Forecast Sensitivity Tests with New Observations

1. Forecast Sensitivity Tests with New Observations Mario Majcen and Jan Paegle University of Utah Salt Lake City Utah

2. Outline • Background • Motivation • Goals • Tools • Results • Summary and conclusions • Questions

3. Background • Mesoscale convective system observed on January 17th 2003 January 17 at 17:45 UTC January 17 at 23:45 UTC January 18 at 05:45 UTC January 18 at 17:45 UTC

4. Motivation • Model forecasts intercomparison by Dr. Saulo (University of Buenos Aires) • Models: • Global and regional model at CPTEC/INPE (Brazil) • ETA model at CPTEC/INPE (Brazil) • ETA model at the University of Maryland (USA) • RAMS model at University of Sao Paolo (Brazil) • RAMS model at University of Buenos Aires (Argentina) • MM5 model at University of Chile (Chile) • MM5 model at CIMA (Argentina) • All models were initialized with the GDAS analysis at 00 UTC January 17.

5. Motivation • Mean forecasted precipitation accumulation:

6. Motivation • Dispersion between forecasts:

7. Motivation • Forecasted and observed wind profiles (at Mariscal Estigarribia):

8. Outline • Background • Motivation • Goals • Tools • Results • Summary and conclusions • Questions

9. Goals • Goals of this study: • Examine if a new approach with a global variable resolution Euler model could predict this event better • Examine forecast sensitivity to analysis • Examine forecast sensitivity to inclusion of special observations • Compare forecasts and analyses to the radiosonde observations taken at Resistencia, Santiago del Estero and Santa Cruz

10. Tools • Characteristics of models and analyses used in previous studies: • Most of the models used in previous studies have primitive equations dynamical core • All but one are limited area models (lateral boundary conditions may not represent well overturning divergent circulation associated with strong convection and precipitation, J. Paegle 1978,Wang et al 1999) • A global (CPTEC) model had coarse resolution • All models were initialized with the GDAS analysis

11. Tools • Characteristics of the model and analyses used in this study: • Euler equations dynamical core (retains rapidly propagating sound and gravity waves) • A global model (no lateral boundary conditions imposed) • Better resolution in the area of interest • Model was initialized with the GDAS analysis, the CPTEC analysis (with and without special observations)

12. Tools • Uniform resolution grid in Euler model:

13. Tools • Mathematical pole rotation and variable resolution in Euler model:

14. Tools • Increased resolution over the area of interest in Euler model:

15. Outline • Background • Motivation • Goals • Tools • Results • Summary and conclusions • Questions

16. Results 00 UTC 01/17 18 UTC 01/17. • Case description: GDAS analysis 500 mb wind and geopotential height

17. Results 00 UTC 01/17 18 UTC 01/17 • Case description: GDAS analysis 850 mb wind and temperature

18. Results 00 UTC 01/17 18 UTC 01/17 • Case description: 850 mb wind and mixing ratio

19. Results 00 UTC 01/17 18 UTC 01/17 • Case description: Convective Available Potential Energy (CAPE)

20. Results • Experiments performed in this study:

21. Results • Upper air observation sites:

22. Results • Experiment 1: 500mb height anomaly correlation coefficients: black: global, blue: 90S-20S, red: 20N-90N 20 N – 90 N global 90 S – 20 S

23. Results Experiment 1 Observed One-day precipitation accumulation valid at 00 UTC, January 18

24. Results Experiment 1 Observed • One-day precipitation accumulation valid at 00 UTC, January 19

25. Results • Noise/signal ratio of RMS difference between Experiment 1 and the GDAS analysis wind. 850 mb 500 mb

26. Results • Vertical profiles of wind at Santa Cruz 06 UTC January 18. Zonal wind (squares) and meridional wind (circles), solid lines denote observations. GDAS analysis Experiment 1 Obs. u Obs. u Obs. v Obs. v GDAS FCST

27. Results 500mb wind and geopotential height 850mb wind and temperature • Difference between Experiment 2 and Experiment 1 initialization at 00 UTC January 17.

28. Results Experiment 1 Experiment 2 • Comparison of Exp. 1 and Exp. 2 500mb height anomaly correlation coefficients: black- global, blue- 90S-20S, red- 20N-90N

29. Results Experiment 2 Observed • One-day precipitation accumulation valid at 00 UTC, January 18

30. Results Experiment 2 Observed • One-day precipitation accumulation valid at 00 UTC, January 19

31. Results Experiment 1 Experiment 2 • One-day precipitation accumulation valid at 00 UTC, January 18

32. Results Experiment 1 Experiment 2 • One-day precipitation accumulation valid at 00 UTC, January 19

33. Results • Noise/signal ratio of RMS difference between Experiment 2 and Experiment 1 wind at 500mb (circles) and 850 mb (squares). 850 mb 500 mb

34. Results 500mb wind and geopotential height 850mb wind and temperature • Difference between Experiment 2 and Experiment 3 initialization at 00 UTC January 17

35. Results Experiment 2 Experiment 3 • One-day precipitation accumulation valid at 00 UTC, January 18

36. Results Experiment 2 Experiment 3 • One-day precipitation accumulation valid at 00 UTC, January 19

37. Results • Noise/signal ratio of RMS difference between Experiment 2 and Experiment 3 wind at 500mb (circles) and 850 mb (squares). 850 mb 500 mb

38. Results • Vertical profile of temperature at Resistencia at 06 UTC January 17: observed (solid, circles), GDAS analysis (dashed, asterisk), CPTEC analysis (dashed, squares), CPTEC analysis with SALLJEX (dashed, circles).

39. Results • Vertical profile of dew point temperature at Resistencia at 06 UTC January 17: observed (solid, circles), GDAS analysis (dashed, asterisk), CPTEC analysis (dashed, squares), CPTEC analysis with SALLJEX (dashed, circles).

40. Results • Vertical profile of wind at Resistencia at 06 UTC January 17: observed (solid, circles), GDAS analysis (dashed, asterisk), CPTEC analysis (dashed, squares), CPTEC analysis with SALLJEX (dashed, circles).

41. Outline • Background • Motivation • Goals • Tools • Results • Summary and conclusions • Questions

42. Summary and conclusions • The model retains a good predictability in the first 48 hours (500mb height anomaly correlation coefficients greater than 0.8) • The 500mb height anomaly correlation coefficients are greater than 0.6 until about forecast hour 100. • Precipitation is not forecasted well. • Sensitivity to analysis is evident in precipitation prediction. • Sensitivity to additional observations is small. This could reflect limited impact of local observations, or the possibility that the observations were poorly assimilated. • Additional observations have a small impact on these analyses at this time. • None of the three studied analyses represent the atmosphere well at the three locations (Resistencia, Santiago del Estero, Santa Cruz) where special observations were taken during this event. • More research is needed regarding the inclusion of special observations into objective analyses to make certain that good observations are not discarded.

43. Future Work • Repeat the experiments using forthcoming GDAS analyses that are being performed at NCEP for the SALLJEX period. • Study other cases. • Check impact of model treatments of precipitation and turbulent diffusion. • Check impact of global-scale uncertainty.

44. Questions?