431: Attributes Diagrams

The attributes diagrams are constructed using a set of probabilistic forecasts over time and/or space. Results are shown separately for the three categories, and for all the categories pooled together (top left). The reliability statistics are calculated using predictions for all gridpoints / stations / series. By default, the probabilistic forecasts are binned to the nearest 10% (in accordance with the WMO's Standardized Verification System for Long-Range Forecasts (SVSLRF) , but 5% probability bins can be selected using Options ~ Verification Settings . Even though the forecast probabilities are binned, the point on the x -axis is shown at the average of the forecasts in the bin rather than at the centre of the bin. Similarly, the resolution slopes are calculated using the actual forecast probabilities (not binned), as are the Brier and ranked probability scores. (The Brier and ranked probability scores can be calculated using forecast probabilities at the central point of the bin using Options ~ Verification Settings .)

The reliability curve is shown by the thick line, while the thin line of the same colour is a linear regression fit to the reliability curve weighted by the number of forecasts in each probability bin ( Wilks, D. S., and A. H. Murphy, 1998 ). The resolution slopes are calculated from this regression line. The solid 45 degree diagonal shows the line of perfect reliability. The dashed diagonal is the so-called no-skill line (a reliability curve that is shallower than this will score a negative Brier skill score against climatology). The horizontal line represents the line of no resolution and crosses the y -axis at the observed relative frequency for all years. Note that his value is not necessarily the same as the climatological probability of an event since the observed relative frequency is defined only over the retroactive period in the case of retroactive forecasting, and in the case of the double cross-validated forecasts the categories are identified out-of-sample.

The reliability statistics can be saved by right-clicking on the graphs. In a similar manner the graphs themselves can be saved and the titles customised. The graphs can be saved as graphics files, individually or as a montage, by right-clicking anywhere in the child window and selecting Export from the pop-up menu. A default name is given to the graphics file, but this name can be changed using the browse button. The image quality for all the graphics formats can be improved by increasing the size of the image (see Options ~ Graphics ~ Graph Scaling ). The graphics titles can be set using the Customise option upon right-clicking in the child window. Further options for customising the graphs, including adjusting the size of the fonts, and the size of the images are available from Options ~ Graphics .