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Estimating Evapotranspiration Trends in the Eastern United States: 1903-2002

Estimating Evapotranspiration Trends in the Eastern United States: 1903-2002. Genevieve Noyce Mount Holyoke College Research and Discover Program Dr. Lahouari Bounoua Biospheric Sciences Branch (614.4) NASA Goddard Space Flight Center. Evapotranspiration, Vegetation and Climate.

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Estimating Evapotranspiration Trends in the Eastern United States: 1903-2002

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  1. Estimating Evapotranspiration Trends in the Eastern United States: 1903-2002 Genevieve Noyce Mount Holyoke College Research and Discover Program Dr. Lahouari Bounoua Biospheric Sciences Branch (614.4) NASA Goddard Space Flight Center

  2. Evapotranspiration, Vegetation and Climate • Evapotranspiration cools air and changes surface water balance • Vegetation affects climate through transpiration • Variability of vegetation/climate interaction over time • Transpiration related to atmospheric CO2 http://evolution.berkeley.edu http://www.hbrc.govt.nz

  3. Physiological Responses • Downregulation: decrease in leaf conductance to conserve water • Observed in some experiments with elevated CO2(Sellers, Bounoua et al. 1996) • Model incorporating downregulation predicts less evapotranspiration and higher temperatures (Sellers, Bounoua et al. 1996, Bounoua et al. 1999) • Runoff increase more than precipitation • Other models showed similar results(e.g. Betts et al. 1997, Nohara et al. 2006) • Results confirmed for large basins (Gedney et al. 2006)

  4. Precipitation: 5.0% increase Nohara et al., 2006: 19 climate models participating in IPCC AR4 Runoff: 8.9% increase

  5. Are these models accurately replicating observations? • Determine if observed historical trends match predictions • Estimate 20th century evapotranspiration using water budget method “Provide information about future changes in global carbon cycling and terrestrial and aquatic ecosystems for use in ecological forecasting and as inputs for improved climate change projections.” -NASA Carbon Cycle & Ecosystems focus area

  6. Evapotranspiration Precipitation Surfacestorage Runoff Aquifer recharge

  7. Study Area and Data Sources USGS • Precipitation: Dai et al. 1997 • Runoff: USGS WaterWatch • Recharge: Wolock 2003, USGS

  8. Aquifer Recharge Runoff Withdrawal Aquifer recharge Base flow Wolock 2003

  9. Precipitation and Runoff

  10. Evapotranspiration

  11. Climate Implications Surface Temp. °C Bounoua et al.

  12. Thanks to: Research and Discover Program NASA GSFC Betts, R.A., P.M. Cox, S.E. Lee, and F.I. Woodward. 1997. Contrasting physiological and structural vegetation feedbacks in climate change simulations. Nature 387: 796-9. Bounoua, L., G.J. Collatz, P.J. Sellers, D.A. Randall, D.A. Dazlich, S.O. Los, J.A. Berry, I. Fung, C.J. Tucker, C.B. Field, and T.G. Jensen. 1999. Interactions between vegetation and climate; Radiative and physiological effects of doubled atmospheric CO2. Journal of Climate 12: 309-24. Dai, A., I.Y. Fung, and A.D. Del Genio. 1997. Surface observed global land precipitation variations during 1900-88. Journal of Climate 10: 2943-62. Gedney, N., P.M. Cox, R.A. Betts, O. Boucher, C. Huntingford, and P.A. Stott. 2006. Detection of a direct carbon dioxide effect in continental river runoff trends. Nature 439: 835-837. Sellers, P.J., L. Bounoua, G.J. Collatz, D.A. Randall, D.A. Dazlich, S.O. Los, J.A. Berry, I. Fung, C.J. Tucker, C.B. Field, and T.G. Jensen. 1996. Comparisons of radiative and physiological effects of doubled atmospheric CO2 on climate. Science 271: 1402-1406. Nohara, D., A. Kitoh, M. Hosaka, and T. Oki. 2006. Impact of climate change on river discharge projected by multimodel ensemble. Journal of Hydrometeorology 7: 1076-87. Slayback, D.A., J.E. Pinzon, S.O. Los, and C.J. Tucker. 2003. Northern hemisphere photosynthetic trends 1982-1999. Global Change Biology 9: 1-15. United States Geological Suvery. 2009. WaterWatch. Accessed 16 June 2009. http://ga.water.usgs.gov/edu/wuir.html Wolock, D.M. 2003. Base-flow index grid for the conter­minous United States. U.S. Geological Survey Open-File Report 03–263, digital dataset. Accessed 16 July 2009. http://water.usgs.gov/lookup/getspatial?bfi48grd

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