Wind components_log fit for NAN values

[vikkbala]

Hello Dongqi Lin,

Hope you are doing well.

I am Vigneshkumar Balamurugan, a PhD candidate at TUM, Germany.

Thanks for the nice tool to process the dynamic driver for PALM model run.

I am having an issue with the wind components from WRF4PALM. Since our WRF model result's lowest level is above 500m, the wind components processed by WRF4PALM create unrealistic values (see the the figure attached). I think it is because of applying the logarithmic fit to wind components. I would be like to get your help/suggestion regarding this. It would nice if you could help us at your earlier convenience. Please let me know if you also need more information.

Thanks,
Vigneshkumar B

[dongqi-DQ]

Hi Vigneshkumar,

Yes, I'm aware that the log fit could be problematic sometimes. At the moment, I'm the only person maintaining this code, so I cannot guarantee when I'll have time to fix it.

I included WRF 10 m winds and 2 m PT and QV in the current version of WRF4PALM, but maybe this did not improve the surface estimation. I was informed by another user via email that he found the earliest version of the fit works better in his case (see issue #39). You can try to reverse the code back to the older version, but I think the main issue is that we need further development of the algorithm.

Another thing is that if you have the lowest level of 500 m in WRF, then it usually means that your topography at the PALM domain lateral boundaries is around 500 m. If you include the topography, these unrealistic values usually won't be included in the simulations. If you don't have a static driver, you can have a look at our tool GEO4PALM.

One of our users suggested that the WRF tool developed by the PALM team themselves has some functions to deal with this in a better way. It, however, requires a static driver. This could be integrated into WRF4PALM. But again, this won't happen until I find enough spare time.

Cheers,
Dongqi

[vikkbala]

Dear Dongqi Lin,

Thanks for your quick reply. It is really helpful. The older version of codes work fine. The interpolation make sense.

We noticed an another problem regarding the terrain height in the PALM.

We also used GEO4PALM to create a static driver, which also have terrain height information (zt). After we run the PALM model and look at the results, we believe the terrain height information is not read by PALM.

Example, we have very unrealistic wind data from the model simulations (please look at the attached figure; wind speed is very high; more than 50-100m/s).

It is because we have very high wind values in dynamic driver at lower heights; the figure I attached in my previous message.
It can only happen if PALM model didn't read the terrain height and assumed terrain height =0. Then the PALM model used the dynamic driver without considering terrain height information.

In the PALM model namelist,

topography = 'read_from_file',

It would be nice if you could help on this (whether we made some mistakes in PALM namelist)

Thanks for your time for this matter.

[dongqi-DQ]

I think the issue with terrain height is that PALM usually automatically adjusts the topography height based on the lowest point of the terrain to save computation. For example, if you have the lowest terrain height of 200 m in your domain, then PALM will apply a deduction of 200 m to the entire domain—so your 500 m terrain will become 300 m.

PALM documentation and ticket system should have more information. GEO4PALM and WRF4PALM have a parameter z_origin, which is 0.0 m by default. You may need to adjust this value based on your case.

[vikkbala]

Dear Dongqi Liu,

Thanks for the information.

regards,
Vigneshkumar B