Climate and Energy Action Plan (CEAP)

CLIMATE TRENDS & PRO JECTIONS | CITY OF ASHLAND, OREGON | FINAL REPORT | 21 Extreme Precipitation Extreme precipitation projections are examined using three standard metrics: 1) extreme precipitation frequency, as represented by the number of days with more than 20 mm of precipitation , 2) extreme precipitation am ount, as represented by the total amount of precipitation falling on days with precipitation above the 95th percentile, and 3) maximum length of consecutive dry days, or the longest dry spell . Extreme Precipitation Frequency Projections of extreme precipit ation frequency are presented as the change in the number of days with more than 2 0 mm of precipitation ( Figure 13). The range of future changes in the number of days with more than 20 mm o f precipitation in Ashland is -0.4 to +1.1 days for the 2050s and -0.5 to +2.2 days for the 2080s , using all models and both emissions scenarios (refer to Table 2). The multi -model mean projects that the number of extreme precipitation days will increase by 0.7 days by th e 2080s under the high emissions scenario compared to the historic baseline (1950 -2005). It is important to note that some models project decreases in extreme precipitation. Figure 13. Extreme (>20mm) precipitation days projections for Ashland as simulated by 18 downscaled global climate models for the historical period (1950 -2005) and future (2006 -2099) under a low (RCP4.5) and high (RCP8.5) greenhouse gas emissions scenario. Solid line and shading depicts the 18 -model mean and ran ge, respectively. The multi -model mean differences for the 2050s (2040 -2069 average) and 2080s (2070 -2099 average) compared to the historical baseline (1950 -2005) are displayed . Extreme Precipitation Amount Extreme precipitation is considered to have occ urred on days exceeding the 95th percentile of daily precipitation amounts. The total amount of precipitation during the year that falls during such days is projected to increase in Ashland by 1.3 inches for the multi -model average by the 2080s under the h igh emissions scenario compared to the historic baseline (1950 -2005) ( see Figure 14). However, some models project decreases in the total amount of precipitation falling on extreme precipitation days. The range across all models a nd both emissions scenarios of future changes in the amount of precipitation falling on extreme days is -0.5 to +2.1 inches for the 2050s and -0.2 to +3 .4 inches for the 2080s ( Table 2). Ashland >20mm Precipitation Da ys Pr ojectionsDays Histor ical Low (RCP4.5) High (RCP8.5) 2050s +0.2 da ys2050s +0.3 da ys 2080s +0.4 da ys2080s +0.7 da ys 02468101214 1950 1970 1990 2010 2030 2050 2070 2090