Where do winds come from? A new theory on how water vapor condensation influences atmospheric pressure and dynamics

Abstract

Abstract. Phase transitions of atmospheric water play a ubiquitous role in the Earth's climate system, but their direct impact on atmospheric dynamics has escaped wide attention. Here we examine and advance a theory as to how condensation influences atmospheric pressure through the mass removal of water from the gas phase with a simultaneous account of the latent heat release. Building from fundamental physical principles we show that condensation is associated with a decline in air pressure in the lower atmosphere. This decline occurs up to a certain height, which ranges from 3 to 4 km for surface temperatures from 10 to 30 • C. We then estimate the horizontal pressure differences associated with water vapor condensation and find that these are comparable in magnitude with the pressure differences driving observed circulation patterns. The water vapor delivered to the atmosphere via evaporation represents a store of potential energy available to accelerate air and thus drive winds. Our estimates suggest that the global mean power at which this potential energy is released by condensation is around one per cent of the global solar power -this is similar to the known stationary dissipative power of general atmospheric circulation. We conclude that condensation and evaporation merit attention as major, if previously overlooked, factors in driving atmospheric dynamics.

Sensitivity of Amazon Regional Climate to Deforestation

“…The role of the forest in the water recycling has been explored since the late 1970s [9], and recent work by Makarieva et al [22] suggests an active role of the vegetation in the regional water cycle. Therefore, land cover changes through atmospheric feedbacks can have a striking impact on the local, regional and even global mean climate as well as climatic extremes and variability [23] [24].…”

Monitoring Rainfall Patterns in the Southern Amazon with PERSIANN-CDR Data: Long-Term Characteristics and Trends

“…This seasonal behavior is mainly driven by synoptic atmospheric patterns, i.e., (1) the high pressure of the Brazilian and South Atlantic anticyclone from May to September; and (2) the interactions between the Intertropical Convergence Zone and the South Atlantic Convergence Zone during austral summer [37]. Beyond these seasonal mechanisms, rainfall is influenced by: (1) the atmospheric flow of water vapor from the Atlantic Ocean and connections with the Atlantic and Pacific sea surface temperatures [21,[38][39][40]; and (2) a large hydrological recycling process above the forests [41][42][43][44]. The large uncertainty of the ocean and continent surface coupling [39,45,46] drives regional and interannual rainfall variability, while the strong heterogeneity of the structure and intensity of the convection related to evapotranspiration influences fine/local spatio-temporal variability.…”

Quantifying the global atmospheric power budget

“…Its global value T c = 270 K is estimated in Appendix A. Details of theoretical estimate (25) were elaborated elsewhere (see Makarieva et al, 2013bMakarieva et al, , 2015a and references therein). Here we discuss not the result per se, but its implications for understanding the atmosphere as a heat engine.…”