Describe the Enhancement

MET currently supports the FBIAS1 percentile threshold option. For example, you can set "obs.cat_thresh = >20;" and set "fcst.cat_thresh = ==FBIAS1;". MET will replace ==FBIAS1 with the actual threshold value that will result in a frequency bias of 1.0. This is essentially de-biasing the forecast. However, we did find one case where setting the FBIAS to value different from 1.0 would actually be useful, and then is in setting the MODE merge_thresh option.

This tasks is to enable MET to support ==FBIAS{N} where N is a floating point value. Make sure to test this in MODE:

conv_thresh  = ==FBIAS1;
merge_thresh = ==FBIAS0.9;

As discussed via @sethlinden and @JohnHalleyGotway, enhance unit_perc_thresh.xml to exercise all possible permutations of threshold types:

• Using ==FBIAS{n} thresholds in the fcst and obs dictionaries (x 2)
• Setting n = 1.0, <1.0, and >1.0 (x 3)
• Exercise by inequality types for the other threshold: < and > (x 2)
  Recommend doing this in Grid-Stat and including all 12 permutations described above.

We should also manually test this in MODE, setting fcst.conv_thresh = ==FBIAS1.0 and fcst.merge_thresh ==FBIAS0.9. We should make sure that this actually works and we may, or may not, actually use that for an additional unit test.

Time Estimate

Many days.

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Funding Source

2712221 - managed by @michelleharrold

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• Select engineer(s) or no engineer required: @sethlinden
• Select scientist(s) or no scientist required: Michelle, or could be reassigned to another scientist on AF projects.

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Define Related Issue(s)

Consider the impact to the other METplus components.

• METplus, MET, METdatadb, METviewer, METexpress, METcalcpy, METplotpy
  Need to check with METviewer and/or METdatadb to make sure they're able to parse thresholds like '==FBIAS0.8'.

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