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Titel |
Wind variability and sheltering effects on measurements and modeling of air-water exchange for a small lake |
VerfasserIn |
Corey D. Markfort, Emily Resseger, Fernando Porté-Agel, Heinz Stefan |
Konferenz |
EGU General Assembly 2014
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Medientyp |
Artikel
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Sprache |
Englisch
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Digitales Dokument |
PDF |
Erschienen |
In: GRA - Volume 16 (2014) |
Datensatznummer |
250096006
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Publikation (Nr.) |
EGU/EGU2014-11486.pdf |
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Zusammenfassung |
Lakes with a surface area of less than 10 km2 account for over 50% of the global cumulative
lake surface water area, and make up more than 99% of the total number of global lakes,
ponds, and wetlands. Within the boreal regions as well as some temperate and tropical areas,
a significant proportion of land cover is characterized by lakes or wetlands, which can have a
dramatic effect on land-atmosphere fluxes as well as the local and regional energy
budget. Many of these small water bodies are surrounded by complex terrain and
forest, which cause the wind blowing over a small lake or wetland to be highly
variable. Wind mixing of the lake surface layer affects thermal stratification, surface
temperature and air-water gas transfer, e.g. O2, CO2, and CH4. As the wind blows from
the land to the lake, wake turbulence behind trees and other shoreline obstacles
leads to a recirculation zone and enhanced turbulence. This wake flow results in the
delay of the development of wind shear stress on the lake surface, and the fetch
required for surface shear stress to fully develop may be ~O(1 km). Interpretation of
wind measurements made on the lake is hampered by the unknown effect of wake
turbulence.
We present field measurements designed to quantify wind variability over a sheltered
lake. The wind data and water column temperature profiles are used to evaluate a new method
to quantify wind sheltering of lakes that takes into account lake size, shape and the
surrounding landscape features. The model is validated against field data for 36 Minnesota
lakes. Effects of non-uniform sheltering and lake shape are also demonstrated. The effects of
wind sheltering must be included in lake models to determine the effect of wind-derived
energy inputs on lake stratification, surface gas transfer, lake water quality, and fish habitat.
These effects are also important for correctly modeling momentum, heat, moisture and trace
gas flux to the atmosphere. |
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