The mean and standard deviation from the full set of 51 forecast (i.e. the 50 perturbed forecasts plus the control forecast) are computed for temperature at pressure level 850 and 500hPa and geopotential on pressure level 1000 and 500hPa.

Horizontal resolution

- 0.25 x 0.25 degrees latitude-longitude grid, or multiples thereof (leg 1)

- 0.5 x 0.5 degrees latitude-longitude grid, or multiples thereof (leg 2)

- the Gaussian grid appropriate to the forecast model in use. The following Gaussian grid numbers are supported: 320, 200, 160, 128, 80, 48 and 32 (320 and 200 only for VarEPS leg 1 data).

- any sub-area

Verifying times

- T+3 to T+144 (inclusive) at 3 hour intervals and T+144 to T+360 at 6 hour intervals

Ensemble Mean and Ensemble Standard Deviation requirements

The following command language parameters are specific for the ensemble mean and ensemble standard deviation requirements. Other DIS parameters are listed under the general Monthly Forecast requirements above.

TYPE

ENSEMBLE MEAN

ENSEMBLE STANDARD DEVIATION

[EM]]

[ES]

DOMAIN

GLOBAL

[G]

NUMBER

OFF

LEVTYPE

PRESSURE LEVEL

[PL]

LEVELIST

1000/500

850/500

(PARAM=Z only)

(PARAM=T only)

GRID

*/*

AUTOMATIC [AUTO]

If the form a/b is used, a latitude-longitude grid is defined, where:

a= grid resolution (deg.) along a latitude line (i.e. East/West)

b= grid resolution (deg.) along a longitude line (i.e. North/South)

0.5/0.5 or multiples thereof;

If a single positive integer is coded, it is interpreted as Gaussian grid number for grids defined as GAUSSIAN=REDUCED or REGULAR. The following Gaussian grid numbers are supported: 200, 160, 128, 80, 48 and 32 (200 and 160 only for VarEPS leg 1 data);

AUTOMATIC - values for the parameter GRID will be defined automatically based on STREAM/DOMAIN as well as RESOL/ GAUSSIAN parameter values;

STEP

* (hours)

l gives forecast time step(s);

3/to/144/by/3 and 144/to/360/by/6

NB ALL, is not permitted.

PARAM

Field name abbreviation

NB ALL is not permitted.

Available parameters are listed in the Table 5.3.

GRIB section 1 definition for Ensemble Mean and Ensemble Standard Deviation products

By convention, ECMWF always uses octet 41 to define which set of local definitions follow. For these products local definition 30 (as described above) is used with the exception of octets 43 and 50:

Table 5.5 GRIB section 1 definition for Ensemble Mean and Ensemble Standard Deviation products

Octet

Ksec1

element

Contents

Type:

17 = Ensemble means

18 = Ensemble standard deviations

When element 39 = 17, this is an ensemble mean and

the number is set to 0.

When element 39 = 18, this is an ensemble standard

deviation and the number is set to 0.

The total number of forecasts in an ensemble; the

number includes the control forecast.

12-03-2010