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“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

“Large Eddy Simulation” modeling of MARBLL observations

Tanguy Bertrand, François Forget, Aymeric Spiga, and the LMD team

Laboratoire de Météorologie Dynamique, Paris, France

slide2

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

slide3

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)

slide4

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)

slide5

Laser Shots in the LES Model

Changingelevation angle: 0°, 90° …

90°: the radial windobserved correspond to the vertical component of the wind (convection)

slide6

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

slide7

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

slide8

Time Scale of Convective Structures

Simulation timestep: 2s

LT: 15:00

Position 1

slide9

Time Scale of Convective Structures

Simulation timestep: 2s

LT: 15:00

Position 2

slide10

Time Scale of Convective Structures

Simulation timestep: 2s

LT: 15:00

Position 3

slide11

Time Scale of Convective Structures

Simulation timestep: 100s

LT: 14:00-15:00

Position 2

Position 1

slide12

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

slide13

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

slide14

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

slide15

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

slide16

Horizontal Laser Shot: Angle Error

What if the shotis not exactly horizontal and has an angle error of few degree ?

slide17

Horizontal Laser Shot: Angle Error

What if the shotis not exactly horizontal and has an angle error of few degree ?

Local slope

slide18

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

slide19

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

slide20

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

slide21

45° Laser Shot: 2° Angle Error

Simulation timestep: 100s

LT: 14:00-15:00

Background wind: 15 m/s

slide22

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/