1. 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

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

3. Models, observations, & methods
14 climate models from Coupled Model Intercomparison Project, Phase 3 (CMIP3)
Model resolution ~ º
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

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

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

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

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

8. Overall model evaluation based on six metrics
Model average
BETTER
WORSE

9. 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

10. 21st Century Climate Projections
Changes with respect to for three future time periods: (early century), (mid century), and (late century).
B1 (lower emissions) and A2 (higher emissions) scenarios are shown.

11. Temperature change Warmer Seasonal differences Model spread
Scenario impact

12. Precipitation change
Wetter
Seasonal differences
Model spread

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

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

15. 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

16. Thank you