A Comparison of 1-Way and 2-Way Nesting in the WRF-LES Framework

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2013-05

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Abstract

The Weather Research and Forecasting (WRF) model is a numerical model designed for numerical weather prediction of the Earth’s atmosphere. Although it is commonly used for mesoscale modeling, it is capable of running Large Eddy Simulations, or LES. LES is an approach to directly solve turbulent eddies within the atmospheric boundary layer by filtering the Navier-Stokes equations and directly resolving the large, turbulent eddy fields. This is most useful for boundary layer applications, which is the region of the atmosphere in which we spend the majority of our lives. LES typically works with a smaller domain due to having a much smaller grid size than mesoscale models and can be used for applications such as simulating flow over topography, flow through wind farms, and convective initiation in thunderstorms. One useful feature in numerical models is placing a higher resolution domain within a coarser, parent domain. This feature is called nesting and is useful for more accurately resolving the areas of interest, while still resolving the surrounding environment that may affect the area of interest. Nesting can be done in two ways: 1-way nesting, and 2-way nesting. The two nesting techniques are very similar, but can produce extremely different results. Here, the two techniques are compared in a variety of ways to determine the usefulness, accuracy, and any unwanted issues that may result from using nests in a numerical simulation.

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Keywords

Large eddy simulation (LES), Nesting, Atmospheric boundary layer, Weather research and forecasting (WRF), Climate modeling, Numerical weather prediction

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