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Objective

Using the G.R.A.C.E. Satellites ’ Water Storage Anomaly Dataset to Identify Regional Scale Drought Conditions. Alys Thomas Hydrology and Climate Research Group Dept. of Earth System Science University of California, Irvine 2013 AMS Annual Meeting, Austin.

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Objective

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  1. Using the G.R.A.C.E. Satellites’ Water Storage Anomaly Dataset to Identify Regional Scale Drought Conditions Alys ThomasHydrology and Climate Research GroupDept. of Earth System ScienceUniversity of California, Irvine2013 AMS Annual Meeting, Austin

  2. How can we identify and characterize drought using GRACE satellites Objective cm eqv. water height

  3. The GRACE mission provides monthly, global maps of Earth's gravity and how it changes as the mass distribution shifts • Large scale gravity changes attributed to mass movement of water on and beneath the surface • Helps us understand how water moves from the land to the ocean and back again • DATASET • Release 5 Land data from Uni. Texas Center for Space Research (CSR) • Monthly time steps: March 2003- August 2012 • Mean is removed to produce terrestrial water storage anomalies (TWSA) on 1° grids • Units: CM of equivalent water thickness The Gravity Recovery And Climate Experiment Courtesy of CSR & JPL, http://www.csr.utexas.edu/grace/gallery/

  4. Back to the basics: • Once variable (i.e. rainfall, streamflow, water storage, etc.) crosses a given threshold, it enters into a dry/drought period • The length of time it stays under and deviates from that threshold give us the severity of the drought event Examples: Characterizing drought with GRACE data Yevjevich (1967) Mishra et al. (2009) Keyantash and Dracup (2002)

  5. Amazon River Basin • Hydrologically-defined • Area: ~6,100,000 km2 • Two well-documented meteorological droughts during GRACE period (2005 & 2010) • High Plains Region (U.S.) • Not hydrologically defined • Area: ~2,000,000 km2 • Two documented droughts during GRACE period (Severest drought late 2010 to present) Study Areas

  6. Processing of GRACE data: • Global 1° gridded GRACE product downloaded • Scale factors (provided) and interpolation of missing months • Monthly climatology (TWSA) calculated using ~9 years of TWSA data • GRACE anomalies converted from ‘cm’ to ‘km’ of eqv. water height • Masks for study areas used to calculate the spatial averages • Regional average storage anomalies (km) were then multiplied by the region’s area (km2) resulting in: regional-average water storage volume change (km3) Methodology

  7. Storage Temporal Characteristics: AMAZON

  8. Storage Temporal Characteristics: HIGH PLAINS

  9. Water storage with the climatology removed: Assign a dryness threshold (zero) based on storage values with monthly climatology removed Negative = dry/drought Positive = wet/flood Determining Drought Severity

  10. Drought Magnitude & Duration: AMAZON

  11. Drought Severity: AMAZON -2406 -3874 -1293 -3458 (DEFICIT)

  12. Drought Magnitude & Duration: HIGH PLAINS

  13. Drought Severity: HIGH PLAINS -622 -2323 (DEFICIT) -3827

  14. Amazon: • Dec 2004 – Dec 2005 drought ~ 298 km3 Severest mo. (Aug2005): 499 km3 • Feb 2010 – Mar 2011 drought ~ 247 km3 Severest mo. (Oct2010): 463 km3 Averagevolume of water missingfrom region per drought event: • Southern Plains: • Oct 2010 – Aug 2012 drought ~ 166 km3 Severest mo. (Jun2012): 348 km3 Drought: Impacts on Water Storage

  15. THIS IS WHAT GRACE SAW . . . • Monthly observations of terrestrial water storage variability from GRACE satellites reveal extended periods of relatively dry conditions: • Amazon River Basin in 2005 and 2010 • Southern Plains region in 2006 and 2010-present • Analyzing water storage anomalies without their 9-year monthly climatology allow us to define a dryness threshold for each region • We can then determine GRACE-identified drought magnitude, duration, and severity in units of volume of water “missing” from the system during drought and how much is needed to “recover” • Future work: • Spatial characteristics within these regions • Linking “missing” water storage numbers with water management • Application to other regions Summary

  16. Funding: NASA Graduate Student Research Project • Many thanks to: • Jay Famiglietti, J.T. Reager, Matt Rodell, Bailing Li, Caroline de Linage, Hiroko Beaudoing Hydrospheric and Biospheric Sciences • Keyantash, J. A., and J. A. Dracup, 2002: The quantification of drought: An evaluation of drought indices. Bull. Amer. Meteor. Soc., 83, 1167–1180 • Landerer F.W. and S. C. Swenson, Accuracy of scaled GRACE terrestrial water storage estimates. Water Resources Research 2012. • Mishra, K., V. P. Singh, and V. R. Desai, Drought characterization: a probabilistic approach, Stoch Environ Res Risk Assess (2009) 23:41–55, DOI 10.1007/s00477-007-0194-2. • Swenson S.C , D. P. Chambers, and J. Wahr: Estimating geocenter variations from a combination of GRACE and ocean model output. J Geophys. Res.-Solid Earth, Vol 113, Issue: B8, Article B08410. 2008. Contact Alys Thomas: thomasac@uci.edu

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