Assessing potential future changes in atmospheric rivers over the western coast of the U.S.
Do dynamically downscaled, higher-resolution regional climate model simulations from the North American Coordinated Regional Climate Downscaling Experiment (NA-CORDEX) offer clear, stakeholder-relevant benefit to the understanding of current causes and future projections of precipitation amount, type, and distribution for the Western United States?
Need and Benefit
The proposed research explicitly responds to a wide variety of real-world needs, addressing many Priority Areas identified by water resource managers, including Reclamation staff, in Brekke et al. (2011). The CORDEX project maintains peer-reviewed region-specific literature summaries (1.02). The proposed research builds on demonstrated success in improving accuracy of global and regional climate simulations (2.01) and directly responds to the need for downscaled data (2.02). Evaluations of downscaling methodologies for effectiveness (2.03, 2.04) will be outputted by the proposed research. Improved understanding of orographic and other fine-scale drivers of extreme precipitation in the atmosphere addresses 3.06 and offers better input data for the surface hydrology aspect of this problem in 4.03. The proposed research would reduce uncertainty in regional climate projections, particularly with regard to downscaling (7.02). In short, the proposed research offers insight into issue after issue which has been identified as a "gap" impeding effective utilization of temperature and precipitation projections by water resource managers.
This proposal provides the opportunity for Reclamation to interrogate the GCM-RCM data sets and identify how well meteorological phenomena that impact our water supplies are represented in the models over the historical record using a dynamically consistent approach (as opposed to statistical downscaling). This provides some baseline measure for assessing the models' ability to represent the phenomena in future scenarios. These results could then potentially be used to inform hydrologic uncertainty in a variety of potential future scenarios. Reclamation planning studies routinely incorporate projections of temperature and precipitation into future hydrology datasets; improvement in the relevance of these datasets would have direct short- and long-term benefit to Reclamation.
If the research is not funded Reclamation will continue using current data sources and methods, with all of the gaps identified above, for the foreseeable future. If similar research does occur without Reclamation funding, which is not a given and could take any number of years, it would likely not be directed at the needs of Western water managers.
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