This page contains a few rules on the UERRA parameters. A complete list of all the parameters and GRIB2 encoding is given here.

UERRA parameters rules

Units

Accumulations

Instantaneous fields

Parameters archived since previous post-processing

Fluxes

Missing values

Grid and resolution

Types of forecasts

GRIB2 encoding

ECMWF encoding/decoding Software

ECMWF makes available a GRIB decoding library (grib_api) for the benefit of the WMO community. grib_api can be freely downloaded from here and the documentation can be found here. The grib_api provides a simplified access to GRIB2 headers through a set of virtual keys documented here

Encoding

1) UERRA production status of processed data

Octet 36 of section 1 of a GRIB2 message contains the Production status of processed data. The WMO has added two values to table 1.3 Production status of data:

The value 9 should be used when testing and 8 for operational data.

2) Control and perturbed forecasts

Control and perturbed forecasts are identified in section 1 and 4. The following tables explains how to code them in GRIB2:

Section 1
Octets Example perturbedExample control
21typeOfProcessedData=4 =3 


Ensemble (section 4, template 4.61)
Octets Example perturbedExample control
35type of ensemble forecast= 255 (missing) = 255 (missing) 
36perturbation number= 7= 0
37number of forecasts in ensemble= 51= 51

3) Time component and reforecasts

 

real-timere-forecast
daily averagedaily average
accumulationsaccumulations
instantaneousinstantaneous
maximum over the last 6 hoursmaximum over the last 6 hours
minimum over the last 6 hoursminimum over the last 6 hours


4) Examples of GRIB2 files

 

 real-timere-forecast
Daily average  Control  PerturbedControl Perturbed
Accumulations  Control  PerturbedControl  Perturbed
Instantaneous  Control  PerturbedControl Perturbed
Maximum over the last 6 hours  Control  PerturbedControl Perturbed
Minimum over the last 6 hours  Control Perturbed