A National Strategy for Advancing Climate Modeling (2012) / Chapter Skim
Currently Skimming:
11 Synergies Between Weather and Climate Modeling
11 Synergies Between Weather and Climate Modeling
Pages 197-208
The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.
From page 197... ...
The ultimate realization of seamless prediction is a single "unified" modeling system designed to work across a broad range of time scales and spatial resolutions, from initialized weather predictions to long-term projections. There are several requirements for a unified weather and climate prediction system: • data assimilation capability, i.e., to make best use of available observations to generate initial conditions, to facilitate analysis of model parameter sensitivity and uncertainty quantification, and to assess the incremental benefit of new observations; • unified physical parameterizations and numerical algorithms that can be ap plied across all scales at which they are needed; 197
|
From page 198... ...
Similarly, climate models used for projections on decadal to centennial time scales have relatively coarse spatial resolutions for reasons of computational efficiency and thus do not accurately simulate phenomena that may be important on small space and time scales, such as mesoscale convective complexes or tropical cyclones. These choices reflect both limitations on resources, such as computer power, and an attempt to simplify and streamline the problem under consideration.
|
From page 199... ...
In this report, this testing is referred to as "seamless prediction" but not "unified modeling," because it does not necessarily require a data assimilation capability that a unified weather-climate forecast model should have to make real-time forecasts. Over the past decade, this approach has started to gain popularity following the development of software infrastructure such as the Climate Change Science Program-Atmospheric Radiation Measurement Parameterization Testbed (Phillips et al., 2004)
|
From page 200... ...
Finding 11.1: One useful form of seamless prediction is the testing of climate models in a weather forecast mode. Unified weather-climate modeling has further potential benefits, including improved weather forecasts, data assimilation, and reanalysis, and more efficient use of resources.
|
From page 201... ...
Thus, one challenge is to optimize the information gained by using a new model to make short-term predictions, while not being overwhelmed with the necessary infrastructure development associated with data assimilation and model initialization. For weather prediction, detailed analyses of the observed state of the atmosphere are required, but uncertainties in this initial state grow rapidly over several days.
|
From page 202... ...
Finding 11.3: An important challenge for unified modeling (and climate modeling as a whole) is developing improved parameterizations that can work across a range of scales spanning weather and climate applications.
|
From page 203... ...
UKMO/Hadley Centre The most mature unified modeling system is run by UKMO and its climate modeling branch, the Hadley Centre. The Met Office Unified Model, MetUM, was first documented by Cullen (1993)
|
From page 204... ...
. Both centers have invested heavily in the climate-model strategy of reduction of systematic biases in their forecasts; this aspect of unified model development has clearly been beneficial to their weather forecasts.
|
From page 205... ...
The resulting tuned model slightly improves on the weather forecast skill of the original ECMWF model version and substantially reduces climate biases to a level well below the mean over all CMIP3 coupled models (Hazeleger et al., 2010) , showing the value of a seamless approach.
|
From page 206... ...
unified weather-climate prediction system capable of state-of-the-art forecasts from days to decades, climate-quality data assimilation, and reanalysis. This prediction system would be a collaboration among operational weather forecast centers, data assimilation centers, climate modeling centers, and the external research community.
|
From page 207... ...
A further management challenge is harmonizing model development for weather versus climate applications. For weather applications, it is advantageous to update the modeling system whenever a proposed change has been demonstrated to improve the forecast skill, because the main application is weather forecasts with a shelf life of a few days.
|
From page 208... ...
The main goals would be to evaluate and improve model representations of "fast" physical processes that vary strongly on these time scales and to optimize uncertain parameters within these representations. Recommendation 11.1: To fully exploit a multiscale approach to model advancement, the United States should nurture a unified weather-climate prediction system capable of state-of-the-art forecasts from days to decades, climate-quality data assimilation, and Earth-system reanalysis.
|
Key Terms
This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More
information on Chapter Skim is available.