Report On First Round Of Benchmarks
Creators: name: Sanz Rodrigo, Javier
name: Chávez Arroyo, Roberto A.
name: Moya, Iván
name: Ivanell, Stefan
name: Arnqvist, Johan
Publisher: name: Zenodo
Year: 2017
Subjects: wind energy, wind resource assessment, external conditions, benchmarking, diurnal cycle, GABLS3, Ryningsnäs, model-chain

description: This report summarizes the first round of benchmarks conducted under the <strong>NEWA validation strategy</strong>. An update of the validation program is provided with a schedule of forthcoming benchmarking activities based on the availability of experimental data. This report is the first of a series of three annual reports on NEWA benchmarks.

The first phase of the project has resulted in three main activities with a common objective of defining a baseline model-chain both at mesoscale and microscale levels.

The <strong>Mesoscale Sensitivity Test</strong> consisted on executing a sensitivity analysis of the WRF model coordinated by the NEWA mesoscale group around four European regions. This activity has been reported separately in deliverable 3.1 and concluded with the definition of a reference WRF set-up that will be used to produce the European Wind Atlas. Validation of this reference WRF configuration will be conducted in connection to the beta run of the wind atlas using available tall mast data from research and industry sites.

The <strong>Ryningsnäs Blind Test</strong> benchmark gathered a group of microscale modelers to simulate the mean profile of an atmospheric boundary layer (ABL) above a heterogeneous forest canopy on flat terrain and neutral atmospheric conditions. This benchmark tested canopy models that can use high-resolution canopy maps generated from aerial lidar scans. The results are currently compiled in to an article. The main findings are that the involved modeling groups, using models ranging from advanced industrial codes to state-of-the-art research codes, shows good agreement regarding mean wind profiles. The magnitude of the turbulent kinetic energy (TKE) generally match the observed one, but does not show the same directional dependence as the observed. The inability to model non-neutral conditions was striking. The learning outcome from the benchmark consortium is large and many key questions for future studies in the Hornamossen, i.e., from the extensive Swedish measurement campaign launched within NEWA, benchmark are defined.

The <strong>GABLS3 diurnal-cycle</strong> benchmark for wind energy applications revisited the original case developed by the boundary-layer meteorology community and adapted it to match the specific objectives of NEWA. Here, microscale modelers were asked to demonstrate that they can reproduce a real diurnal cycle with varying atmospheric stability and using input forcing produced offline from a mesoscale model (proxy for a wind atlas database). Mesoscale tendencies generated from WRF were provided as input to drive ABL RANS and LES models. All the models showed good consistency at assimilating tendencies even though some scatter remains depending on the particular settings of each code.

At this stage, we arrive to the first important milestone of the NEWA model-chain development, namely, the definition of a <strong>reference model-chain</strong> that includes:


	A reference WRF configuration derived after sensitivity analysis in various European regions.
	A reference canopy model implementation in microscale ABL models that can use high-resolution aerial lidar scans.
	A methodology for offline coupling of microscale models with mesoscale tendencies and transient turbulence modeling of varying atmospheric stability conditions.


Next round of benchmarks will use experimental data recently produced by NEWA experiments to test these reference models in complex terrain, coastal and offshore environments. Meso-micro methodologies will be compared in terms of annual wind resource statistics using a hierarchy of models of varying fidelity levels. This will allow differentiating methods suitable for planning (wind atlas) or design phases of wind energy projects.