Radon as an Indicator of Nocturnal Atmospheric Stability: A Simplified Theoretical Approach

Yasutaka Omori, Hiroyuki Nagahama

Research output: Contribution to journalArticlepeer-review

4 Citations (Scopus)


Nocturnal evolution of radon concentration and the height of a box model, which is determined from radon concentration and local radon flux at the ground, are used as indicators of nocturnal atmospheric stability in single-height observations. However, quantitative relationships between these indicators and meteorological conditions, including the turbulent diffusion coefficient, have not yet been well established. Here, we construct a simple model based on the heat exchange process of the lower atmosphere to relate these parameters. The model neglects radiative flux divergence and assumes a uniform constant radon flux, making it most applicable to low wind conditions at sites well-removed from coastal influences, when advective effects are minimal. The model shows that the box height (equivalent mixing height) can be determined from near-surface parameters including sensible heat flux and the decrease in potential temperature after sunset. For these parameters, static stability and mechanical mixing components are incorporated. In addition, the constructed equations suggest the equivalent mixing height is proportional to the inversion layer height with a slope that depends on the vertical profile of potential temperature. The equivalent mixing height can be also related to the turbulent diffusion intensity. We demonstrate that radon observations at a single height are useful for monitoring nocturnal atmospheric stability.

Original languageEnglish
Pages (from-to)351-359
Number of pages9
JournalBoundary-Layer Meteorology
Issue number2
Publication statusPublished - 2016 Feb 1


  • Equivalent mixing height
  • Inversion layer
  • Radon
  • Sensible heat flux
  • Turbulent diffusion

ASJC Scopus subject areas

  • Atmospheric Science


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