The Iowa Atmospheric Observatory: Revealing the Unique Boundary-Layer Characteristics of a Wind Farm

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2019-01-25
Authors
Takle, Eugene
Rajewski, Daniel
Purdy, Samantha
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Takle, Eugene
Distinguished Professor Emeritus
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Agronomy

The Department of Agronomy seeks to teach the study of the farm-field, its crops, and its science and management. It originally consisted of three sub-departments to do this: Soils, Farm-Crops, and Agricultural Engineering (which became its own department in 1907). Today, the department teaches crop sciences and breeding, soil sciences, meteorology, agroecology, and biotechnology.

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The Department of Agronomy was formed in 1902. From 1917 to 1935 it was known as the Department of Farm Crops and Soils.

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1902–present

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  • Department of Farm Crops and Soils (1917–1935)

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Agronomy
Abstract

The Iowa Atmospheric Observatory was established to better understand the unique microclimate characteristics of a wind farm. The facility consists of a pair of 120 m towers identically instrumented to observe basic landscape-atmosphere interactions in a highly managed agricultural landscape. The towers, one within and one outside of a utility-scale low-density array wind farm, are equipped to measure vertical profiles of temperature, wind, moisture, and pressure and can host specialized sensors for a wide range of environmental conditions. Tower measurements during the 2016 growing season demonstrate the ability to distinguish microclimate differences created by single or multiple turbines from natural conditions over homogeneous agricultural fields. Microclimate differences between the two towers are reported as contrasts in normalized wind speed, normalized turbulence intensity, potential temperature, and water-vapor mixing ratio. Differences are analyzed according to conditions of no wind farm influence (i.e. no-wake) vs. wind farm influence (i.e. waked flow) with distance downwind from a single wind turbine or a large group of turbines. Differences are also determined for more specific atmospheric conditions according to thermal stratification. Results demonstrate agreement with most, but not all, currently available numerical flow field simulations of large wind farm arrays and of individual turbines. In particular, the well documented higher night-time surface temperature in wind farms is examined in vertical profiles that confirm this effect to be a “suppression of cooling” rather than a warming process. A summary is provided of how the wind-farm boundary layer differs from the natural boundary layer derived from concurrent measurements over the summer of 2016.

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This is a manuscript of an article published as Takle, Eugene S., Daniel A. Rajewski, and Samantha L. Purdy. "The Iowa Atmospheric Observatory: Revealing the Unique Boundary-Layer Characteristics of a Wind Farm." Earth Interactions (2019). doi: 10.1175/EI-D-17-0024.1. Posted with permission.

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Tue Jan 01 00:00:00 UTC 2019
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