English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Plus monthly

Global: Zendy Tools annual

Global: Zendy Tools monthly

Global: Zendy Free Plan

The nonlinear Penman and Penman-Monteith equations, widely used forestimating surface evapotranspiration at regional and global scales, werederived from turbulent transport of heat fluxes and thus apply to subhourlyscale. However, these equations have been directly applied withhydrometeorological variables averaged at longer time intervals, leading tobiases due to their nonlinearities. To address this problem, we used globaleddy covariance flux data and Taylor expanded Penman and Penman-Monteithequations to explore their nonlinear components and the biases associated withthe timescales mismatch. We found relatively small biases when applying Penmanequation at longer timescale, in which the biases in equilibriumevapotranspiration mainly stem from the temperature-radiation covariance,whereas the biases in evapotranspiration due to drying power of air primarilycome from the higher-order terms. Most of these biases can be corrected bylinear regressions of first-order approximations. For Penman-Monteithequations, the corresponding biases are relatively larger but can besignificantly reduced when daytime median stomatal conductance is used alongwith the first-order approximation of Penman-Monteith equation, suggesting theimportance of diurnal variation of latent heat fluxes. The nonlinearityexplored here serves as a reminder of the mismatched timescales for applyingPenman and Penman-Monteith equations.

Nonlinearities of Penman and Penman-Monteith Equations across Multiple Timescales