Impact plots

When a forecast system is upgraded (i.e. better models or better post-processing) it can be useful to see what impact the new forecasts have. This reasons for improvements can be difficult to be gleaned from basic scores such as mean absolute error. The impact diagram helps reveal how a new system is getting better forecasts. Are the improvements caused by better forecasts at low temperatures? Are improvements due to a reduction in a few really large errors?

The impact diagram is invoked by the -type impact option. It is applied to whatever metric is specified using -m:

verif ECMWF.nc MEPS.nc -m mae -type impact -sp -r 0:0.5:10

To show the impact on a map use:

verif ECMWF.nc MEPS.nc -m mae -type mapimpact -maptype simple