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“Large Eddy Simulation” modeling of MARBLL observations

“Large Eddy Simulation” modeling of MARBLL observations. Tanguy Bertrand, François Forget, Aymeric Spiga , and the LMD team Laboratoire de Météorologie Dynamique, Paris, France. The Mars Large Eddy Simulation (LES) Model. Ideal Tracer Transport by Convective vertical Motions. 15 km

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“Large Eddy Simulation” modeling of MARBLL observations

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  1. “Large Eddy Simulation” modeling of MARBLL observations Tanguy Bertrand, François Forget, Aymeric Spiga, and the LMD team Laboratoire de Météorologie Dynamique, Paris, France

  2. The Mars Large Eddy Simulation (LES) Model Ideal Tracer Transport by Convective vertical Motions 15 km 10 km 5 km 0 km Microscale Model: Gridspacing 10-100 m Resolve convection in the MartianBoundary Layer Simulate the environmentobserved by the lidar

  3. Laser Shots in the LES Model Ateach point of the line of sight, the LES gives: U, V, W and the radial windcanalsobeextracted Example of shot: elevation 45°, towards East The Lidar seesonly the component of the windthatis in its line of sight (radial wind)

  4. Laser Shots in the LES Model Background windtowards East Addition of large-scale background wind: 5 m/s, 15 m/s Distinguish large-scale and small-scale horizontal winds (gusts)

  5. Laser Shots in the LES Model Changingelevation angle: 0°, 90° … 90°: the radial windobserved correspond to the vertical component of the wind (convection)

  6. Laser Shots in the LES Model Background windtowards East Changing azimut angle: 0°, 90° … At 0° elevation, using one azimut angle willyieldstrongerwinds: itwillbe the direction of large-scalewinds

  7. Laser Shots in the LES Model Wecanalsocollect LES data: Atdifferent local times: In the morning, in the afternoon (evolution of wind structures) For a certain duration: time step 2s, 50s, 100s … (time scale of convective structure) Atdifferentlocations (in a downdraft/updraft) How many laser shots do weneed and for how long ? Wind structures: Horizontal section of vertical winds Maximum vertical winds in the PBL with altitude and time

  8. Time Scale of Convective Structures Simulation timestep: 2s LT: 15:00 Position 1

  9. Time Scale of Convective Structures Simulation timestep: 2s LT: 15:00 Position 2

  10. Time Scale of Convective Structures Simulation timestep: 2s LT: 15:00 Position 3

  11. Time Scale of Convective Structures Simulation timestep: 100s LT: 14:00-15:00 Position 2 Position 1

  12. Time Scale of Convective Structures Position 2 Position 1 Averaged on 1H, vertical windsat one point shouldbe close to 0 m/s Shot 1 at a position privileged for updrafts Need for ideal LES

  13. Time Scale of Horizontal Structures Mean horizontal winds(East component) over domain and time Simulation timestep: 100s LT: 14:00-15:00 Background wind: 15 m/s

  14. Time Scale of Horizontal Structures Horizontal shot in the direction of large-scalewind Simulation timestep: 2s LT: 15:00 Background wind: 5 m/s Simulation timestep: 100s LT: 14:00-15:00 Background wind: 15 m/s

  15. Time Scale of Horizontal Structures 45° shot in the direction of large-scalewind East wind component profile Simulation timestep: 2s LT: 15:00 Background wind: 5 m/s Simulation timestep: 100s LT: 14:00-15:00 Background wind: 15 m/s

  16. Horizontal Laser Shot: Angle Error What if the shotis not exactly horizontal and has an angle error of few degree ?

  17. Horizontal Laser Shot: Angle Error What if the shotis not exactly horizontal and has an angle error of few degree ? Local slope

  18. Horizontal Laser Shot: Angle Error What if the shotis not exactly horizontal and has an angle error of few degree ? Local slope Stones Shot not exactly horizontal 2° error angle ̴ 200 m 6 km

  19. Horizontal Laser Shot: Angle Error What if the shotis not exactly horizontal and has an angle error of few degree ? Simulation timestep: 100s LT: 14:00-15:00 Background wind: 15 m/s 2° shot 0° shot

  20. Horizontal Laser Shot: Angle Error What if the shotis not exactly horizontal and has an angle error of few degree ? Simulation timestep: 100s LT: 14:00-15:00 Background wind: 15 m/s Vertical winds 0° shot Vertical winds 5° shot

  21. 45° Laser Shot: 2° Angle Error Simulation timestep: 100s LT: 14:00-15:00 Background wind: 15 m/s

  22. CONCLUSION LES model: necessary to improve MARBLL science and design Characterization of wind structures and their time scale Variability of simulations: LT, position, background wind, … Assessement of the sensitivityof pointingerror Need for optimal LES: timestep, domain dimension, distance betweentwo points of the line of sight, finer profile in the first hundred of meters, background wind… ? Database: all figures online: http://www.lmd.jussieu.fr/~tblmd/MARBLL/

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