by Bob Henson
Weather modelers on five continents have joined
forces to produce a treasure trove for researchers.
The THORPEX Interactive Grand Global Ensemble
(TIGGE) involves ten operational weather forecasting
centers around the globe (see map). Up to four
times a day, each TIGGE center provides a selection
of the numerical output from each member of its
short- and medium-range ensemble weather prediction
systems.
The result is an impressive “ensemble
of ensembles,” with as many as 259 separate
model runs from the ten centers. These are
made available to researchers 48 hours after
each forecast’s
initial time. The built-in delay can be bypassed
for major projects of special interest to
THORPEX, though it can still take up to 36
hours after model initialization for large volumes
of data to arrive. Once submitted, data requests
typically take a few hours to fulfill, allowing
time to process and transmit the data.
The
three TIGGE archive centers (red dots) receive
data from ten participating forecast agencies:
Australia’s Bureau of Meteorology (BOM),
China Meteorological Administration (CMA), Canadian
Meteorological Centre (CMC), Brazil’s Centro
de Previsão de Tempo e Estudos Climáticos
(CPTEC), European Centre for Medium-Range Weather
Forecasts (ECMWF), Japan Meteorological Agency
(JMA), Korea Meteorological Administration (KMA),
Météo France, US National Centers
for Environmental Prediction (NCEP), and UK Met
Office (UKMO). (Illustration courtesy Douglas Schuster,
NCAR.)
 TIGGE was
designed at a workshop hosted in 2005 by
the European Centre for Medium-Range Weather
Forecasts, with the ten centers officially joining
between late 2006 and early 2008. “We wanted
to establish closer cooperation between the
academic and operational worlds,” says ECMWF’s
Philippe Bougeault. The output is now available
from data archive centers at ECMWF, the China
Meteorological Agency, and NCAR (see “On
the Web”).
Each day some 240 gigabytes (billions
of bytes) of data flow from the operational
centers into the TIGGE system in a framework
organized by ECMWF’s Baudouin Raoult. The
archive now holds more than 100 terabytes
(trillions of bytes). The interface between the
centers and the TIGGE archive is based on the Internet
Data Distribution/Local Data Manager protocols
from UOP’s Unidata
program. This interface has been specially
configured for TIGGE by Unidata’s Steve Emmerson,
Steven Chiswell, and Tom Yoksas, based on
interoperable software provided to each data center.
To date, 70 users have downloaded more than a
terabyte of data from NCAR’s TIGGE Archive
Center, according to Douglas Schuster, who
manages NCAR’s TIGGE hub. The access rate
at NCAR should get a boost once a set of
upgrades goes online this summer, says Schuster.
He’s
been working
on the project with a number of other staff
in NCAR’s Computational and Information Systems
Laboratory, including David Brown, Luca Cinquini,
Richard Grubin, David Stepaniak, Hannah Wilcox,
and Nathan Wilhelmi.
By mid-2008, users of
the NCAR portal will be able to specify grid
resolution and spatial area across multiple
models. “Once
this becomes available, we expect our usage
to increase markedly,” says Schuster. Later
on, as part of TIGGE’s second phase (which
still awaits funding), a data-access mechanism
will allow users to download data directly
from each of the ten participating centers using
a common interface.
Young-Youn Park (Korea Meteorological
Agency) carried out some of the first analyses
of TIGGE’s
grand ensemble while visiting Roberto Buizza
at ECMWF. Park found that the tropics are
the main area where forecasts will benefit
from TIGGE. As summarized by ECMWF’s Bougeault, “Single-model
ensembles underestimate the spread of actual
conditions in the tropics. Multi-model ensembles
such as TIGGE do much better.”
Happily for
researchers, all of the TIGGE data are available
for research and education at no cost through
a simple electronic registration process, as David
Parsons notes. Now on leave from NCAR, Parsons
is working at the World Meteorological Organization
in Geneva and serving as chief of the World
Weather Research Program, which includes THORPEX
and this summer’s THORPEX Pacific
Asian Regional Campaign (T-PARC).
T-PARC, the first major field program to
draw on TIGGE, will include a vast net of
observations stretching across much of the
western Pacific and eastern Asia. The study
will examine the impact of typhoons that
originate in the northwest Pacific, the world’s
most prolific breeder of tropical cyclones. As
these storms curve north and east, they often influence
weather across the North Pacific, North America,
and beyond. Forecasters will call on TIGGE’s
compendium of model output to help guide data collection
during T-PARC.
The ultimate goal of TIGGE, says
Parsons, is to pave the way for even closer
linkages between national and international
forecasting centers, perhaps even including a full-scale prediction
effort that incorporates the work of each
center. Planners envision this Global Interactive
Forecast System (GIFS), as it’s been labeled,
as building on the first two phases of TIGGE,
with an end-to-end system possible as soon as the
mid-2010s.
David Parsons.
(Photo by Carlye Calvin.) A GIFS working group has described the
system’s
potential benefits in a draft plan led by
Zoltan Toth (NOAA). For instance, the system
might find a 10% chance that a major typhoon will
strike a densely populated Asian coastline eight
days out. By marshalling a wide range of observing
and modeling resources, the system would then zero
in on the threat, issuing special forecasts
with enhanced resolution. Even if the typhoon were
to eventually miss the coast, this coordinated
approach might be able to detect the change in
course and sound the “all clear” up
to 36 hours sooner than would otherwise be possible.
That, in turn, could save millions of people from
the expense and inconvenience of needless evacuation.
Achieving
this ideal will take time as well as dedication. “It
was not a trivial task to organize TIGGE,” says
Parsons. He notes that the forecasting centers
had to agree to share data, while research
and operational scientists had to agree on what
fields to provide and address various formatting
issues.
Overall, says Parsons, “TIGGE is
a success story for the World Weather Research
Program and THORPEX. We hope it will help improve
prediction, advance knowledge of the behavior of
the Earth system, provide users with advanced weather
products, and serve as a model for future cooperative
efforts on other predictive problems, such
as seasonal time scales.” ♦
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