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Balanced Coupling of Vertical Motion and Diabatic Forcing in Variational Data Assimilation

This research focuses on enhancing variational data assimilation (VDAS) for precipitation analysis using advanced methods to couple vertical motion with moist diabatic balance. Collaborating with Meteorological Service Canada, this study extends Meso3D-Var to 4D-Var, integrating divergence and mass fields for a more effective analysis. Key features include the innovative use of adiabatic and diabatic balance, improving analysis increments at 500 hPa, and addressing issues like spin-up effects and precipitation assimilation. This work aims to enhance numerical weather prediction, especially in diabatic regions.

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Balanced Coupling of Vertical Motion and Diabatic Forcing in Variational Data Assimilation

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  1. Balanced Coupling Between Vertical Motion and Diabatic Forcing for Variational Data Assimilation Luc Fillion Collaborators: Monique Tanguay, Nils Ek, Christian Page, Simon Pellerin, Michel Desgagne Meteorological Service Canada Dorval, Québec, Canada

  2. Development of a Limited Area VDAS(Main Focus: Precipitation) Unified Global/LA Variational analysis code. Main features (at the present time: 1st Sept 2005): 1. Extension of Meso3D-Var to 4D-Var (june 2005). 2. Coupling of Divergence and Mass fields using Moist Diabatic Balance Operators directly in the Variational Analysis.

  3. 500 hPa wind analysis increments: FGAT Versus 4D-Var 1 UU-Obs at 500 hPa at 0h

  4. Meso 4DVar wind analysis increments at 500 hPa Time Assimilation window: 6h

  5. Adiabatic Balance (Mike Fisher’s approach at ECMWF) ------------------------

  6. Diabatic Balance (Kasahara & Krishnamurti’s dream!) ------------------------

  7. Diabatic Balance Included 24 August 2004; 12 UTC

  8. ~ 500 hPa Wind Increments

  9. Total w (μbs-1) at 500 hPa

  10. w mbs-1

  11. Kain-Fritsch Temperature Tendency 500hPa 850 hPa

  12. RHS Convective Forcing of w Equation Mesovar_L: 50 km; 58 Levels

  13. 500 hPa Wind Increments due to Convective Forcing

  14. 850 hPa Wind Increments due to Convective Forcing

  15. Summary: Benefits of the coupling 1. Better I.C. for NWP over diabatic regions. 2. Spin-up effects should be reduced 3. Can improve Precipitation Assimilation 4. Can potentially be extended down to Kilometric XD-Var Data Assimilation; i.e. See Christian Page ‘s talk at 12h45 !

  16. Regional model

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