Publication Date:
2014-07-01
Description:
Land surface models use different formulations of stomatal conductance and plant hydraulics, and it is unclear which type of model best matches observed surface-atmosphere water flux. We use the NACP (North American Carbon Program) dataset of latent heat flux (LE) measurements from 25 sites and predictions from 9 models to evaluate models’ ability to resolve sub-daily dynamics of transpiration. Despite overall good forecast at the seasonal scale, models have difficulty resolving the dynamics of intra-daily hysteresis. The majority of models tend to underestimate LE in the pre-noon hours and overestimate in the evening. We hypothesize that this is a result of un-resolved afternoon stomatal closure due to hydrodynamic stresses. Although no model or stomata parameterization was consistently best or worst in terms of ability to predict LE, errors in model-simulated LE were consistently largest and most variable when soil moisture was moderate and VPD was moderate to limiting. Nearly all models demonstrate a tendency to underestimate the degree of maximum hysteresis which, across all sites studied, is most pronounced during moisture limited conditions. These diurnal error patterns are consistent with models’ diminished ability to accurately simulate the natural hysteresis of transpiration. We propose that lack of representation of plant hydrodynamics is, in part, responsible for these error patterns.
Print ISSN:
0148-0227
Topics:
Biology
,
Geosciences
Permalink