This page is intended to introduce the reader to the basic features of the unified costing formula of ECMWF Realtime Products. Please use it as a tutorial only.
In order to find out what resolutions are available for the individual product sets please consult the Catalogue of Realtime Data.

The unified costing formula for a single item is defined by

EPU per item = B * A * R * E * V * D * M,

where the definition of an item can be found in Tariffs. The base cost B and the valid factor V are currently fixed to 20 EPUs and 1, respectively. The MME factor M is set to 1 for ECMWF products. The ensemble factor E and the dataset factor D are fixed for each product set and specified below.

The resolution factor R is defined using the current high-resolution operational model and the chosen resolution Res_chosen (e.g. T159, N255 or 2.5 for spectral, gaussian or lat./long):

Res_chosen

spectral resolution

Gaussian grid

lat./long grid

Res_chosen

1279

Res_chosen

640

0.140625

Res_chosen

The area factor A is defined as the ratio between the area chosen and the area of the globe:

Area_chosen

Definition of A

	North:
West:		East:
	South:

(North - South) * (East - West)

360 * 180

predefined areas: Full Globe North Hemisphere South Hemisphere Europe

Please note: Values of the latitude in the southern hemisphere are negative, so are values of the longitudes west of the Greenwich meridian. For ocean wave fields, the area factor A takes into account the ratio land/sea over the provided area. However for reasons of simplicity we will ignore it here. For spectral resolutions the fields can be provided globally only.

The costing examples below assumes that one single item is delivered with each dissemination, i.e. one parameter, one forecast-step and one base-time is chosen. EPU's in the tables below are computed on an annual basis.

Forecasting System	delivery frequency	Number of deliveries per year (dpy)
Medium-range Forecasts	daily	365
Monthly Forecasts	weekly	52
Seasonal Forecasts	monthly	12

EPU per item per year = B * A * R * E * V * D * M * dpy

The values in EPUs below are now easily computed,

Costing for GRIB Fields

Note: Fill in above a resolution or grid first.

Medium-range Forecasts

Product Set Number, Name and highest available resolution			D	E	EPUs
I-i	Fields from the deterministic atmospheric model	T1279	1	1
II-i	Fields from the global ocean wave model	0.25°	1	1
II-ii	Fields from the European waters ocean wave model	0.125°	1	1
III-i	Fields from the atmospheric EPS	T639	1	1.4
III-ii	Clusters from the atmospheric EPS	1.5°	1	1
III-iii	Probabilities from the atmospheric EPS	N320	1	1
IV-i	Fields from the ocean wave EPS	0.5°	1	1.4

Seasonal Forecasts

Product Set Number, Name and highest available resolution			D	E	EPUs
V-i	Monthly means of ensemble means	T159	40	1
V-ii	Monthly mean anomalies of ensemble means	T159	80	1
V-iii	Monthly means of individual ensemble member forecasts	T159	40	1.4
V-iv	Monthly mean anomalies of individual ensemble member forecasts	T159	80	1.4
V-v	Individual forecast runs (daily real-time)	T159	2	1.4

Monthly Forecasts

Product Set Number, Name and highest available resolution			D	E	EPUs
VI-i	Weekly means of ensemble means	T319	15	1
VI-ii	Weekly mean anomalies of ensemble means	T319	30	1
VI-iii	Weekly means of individual ensemble member forecasts	T319	15	1.4
VI-iv	Weekly mean anomalies of individual ensemble member forecasts	T319	30	1.4
VI-v	Individual forecast runs (daily real-time and hindcast)	T639	1	1.4
VI-vi	Probabilities	N160	1	1

Costing for BUFR Fields: Time Series of Weather Parameters

The costing of Time Series is computed according to the description in Tariffs under Price of Time Series.
Please note: Area Factor and Resolution Factor are fixed according to the Tariffs.

Product Set Number and Name		D	E	A	R	EPUs
I-ii	Fields from the deterministic atmospheric model	1	1	0.000092592	1	221.70
III-iv	Fields from the atmospheric EPS (10 days)	1	1.4	0.000092592	0.5	155.19

The costing of the Time Series of Weather Parameters from Product Set III-i up to day 15 involves 2 different resolution factors. The resolution factor for the first 41 time steps (up to day 10) is R₁ and for the last 20 time steps (last 5 days) is R₂.

Product Set Number and Name		D	E	A	R₁	R₂	EPUs
III-iv	Fields from the atmospheric EPS (15 days)	1	1.4	0.000092592	0.5	0.25	193.04

18.01.2010