Describe the Problem

When testing the verification of the climatology-based probabilities for NOAA/CPC with Grid-Stat, John Opatz discovered an apparent bug in MET's computation of the climatological cumulative distribution function values.

While the issue was identified using CPC data, it is also apparent in the existing unit test output:
climatology/grid_stat_PROB_GFS_CLIMO_1.0DEG_150000L_20120409_120000V_pairs.nc

I also found a bug in derive_climo_prob(). When the observation threshold is defined relative to climatology (e.g. >CDP67), the climatological probability value should be constant. However, the constant value should depend on the inequality type, where <CDP{N} has climo probability p=N/100 while >CDP{N} has probability 1.0-p.

This task is to fix both of these bugs.

Expected Behavior

The climo CDF value is computed as the area (between 0 and 1) of the climo distribution to the left of the observation value. However, MET is not computing that correctly.

Environment

Describe your runtime environment:
1. Machine: NB output on kiowa.

To Reproduce

Describe the steps to reproduce the behavior:
1. Inspect the file: climatology/grid_stat_PROB_GFS_CLIMO_1.0DEG_150000L_20120409_120000V_pairs.nc
2. Using ncview, note the values for i=8, j=77:
obs = 13.1514, climo_mean = 3.21593, climo_stdev = 7.9448, climo_cdf = 0.359584
3. Note that the obs > climo_mean but climo_cdf < 0.5. When the obs value greater than the climo mean, the CDF should be greater than 0.5.

So there's a bug in this computation!

Relevant Deadlines

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Funding Source

2788881

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