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SiSPAT-Isotope model Better estimates of E and T

SiSPAT-Isotope model Better estimates of E and T. Jessie Cable Postdoc - IARC. Very green landscapes that are fluxing water to the atmosphere. - Combination of vascular and non-vascular plants - Different water flux dynamics necessitate distinguishing between them (E and T vs. ET).

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SiSPAT-Isotope model Better estimates of E and T

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  1. SiSPAT-Isotope modelBetter estimates of E and T Jessie Cable Postdoc - IARC

  2. Very green landscapes that are fluxing water to the atmosphere

  3. - Combination of vascular and non-vascular plants - Different water flux dynamics necessitate distinguishing between them (E and T vs. ET) Transpiration Transpiration = Plants control the water vapor flux Evaporation = mosses are an evaporating surface (BUT, they are NOT bare ground) Evaporation http://www.marietta.edu/~biol/biomes/images/wetlands/sphagnum_6449a_A80.jpg

  4. Rainfall recycling and watershed/soil water balance ET CREW-NASA Changes in landscape / vegetation distributions impact magnitude and partitioning of ET Need better assessment of E and T Need more accurate representation of E and T in atmosphere, hydrological, or vegetation growth models Tape et al. 2006

  5. Little data exist to validate the partitioning of E and T in SVAT (Soil Vegetation Atmosphere Transfer) models • Concentration measurements of stable isotopes of water in soil, plants, and vapor can aid in partitioning / quantifying E and T • E and T differentially impact concentration of isotopes in soil or vapor • soil stable isotope concentrations useful for • determining plant rooting profiles (for validation of root extraction submodels in SVAT) • better quantification of water transfer within soils (vapor diffusion coefficients and hydraulic properties) H2O 1H, 2H 16O, 18O

  6. SiSPAT-Isotope modelBraud et al., Journal of Hydrology 309 (2005) 277-300, 301-320 • Modification of the pre-existing 1D SiSPAT model (Simple Soil Plant Atmosphere Transfer model) to include transport of stable isotope species to better estimate E and T • Coupled heat, water, and isotope transport equations solved for temperature and matric potential and isotope profiles • forced by air temp, humidity, wind speed, incoming solar and long wave radiation, rainfall • bare ground, saturated soils, steady state conditions (equilibrium between vapor and liquid phases for isotopes) • Currently focused on estimating kinetic fractionation coefficient

  7. Issues with adding isotope transport • Correctly accounting for fractionation associated with molecular diffusion • turbulent vs molecular diffusion affecting resistance to isotope vapor flux • Need a plant component and proper treatment of plant physiology • Kinetic fractionation factor for drying soils and non-saturated conditions 1H, 2H 16O, 18O

  8. Data-model integration issues • The solution of the isotope species transport equation requires high resolution of the vertical profile near the surface (particularly to capture the vapor return) • Problem: require fine time steps that field sampling can not yet provide

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