TMT.XXX.PRE.05.0XX.DRF01

Meteorological study of an event of turbulence in TMT sites: Case of 13 August of 2006

O. Cuevas, A. Chacón & M. CureAstroMeteorology group - Universidad de Valparaíso - Chile

S. Els1,3, M. Schoeck2,3, R. Riddle3, W. Skidmore3 & T. Travouillon3

Optical Turbulence - Meteorology Conference, 16 September 2008, Sardegna, Italy

1Cerro Tololo Inter-American Observatory, La Serena, Chile2TMT Observatory Corporation, Victoria, Canada3TMT Observatory Corporation, Pasadena, USA

1/19

TMT.XXX.PRE.05.0XX.DRF01

Summary

1. The case: “August 13, 2006: a peculiar night in TMT sites testing?”

2. MM5 implementation

3. Synoptic analyses (satellite images and MM5 model)

4. Local analyses (station weather data and MM5 model system)

5. Trajectories analyses

6. Comparison between MM5 data and observed data

7. Conclusions and future work

2/19

N

Tolar: 21.964º S, 70.099º W,

2290 m.a.s.l.

Armazones:24.58º S, 70.189º W,

3064 m.a.s.l.

Tolonchar:23.933º S, 67.975º W,

4477 m.a.s.l.

The case August 13, 2006: a peculiar night inTMT sites testing?

3/19

Domains made for TMT sites

MM5 model systemDomain 1 80 x 80 grid points

27 km horizontal resolution

Domain 2 97 x 70 grid points9 km horizontal resolution

Domain 3 130 x 160 grid points3 km horizontal resolution

TMT sites in domain 34/19

MM5 set up

1. Boundary condition from GFS to 00UTC:1.25º x 1.25º horizontal resolution (~100 km)

12 pressure levels, 1000 to 100 hPa

2. Integration of 30 sigma levels

3. Parameterization

Explicit moisture scheme SchultzCumulus schemes Kain-Fritsch 2Planetary boundary layer EtaAtmospheric radiation RRTM

4. Time stepDomain 1 81 s Output 10 mDomain 2 27 s Output 10 mDomain 3 9 s Output 10 m

5/19

Synoptic analyses

500 hPa level between 00UTC to 09UTC-Shadows color is a relative vorticity- Wind in blue barbs- Geopotential height in black lines

Infrared 00UTC

Infrared 09UTC6/19

Water vapor 00 UTC

Water vapor 09 UTC

Jet Stream

250 hPa level between 00UTC to 09UTC-Shadows color is max wind velocity (Jet-Stream)- Streamline in blue color

7/19

Tolar

W-E cross section over Tolar between 00UTC to 09UTC.-Potential temperature in red lines- wind in vectors

Tolar

WSEN

8/19

Tolar

Thermal break between 2 km to 7 km

9/19

05UTC 06UTC

07UTC

Richardson number in Tolar

No signal of turbulence with Ri<0.25

05UTC 06UTC

07UTC

Ri - 00UTC to 09 UTC

Tolar

10/19

Tolonchar

W-E cross section over Tolonchar between 00UTC to 09UTC.-Potential temperature in red lines- wind in vectors

WSEN

11/19

Tolonchar

03 UTC 04 UTC

05 UTC

Gravity waves caused by the mountain range

12/19

Richardson NumberTolonchar

Ri - 00UTC to 09 UTC

03UTC 04UTC

05UTC

Tolonchar

13/19

Armazones

W-E cross section over Armazones between 00UTC to 09UTC.-Potential temperature in red lines- wind in vectors

Armazones

WSEN

14/19

Richardson NumberArmazones

Turbulence with Ri<0.25 over Armazones.No relationship with optical turbulence

Ri - 00UTC to 09 UTC

Armazones 03UTC 05UTC

07UTC

15/19

1 km 2 km

4 km 8 km

Flow from south in low levels

Flow from north in low levels

Normal flow from the west in middle an high levels

Tolar

Tolonchar

Armazones

Trajectories

16/19

Wind direction near of the surface and trajectories at 1 km

WSEN

WSEN

WSEN

17/19

TMT.XXX.PRE.05.0XX.DRF01

Conclusions

1. The synoptic study shows that the 2nd Region is in a anticyclonic domain.

2. The Jet Stream intensifies raises during the night.

3. Relative humidity increase during the night, advection from the NW in the satellite image. Less intense at Armazones.

4. Potential temperature breaks, maybe due to gravity waves at Tolar, similar at Armazones.

5. Origin of turbulence at Tolonchar remains unclear as gravity waves remain steady in time due to closeness to the Andes mountain range.

6. No obvious relation between Ri and Cn2.

7. Most probable correlation is observed between Tpot and Cn2.

18/19

TMT.XXX.PRE.05.0XX.DRF01

Future work

1. Increase horizontal to 1 km and vertical resolution to ~100 m of the MM5 model.

2. Investigate other cases using also simulation results of Richardson number and TKE (Turbulent Kinetic Energy).

3. Sensitivity study of MM5 model to input parameters: NCEP v/s ECMWF.

Acknowledgement

We thank Marc Sarazin (ESO) for his comments and support.The authors gratefully acknowledge the support of the TMT partner institutions.They are the Association of Canadian Universities for Research in Astronomy (ACURA), the CaliforniaInstitute of Technology and the University of California. This work was supported as well by theGordon and Betty Moore Foundation, the Canada Foundation for Innovation, the Ontario Ministry ofResearch and Innovation, the National Research Council of Canada, the Natural Sciences andEngineering Research Council of Canada, the British Columbia Knowledge Development Fund, theAssociation of Universities for Research in Astronomy (AURA) and the U.S. National Science Foundation.

19/19