idealised cases - implications of 1d base state

[MaVy]

Hello,

I would like to run a WRF idealised simulation prescribing a 3D wind field.
I have modified module_initialize_ideal.F accordingly, following the example of the 'em_b_wave 'case for which a 2D wind field is prescribed, and got my wrfinput file ready to go.
However, I don't quite understand the implications of computing the 'base state' as a 1D field.
In particular, there are two aspects of how WRF ideal works that are not clear to me and I would be grateful if you could help me understand (bearing in mind that I have read the Technical Notes/User guide but my questions are still unanswered):

1) As far as I understand, using a 1D sounding to compute the base state is the default behaviour for WRF and this is the only way the model can work. The em_b_wave case uses the middle column values from the input sounding to compute the base state, and I have also selected a 'column of interest' for my calculations.
I wonder how this choice affects the final 'full state' (base state + perturbation), as each column in my input sounding has a different wind direction.
How is the base state actually used? is this single column used to compute the full state at all other grid-points?

2) I am running dry simulations (dry_sounding=.true.). In this case, wouldn't the perturbations quantities be zero as base state = full state?

I would be grateful if you could help me understand how WRF works in relation to the above points, so that I can be sure I am simulating what I need to (!).

Thank you very much in advance for your help,

Vittoria

 

[Ming Chen]

Hi Vittoria,
Please see my answers below:
1) As far as I understand, using a 1D sounding to compute the base state is the default behaviour for WRF and this is the only way the model can work. The em_b_wave case uses the middle column values from the input sounding to compute the base state, and I have also selected a 'column of interest' for my calculations.
I wonder how this choice affects the final 'full state' (base state + perturbation), as each column in my input sounding has a different wind direction.
How is the base state actually used? is this single column used to compute the full state at all other grid-points?

Most of the ideal cases in WRF (e.g., em les , em_hill2d_x, etc) use a 1D sounding as input to compute base state. Note that base state (should be dry state) and perturbation state are required for WRF, and the input sounding is always a moist sounding, which is used to calculate the base state. Base state is used to define vertical coordinate and dry column pressure.
However, em_b_wave uses a 2D dataset as input. Note that this 2D dataset is specifically created for the ideal em_b_wave case. It is not a random 2D sounding input dataset. Unfortunately the code to create this dataset is no longer available.

2) I am running dry simulations (dry_sounding=.true.). In this case, wouldn't the perturbations quantities be zero as base state = full state?
I am not sure of this. Please print out some variables and compare with your input data to confirm whether they are the same or not.