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  • Author or Editor: Wayne M. Angevine x
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Wayne M. Angevine
,
Alison W. Grimsdell
,
Leslie M. Hartten
, and
A. C. Delany

This article describes the 1995 and 1996 Flatland boundary layer experiments, known as Flatland95 and Flatland96. A number of scientific and instrumental objectives were organized around the central theme of characterization of the convective boundary layer, especially the boundary layer top and entrainment zone. In this article the authors describe the objectives and physical setting of the experiments, which took place in the area near the Flatland Atmospheric Observatory, near Champaign–Urbana, Illinois, in August–September 1995 and June–August 1996. The site is interesting because it is extremely flat, has uniform land use, and is in a prime agricultural area. The instruments used and their performance are also discussed. The primary instruments were a triangle of UHF wind-profiling radars. Rawinsondes and surface meteorological and flux instruments were also included. Finally, some early results in terms of statistics and several case studies are presented.

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Joseph B. Olson
,
Jaymes S. Kenyon
,
Irina Djalalova
,
Laura Bianco
,
David D. Turner
,
Yelena Pichugina
,
Aditya Choukulkar
,
Michael D. Toy
,
John M. Brown
,
Wayne M. Angevine
,
Elena Akish
,
Jian-Wen Bao
,
Pedro Jimenez
,
Branko Kosovic
,
Katherine A. Lundquist
,
Caroline Draxl
,
Julie K. Lundquist
,
Jim McCaa
,
Katherine McCaffrey
,
Kathy Lantz
,
Chuck Long
,
Jim Wilczak
,
Robert Banta
,
Melinda Marquis
,
Stephanie Redfern
,
Larry K. Berg
,
Will Shaw
, and
Joel Cline

Abstract

The primary goal of the Second Wind Forecast Improvement Project (WFIP2) is to advance the state-of-the-art of wind energy forecasting in complex terrain. To achieve this goal, a comprehensive 18-month field measurement campaign was conducted in the region of the Columbia River basin. The observations were used to diagnose and quantify systematic forecast errors in the operational High-Resolution Rapid Refresh (HRRR) model during weather events of particular concern to wind energy forecasting. Examples of such events are cold pools, gap flows, thermal troughs/marine pushes, mountain waves, and topographic wakes. WFIP2 model development has focused on the boundary layer and surface-layer schemes, cloud–radiation interaction, the representation of drag associated with subgrid-scale topography, and the representation of wind farms in the HRRR. Additionally, refinements to numerical methods have helped to improve some of the common forecast error modes, especially the high wind speed biases associated with early erosion of mountain–valley cold pools. This study describes the model development and testing undertaken during WFIP2 and demonstrates forecast improvements. Specifically, WFIP2 found that mean absolute errors in rotor-layer wind speed forecasts could be reduced by 5%–20% in winter by improving the turbulent mixing lengths, horizontal diffusion, and gravity wave drag. The model improvements made in WFIP2 are also shown to be applicable to regions outside of complex terrain. Ongoing and future challenges in model development will also be discussed.

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