Rapid Refresh (RAP) Forum
RUC isobaric output-smoothed?
Posted By: Todd Hutchinson
Date: 5-September-03 1639Z
1. Are the RUC output wind fields on pressure surfaces smoothed?
I've been trying to use the RUC isobaric output to initialize some MM5 model runs. In doing so, I have noticed that MM5 has a large spinup period when using the RUC for initialization (as compared to initializing with the Eta). In investigating further, I have found that the 500 mb RUC wind fields at forecast hour 0 appear to be much smoother than the 500 mb Eta 0-hour forecast wind fields valid at the same time.
Further, in comparing the RUC wind field and vertical motion, there does not appear to be much convergence/divergence near areas of rising/sinking motion (this is a very subjective evaluation).
I suspect that the wind field (on pressure coordinates) is being smoothed. I found the following statement in the RUC Technical Procedures Bulletin:
6.c. Basic 3-D output variables
This says that "isobaric heights" are smoothed. But, it does not say whether winds on isobaric surfaces are smoothed.
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