[Met_help] Asking for a little help

[John Halley Gotway]

Kefeng,

Good questions.

I have a question for you.  Do you by any chance have "R" available on your system?  It's an open-source statistical scripting language.  If so, try running the R code I've attached on some of your
MODE output files.  Here's how you'd run it:

Rscript mode_summary.R mode_*_obj.txt
(where "mode_*_obj.txt" grabs one or more MODE output object stats files)

This Rscript summarizes one or more MODE output files.  I've also attached an ASCII file named "mode_summary_example.txt" that gives sample output from this script.

OK, getting to your question... here's how CSI is defined:
CSI = (hits)/(hits + misses + false alarms)

You can actually compute CSI on MODE output one of two ways, with regards to object counts or object areas:

(1) With regards to object counts:
hits         = (count of fcst matches + count of obs matches)/2
misses       = (count of unmatched obs objects)
false alarms = (count of unmatched fcst objects)

(2) With regards to object areas:
hits         = (area of fcst matches + area of obs matches)/2
misses       = (area of unmatched obs objects)
false alarms = (area of unmatched fcst objects)

Hopefully, somewhere in the MWR article, it'll say which method was used for computing this type of object-based CSI.  All of these counts and areas should show up in the output of "mode_summary.R".
If you're comfortable using R, I'd suggest modifying the script to compute these CSI values for you.

Personally, I like computing CSI using areas, but I think you'll find that this leads to very large values of CSI that are very often near 1.

Hope that helps.

John


Zhu,Kefeng wrote:
> Hi, John:
> 
> 
>       Do you have any detail documents about how to calculate the Object-based scores, like CSI? Although i have read through the MET user guider and the article of objected-based published in Monthly Weatherly Review, I'm still confused about the concept of matches, misses and false alarms of the two objects. Since the two objects are not in the same location and differ in size and grid numbers, I'm wondering how to define matches, misses and false alarms?
> 
>       Thanks a lot!
> 
> Kefeng  
> 
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