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I-GEM Project Impact of Groundwater in Earth system Models ANR/MoST 2014-2018

Explore GW impacts on climate and water resources through model analyses. Compare climate sensitivity to different GW parameters. Advance interdisciplinary research in global water cycle. Scientific tasks focus on WTD patterns, land/atmosphere feedback, climate change impact on water resources. Off-line and on-line model runs ongoing. Analysis of simulated climate impacts in progress.

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I-GEM Project Impact of Groundwater in Earth system Models ANR/MoST 2014-2018

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  1. I-GEM ProjectImpact of Groundwater in Earth system ModelsANR/MoST 2014-2018 Overview of the first results Agnès Ducharne, Rong-You Chen, et al. Advancement meeting of the GEM project February 29th, 2016

  2. IGEM overview Objectives: • Explore the impacts of GW on regional and global climate, and its links to water resources availability,through model analyses • Compare the sensitivity of simulated climate to different GW parametrizations within 3 different climate models • Consolidate the potential of France and Taiwan in the interdisciplinary research field of the global water cycle

  3. Outline • IGEM and Task1 • Resultsfrom the 3 models at global scale (fromRong-You) • Comparison of the 3 reference simulations • Comparedsensitivity to WTD • Spatial patterns based on ORCHIDEE • Witheffect of dynamic LAI • WTDc • How to computeit? • Effect of differentthersholds • Main drivingfactors: highestWTDc in transition zones • Future work

  4. IGEM overview Scientific Tasks: • Sensitivity to fixed water table depths (WTD), to identify the patterns of “active WTD”, below which GW do not impact regional climate • Dynamic WTD over the recent period, to assess the potential of realistic GW parametrizations to improve the simulated climate, with a focus on land/atmosphere feedback and the persistence/memory in the Earth system • Dynamic WTD and climate change, with 2 complementary questions: (1) What is the influence of GW on the climate change trajectory? (2) What is the impact of climate change on water resources (including GW)? • Dynamic WTD with withdrawals, which artificially increase soil moisture via irrigation, with potential impacts on climate until water resources get exhausted.

  5. Advancement of T1 Off-line runs: • 3 LSMs: ORCHIDEE, SURFEX, CLM • Princeton forcing over 1979-2010 (32 years), 3-hourly at 1° resolution, with correction of total precipbased on GPCC (B. Decharme) • Reference in the standard configuration + 7 simulations withforced water table depth (WTD) between 10 and 0.5 m • Spin-up to reachequilibriumbeforestarting the analysed simulations • All simulations finished in January 2016, analysis in progress On-line runs: • Following the AMIP protocol, with spin-up for initialization • Simulations in progress in the three groups…

  6. Off-line reference simulations

  7. Rodell et al. 2015: Eland = 1. 32 mm/d Coulditbe possible to have a (red) bar for the value by Rodell et al.?

  8. Rodell et al. 2015: Qland = 0.86 mm/d Coulditbe possible to have a (red) bar for the value by Rodell et al.?

  9. Sensitivity to WTD • The threeLSMs are forcedwithseveralWTDsfollowingCampoy et al. • WTD = 10, 8, 5, 3, 2, 1 and 0.5 m • Constant WTDs are achievedowing to an upward water flux, Qforce, opposing ET • SURFEX and CLM include an explicit WG reservoir, withhydraulicconnectionbetween WTD and soil if WTD>Dsoil

  10. Coulditbe possible to place the CON simulation at the right side? Equivalent verydeep WTD)

  11. Coulditbe possible to place the CON simulation at the right side? Equivalent verydeep WTD)

  12. Coulditbe possible to place the CON simulation at the right side? Equivalent verydeep WTD)

  13. Coulditbe possible to place the CON simulation at the right side? Equivalent verydeep WTD)

  14. Spatial patterns based on ORCHIDEE REF, Qle, pluriannual mean

  15. Pluri-annual means, WTD (m) WTD1 WTD05 WTD2 WTD3

  16. Pluri-annual means, Qle (W/m2) WTD10-REF WTD8-WTD10 WTD5-WTD8 WTD3-WTD5

  17. Pluri-annual means, Qle (W/m2) WTD2-WTD3 WTD1-WTD2 WTD05-WTD1

  18. Why so many negative values?  for WTD05-WTD1 - + TVeg ESoil - + ECanop LAI

  19. Why so many negative values?  for WTD05-WTD1 - + ra Epot • In the Amazon, the net effectis a decrease in ET, TVeg and LAI: • The first effect of WTD riseis to increase SM in the top layers, thusESoil • (TVegislessdirectly sensitive as itcandraw water from the deeperlayers, • and water is not verylimiting on Tveg in the Amazon) • This reduces the need for TVeg to satisfy the evaporativedemand • Thus, TVegdecreases, so LAI decrease, with positive feedback loop (via 2 effects, of TVeg on PhS and LAI on baresoil fraction) • ECanopincreasesaltogether, as Epotincreases (becauseTsincreases, witheffects on qs(Ts) and ra, despite LAI decrease) • The final effect on ET isdriven by TVegdecrease (TVegis the largest contribution to ET)

  20. WTD1: ESoil/TVeg

  21. F1M2L22: ESoil/TVeg The fraction of land where Esoil>Tveg is very large in the REF simulation with ORCHIDEE Only the wettest areas escape this « oddity ». The comparison with WTD1 shows it may come from a lack of water (too much Qs?) It may also come from excessive ESoil rates or bare soil fractions (with feedback to Tveg/LAI)

  22. Critical WTD • WTDc = the deepest WTD to achieve a significant change in ET • Main questions: • How does WTDc compare with maps of WTD (Fan et al., 2013) and hydrogeological properties? • Are there distinct features in soil moisture transition zones, known to be hot-spots of strong land-atmosphere coupling (Koster et al., 2004; Dirmeyer, 2011)?

  23. How to estimate the WTDc? • WTDc = critical WTD = the deepest WTD to achieve a significant change in ET • Based on derivatives of the ET changes with respect to WTD, which can be seen as measures of how the sensitivity of ET to a unit change in WTD evolves with WTD • WTDc involves choosing a threshold ET sensitivity value, below which we can assume that the ET changes resulting from WTD variations are small • It can be 10 W/m2, or 10% of ET(REF), given that 10% is often taken as the precision of ET measurements (Dirmeyer et al., 2000), or…?

  24. Principle based on global scale means In the followingmaps, I located the variation rate betweentwoconsecutiveWTDs at mid WTD range, whileitislocated at the highest WTD in the graphs below For a threshold of 1%, WTDc  1m

  25. Pluri-annual means, Qle/Qle(REF)/WTD (%/m); threshold = 10%/m WTD05-WTD1 WTD1-WTD2 WTD2-WTD3 WTD3-WTD2

  26. WTDc,threshold = 10%/m WTD05-WTD1 WTD1-WTD2 WTD2-WTD3 WTD3-WTD2

  27. WTDc,threshold = 5%/m WTD05-WTD1 WTD1-WTD2 WTD2-WTD3 WTD3-WTD2

  28. WTDc,threshold = 1%/m (stopping at WTD5) WTD05-WTD1 WTD1-WTD2 WTD2-WTD3 WTD3-WTD2

  29. WTDc,threshold = 1%/m WTD05-WTD1 WTD1-WTD2 WTD2-WTD3 WTD3-WTD2

  30. WTDc,threshold = 10 W/m2/m (stopping at WTD5) The thresholdis 0.1 W/m2 WTD05-WTD1 WTD1-WTD2 WTD2-WTD3 WTD3-WTD2

  31. WTDc,threshold = 10 W/m2/m The thresholdis 0.1 W/m2 WTD05-WTD1 WTD1-WTD2 WTD2-WTD3 WTD3-WTD2

  32. Top: thresholdis 0.1 W/m2 Having a 1% or 0.1 W/m2 threshold leads to the same kinds of patterns in wet climates. But it makes a difference in the arid/semi-arid zones, where the WTDc is much deeper if the threshold is 0.1 W/m2 (from 4m to 6.5m).

  33. With less stringent thresholds, the WTDc is not as deep, although 10% or 5% do not make a large difference.

  34. Looking for explaining factors : highest WTDc in « transition zones »? The thresholdis 0.1 W/m2 WTD05-WTD1 WTD1-WTD2 WTD2-WTD3 WTD3-WTD2

  35. Possible explaining factors – Aridity factor P/Rn Where very arid, the WTDc si not the largest Where wet, the WTDc is very shallow (< 2m)

  36. Possible explaining factors - LAI LAI and aridity are strongly correlated

  37. Possible explaining factors - Texture In arid zones, sandy soils exhibit a shallower WTDc Calyish soils may have a deeper WTDc, to be confirmed

  38. Future work • Map WTDc patterns for the three LSMs • Work again the on the threshold • 0.1 W/m2 may be too small; 10 W/m2 is probably too high • Compare with maps of WTD (Fan et al., 2013) and hydrogeological properties • Compare with LA coupling strength criteria • Compare off-line and online WTDc • EGU 2016 and GRL paper in prep. • Assess the impact of GW onto the simulated climate (water cycle, circulation, energy budget)

  39. Thank you for your attention Advancement meeting of the GEM project February 29th, 2016

  40. Pluri-annual means, Qle/WTD (W/m2/m); threshold = 10 W/m2/m WTD1-WTD05 WTD2-WTD1 WTD3-WTD2 WTD5-WTD3

  41. off line simulation Flux term

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