Experimental evidence of condensation-driven airflow
P. Bunyard1, M. Hodnett2,a, G. Poveda3, J. D. Burgos Salcedo4, and C. Peña51IDEASA, Universidad Sergio Arboleda, Bogotá, Colombia 2Centre for Ecology & Hydrology, Wallingford, UK 3Department of Geosciences and Environment, Universidad Nacional de Colombia, Sede Medellín, Colombia 4Corporación para la Investigación y la Innovación – CIINAS, Bogotá, Colombia 5Facultad de Matemática, Universidad Sergio Arboleda, Bogotá, Colombia aretired
Received: 20 Aug 2015 – Accepted for review: 05 Oct 2015 – Discussion started: 27 Oct 2015
Abstract. The dominant "convection" model of atmospheric circulation is based on the premise that hot air expands and rises, to be replaced by colder air, thereby creating horizontal surface winds. A recent theory put forward by Makarieva and Gorshkov (2007, 2013) maintains that the primary motive force of atmospheric circulation derives from the intense condensation and sharp pressure reduction that is associated with regions where a high rate of evapotranspiration from natural closed-canopy forests provides the "fuel" for cloud formation. The net result of the "biotic pump" theory is that moist air flows from ocean to land, drawn in by the pressure changes associated with a high rate of condensation.
To test the physics underpinning the biotic pump theory, namely that condensation of water vapour, at a sufficiently high rate, results in an uni-directional airflow, a 5 m tall experimental apparatus was designed and built, in which a 20 m3 body of atmospheric air is enclosed inside an annular 14 m long space (a "square donut") around which it can circulate freely, allowing for rotary air flows. One vertical side of the apparatus contains some 17 m of copper refrigeration coils, which cause condensation. The apparatus contains a series of sensors measuring temperature, humidity and barometric pressure every five seconds, and air flow every second.
The laws of Newtonian physics are used in calculating the rate of condensation inside the apparatus. The results of more than one hundred experiments show a highly significant correlation, with r2 > 0.9, of airflow and the rate of condensation. The rotary air flows created appear to be consistent both in direction and velocity with the biotic pump hypothesis, the critical factor being the rate change in the partial pressure of water vapour in the enclosed body of atmospheric air. Air density changes, in terms of kinetic energy, are found to be orders of magnitude smaller than the kinetic energy of partial pressure change.
The consistency of the laboratory experiments, in confirming the physics of the biotic pump, has profound implications for current mathematical climate models, not just in terms of predicting the consequences of widespread deforestation, but also for better understanding the atmospheric processes which lead to air mass convection.
Bunyard, P., Hodnett, M., Poveda, G., Burgos Salcedo, J. D., and Peña, C.: Experimental evidence of condensation-driven airflow, Hydrol. Earth Syst. Sci. Discuss., 12, 10921-10974, doi:10.5194/hessd-12-10921-2015, 2015.