Nested Model Runs: Ndown

One-way nesting using ndown

WRF supports two separate one-way nested options. In this section, one-way nesting is defined as a finer-grid-resolution run, made as a subsequent run after the coarser-grid-resolution run, where the 'ndown' program is run in-between the two simulations. The initial and lateral boundary conditions for this finer-grid run are obtained from the coarse grid run, with input from higher resolution terrestrial fields (e.g. terrain, landuse, etc.), and masked surface fields (such as soil temperature and moisture). the program that performs this task is 'ndown.exe.'

For this example we are going to use the Hurricane Matthew Case. As we have already unpacked GRIB date (ungrib.exe) for this case, we will skip this step.
 

Program flow:

• Make a coarse grid run (This is something you typically already have done prior to deciding to run ndown).
• STEP 1: WPS is run for both domains
• STEP 2: real.exe is run for both domains
• STEP 3: ndown is run for both domains
• STEP 4: Make the fine-grid WRF run

Program flow for a complete one-way nested setup.

Let's get started