WRF Domain Wizard

Step-by-Step Tutorial: Defining Mesoscale Grids in WRF Domain Wizard

Setting up an accurate spatial domain is the most critical first step when running the Weather Research and Forecasting (WRF) model. WRF Domain Wizard—a graphical user interface (GUI) for the WRF Preprocessing System (WPS)—simplifies this process. It eliminates the need to manually calculate complex grid coordinates in the namelist.wps file.

This tutorial provides a clear, step-by-step workflow to define mesoscale grids, configure map projections, and establish nested domains using WRF Domain Wizard. Step 1: Initialize a New Domain Project

Before defining grid boundaries, you must establish a clean project environment within the software. Launch the WRF Domain Wizard application. Click on the Domain menu at the top left of the interface.

Select New from the dropdown menu to open the domain creation wizard.

Enter a precise, recognizable Domain Name (e.g., Hurricane_Sandy_Mesh). Click Next to proceed to the map projection screen. Step 2: Select the Map Projection

WRF requires a flat map projection to represent the Earth’s curved surface. Choosing the correct projection minimizes spatial distortion in your region of interest. Locate the Projection dropdown menu. Select the projection that fits your target latitude:

Lambert Conformal: Ideal for mid-latitudes (e.g., North America, Europe). Mercator: Best for tropical and equatorial regions.

Polar Stereographic: Required for high-latitude polar regions.

Define the True Latitudes (typically matching the center or boundaries of your study area) and the Central Meridian (the central longitude of your grid). Step 3: Configure the Parent Domain (Grid 1)

The parent domain (d01) establishes the outermost boundaries and the coarsest resolution of your simulation. Navigate to the Grid Center fields.

Input the exact Center Latitude and Center Longitude of your target simulation area.

Set the Horizontal Resolution (e.g., 30 km or 27000 meters) in the DX and DY fields.

Enter the Grid Dimensions by specifying the number of grid points in the X (west-east) and Y (south-north) directions.

Click Update Map to visually render the bounding box over the geographic map. Step 4: Define Nested Domains (Optional)

Mesoscale features often require higher resolution over a specific sub-region. Nesting allows you to embed finer grids inside the parent domain.

Click the New Nest button on the toolbar or right-click the map canvas.

Draw the nest: Click and drag your mouse over the map to draw a smaller bounding box inside the parent grid.

Adjust the Nest Ratio (typically 3:1 or 5:1). For example, a 3:1 ratio inside a 30 km parent grid results in a 10 km nested grid.

Fine-tune the start positions (i_parent_start and j_parent_start) in the dimensions panel to ensure the nest sits comfortably away from the parent boundaries to prevent boundary errors. Step 5: Verify Grid Specifications

Reviewing the grid layout before exporting prevents simulation failures during the WPS execution phase.

Inspect the visual map to confirm that the domains fully cover your geographic areas of interest (e.g., coastlines, mountain ranges).

Check that the nested domains maintain at least a 5-to-10 grid-point buffer from the edges of the parent domain.

Confirm that the total number of grid points consists of clean numbers (ideally factors of 2, 3, and 5) to optimize parallel processing efficiency. Step 6: Save and Export the Namelist

The final step translates your visual layout into the raw text configuration required by WRF. Click the Save button in the Domain Wizard interface. Select Export to namelist.wps.

Choose your target destination folder (typically your WPS installation directory).

Open the generated namelist.wps file in a text editor to verify that the &share and &geogrid sections accurately reflect your GUI selections.

Your mesoscale grids are now successfully defined and formatted, ready for the geogrid program to ingest terrain and land-use data.

To help refine your specific modeling workflow, could you share a few details? What geographic region are you simulating?

What horizontal grid resolution (in kilometers) do you plan to use?

Will you be running a single domain or multiple nested domains?

I can provide tailored advice on optimization and projection choices based on your answers.