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| Titel |
Evaluation of advection-aridity complementary relations at the lab scale |
| VerfasserIn |
Stanislaus J. Schymanski, Milad Aminzadeh, Michael L. Roderick, Dani Or |
| Konferenz |
EGU General Assembly 2015
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250103579
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| Publikation (Nr.) |
 EGU/EGU2015-4776.pdf |
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| Zusammenfassung |
| A common view of evaporation from terrestrial surfaces considers limitations due to water
supply in arid regions, and atmospheric demand (or energy) limitations to evaporation from
wet surfaces in temperate regions. Evidence suggests that at large scales, energy and water
limitations are not independent. While a surface dries and a larger fraction of the radiative
energy is converted into sensible heat, that heat is injected into the air and altering its
properties. This land-atmosphere feedback gives rise to the so-called complementary
relationship (Bouchet 1963), referring to the simultaneous decrease in actual evaporation
while potential evaporation increases as the surface dries. The effect of surface drying on
atmospheric water demand is two-fold: an increase in air temperature and a decrease in water
vapour content for fixed advective exchange rate across the system boundaries. To
isolate the various mechanisms and improve understanding of the feedbacks, we
designed an insulated wind tunnel, where wind speed, radiation, surface moisture and
exchange rates of air and heat across the boundaries are controlled. Preliminary results
show the magnitude of the feedbacks in terms of air and surface temperatures, and
evaporation rates from drying and wet surfaces simultaneously. Experimental and
associated simulation results provide a direct demonstration of the roles of advective
exchange and the interplay between atmospheric boundary layer thickness and temporal
variations in radiative energy input in determining the strength of surface-atmosphere
feedbacks and the resulting phenomenon known as the complementary relationship. |
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