Event Classification Methods Comparison and Validation

As a means of validation for the methods we use for identifying NAM surge events, a comparison between those methods of Fuller and Stensrud (2000) and our methods will be shown.

To classify a surge event as 'valid,' it's occurrence must be concurrent with or proceed within two days a day where the accumulated daily precipitation for the Phoenix, Tucson and Yuma sites exceeds 0.13 inches, i.e., 80th percentile. Though there exist a potential for heavy rainfall at only one station to cause the threshold to be exceeded, using a validation method that depends on spatially-disperse precipitation readings lends itself to determine a procedure of surge classification that better identifies surges that produce widespread precipitation events.


Since, Fuller and Stensrud (2000) identified surge events in July and August, events that our methods found in June and September for these years will be ignored for the validation.


Results for the period of July-August for 1980-1984:

Rainy days above 80th percentile: 36

Events:
Fuller and Stensrud (2000) = 35
Current study = 20

Surge events with rain event within 2 days, i.e., valid events:
Fuller and Stensrud (2000) = 24 (69%)
Current study = 16 (80%)


Though Fuller and Stensrud's methods identified more valid surge events, our methods identified valid surge events with a greater precision. By using the methods of Fuller and Stensrud (2000) one would identify more valid surge events during this period, but they would also risk identifying an increased percentage of invalid surge events, a.ka. false-alarm surges, 31% compared 20% using our current methods.


-jamie