Figure 5
From: Climate information, outlooks, and understanding–where does the IRI stand?
Reliability analysis for 0.5-month lead forecasts of global precipitation. Forecast data for all seasons are used during 1997–2013. The green curve pertains to forecast probabilities for above-normal precipitation, the orange curve forecast probabilities for below-normal precipitation, and the gray curve for near-normal precipitation. For above and below normal, least squares regression lines are shown, weighted by the sample sizes represented by each point. Points representing probability intervals that are forecast in a relatively greater proportion of the time are shown using larger symbols. The diagonal y = x line represents perfect reliability. The colored marks on the axes show the overall means of the forecast probabilities (x-axis) or observed relative frequencies (y-axis). The lower panel shows the frequency with which each interval of probability was forecast, where interval widths are 0.05 (e.g., 0.175–0.225 is labeled as 0.20), except that the climatological (0.333) probability is also explicitly shown.