Simple Biosphere Model Si B Results from WLEF
Simple Biosphere Model (Si. B) Results from WLEF: Motivation for Wetlands Module Ian T. Baker Colorado State University Department of Atmospheric Science
Plots are monthly mean diurnal composites Observational data is solid line with +/- one S. D. shaded Si. B data is plotted as dashed line In general, Si. B LE fluxes look good when compared to observations
Si. B sensible heat fluxes don’t compare to observations nearly as well as LE Si. B H commonly twice as large as observed Comparison is worst earlier in the day-late afternoon is not as bad Best comparison is 1998 when June-July precip was very low
However… • We know that observed energy budgets don’t balance. Fluxes are commonly underestimated by 10 -30% (Davis et al. , 2003; Twine et al. , 2000; Desjardins et al. , 1997; Mahrt, 1998 ) • Si. B energy budget balances-we program it that way • Si. B H was too large, but Si. B LE compared well with obs; we can’t arbitrarily increase observed H to balance energy • If we assume underestimation of observed H and LE to be uniformly distributed, then Bowen Ratio of observations should be correct
Bowen Ratio confirms the earlier comparisons; Si. B H is too high relative to LE Possible reason: Si. B does not have wetlands in its formulation In these simulations, all land area we simulated to compare to tower data was treated as ‘mixed forest’
This is what Si. B thinks the area looks like This is what it really looks like
So we created a primitive ‘wetland’ in Si. B Surface reservoir (puddles) held at a constant depth of ~2 mm Soil water layer 2 (root zone) held at constant saturation
With our ‘wetland’ tiled in at 40%, model Bowen Ratios compare much more favorably with observations 40% wetland compares reasonably with published descriptions of the WLEF area (Mackay et al. , 2003)
OBJECTIVE/RESEARCH PLAN We work extensively with data from both the WLEF and Amazonian (LBA) flux towers Wetlands are important to fluxes in both areas • WLEF – perennial • Amazon- wet/dry season variations We’d like to improve simulation of wetlands within Si. B • Latent and sensible heat fluxes • Photosynthesis/carbon assimilation(including isotopes) • respiration
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