Hi,
The wind speed I got from my OpenIFS simulation is extremely high around Arctic region, and I can’t find the reason. The wind speed is calculated by u and v by myself. I have checked the value of u and v, and they are both bad. Other parameters, such as potential temperature or specific humidity on pressure level, and surface wind speed still work well. What should I do to scale the wind speed around polar point?
The wind speed on 850hPa looks like:
It is the first time point of my run.
Best wishes,
Xueqing
Hi Xueqing,
It’s not easy to say something definite without knowing more about your experiment.
If this is the first time step of your run after initialisation, then the model should still be influenced to a large extent by its initial conditions. Have you checked if it is only the wind field that shows unusual values? E.g. have you looked at other variables such as mean sea level pressure (msl), 2m temperatures (2t), or 10 metre wind field (10u, 10v) etc. Do they look OK?
The location near the Pole is a bit suspicious. Can I please ask what model grid resolution and what dynamical timestep you are using?
Cheers,
Marcus
Hi Marcus,
Other variables, at least those I checked, all looks OK, including mslp, 2t, and 10 metre wind speed. The black contours in the map shows mslp. The timestep I use is 12 minutes (TSTEP=720) and grid resolution is T639_4.
Regards,
Xueqing
OK, thanks, it’s reassuring to know the other fields look OK.
I still believe this is likely related due to the proximity to the Pole (singularity) and the high wind speed could result from various factors. It could be vector representation at the Pole, an interpolation artifact, or the way how the spectral data is converted to the plotting grid etc.
How do you calculate wind speed (do you use vo and d?).
Could you try to omit the top latitude row at the Pole and interpolate the wind field from the remaining data, and check if this problem persists?
Regards,
Marcus
Hi Marcus,
I’m sorry to make you misunderstand. The calculation I mean is (u**2+v**2)**0.5 but not ws from model output. The u and v are outputs from model.
Now I calculate u & v from vo and d and the problem is solved.
Most of setting in my run are the default. It is from my control simulation. But I’m surprised t cannot use the wind components from model output directly. Is it a special case? I take u & v from spectral fields file(ICMSH).
Regards,
Xueqing
Correctly representing wind vectors near the Poles is a known issue (Pole singularity), often with spikes in the derived wind speeds. I believe that this was the case in your earlier plots.
Other colleagues have much more expertise with this than I have, but if you search for “wind speed near the Poles in numerical models” on the web then you can probably find lots of material about this.
Glad you have now a better looking wind field.
Best wishes,
Marcus
