Comment on 'ShangS. 2012. Calculating actual crop evapotranspiration under soil water stress conditions with appropriate numerical methods and time step. Hydrological Processes26: 3338–3343. DOI: 10.1002/hyp.8405'. Issue 11 (9th February 2014)

• Record Type: Journal Article
• Authors: Yatheendradas, Soni; Narapusetty, Balachandrudu; Peters‐Lidard, Christa; Funk, Christopher; Verdin, James
• Is Part Of: Hydrological processes. Volume 28:Issue 11(2014:Mar.)
• Page Start: 3338
• Page End: 3343
• Publication Date: 2014-02-09
• Subjects: Hydrology -- Periodicals; Hydrology -- Research -- Periodicals; Hydrologic models -- Periodicals; Hydrological forecasting -- Periodicals; 631.432
• DOI: 10.1002/hyp.10138
• Languages: English
• ISSNs: 0885-6087

Abstract

<abstract abstract-type="main"> <title>Abstract</title> <p>A previous study analyzed errors in the numerical calculation of actual crop evapotranspiration (ET_a) under soil water stress. Assuming no irrigation or precipitation, it constructed equations for ET_a over limited soil‐water ranges in a root zone drying out due to evapotranspiration. It then used a single crop‐soil composite to provide recommendations about the appropriate usage of numerical methods under different values of the time step and the maximum crop evapotranspiration (ET_c). This comment reformulates those ET_a equations for applicability over the full range of soil water values, revealing a dependence of the relative error in numerical ET_a on the initial soil water that was not seen in the previous study. It is shown that the recommendations based on a single crop‐soil composite can be invalid for other crop‐soil composites. Finally, a consideration of the numerical error in the time‐cumulative value of ET_a is discussed besides the existing consideration of that error over individual time steps as done in the previous study. This cumulative ET_a is more relevant to the final crop yield. Published 2014. This article is a U.S. Government work and is in the public domain in the USA.</p> </abstract>