University of WA Climate Impact Group 4/15/2016

• gas scenario, and another based on a warmer model run and a high scenario.2 Both will include the years 1980 through 2099. CIG researchers will develop estimated changes in exceedance probabilities for the city of Everett (e.g.: changes in the 2-, 10-, and 50-year events). Results will be summarized in terms of the change in both the magnitude (percent increase/decrease) and probability of heavy rain events (e.g.: how frequently will the 10-year event occur in the future?).The specific metrics analyzed will be determined in consultation with project sponsors. Changes will be evaluated for both short- (1 hour) and long-duration (48-72 hour) precipitation events. In addition, city planners will identify several locations for which CIG researchers will produce an hourly record of simulated precipitation for the full 215t century.These can be used as input to hydrologic models, or simply as a complement to the changes in exceedance probabilities described above. Each location must have daily observations of precipitation that are sufficient for bias-correction ("'30-year record is ideal)—researchers at CIG will help identify and evaluate available weather observations. For each site, an hourly time series of 21st century precipitation will be produced, obtained by bias-correcting simulated precipitation to match the observations. Finally, this scope includes staff time for additional analyses and products that are as yet defined, and will be specified over the course of the project based on the needs of City staff. Products 1. Projected change in the intensity, duration, and frequency of heavy rain events for the City of Everett. 2. Hourly time series of precipitation for historical and two future projections, developed for specific locations of interest (selected in consultation with city staff). 3. Additional data products, to be defined in collaboration with the City of Everett. 4. A short report describing the methodology and summarizing the results, including graphics and tabulated summaries. UW researchers will work with city staff to ensure that products can be used as input to planning and hydrologic modeling. Timeline Start date: 03/01/2016. Final products: 12/31/2016. 2 For more information on regional climate projections and greenhouse gas scenarios,see the CIG State of Knowledge report: http://cses.washington.edu/cigireports.shtml#sok Impacts from Climate Change On Stormwater in Everett KC—UW Agreement Page 7