CARPE DIEM

1. CARPE DIEM 5th meeting. Dublin, December 2003. Bernat Codina, Miquel Picanyol Dept. of Astronomy and Meteorology University of Barcelona

2. WP 3: Data assimilation • Contribution to WP3 (Data Assimilation): • Experiment comparison between the IAU and nudging methods. • Assess the impact on the precipitation field.

3. WP 3: Data assimilation • Description of the experiment: • Corrections on the T,u,v,q and ps variables are introduced via IAU and nudging methods. • Assimilation frequency: 6 and 3 hours. • 10 different cases.

4. WP 3: Data assimilation Methodology: “Perfect OBS” First guess + Observations First guess IAU/Nudging First guess Control

5. WP 3: Data assimilation Surface temperature

6. WP 3: Data assimilation U 850hPa

7. WP 3: Data assimilation Sfc – 500hPa RH

8. ME = 4.1 ME = 4.2 ME = 1.2 RMSE = 14.1 RMSE = 17.7 RMSE = 17.9 ME = -0.8 RMSE = 14.9 ME = -0.7 RMSE = 12.6 WP 3: Data assimilation Total precipitation

9. ME = 0.8 ME = 1.1 ME = -0.2 RMSE = 9.3 RMSE = 6.9 RMSE = 16.8 ME = -0.04 RMSE = 12.4 ME = 0.2 RMSE = 7.1 WP 3: Data assimilation Total precipitation

10. ME = 6.0 ME = 6.6 ME = -0.2 RMSE = 23.4 RMSE = 19.4 RMSE = 23.8 ME = 0.2 RMSE = 22.9 ME = 0.5 RMSE = 19.0 WP 3: Data assimilation Total precipitation

11. WP 3: Data assimilation Total precipitation mean error

12. WP 3: Data assimilation Total precipitation RMSE

13. WP 3: Data assimilation • Conclusions: • Best results in 3-hour frequency assimilation. • IAU tends to overestimate precipitation. • 3-hour nudging assimilation minimizes the total precipitation RMSE. • Verification of precipitation: • RMSE severely penalizes mislocation errors. • Other verification methods could be applied. [Ebert & McBride, 2000]