The standard procedures for verification of surface variables are defined in the Manual on the Global Data-processing and Forecasting System: Annex IV to the WMO Technical Regulations (available from WMO library at https://library.wmo.int/index.php?lvl=notice_display&id=12793), appendix 2.2.34.
ECMWF in the capacity of LC DNV collects and archive the scores. Data are
At the WMO Commission for Basic Systems (CBS) ET-OWFPS Meeting on 22-24 October 2014 in Geneva, a draft document on standardized surface verification of deterministic NWP products was agreed. The document specifies the content of the future exchange of surface scores between global centres and is available here: Standardized Surface Verification for Deterministic NWP
ECMWF will be collecting and archiving the scores. Data will be exchanged in an ASCII-based format which is simple but flexible and is similar to the format used WMO exchange of domain-averaged upper-air scores.
Data format
Data file consists of score values and corresponding metadata in an ASCII format.
Every score value is described by the full set of key attributes, like its parameter, station id, month, step etc. Parameters describing one score value at one station are organised into a record. Each record corresponds to one score value. A record is a collection of pairs key=value separated by commas. A record spans one line. Value of the key which is not given in the current record is inherited from the previous record, except for the value parameter v which has to be present in each record.
Each record has the following format:
centre=centre, model=model_id, d=yyyymm, t=time, s=forecast_step, st=station_id, lat=latitude, lon=longitude, lam= model_grid_latitude , lom= model_grid_longitude , se=station_elevation, me=model_orography_elevation, par=parameter, sc=score, th=event_thresholds, n=sample_size, v=mean_value |
If the value is not available the record either should not be given at all or the value should be set to NIL (v=nil); every record must contain the key v (value of key v is not inheritable from previous record).
Example
Code Block |
---|
centre=ecmf,model=0001_fc,d=201410,t=0,s=24,st=11520,lat=50.02,lon=14.38,se=302,me=248,par=tp24,sc=me,ev=na,n=31,v=0.95
s=48,v=1.15
s=24,sc=ct,th=5,v=1,16,12,2
s=48,v=3/13/11/4 |
Values of keys
- centre (4-characters string) is the WMO identifier of the originating centre (ammc, cwao, ecmf, edzw, egrr, kwbc, lfpw, rjtd, rksl, rums etc);
model_id (a string, not containing a comma or vertical bar) is free model identifier assigned by the originating centre (to distinguish between potentially different models provided by the centre);
- yyyymm is the month of the mean, where yyyy is the year and mm is the month (01-12);
- time is the validity time (in hours UTC) of the forecasts verified;
- forecast_step is the length of the forecast (in hours);
- station_id (a number) is the WMO ID of the observation station verifying the forecasts;
- latitude is the latitude of the observation station verifying the forecasts;
- longitude is the longitude of the observation station verifying the forecasts;
- model_grid_latitude (non-mandatory) is the latitude of the model grid point used to extract the forecast at the observation location;
- model_grid_longitude (non-mandatory) is the longitude of the model grid point used to extract the forecast at the observation location;
- station_elevation is the elevation of the observation station above the mean sea level in meters;
- model_orography_elevation is the elevation of the model orography at the observation location;
- parameter is the verified model output parameter:
parameter | description | unit |
---|---|---|
t2m | air temperature at 2 meters above the model orography, corrected to the actual station elevation using the constant lapse rate 6.5K/1000m | K |
td2m | dewpoint at 2 meters above the model orography | K |
rh2m | relative humidity at 2 meters above the model orography | % |
tp06 | total precipitation accumulated over previous 6 hours | mm |
tp24 | total precipitation accumulated over previous 24 hours | mm |
ff10m | wind speed at 10 meters above the model orography | m/s |
dd10m | wind direction at 10 meters above the model orography | deg |
tcc | total cloud cover | 0-1 (convert to okta for contingency table) |
- score is the name of the verification score or statistic:
score | description | ||||||||||||||||||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
me | mean error (bias) | ||||||||||||||||||||||||||||
mae | mean absolute error | ||||||||||||||||||||||||||||
rmse | root mean square error | ||||||||||||||||||||||||||||
ct | contingency table values, The rank of a contingency table is defined by number of values in the key event_thresholds
NB. Please note how those contingency tables are constructed.
but following the definition of 2x2 contingency table on the left the table should be
|
v=C/A/D/B | |||||||||||||||||||||||||||
v=G/D/A/H/E/B/I/F/C | |||||||||||||||||||||||||||||
v=M/I/E/A/N/J/F/B/O/K/G/C/P/L/H/D |
- event_thresholds is a value or values of threshold(s) defining events for contingency tables; number of values in event_thresholds defines the rank of the contingency table; multiple values are separated by a forward slash /
event_threshold | description |
---|---|
15 | threshold for a 2x2 contingency table, e.g. if par=ff10m this is an event of 10m wind speed |
5/10/15 | thresholds for a 4x4 contingency table for 10m wind speed |
- sample_size is number of observations used to compute the monthly mean at the given station;
- mean_value is the value or values of the score mean computed based on the forecast initiating at time time UTC, verifying in the month yyyymm, for the forecast length forecast_step hours; in case of nxn contingency table these are the n2 values delimited by forward slashes (see the score table above)
Procedures for exchange of data
Resources
- The format of the reports of the station-based verification scores.
- The procedures for the exchange of (surface) verification reports.
- The remarks on the implementation of the surface verification reports at ECMWF.
- Answered Questions on the surface verification exchange
...