Improving the Effectiveness of U.S. Climate Modeling (2001) / Chapter Skim
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Responding to Climate Modeling Requirements
Responding to Climate Modeling Requirements
Pages 51-68
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From page 51... ...
new modes of organization and management. 5.1 COMPUTATIONAL RESOURCES REQUIRED Model Resolution A weather or climate model begins with fundamental equations governing the motions of the atmosphere, oceans, and sea ice, which are derived from physical laws, particularly the conservation of mass, momentum, and energy (e.g., Washington and Parkinson, 1986~.
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From page 52... ...
A sea ice model must be embedded in the ocean model in order to get the surface albedo of Earth correct and to ensure the correct salt balance of the ocean. Because the ocean heat capacity is large and changes slow, it generally takes about 10,000 model years to spin up a coupled climate model to equilibrium, although acceleration techniques are available to speed the process.
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From page 53... ...
Therefore 5~102~ floating point operations are needed to develop a model. We see that on the order of 10-100 Tflops of sustained computer speed is needed to develop climate models at the specified resolution in reasonable amounts of time (Table 5-1~.
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From page 54... ...
Model development and climate simulation require the greatest capability. Weather Prediction Ensembles of 10-day forecasts with an atmosphere-only model are required.
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From page 55... ...
Thus, global warming projections put similar demands on high-end computing as simulation, and we can similarly conclude that a 10-100-Tflops computer would satisfy the needs for global warming projections. Additional computational demands arise when downscaling global warming projections to specific regions.
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From page 56... ...
of the performance of current parallel climate models show that these machines do not compete effectively with Japanese VPPs in performance. Air-cooled Japanese vector machines are about 40 times faster (per processor)
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From page 57... ...
It is no coincidence that in countries other than the United States, the great majority of weather services and climate research institutions have purchased, or are about to purchase, Japanese parallel vector computers. We note finally that a previous NRC report (NRC, 1998a)
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From page 58... ...
5.4 FOSTERING COOPERATION WITH A COMMON MODELING INFRASTRUCTURE The Efficiency of Cooperation Small modelers in the United States have modern workstations available to them, sometimes with more than one processor. These workstations can be used for coarse-resolution ocean models run for tens of model years; high-resolution atmospheric models for a few days or weeks; development of radiation codes, boundary layer models in the atmosphere and ocean, and new numerical schemes; and the diagnosis and analyses of observed data and the output of large models.
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From page 59... ...
, but the full potential of interaction can be realized only if access to computers and the free availability of models and model output is assured on a mutually beneficial basis. Common Modeling Infrastructure The process of developing, evaluating, and exercising complex models and model components is resource intensive.
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From page 60... ...
A CMI does not imply a common model; it is simply the set of standards and protocols that ensures common features of different models and compatibility of files not only among different models but also with observational data. Once established the CMI group recommended the creation of core models devoted to a particular modeling focus (e.g., numerical weather prediction, seasonal-to-interannual prediction, decadal variability)
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From page 61... ...
Community Modeling Repository A comprehensive and well-supported community modeling resource will allow the full potential of established coding frameworks and data standards to be realized. The repository will house a full array of model components and physical parameterization codes, including full dynamical cores and integrated physics packages of one or more "standard" models (supported by large development and support efforts in the national program)
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From page 62... ...
The staff will actively solicit continuing expansions and updates of the repository, ensure compliance with standards, and support the use of repository resources throughout the community. Several other common needs can also be effectively met through a repository including statistical analysis, diagnostic and visualization tools, standard algorithms (such as model clocks and calendars)
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5.6 NEED FOR CLIMATE SERVICES AND MANAGEMENT ISSUES The current approach of expecting existing organizations within the USGCRP to deliver climate information products as an activity ancillary to their primary missions has not been successful (NRC, 1998a)
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The discussion then will delineate the properties of this Climate Service needed to deliver climate information products. Institutional and Incentive Issues The Climate Service must have a clearly defined mission, focused on the delivery of the product and the assurance of product quality.
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Business practices: 1. success of the Climate Service must be a critical metric for success of the hosting agencies; 2.
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From page 66... ...
, "A research program can maintain a permanent observing system only when the system is relatively cheap and does not inhibit other research objectives. When there is an operational need for a system, funding must not come from research sources, else the building of a permanent observing system could ~raduallv impoverish the research enterprise." Developing societally valuable research that leads to climate information products should lead to a clear transition path whereby the products find a home in the Climate Service.
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From page 67... ...
how a climate model is tested (against past and present climate, testing of parameterization schemes against special data sets, studying the way the model responds to data input if run as a weather model)
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From page 68... ...
A new way of focusing resources to meet the specific challenges posed by these various demands implies a less fragmented and therefore more centralized mode of addressing these problems. The nature of the institutional and management requirements were discussed in terms of a Climate Service, which here is the designation for the organizational entity that would create the climate information products and manage the climate modeling activities that would deliver these products.
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