Preprints
https://doi.org/10.5194/gmd-2021-274
https://doi.org/10.5194/gmd-2021-274

Submitted as: model evaluation paper 22 Nov 2021

Submitted as: model evaluation paper | 22 Nov 2021

Review status: this preprint is currently under review for the journal GMD.

Evaluation of a forest parameterization to improve boundary layer flow simulations over complex terrain

Julian Quimbayo-Duarte1, Johannes Wagner2, Norman Wildmann2, Thomas Gerz2, and Juerg Schmidli1 Julian Quimbayo-Duarte et al.
  • 1Institute for Atmospheric and Environmental Sciences, Goethe University Frankfurt, Frankfurt am Main, Germany
  • 2Deutsches Zentrum für Luft- und Raumfahrt e.V., Institut für Physik der Atmosphäre, Oberpfaffenhofen, Germany

Abstract. We evaluate the influence of a forest parametrization on the simulation of the boundary layer flow over moderate complex terrain in the context of the Perdigão 2017 field campaign. The numerical simulations are performed using the Weather research and forecasting model using its large eddy simulation mode (WRF-LES). The short-term high resolution (40 m horizontal grid spacing) and long-term (200 m horizontal grid spacing) WRF-LES are evaluated for an integration time of 12 hours and 1.5 months, respectively, with and without forest parameterization. The short-term simulations focus on low-level jet events over the valley, while the long-term simulations cover the whole intensive observation period (IOP) of the field campaign. The results are validated using lidar and meteorological tower observations. The mean diurnal cycle during the IOP shows a significant improvement of the along-valley wind speed and the wind direction when using the forest parametrization. However, the drag imposed by the parametrization results in an underestimation of the cross-valley wind speed, which can be attributed to a poor representation of the land surface characteristics. The evaluation of the high-resolution WRF-LES shows a positive influence of the forest parametrization on the simulated winds in the first 500 m above the surface.

Julian Quimbayo-Duarte et al.

Status: open (until 17 Jan 2022)

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Julian Quimbayo-Duarte et al.

Julian Quimbayo-Duarte et al.

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Short summary
This model evaluation has as an ultimate objective to improve boundary layer flow representation over complex terrain. The numerical model is tested against observations retrieved during the Perdigão 2017 field campaign (moderate complex terrain). We observed that the inclusion of a forest parametrization in the numerical model significantly improves the representation of the wind field in the atmospheric boundary layer.