New findings about the complementary relationship-based evaporation estimation methods

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A novel approach has been found to estimate the equilibrium surface temperature (Te) of wet environment evaporation (Ew) on a daily basis. Employing this temperature in the Priestley-Taylor equation as well as in the calculation of the slope of the saturation vapor pressure curve with pan measurements improved the accuracy of long-term mean evaporation (E) estimation of the Advection-Aridity (AA) model when validated by Morton's approach. Complementarity of the potential evaporation (Ep) and E terms was considered both on a daily and a monthly basis with the involved terms always calculated daily from 30 yr of hourly meteorological measurements of the 1961-1990 period at 210 SAMSON stations across the contiguous US. The followings were found: (a) only the original Rome wind function of Penman yields a truly symmetric Complementary Relationship between E and Ep which makes the so-obtained Ep estimates true potential evaporation values; (b) the symmetric version of the modified AA model requires no additional parameters to be optimized; (c) for a long-term mean value of evaporation the modified AA model becomes on a par with Morton's approach not only in practical applicability but also in its improved accuracy, especially in arid environments with possible strong convection; (d) the latter two models yielded long-term mean annual evaporation estimates with an R2 of 0.95 for the 210 stations, which is all the more remarkable since they employ very different approaches for their Ep calculations; (e) with identical apparent Ep values the two models yielded practically identical long-term mean annual evaporation rates; (f) with the proper choice of the wind function to estimate apparent Ep the long-term mean annual E estimates of the modified AA model are still very close (R2 = 0.93) to those of the Morton approach.

Original languageEnglish
Pages (from-to)171-186
Number of pages16
JournalJournal of Hydrology
Issue number1-4
Publication statusPublished - Jun 15 2008


  • Advection-Aridity model
  • Apparent potential evaporation
  • Areal evaporation
  • Complementary relationship
  • Evapotranspiration
  • Potential evaporation
  • Wet environment evaporation

ASJC Scopus subject areas

  • Water Science and Technology

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