Filtering

By default, Verif uses all dates, leadtimes, and locations that files have on common when computing a score. However, statistics on subsets of the full dataset can also be done by using filtering options.

Filtering locations

Use the -l option to select a subset of stations:

verif ECMWF.nc MEPS.nc -m obsfcst -l 18700

This command selects only data for the location with an id of 18700 (which happens to the official station of the Norwegian Meteorological Institute in Oslo).

Other subsetting options include -latrange, -lonrange, and -elevrange. For example the following would only select locations on the West coast of Norway at altitudes below 50 meters:

verif ECMWF.nc MEPS.nc -m obsfcst -latrange 50,70 -lonrange 4,6 -elevrange 0,50

To exclude a set of stations, use -lx. This is a good option to use for excluding a small number of stations, instead of having to provide a long listing of stations to -l.

Filtering leadtimes

verif ECMWF.nc MEPS.nc -m obsfcst -o 12,18,36

This selects lead-times 12, 18 and 36 (in this case these two lead-times represent precipitation during the daytime only).

Filtering dates

verif ECMWF.nc MEPS.nc -m obsfcst -d 20160101:20161031

This selects forecast dates in October 2016. Lists of numbers can be created by separating numbers with commas and ranges of numbers using colons. The colons follow MATLAB syntax, such as <start>:<end> and <start>:<step>:<end> where 0:3:13 would yield 0,3,6,9,12. Commas and colons can be used together (i.e. 1,3:5,9 would yield 1,3,4,5,9).

Filtering time of day

Forecast systems can initialize the forecast multiple times a day. To subset based on initializtion hour, use -tod:

verif ECMWF.nc MEPS.nc -m obsfcst -tod 0

Filtering based on observed values

verif ECMWF.nc MEPS.nc -m obsfcst -obsrange 10,20

This selects cases where the observed values was between 10 and 20.