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Impact study with observations assimilated over North America and the North Pacific Ocean at MSC

Impact study with observations assimilated over North America and the North Pacific Ocean at MSC. St éphane Laroche and Réal Sarrazin Environment Canada. 4th Workshop on the impact of various observing systems on NWP Geneva, Switzerland, 19-21 May 2008. Main objectives.

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Impact study with observations assimilated over North America and the North Pacific Ocean at MSC

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  1. Impact study with observations assimilated over North America and the North Pacific Oceanat MSC Stéphane Laroche and Réal Sarrazin Environment Canada 4th Workshop on the impact of various observing systems on NWP Geneva, Switzerland, 19-21 May 2008

  2. Main objectives • Estimate the current value of radiosonde and aircraft data available over North America, as well as the impact of satellite data over the North Pacific Ocean • Examine the propagation of the impacts over the North American continent and the adjacent Atlantic Ocean • Assess the sensitivity of the results with respect to • the analysis scheme • the resolution of the forecast model • the weather regime

  3. Data assimilation and forecast systems - Analysis schemes: 4D-Var (6h window) and 3D-Var (FGAT) - Inner loop resolution: T108 (~180 km) - Outer loop resolutions: 100 km and 33 km Observations assimilated in the control experiments (Jan. and Feb. 2007) - Latest upgrade (2008) also includes AIRS, QuikSCAT and SSM/I data

  4. Observing System Experiments

  5. North America Z500 RMSE for the control experiments and latest upgrade of the MSC global analysis-forecast system

  6. Data denial and verification regions

  7. Aircraft reports assimilated during January and February 2007 and radiosonde stations (black dots)

  8. Impact of radiosondes over North America (4D-Var / 100 km) RMSE differences for Z500

  9. Impact of aircraft data over North America (4D-Var / 100 km) RMSE differences for Z500

  10. Impact of satellite data over the North Pacific Ocean (4D-Var / 100 km) RMSE differences for Z500

  11. Impact of satellite data over the North Pacific Ocean (4D-Var / 100 km) RMSE differences for U250

  12. FIs for Z500 over regions of North America and North Atlantic Satellite data denied over the North Pacific Ocean Radiosonde data denied over North America Aircraft reports denied over North America Ascent/Decent Aircraft reports denied over North America

  13. FIs for U250 over regions of North America and North Atlantic Satellite data denied over the North Pacific Ocean Radiosonde data denied over North America Aircraft reports denied over North America Ascent/Decent Aircraft reports denied over North America

  14. Comparison of FIs for Z500 from 4D-Var and 3D-Var Satellite data denied over the North Pacific Ocean Radiosonde data denied over North America Aircraft reports denied over North America 4D-Var 3D-Var

  15. Impact of satellite data over the North Pacific Ocean Z500 3D-Var 4D-Var 12h 48h

  16. Impact of satellite data over the North Pacific Ocean U250 3D-Var 4D-Var 12h 48h

  17. Impact of global and local (North America) data-denials Z500 RMSE differences for radiosonde data 4D-Var / 100 km Denial over North America Denial over the globe 24h 72h

  18. Impact of global and local (North America) data-denials Z500 RMSE differences for radiosonde data Radiosonde data denied over North America Radiosonde data denied over the globe 4D-Var 3D-Var

  19. Sensitivity to analysis scheme and model horizontal resolution 24h Z500RMSE differences for aircraft data denied over North America 3D-Var 4D-Var 100 km 33 km

  20. Sensitivity to analysis scheme and model horizontal resolution FIs for Z500 4D-Var / 100 km aircraft data denied over NA 3D-Var / 100 km aircraft data denied over NA 4D-Var / 33 km aircraft data denied over NA 3D-Var / 33 km aircraft data denied over NA 4D-Var 3D-Var

  21. Sensitivity to analysis scheme and model horizontal resolution FIs for U250 4D-Var / 100 km aircraft data denied over NA 3D-Var / 100 km aircraft data denied over NA 4D-Var / 33 km aircraft data denied over NA 3D-Var / 33 km aircraft data denied over NA 4D-Var 3D-Var

  22. Sensitivity to analysis scheme and model horizontal resolution RMSE for Z500 and U250 over the United States U250 Z500 100 km 33 km

  23. Sensitivity to analysis scheme and model horizontal resolution RMSE for Z500 and U250 over the United States U250 Z500 100 km 33 km

  24. Effect of the weather regime on the impacts January February Z500 Anomaly Z500 48h RMSE diff.

  25. Effect of the weather regime on the FIs Satellite data over the North Pacific Ocean Radiosonde data over North America Aircraft reports over North America January February

  26. Conclusions (1) • Summary of the impact results over North America for January and February 2007: • The quality of the forecast over the Canadian Arctic heavily relies on the radiosonde network, even though surface stations and MODIS winds are assimilated. • Over the eastern part of the North American continent, the radiosonde and aircraft data are still the main contributors to the forecast skill at short forecast ranges, but beyond 48h the impact of satellite data available over the North Pacific Ocean may be greater depending on the weather regime. • The primary source of forecast improvements over the western North America is provided by the satellite data over the North Pacific Ocean, even at short forecast ranges.

  27. Conclusions (2) • The impact of the radiosonde network over northern Canada is more important in the 3D-Var context. Moreover, this impact is further enhanced when radiosonde data are omitted over the globe. Therefore, 4D-Var seems superior to 3D-Var to exploit the fewer observations available over northern Canada and is less sensitive to the removal of data outside that region. • However, for the experiments in which the satellite data over the North Pacific Ocean, the impact with 3D-Var is not systematically larger than with 4D-Var: the short-range impact over the United States is more important in the 4D-Var context. • We also found that the short-range impact is smaller in 4D-Var than in 3D-Var for Z500, but it is the opposite for U250. Further work is needed to explain why the impact variations are not the same for these fields when comparing 4D-Var and 3D-Var results. • Overall, the impact results are less sensitive to the change of resolution of the forecast model than to the change of data assimilation scheme.

  28. Conclusions (3) • The weather regime that prevails during the period under investigation (i.e. January and February 2007) had a noticeable effect, especially on the propagation of the impact from the satellite data over the North Pacific Ocean at longer forecast ranges. • As indicated by the variability of the results from the various sensitivity tests, the forecast impact over a given region may change by 5 to 15% depending on the analysis scheme, the forecast resolution, or the weather regime that prevails during the period investigated.

  29. Thank you for your attention! 4th Workshop on the impact of various observing systems on NWP Geneva, Switzerland, 19-21 May 2008

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