Activity 2: Designing Nested Domains
In this Activity, we will learn how to design nested domains. You should attempt the activity only after you have read and studied this week's Tutorial. There, you will learn the skills needed for you to complete this task.
Working with nests in WPS is not complicated. You need to be aware of a few things, such as:
- The more nests you add, the slower your experiment will get
- Always remember to use a ratio for the nest, such as the 3:1 ratio we have studied
- You will need to tell namelist.wps the number of domains you will be working with. So, for example, if you have an experiment with 30 km (parent domain), 10 km (first nest) and 3.3 km (second nest), then you have a total of 3 domains. This needs to be specified in the namelist.wps as:
- max_dom = 3
- For each nest you have, you will need to add an extra column for some parameters in your namelist.wps file
Let's try the following activity in order for you to see how nesting works in WPS.
Open your e-WRF installation and after that, open a Terminal window. Let's now create a new folder called "NEST", where we will be creating working with our experiment. So, here are the commands:
namelist.wps using a parent domain and two nests
After you edited your namelist, do the following:
- Make a plot of your domain using plotgrids.ncl (see Figure below)
- Run geogrid.exe After you run geogrid.exe, if your simulation is successful, you should see the words "Successful completion of geogrid." You should also see three new files there (which you can list using the "ls" command) :
- $ ncview geo_em.d01.nc
- $ ncview geo_em.d02.nc
- $ ncview geo_em.d03.nc
Figure 1 - Plot created for the experiment design using plotgrids.ncl. Here, you can see the parent domain at 30 km resolution (d01), as well as the first nest at 10 km resolution (d02) and the second nest at 3.3 km resolution (d03).
Note: if you have any questions along the way, you can post them on the Facebook group.