Coordinate Rotation

If the sonic sensor in a covariance system is not well leveled, the covariance calculations will produce errors. One may rotate the data to obtain the accurate ET data. There are different rotation methods. The traditional method is to set the vertical wind velocity (W) to be zero and the mean wind direction to be perpendicular to the W direction (Tanner and Thurtell, 1969; Kaimal and Finnigan, 1994). Other rotation methods were also developed (Lee et al., 2004). The errors (unrotated flux) depend on the instrument tilting level. The larger the tilting angle, the larger the errors (unrotated flux). Usually, the error is about 0-25% (http://www.licor.com/env/Products/GasAnalyzers/eddyPresentation/EC_master_Presentation _files/_frame.htm).

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Renewable Energy 101

Renewable Energy 101

Renewable energy is energy that is generated from sunlight, rain, tides, geothermal heat and wind. These sources are naturally and constantly replenished, which is why they are deemed as renewable. The usage of renewable energy sources is very important when considering the sustainability of the existing energy usage of the world. While there is currently an abundance of non-renewable energy sources, such as nuclear fuels, these energy sources are depleting. In addition to being a non-renewable supply, the non-renewable energy sources release emissions into the air, which has an adverse effect on the environment.

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