How important is spatial resolution: Case studies at 48, 12 and 4 km for the U.S., Latin America and Southern Asia
- ORNL
A critical role for regional climate models is downscaling coarse spatial resolution global model simulations of climate change to the much higher resolution required for assessment of regional changes and impacts. But what degree of downscaling is required? Fully coupled global climate models typically have resolutions of at best 100-200 km. The most recent set of IPCC reports suggest that the scale of regional/local impacts to climate change are on the order of 10 km. The scale mismatch is obvious, but less clear is what degree the climate simulations must be downscaled to meet the needs of impacts studies - other non-climate factors might also be crucial or even dominant. We have made a series of simulations with the WRF ARW for the U.S., large portions of Latin America, and South and Southeast Asia. Each set of runs includes a large outer domain at 48 km; an intermediate domain at 12 km (that is the primary basis for model results and interpretations); and one or more 'exploratory' inner domains at 4 km. The latter include regions with complex topography as well as both homogeneous and inhomogeneous land surface types. For each region a multi-year control forced by NCEP reanalyses has been made. Experiments for Asia are focusing on the effects of deforestation, while those for the U.S. and Latin America are focusing on IPCC climate change scenarios (A1FI for the U.S. and A2 for Latin America). Large-scale forcings for the latter two are provided by NCAR CCSM IPCC AR4 simulations. Preliminary results suggest that the higher resolutions have much more structure in standard climate quantities such as temperature or precipitation. Less obvious, however, is how realistic these structures are. In some cases, they clearly follow the better resolution of topography; in other instances the reason is less certain. Furthermore, observational datasets are frequently inadequate in assessing realism, especially for the non-U.S. domains. Finally, this work raises the issue of the trade-off between the length and the resolution of regional climate model simulations. Which is more important - long runs at medium resolution, or shorter runs at higher resolution?
- Research Organization:
- Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
- DOE Contract Number:
- DE-AC05-00OR22725
- OSTI ID:
- 982166
- Resource Relation:
- Conference: AGU Fall Meeting, San Francisco, CA, USA, 20091214, 20091214
- Country of Publication:
- United States
- Language:
- English
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