Minnesota | EPFL Graph Search

Le Minnesota ( ; en anglais : ou ) est un État du Midwest des États-Unis, bordé à l’ouest par le Dakota du Nord et le Dakota du Sud, au nord par les provinces canadiennes du Manitoba et de l'Ontario, à l’est par le lac Supérieur et le Wisconsin et au sud par l’Iowa. Toponymie Le mot Minnesota vient de « mní sóta », nom donné au fleuve Minnesota en Lakota, tribu Sioux. Mní (parfois mini, ou minne) peut être traduit comme l'eau. Mní sóta est alors traduit comme « l'eau de couleur de ciel ». Beaucoup d'endroits dans l'état contiennent le mot de la langue lakota pour l'eau, tels que des chutes de Minnehaha (la chute d'eau), Minneiska (l'eau blanche), Minnetonka (la grande eau), Minnetrista (l'eau tordue), et Minneapolis, combinaison du mot mni et du mot grec pour « ville », polis, signifiant donc « la ville de l'eau ». Histoire Histoire du Minnesota Les premières traces d'occupation humaine dans l'État remontent à , avec les ossements d'un individu surnommé le

Wind variability and sheltering effects on measurements and modeling of air-water exchange for a small lake

Corey Dean Markfort, Fernando Porté Agel

Lakes with a surface area of less than 10 km^2 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.

2014

Wind variability and sheltering effects on measurements and modeling of air-water exchange for a small lake

Corey Dean Markfort, Fernando Porté Agel

2014