Physics of Equilibration: Energy and Water Conservation

1. Physics of Equilibration: Energy and Water Conservation Kendal McGuffie Department of Applied Physics University of Technology Sydney iPILPS workshop April 2005

2. IPILPS Phase 1 Workshop Goals To demonstrate that Isotopically-enabled Land Surface Schemes (ILSSs) generate plausible simulations at the diurnal scale of the exchanges of Stable Water Isotopes (SWIs) at the soil, plant, air interfaces or to identify their shortcomings and propose ways of improving the simulations. • Specific Foci: • are simulation diffs due to (i) sensitivity to forcing; (ii) parameterisation differences; (iii) both? • is Craig & Gordon ‘adequate’? ( & if not what is required?) • on diurnal scales how large are SWI differences; what observations could illuminate ‘adequacy’?

3. PILPS invented some numbers • Spin up time: • Ideally, the time till year n is identical to year n+1 • PILPS defined as <0.1Wm-2 difference between years n and n+1for latent and sensible fluxes (Yang et al. 1995) • Soil moisture reservoir the important control on equilibration

4. Yang et al (1995)

5. PILPS invented some diagrams Variety of methods for simulating land surface fluxes gives different net radiation and different partitioning of sensible and latent fluxes. This portrayal of results invented for PILPS and used to classify and analyse results since mid 1990s. Sensible latent partitioning is important performance measure for energy/moisture treatments in land surface schemes. Results from sensitivity tests at Cabauw net radiation = observed (dot) Zero net radiation From Qu et al., 1998

6. Munich Manaus Model results normalised zero Tumbarumba PILPS plots show sensible and latent fluxes wrt to net radiation. Should be on a straight line. Zero line

7. Munich Manaus Tumbarumba

8. iPILPS challenges: create metrics • Annual mean is likely not hard (fractionation coefficient a weak function of temperature) • Would be similar to getting the equator-to-pole temperature gradient correct • Focus on “…plausible simulations at the diurnal scale of the exchanges of Stable Water Isotopes (SWIs) at the soil, plant, air interfaces…” • Comparing isotopes is a higher order problem. Depends on nature of simulation of water fluxes. e.g. lifetime in various reservoirs. • This ought to provide a gateway to isotopic characterization of land surface processes.

9. mwl residual dD evaporate d18O

10. Munich Manaus Meteoric water line Tumbarumba Yellow: evap Light blue: runoff Light green: transpired water

11. Meteoric water line runoff Munich Manaus trans evap Tumbarumba Monthly means C-evap not where expectedothers very close to mwl Yellow: evap Light blue: runoff Light green: transpired water

12. Strategy for a first look • Examine gross fluxes and isotopic characteristics of these fluxes • Ecanop+Esoil • Qsb+Qs • Tveg

13. jan jul jan jul Munich Manaus evap evap transp transp runoff runoff jan jul • Actual fluxes over diurnal cycle • some oddities • range is large for Tveg • units in evap/runoff? evap transp runoff Tumbarumba

14. Munich jan jul Manaus jan jul evap evap transp transp runoff runoff jan jul • Features: • poor agreement in amplitude • phase agreement when diurnal variation evap transp 18O runoff Tumbarumba

15. Some questions • Why the variation in amplitude of diurnal cycles in deltas? • What mechanisms are causing isotope variations? • Water residence times? • Reservoir size? • Position in ‘PILPS’ space? • Physics differences (bucket/SVAT)

16. spares-follow

17. jan Munich jan jul Manaus jul jan jul Mostly dD Tumbarumba

18. Daily plots arranged by station This presentation created with images taken from ipilps web on Sat 16/4/05

19. Relation between fluxes and deltas Munich

20. Manaus

21. Tumbarumba

22. Munich Manaus Tumbarumba