General question about namelist setup for WRF spatial downscaling of windspeed data?

[spencerp]

I am very new to using WRF, and am currently doing a lot of exploring and experimentation. My goal is to essentially do spatial downscaling of windspeed data for a single timestep. I am only interested in spatial scaling, not temporal scaling.

This is the setup I have in mind, does it make sense?
- Use a single GFS input gribfile forecast that has the coarse spatial wind data I am interested in downscaling. For example a 6 hour forecast from 2024_01_01_00:00.
- Configure namelist.wps and namelist.input with the start and end datetimes all being the same datetime of the gribfile (2024_01_01_00:00)
- Create two domains, where the child domain has my desired parent_grid_ratio, 3, for example

My questions are related to setting up the start_date and interval:
1. Since I am interested in spatial downscaling (not time downscaling) how do I set interval_seconds in my namelist files? I only have one input gribfile for my single timestep, so there is no interval between my input data.
2. For my example input gribfile, which is a 6 hour forecast initialized at 2024_01_01_00:00, would my start datetime be 2024_01_01_00:00, with my end datetime being 2024_01_01_06:00, because I have a 6 hour forecast? Or would the start and end datetime both be 2024_01_01_00:00 (which is the forecast initialization time) because I am not downscaling in time?

I appreciate any advice and I am happy to provide clarification if needed, thanks!

 

[Ming Chen]

Please see my answers below:

I am very new to using WRF, and am currently doing a lot of exploring and experimentation. My goal is to essentially do spatial downscaling of windspeed data for a single timestep. I am only interested in spatial scaling, not temporal scaling.

This is the setup I have in mind, does it make sense?
- Use a single GFS input gribfile forecast that has the coarse spatial wind data I am interested in downscaling. For example a 6 hour forecast from 2024_01_01_00:00.

You cannot use just a single GFS data file. This is because WRF run requires initial and boundary conditions, and you will need at least two times of GFS data to produce boundary forcing for WRF.

- Configure namelist.wps and namelist.input with the start and end datetimes all being the same datetime of the gribfile (2024_01_01_00:00)
- Create two domains, where the child domain has my desired parent_grid_ratio, 3, for example

start and end datetimes cannot be same. end time must be later than start time. and at least two times of GFS data are required.
you an run single domain or nested domain, depending on the resolution you need.

My questions are related to setting up the start_date and interval:
1. Since I am interested in spatial downscaling (not time downscaling) how do I set interval_seconds in my namelist files? I only have one input gribfile for my single timestep, so there is no interval between my input data.

GFS analysis data are at intervals of 6-hr. time interval must be the same as the interval of your inpout data

2. For my example input gribfile, which is a 6 hour forecast initialized at 2024_01_01_00:00, would my start datetime be 2024_01_01_00:00, with my end datetime being 2024_01_01_06:00, because I have a 6 hour forecast?

This is corrcet.

I appreciate any advice and I am happy to provide clarification if needed, thanks!