[Met_help] MET questions

[Daniel Schaffer]

Hello (presumbably John)

We are thinking about running MET grid_stat to generate dichomomous counts from forecast and observed convection data in the next few weeks.  You may recall I had some email exchanges with you last January relating to this during some initial investigation I did.  Now, upon revisiting this, a couple of new questions have come up.

1. From my reading of the MET 1.1 User's guide, it appears that I can specify a threshold that applies to both the forecast and obs fields.  However, I don't see how I can specify different thresholds for the forecast and obs.  For our convection data, the forecast and obs are not on the same scale.  Is there any easy code change I could make that would extend MET to handle this case?  My other option is to put the forecast and obs data on the same scale prior to running MET.

2. I want to ensure I am clear on how the neighborhood analysis works.  The documentation on page 5-7 says that "forecast and observation coverage" fields are computed from the raw fields and a raw threshold value.  Suppose my nbr_width is 3 so I have 9 grid points including the center grid point of interest.  Then if 6 boxes exceed the threshold and 3 do not, the coverage value at that grid point is 2/3?  And then the coverage field is computed by repeating this exercise over all grid points?  And then, finally, the nbr_frac_threshold is use to create neighborhood contingency tables from the paired forecast/obs coverage grids in exactly the same way as in the case without neighborhoods.  So, for example, if at the gridpoint mentioned above, the forecast coverage is 2/3, the obs coverage .5 and the nbr_frac_threshold is 0.4 then the "Yes-Yes" count would be incremented?

Thanks,
Dan Schaffer

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Dan Schaffer, Research Associate            e-mail: Daniel.S.Schaffer at noaa.gov
NOAA/OAR/Earth System Research Lab         phone:  (303) 497-7252
Aviation Branch                             fax:    (303) 497-6301
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