TY - JOUR
AU - de Rooij, Gerrit H.
AB -  <h2>Introduction</h2> Zeng and Decker (2009 , hereafter ZD09) recently discussed the effect of truncation errors in a numerical solution of Richards equation often used to model vertical soil water flow in land models for weather and climate studies. They adopted a cross-disciplinary approach by applying an established meteorological method to a soil physical problem. Their solution involved subtracting from the original equation the solution at hydrostatic equilibrium in order to eliminate the truncation errors. There is some confusion in the terminology and in the treatment of Richards equation in ZD09 . This comment is intended to clarify these issues since they can create misunderstandings in the communications between the various disciplines involved in the work of ZD09 . More seriously, the averaging equation for the matric head presented in ZD09 does not conserve energy and the expression for the average water content suffers from mathematically undefined terms that preclude its numerical evaluation for physically acceptable values. The derivation is presented here of a complete set of energy-conserving averaging equations that can replace those of ZD09 . Finally, the point is made that ZD09 effectively implemented a much-needed constant head lower boundary condition for soil water flow in their 
TI - Comments on “Improving the Numerical Simulation of Soil Moisture–Based Richards Equation for Land Models with a Deep or Shallow Water Table”
JF - Journal of Hydrometeorology
DO - 10.1175/2010JHM1189.1
DA - 2009-06-25
UR - https://www.deepdyve.com/lp/american-meteorological-society/comments-on-improving-the-numerical-simulation-of-soil-moisture-based-36qmUVGfT7
SP - 1044
EP - 1050
VL - 11
IS - 4
DP - DeepDyve
ER -