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Presentations at European Geosciences Union 2007 Assembly
(15-20 April, Vienna, Austria)
Biotic pump of atmospheric moisture
as driver of the hydrological cycle on land
A.M. Makarieva, V.G. Gorshkov
Oral presentation in Session CL22 Climate: Past, Present and Future: Land-atmosphere coupling in past, present and future climate (solicited)
Key publication: Makarieva A.M., Gorshkov V.G. (2007) Hydrology and Earth System Sciences, 11: 1013-1033.
Under gravity land inevitably loses water to the ocean. To keep land moistened, the gravitational water runoff must be continuously compensated by the atmospheric ocean-to-land moisture transport. We show that the dependence of annual precipitation on distance from the ocean differs markedly between the worldôs forested and non-forested continent-scale regions. In the non-forested regions precipitation declines exponentially with distance from the ocean with an established global mean e-folding length of several hundred kilometers. In contrast, in forest-covered regions (Amazonia, Equatorial Africa, Siberia) precipitation does not decrease or even grow along several thousand kilometers inland despite significant runoff. This points to the existence of an active biotic pump transporting atmospheric moisture inland from the ocean. Physical principles of the biotic moisture pump are investigated based on the previously unstudied properties of atmospheric water vapor, which can be either in or out of hydrostatic equilibrium depending on the vertical lapse rate of air temperature. A novel physical principle is formulated according to which the low-level air moves from areas with weak evaporation to areas with more intensive evaporation. Thanks to their high leaf area index, natural forests maintain high transpiration fluxes, which support the ascending air motion over the forest and "suck in" moist air from the ocean, which is the essence of the biotic pump of atmospheric moisture. Replacement of the natural forest cover by a low leaf area index vegetation radically changes regional atmospheric circulation and can lead to an up to tenfold reduction in mean continental precipitation and runoff, in contrast to the previously available estimates made without accounting for the biotic moisture pump. The analyzed body of evidence testifies that the long-term stability of a human-friendly terrestrial water cycle is unachievable without the recovery of natural, self-sustaining forests on continent-wide areas.
Interactive flash animations of intriguing atmospheric physical effects.
- Click here and move the carriage on the right axis of the graph up and down to see how the moist atmosphere comes out and returns back to static equilibrium depending on vertical temperature gradient
- Click here and appreciate the difference between the diffusional and dynamic fluxes of atmospheric air; see what happens to a mixture of water vapor and dry air in a temperature gradient
- Click here to see the stationary dynamic motion of moist air under the action of the evaporative force
A new scheme of accounting for the non-radiative heat fluxes
in the atmospheric transfer of thermal photons
A.M. Makarieva, V.G. Gorshkov
Poster presentation in Session PS 3.2 Planetary and Solar System Sciences: Atmospheres of terrestrial planets
See Poster (PDF, 25 x 50 cm) see here.
Full poster text see here.
Full RUSSIAN text see here.
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