However, despite the proliferation
of such models, the idea of a completely integrated approach, says Koch,
is something that NOAA is still working out. “We don’t have one gigantic
model that solves all the problems,” he
says. Even so, one result of this intensive focus on modeling is that NOAA
has made measurable progress at improving the ability to predict extreme
weather more accurately. However, at
NSSL, the focus of which is tornadoes,
hail, and high winds, the difficulty of
such predictions is acute.
Until recently, weather prediction
has mostly relied on a few central
prediction models, but that strategy
has given way to running an ensemble of models, sometimes upward of
40 models, each with slightly different physics or other configurations.
The idea is to create models that can
capture the wide variability in the atmosphere and then combine them so
there is sufficient spread in the characteristics of a complete ensemble.
The ultimate goal of ensemble modeling, then, is to develop a broader
representation of plausible outcomes
while also producing useful estimates
for forecasting.
One problem, however, is that
even with an ensemble of models, the
prediction results are limited by the
quantity and quality of input data.
In the U.S., for example, 142 weather
radars cover the lower 48 states, with
an average spacing of approximately
260 kilometers between them. Because of the Earth’s curvature, more
until recently,
weather prediction
has largely relied
on a few central
prediction models,
but that strategy has
changed to running
an ensemble of
models, each with
slightly different
physics or other
configurations.
than 70% of the U.S. is not covered
by radar in the lowest 1 kilometer of
the atmosphere, which is, of course,
where humans live. It is also where
severe thunderstorms develop. “To
overcome the Earth’s curvature prob-
lem,” says Koch, “you would need to
develop a cost-effective, much-denser
coverage system.”
Another challenge is the weather
processes. What creates severe tur-
bulence, for example, is far from be-
ing completely understood. “There
are gaps in our understanding of pro-
cesses within thunderstorms, and one
of the biggest gaps is the physics of
the precipitation process itself,” says
Koch. “We have an unsatisfactory un-
derstanding of what generates orga-
nized thunderstorms.”
a matter of Volume
Beyond these issues, which have drawn
much attention by researchers in recent years, the sheer volume of data
produced by an ensemble model configuration, which scientists now believe is the most effective way to predict extreme weather, is much more
than the bandwidth of the most advanced networks can handle. In addition, while an ensemble of models can
be tuned to the particular aspect of the
weather it is designed to simulate, rendering the ensemble quickly enough
to be useful for real-time forecasting
remains a challenge, even with today’s
fastest supercomputers.
The power and cooling requirements are formidable for supercomputer-class systems, and the maintenance costs can be exorbitant. So Koch
and other NOAA scientists are looking
beyond traditional supercomputer
systems and are exploring systems
based on graphical processing units
(GPUs). While GPUs are not general
purpose, they do offer performance
advantages over general-purpose CPUs
for certain applications. NOAA has not
made a decision yet about implementing GPU systems, but trials are in an
advanced exploratory phase run at
NOAA’s ESRL.
Mark Govett, chief of the advanced
computing lab at ESRL, has been di-
Technology
PC and Tablet Sales Forecast
industry analysts are less optimistic now than earlier this year
about PC sales for 2011. But the
personal computer’s woes have
little to do with the public’s
enthusiasm for tablets as some
believe, says Stephen Baker, vice
president of industry analysis for
the nPD Group.
research company Gartner
has trimmed its forecast for 2011
PC sales from 9.8% growth just
three months ago to 3.8%, while
rival research firm iDC lowered
its forecast from 7.1% to 4.2%.
the nPD Group would not
release specific numbers, but
Baker characterizes U.S. PC
sales as having been mostly flat
to slightly down, mainly due to
the weak economy. “And also
because people bought record
numbers of computers these last
two years ever since the launch
of Windows 7,” Baker says.
“those new computers won’t
need to be replaced or upgraded
for a while.”
dominated by Apple’s iPads—
have grown dramatically from a
first-year small base, Baker says.
there was no tablet market
until the iPad was released in
April 2010.