Choice of forecast pressure level to interpolate to level of observation.

[jwraby]

Using Point-Stat V11.1.0, my config file has the forecast and observation field setting of P862-876. The WRF output was post-processed to output on pressure levels 862, 869, and 876. The OBS_LVL of my ADPUPA observations are 868.3243 (TMP) and 869.2578 for UGRD and VGRD. How does Point-Stat choose the forecast output pressure level to interpolate vertically to the OBS_LVL of the observation? Thanks.

[CPKalb]

Hi:

For vertical interpolation, if the forecast and observations are at the same level, no interpolation is performed. If they are on different levels, vertical interpolation is performed in the natural log of pressure coordinates (for all variables except specific humidity). In your case, the levels are not exact due to the decimal points, so they will be interpolated. Specifically, the forecasts will be interpolated to the observation level.

Which of the three forecast levels MET will use to do the interpolation to the observation level depends on how your configuration is set up for the forecast variable. If you want it to use the closest, you would want to specify P869 as the level for your forecast variables.

Christina

[CPKalb]

You will likely have to give it a .txt extension to add the file.

[jwraby]

I tried several times to upload the log file, but I can't get it to work.

[jwraby]

I added .txt to the file and tried again, but no change.

[CPKalb]

The other option is to upload it to our ftp site using the instructions.

Christina

[jwraby]

Thanks for the instructions. I can't seem to make it work. I think my question is answered already, so I'll end this discussion. Appreciate the information which has helped me.