Preprints
https://doi.org/10.5194/hess-2018-195
https://doi.org/10.5194/hess-2018-195

  16 Apr 2018

16 Apr 2018

Review status: this preprint has been withdrawn by the authors.

Technical note: rectifying systematic underestimation of the specific energy required to evaporate water into the atmosphere

Andrew S. Kowalski1,2 Andrew S. Kowalski
  • 1Departmento de Física Aplicada, Universidad de Granada, Granada, 18071, Spain
  • 2Instituto Interuniversitario de Investigación del Sistema Tierra en Andalucía, Centro Andaluz de Medio Ambiente (IISTA-CEAMA), Granada, 18071, Spain

Abstract. Not all of the specific energy consumed when evaporating water into the atmosphere (λ) is due to the latent heat of vaporization (L). What L represents is the specific energy necessary to overcome affinities among liquid water molecules, neglecting the specific work done against atmospheric pressure (p) when water expands in volume (V) from liquid to gas (pV work). Here, in the one-dimensional context typifying micrometeorology, the pV work done in such an expansion is derived based on the Stefan flow velocity at the surface boundary, yielding a simple function of the virtual temperature; additionally, an empirical formula is provided that approximates λ quite accurately over a useful range of environmental conditions. Neglect of this pV work term has caused a systematic 3–4 % underestimation of λ, and to some extent inhibited closure of the surface energy balance.

This preprint has been withdrawn.

Andrew S. Kowalski

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Interactive discussion

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Status: closed
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
Printer-friendly Version - Printer-friendly version Supplement - Supplement

Andrew S. Kowalski

Andrew S. Kowalski

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Short summary
This technical note derives the additional specific energy of evaporation, beyond the latent heat of vaporization, as the work done against ambient pressure when water expands from the liquid to the gas phase. The derivation yields a simple function of the virtual temperature, and corrects for a systematic 3–4 % underestimation of the energy required to evaporate water into the Earth's atmosphere.