1 / 24

Structure and Evolution of Microphysics Fields in African Squall Line

This study investigates the mesoscale structure and evolution of microphysics fields in an African squall line using numerical simulations. The results show the statistical characteristics of the mesoscale structure and how they reflect the microphysics fields. The study also aims to compare this squall line with other convective systems worldwide.

teresaksmith
Download Presentation

Structure and Evolution of Microphysics Fields in African Squall Line

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. A numerical study of the structure and evolution of microphysics fields in an African squall line Anne Sophie Daloz Universite de Toulouse ,France Directed by Robert Rogers

  2. Plan • Motivation • Methodology : Meso-NH • Results Mesoscale structure Statistics and microphysics • Future work

  3. Motivation • MCS are responsible of 95 % of annual rainfall in Sahel – AMMA (Analyse Multidisciplinaire de la Mousson Africaine) • An MCS case for simulation was selected that had a long life (48 h,2 lifecycles), a large size ( > 5000 km2) and was very organized • MCS from all over the world have similarities and differences, likely due to the environment (e.g., low level jet, humidity…) : - study the mesoscale structure of the simulated MCS to see if it is consistent with its synoptic environment - Evaluate the statistics of the microphysics fields to see how they reflect the mesoscale structure

  4. Conceptual model of the Mesoscale structure (Houze et al.1989)

  5. low levels Due to the difference of surface temperature between the Ocean and the Land Between 650 and 700hPa Due to the difference in PBL depth in Saharian vs Gulf of Guinee Synoptic environment (from 2005 case) Wind speed at the surface (shaded,m/s) Wind speed at 700 hPa Monsoon flow African Easterly Jet

  6. Mesoscale Convective System from August 15 to 17 2004 08/16 06 UTC 08/15 12 UTC 08/15 18 UTC 08/16 12 UTC 08/16 18 UTC 08/16 00 UTC Aïr Fouta-Djallon

  7. Methodology

  8. Méso-NH • Méso-NH is the non-hydrostatic mesoscale atmospheric model of the French research community. • The model is intended to be applicable to all scales ranging from large (synoptic) scales to small (large eddy) scales and it is coupled with an on-line atmospheric chemistry module . • The parametrisation of the convection in NH model is only used for mesh sizes > 5 km. Below this resolution the model resolve explicitly the deep convection . • The convection scheme used is : Kain-Fritch • The microphysical parametrisation scheme is 3-ICE with ice, snow and graupel equations • Initial and boundary conditions from ECMWF fields

  9. Numerical simulation from August 15 to 16, 2004 Grid-nested model • First domain resolution of 40 km, mesh 151 x 109 • Second domain resolution of 10 km, mesh 217 x 121 • Third domain resolution of 2.5 km, mesh 257 x 193

  10. Results

  11. METEOSAT/MESO-NH • Temperature de brillance (brightness temperature) at 10 microns, second domain - On the right : satellites images from METEOSAT - On the left :Meso-Nh Simulation • Blue : Top of the cold cloud

  12. dBZ Mesoscale structure Horizontal (Left) and Vertical (Right) Profiles of Reflectivity (dBZ) at 3 kms 45 40 35 30 25 20 15 10 5 August 15,2004 at 19 UTC ,Convective phase August 16,2004 at 00 UTC,convective/stratiform phase

  13. dBZ August 16,2004 at 12 UTC, ”stratiform” phase 45 40 35 30 25 20 15 10 5 August 16,2004 at 18 UTC, Re-Convective phase

  14. Mesoscale structurePotential Temperature (K) at 1 km

  15. dBZ Partition on Reflectivity Red = Convective , Yellow = stratiform , Green = Other 45 40 35 30 25 20 15 10 5 August 15,2004 at 19 UTC Convective August 16,2004 at 00 UTC Conv/Strat August 16,2004 at 12 UTC Strat

  16. Statistics and Microphysics Percentage on Partitioning 90 80 70 60 50 40 30 20 10 0 Conv + Strat • Stratiform percentage • Convective Percentage • Others (rain that is not from the stratiform or the convective part ) Conv Strat Conv 19UTC 00 UTC 06UTC 12UTC 18 UTC Universal time of the simulation

  17. Mean profile of vertical motion for the stratiform part Green = 19 UTC, August 15 Blue = 03 UTC, August 16 Red = 12 UTC, August 16 Black = 18 UTC, August 16

  18. CFAD (Contoured Frequency by Altitude Diagram) of vertical motion (m/s) August 16,2004 at 03 UTC August 15,2004 at 19 UTC The contour in the CFAD represents the percentage of points per unit variable per kms August 16,2004 at 12 UTC August 16,2004 at 18 UTC

  19. CFAD of reflectivity for the total MCS (dBZ) August 15,2004 at 19 UTC August 16,2004 at 03 UTC August 16,2004 at 18 UTC August 16,2004 at 12 UTC

  20. CFAD of vertical motion for the convective part (m/s) August 15,2004 at 19 UTC August 16,2004 at 03 UTC August 16,2004 at 12 UTC August 16,2004 at 18 UTC

  21. CFAD of reflectivity for the convective part (dBZ) August 16,2004 at 03 UTC August 15,2004 at 19 UTC August 16,2004 at 12 UTC August 16,2004 at 18 UTC

  22. CFAD of vertical motion part (m/s) Cifelli et al 2002, Southwest Amazon August 16,2004 at 03 UTC

  23. Comparison between Meso-NH and TRMM August 16,2004 at 03 UTC Houze et al 2006, West Africa 90 % 90 %

  24. Future work • Further analysis of this case • Comparison between this MCS and other Meso-NH simulations of convective systems all over the globe (e.g., Midlatitude continental MCS, tropical oceanic MCS, tropical cyclones). • Comparison of convective systems from Meso-NH and MM5 simulations with observations (e.g., Dennis, Katrina ).

More Related