture (VSM), and land surface water inundation (FW). The SWI provides global daily coverage and can detect both anomalous drought and pluvial events that are consistent with more traditional drought metrics (e.g. PDSI, SPEI, USDM), while providing enhanced information on the water cycle components of drought. The SWI provides complementary information on the different aspects of drought, including dynamic surface water changes and slower evolving groundwater conditions. The SWI also enables independent and continuous assessment of global drought and pluvial conditions derived solely from satellite observations. The available SWI record extends from 2003-present, with continuity enabled from ongoing AMSR2 operations.

Example Images

Global SWI map showing drought and pluvial patterns, Aug. 2012

Global SWI map showing drought and pluvial patterns of August 2012

Drought severity maps for Aug. 2012

Drought severity maps for August 2012 assessed by USDM (a), PDSI-Z (b), SWI (c), and the SWI component influence map (d)

Selected Publications

Du, J., J.S. Kimball, J. Sheffield, I. Velicogna, M. Zhao, M. Pan, C. Fisher, H.E. Beck, J.D. Watts, G. A., and E.F. Wood, 2021. Synergistic satellite assessment of global vegetation health in relation to ENSO-induced droughts and pluvials. JGR Biogeosciences, 126, 5, e2020JG006006,

Du, J., J.S. Kimball, I. Velicogna, M. Zhao, L.A. Jones, J.D. Watts, Y. Kim, and G. A, 2019. Multi-component satellite assessment of drought severity in the contiguous United States from 2002 to 2017 using AMSR-E and AMSR2. Water Resources Research, 55, DOI: 10.1029/2018WR024633.

NTSG Personnel

Jinyang Du

John Kimball

Funding Agency