Source: Space Weather
As space weather forecasting matures more attention is being given to how we verify and validate those forecasts. A simple approach is to classify a set of forecasts of space weather events as: (a) the forecast event occurs (a hit), (b) does not occur (a false alarm), (c) does occur but is not forecast (a miss), or (d) no event is forecast and none occurs. The counts of forecasts in each class are then formed into a contingency table from which a wide range of metrics can be derived (example here). This simple approach is sensitive to any quantitative thresholds used to identify an event; for example, does the particle flux exceed some level. If an event falls 1 per cent below the threshold it will be counted as false alarm. Thus, we need more nuanced metrics that take account of this and other cases where thresholds are narrowly missed.
Kahler and Darsey  directly address this problem by exploring how the counts in a contingency table might be weighted to take account of event sizes. The authors apply their ideas in the context of solar energetic particle event forecasts driven by observed intensities of solar flares and solar radio bursts.
Their results suggest that use of weighted counts may better assess forecasts of frequent small events close to event threshold, less so for the prediction of occasional large events. Thus, an event peaking just below threshold might be recognized as a hit with low weight, a more realistic assessment than a false alarm.
This paper shows that this is an important issue for further work, as the authors note, in particular to develop more robust approaches to the verification and validation of forecasts. Such work is timely, not only as space weather forecasting matures, but also to take account of recent advances in the verification of meteorological forecasts, such as the flexing approach presented by Sharpe .
Citation: Kahler, S. W., & Darsey, H. . Exploring contingency skill scores based on event sizes. Space Weather, 19, e2020SW002604. https://doi.org/10.1029/2020SW002604
―Michael A. Hapgood, Editor, Space Weather
Text © 2021. The authors. CC BY-NC-ND 3.0
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