Climate projections for the watershed of the Delaware Estuary Raymond Najjar Department of Meteorology The Pennsylvania State University 2011 Delaware Estuary Science Conference Thanks to Matt Rydzik and Andrew Ross Support: Partnership for the Delware Estuary and EPA Climate Ready Estuaries Program

Goals Assess climate model performance over Delaware Estuary watershed Provide climate projections under two greenhouse gas emissions scenarios

Models, observations, & methods 14 climate models from Coupled Model Intercomparison Project, Phase 3 (CMIP3) Model resolution ~1.5-4.5º Observed radiative forcing for 20th century, and B1 and A2 emissions scenarios for 21st century Daily output for temperature and precipitation Observations from U. Delaware (monthly, from 1901) and North American Regional Reanalysis (daily, from 1979) Model output and observations gridded to 1º resolution

Analysis domain Results presented will be averaged over this 1º × 3º domain

Model evaluation: monthly means Slightly too cool and wet Large precipitation spread

Model evaluation: interannual variability Slightly too variable in temperature Annual cycle in temperature variability good Annual cycle in precipitation variability missed

Model evaluation: intramonthly variability Good, with slight underestimate of precipitation variability

Overall model evaluation based on six metrics Model average BETTER WORSE

Model evaluation for climatic extremes Metric NARR Model average ± 1 s Maximum consecutive dry days in a year 17 14 ± 3 Maximum 5-day precipitation total in a year (mm) 69 63 ± 6 Days per year with precipitation > 10 mm 31 27 ± 4 Percent of annual precipitation due to daily events above the 95th percentile 37 33 ± 5 Number of frost days per year 114 123 ± 28 Growing season length (days) 198 197 ± 25

21st Century Climate Projections Changes with respect to 1980-1999 for three future time periods: 2011-2030 (early century), 2046-2065 (mid century), and 2080-2099 (late century). B1 (lower emissions) and A2 (higher emissions) scenarios are shown.

Temperature change Warmer Seasonal differences Model spread Scenario impact

Precipitation change Wetter Seasonal differences Model spread

Annual frost days and growing season length changes Based on temperature thresholds Fewer frost days, longer growing seasons

Changes in precipitation extremes Increases in heavy precipitation Large spread among models

Summary Model-mean plausible for present climate Early-century results independent of emissions scenario Late century results sensitive to emissions All models warm; factor of two range due to model choice Precipitation projected to increase, particularly in winter and spring Extreme precipitation projected to increase Longer growing season, fewer frost days

Thank you