, Volume 132, Issue 2, pp 227240
First online:
Atmospheric BoundaryLayer Dynamics with Constant Bowen Ratio
 Amilcare PorporatoAffiliated withDepartment of Civil and Environmental Engineering, Duke UniversityEFLUMEPFL Email author
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Motivated by the observation that the diurnal evolution of sensible and latent heat fluxes tends to maintain a constant Bowen ratio, we derive approximate solutions of the ordinary differential equations of a simplified atmospheric boundarylayer (ABL) model. Neglecting the early morning transition, the potential temperature and specific humidity of the mixed layer are found to be linearly related to the ABL height. Similar behaviour is followed by the inversion strengths of temperature and humidity at the top of the ABL. The potential temperature of the mixed layer depends on the entrainment parameter and the freeatmosphere temperature lapse rate, while the specific humidity also depends on the freeatmosphere humidity lapse rate and the Bowen ratio. The temporal dynamics appear only implicitly in the evolution of the height of the boundary layer, which in turn depends on the timeintegrated surface sensible heat flux. Studying the limiting behaviour of the Bowen ratio for very low and very large values of net available energy, we also show how the tendency to maintain constant Bowen ratio during midday hours stems from its relative insensitivity to the atmospheric conditions for large values of net available energy. The analytical expression for the diurnal evolution of the ABL obtained with constant Bowen ratio is simple and provides a benchmark for the results of more complex models.
Keywords
Atmospheric boundary layer Bowen ratio Evaporation Mixed layer Slab model Title
 Atmospheric BoundaryLayer Dynamics with Constant Bowen Ratio
 Journal

BoundaryLayer Meteorology
Volume 132, Issue 2 , pp 227240
 Cover Date
 200908
 DOI
 10.1007/s1054600994008
 Print ISSN
 00068314
 Online ISSN
 15731472
 Publisher
 Springer Netherlands
 Additional Links
 Topics
 Keywords

 Atmospheric boundary layer
 Bowen ratio
 Evaporation
 Mixed layer
 Slab model
 Industry Sectors
 Authors

 Amilcare Porporato ^{(1)} ^{(2)}
 Author Affiliations

 1. Department of Civil and Environmental Engineering, Duke University, Durham, NC, USA
 2. EFLUMEPFL, Lausanne, Switzerland