The Full Picture

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The Thorpex Interactive Grand Global

Ensemble (TIGGE) concept and current status

Philippe Bougeault, European Centre for Medium-Range Weather Forecasts, UK; Co-Chair, GIFS-TIGGE WG

and Zoltan Toth, National Centers for Environmental Prediction, USA; Co-Chair, GIFS-TIGGE WG

en operational weather forecasting centres producing daily

global ensemble forecasts for one-to-two weeks ahead have

agreed to deliver in near-real time a selection of forecast data

to the Thorpex Interactive Grand Global Ensemble (TIGGE) data

archives at the ChinaMeteorological Agency (CMA), European Centre

for Medium-RangeWeather Forecasts (ECMWF) and the US National

Center for Atmospheric Research (NCAR). This is offered to the scien-

tific community as a new resource for research and education. The

objective of TIGGE (GEO taskWE-06-03) is to establish closer coop-

eration between the academic and operational worlds by encouraging

greater use of operational products for research, and to explore

actively the concept and benefits of multi-model probabilistic weather

forecasts, with a particular focus on severe weather prediction.

TIGGE is a key component of Thorpex, which is in turn a major compo-

nent of the World Weather Research Programme (WWRP) of the World

Meteorological Organization (WMO). A key goal of WWRP-Thorpex is

to accelerate improvements in the accuracy of one-day to two-week high-

impact weather forecasts for the benefit of humanity. TIGGEwas initiated

in 2005 at a workshop hosted by the ECMWF. The workshop report has

been published in the WMO series.

The objectives of TIGGE are:

• To enhance collaboration on ensemble prediction, internationally and

between operational centres and universities

• To develop newmethods to combine ensembles fromdifferent sources

and to correct for systematic errors (biases, spread over-/under-estima-

tion)

• To achieve a deeper understanding of the contribution of observation,

initial and model uncertainties to forecast error

• To explore the feasibility and the benefit of interactive ensemble systems

responding dynamically to changing uncertainty

• To enable evolution towards an operational system, the Global

Interactive Forecast System (GIFS).

The highest priority data accumulated in the TIGGE archive are the

ensemble forecasts generated routinely (operationally) at major forecast

centres around the world. This core data stored in the TIGGE archive is

accumulating at a daily rate of approximately 300GB. Additional special

datasets will be added in the future for specific research and applications.

The plan is to implement TIGGE in two steps. In the current phase

(Phase-1), data are collected in near-real time at a small number of central

data archives using existing network and storage capabilities. In Phase-2,

envisaged as soon as possible, data archives will be distributed over a larger

number of centres, instead of all being held centrally, while maintaining

efficient and transparent access to users. This more flexible solution has

the potential to eliminate routine transfers of large data

volumes, but will require substantial software development,

specific funding and coordination with the evolving WMO

information system

Partners and linkages

The TIGGE project is developed under the leadership of the

GIFS-TIGGEWorkingGroup, under Thorpex. Phase-1 data-

bases are developed by three archive and distribution centres:

ECMWF, NCAR and CMA. The operational forecasting

centres supplying daily forecasts are the Bureau of

Meteorology Research Centre (BMRC, Australia); CMA;

Centro de Previsão de Tempo e Estudos Climáticos (CPTEC,

Brazil); ECMWF; Japan Meteorological Agency (JMA);

KoreaMeteorological Administration (KMA); Météo-France;

Meteorological Service of Canada; National Centers for

Environmental Prediction (NCEP, USA), and the UK Met

Office. In addition, the TIGGE website is maintained by

ECMWF; the metadata centre is maintained by NCAR, and

the verification web by JMA. The WGNE/WWRP joint

working group on verification advises the project on verifi-

cation methodology, and the WMO Expert Team on

Ensemble Prediction Systems advises the project on a

number of issues, such as metadata formulation.

TIGGE has strong links with the North American

Ensemble Forecasting System (NAEFS). Although NAEFS

is initially an operational project, TIGGE and NAEFS share

many technical aspects, and NAEFS plans to implement

results from TIGGE. It is believed that TIGGE and NAEFS

will ultimately evolve into a single operational system.

TIGGE is registered as Group on Earth Observations

(GEO) Task WE-06-03. It has general relevance to GEO

societal benefit areas that will benefit from access to

advanced multi-model global weather forecasts and the

derived products, especially in areas related to risk

management, disaster mitigation, energy and health.

TIGGE users

TIGGEwill initially accelerate research at large, and in partic-

ular the scientific programmes of WWRP-Thorpex. For

instance, the forecast demonstration projects (FDP) of

WWRP-Thorpex (e.g. the Beijing 2008 FDP/research

demonstration project), the future field campaigns on adap-

tive observations and the International Polar Year (IPY)

projects will be active users of TIGGE. This research will, in

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EATHER