The Potential Impact of High-End Capability Computing on Four Illustrative Fields of Science and Engineering (2008) / Chapter Skim
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3 The Potential Impact of HECC in the Atmospheric Sciences
3 The Potential Impact of HECC in the Atmospheric Sciences
Pages 37-62
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From page 37... ...
We expect that this improvement will be achieved as the numerical models that portray events in the atmosphere and ocean and on the land surface gain significantly in their resolution and sophistication. Detailed calculation of the feedbacks in the climate system, including the carbon cycle and other elemental cycles, are required for accurate climate prediction.
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From page 38... ...
This chapter identifies the major frontier challenges that the atmospheric sciences are attacking in order to realize that central task. In order to identify those challenges, the committee relied on several recent reports, including the following: • European Centre for Medium-Range Weather Forecasts, 2006, ECMWF Strategy 2006-2015.
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From page 39... ...
These aspects are described in more detail in the section on computational challenges in the atmospheric sciences. Major Challenge 1: Extend the Range, Accuracy, and Utility of Weather Prediction [1]
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From page 40... ...
Major Challenge 2: Improve Understanding and Timely Prediction of Severe Weather, Pollution, and Climate Events [1] The need for accurate weather forecasts becomes especially acute when natural hazards threaten.
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From page 41... ...
Major Challenge 3: Improve Understanding and Prediction of Seasonal-, Decadal-, and Century-Scale Climate Variation on Global, Regional, and Local Scales [1] While detailed weather forecasting cannot be extended beyond a month, climate may usefully be forecasted for several months, even into the next season.
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From page 42... ...
Major Challenge 5: Understand Atmospheric Forcing and Feedbacks Associated with Moisture and Chemical Exchange at Earth's Surface [1] While early theories and numerical models of Earth's atmosphere used a static representation for the lower boundary ("Earth's surface")
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From page 43... ...
Coupled models such as this are essential for understanding climate, and HECC resources are essential to enable the incorporation of enough geochemical and atmospheric chemistry detail. in the sense that changes and trends in the biogeochemistry influence the physical climate at each time step and vice versa.
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From page 44... ...
Thus the reliable prediction of bifurcation requires complex, multicomponent models. Major Challenge 7: Create the Ability to Accurately Predict Global Climate and Carbon-Cycle Response to Forcing Scenarios over the Next 100 Years [1]
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From page 45... ...
Major Challenge 8: Model and Understand the Physics of the Ice Ages, Including Embedded Abrupt Climate Change Events Such as the Younger Dryas, Heinrich, and Dansgaard-Oeschger Events [2] During the last 2 million years (the Pleistocene epoch)
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From page 46... ...
Together, the climatic history of early Venus, Earth, and Mars provides a useful test of our knowledge of climate change. COMPUTATIONAL CHALLENGES IN THE ATMOSPHERIC SCIENCES As noted in the committee's ratings for each of the major challenges, Major Challenges 1-3, 5, and 7 are critically dependent on advances in HECC capabilities, while HECC plays an important though probably not rate-limiting role for Major Challenges 4, 6, and 8.
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From page 47... ...
Such a standard creates substantial demand for supercomputer power, a demand that compounds the needs arising from high spatial resolution and the addition of physical processes. The IPCC climate runs carried out by many research and operational centers used a substantial fraction of the available computer power in the atmospheric community from 2004 through 2006 to satisfy this requirement.
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From page 48... ...
For all timescales, the probabilistic forecasts are useful to decision makers in a wide variety of weather- and climate-dependent enterprises who use quantitative methods to distinguish opportunity and risk and to select specific courses of action. Numerical Weather Prediction The strategy for preparing weather forecasts to assist the public and private sectors with the management of weather risk has evolved dramatically during the era of numerical prediction models.
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From page 49... ...
, advances in numerical representation of small-scale atmospheric processes, including precipitation mechanisms, and greater spatial resolution of the prediction models themselves. In each of these, the dramatic increase in computer power over the past few decades played an essential role.
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From page 50... ...
Thus one of the main roles of Earth-sensing satellites in polar and geosynchronous orbits is to obtain global observations of the atmosphere, ocean, and land that will define atmospheric conditions for the initialization of numerical forecasts. The assimilation of satellite data has increased dramatically over the past decade, not only in quantity but also in the range of characteristics measured, with data from satellites now exceeding data from conventional observations by factors of 10 or more.
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From page 51... ...
Groundwork on the science of those relationships and quantification of uncertainties through coupled biogeochemical, physical, and economic systems are necessary to support the complex decisions that will be made over the coming decades. Threat-Focused Operational Forecasting Contemporary numerical weather forecasts in both deterministic and ensemble form usually s ucceed in anticipating threatening weather conditions, but they do not have adequate internal resolution or resolution of Earth's surface to provide sufficient information on the track and intensity of threatening storms or of local effects.
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From page 52... ...
The upper panel shows the surface isobars at landfall and the simulated track of the hurricane as blue arrows compared with the observed track in black. The lower panel shows a simulated radar image of the rainfall in the hurricane at landfall computed from the distributions of water and ice in the simulated storm.
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From page 53... ...
With observational and forecast systems providing increased rates of information flow in the years ahead, we can anticipate that threat-focused forecasting will become more valuable and will add to the demand for computer capability in numerical weather prediction. Spatial Resolution, Adaptive Grids, and Subgrid Processes The physical processes that determine the dynamics of Earth's atmosphere occur over an enormous range of scales: spatial scales from microns (for water vapor and ice)
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From page 54... ...
In recent years, satellite data have been playing an increasingly important role in weather forecasting as the primary forecast centers process data flows that go well beyond 1 billion observations per day. Satellite observations of winds, temperatures, and humidity over the world oceans, previously a region devoid of data, are contributing greatly to this flow.
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From page 55... ...
In many problems of atmospheric science, the greatest computational challenges (and number of operations) are for data assimilation, not modeling.
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From page 56... ...
Transitioning to New HECC Resources The atmospheric sciences are ready to exploit additional HECC resources right now. Some coupled climate simulations have been performed utilizing up to 7,700 processors.
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From page 57... ...
Already, model development calls for equal investments in software engineering and science. While, as noted above, some additional HECC capacity could be readily absorbed by the atmospheric sciences, the longer-term science goals -- creating the capability for regional climate forecasts and for localized weather forecasts that explicitly model convective processes in enough detail to predict severe weather -- will require significant attention to the overall system.
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From page 58... ...
a new generation of local refinement methods and codes for atmospheric, oceanic, and land modeling. Both efforts should be undertaken with the specific goal of improved models of the global and regional hydrologic cycle, including validation against detailed observational data.
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From page 59... ...
As noted in the section "Computational Challenges in the Atmospheric Sciences," valuable scientific and operational advances would be within reach of the community if additional HECC resources, with computing power up to 10 times greater than that in use, were made available. These advances, which would bring more valuable operational forecasts and better understanding of feedbacks and coupling in Earth's climate, are achievable with the community's current structures.
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From page 60... ...
From weather events in the next hour to climate variations in the next century, these computer predictions and simulations are vital to a wide range of public and private activities involving issues of economics, policy, and sustainability. A number of trends are rapidly increasing the demand for computational capability in the atmospheric sciences.
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From page 61... ...
1979. The ENIAC computations of 1950 -- Gateway to numerical weather prediction.
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