1 / 23

Lascaux Franck Masciadri Elena, Hagelin Susanna

Optical Turbulence in Meso-NH: study of a site with extremely stable conditions (Dome C, Antarctica). Lascaux Franck Masciadri Elena, Hagelin Susanna. INAF – Osservatorio Astrofisico di Arcetri, Florence, Italy. MESO-NH CONFIGURATIONS (1). More details in Lascaux et al. (SPIE 2008).

cassidy-albert
Download Presentation

Lascaux Franck Masciadri Elena, Hagelin Susanna

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. Optical Turbulence in Meso-NH: study of a site with extremely stable conditions (Dome C, Antarctica) Lascaux Franck Masciadri Elena, Hagelin Susanna INAF – Osservatorio Astrofisico di Arcetri, Florence, Italy

  2. MESO-NH CONFIGURATIONS (1) More details in Lascaux et al. (SPIE 2008) -Low horizontal resolution monomodel simulation: Δx=100 km. F C (3205 m) PS A 6000 km -Grid-nested simulation: Δx=1 km in the innermost domain. C GTOPO30 not accurate over Antarctica => Use of RAMPDEM version 2* *Liu, H et al., 2001. “Radarsat Antarctic Mapping Project Digital Elevation Model version 2”. Boulder, CO; National Snow and Ice Data Center. Digital media. GTOPO30 Zoom over Dome C Area 3250m A C (3230 m) PS C 400 km 80 km 3000km C 3220m Domain 2: Δx=5 km Domain 1: Δx=25 km Domain 3: Δx=1 km

  3. MESO-NH CONFIGURATIONS (2) -Calibration (see last slides) made with this configuration (in grid-nesting mode only). + MASDEV 4.7 bug 4 + SURFEX 4.7 with -LPHYSDOMEC=T (physics adapted to Dome C) -LDEEPSOIL=T (force surface temperature towards a climatological value) -Vertical grid: 1st point at 2 m, 12 points in 100 m, and H=600 m above 3.5 km (ok for Dome C, flat orography) RAMPDEMv2 -Grid-nested simulation: Δx=1 km in the innermost domain. 3230m A C C PS 400 km 80 km 3000km (3230 m) C 3200m Domain 3: Δx=1 km; t=3 s Domain 2: Δx=5 km Domain 1: Δx=25 km

  4. H (KM) H (KM) H (M) 0 5 10 15 20 0 0.2 0.4 0.6 0.8 1 0 50 100 150 200 250 (K) 180 190 200 210 220 230 240 210 215 220 225 230 235 240 205 210 215 220 225 230 235 240 RS ANA MM GN RS ANA MM GN SIMULATED VERTICAL PROFILES ABOVE DOME C Meteorological parameters (Lascaux et al., 2009) TEMPERATURE WIND SPEED H (KM) 0 5 10 15 20 H (KM) H (M) 0 0.2 0.4 0.6 0.8 1 0 50 100 150 200 250 (m/s) 0 5 10 15 20 25 30 0 5 10 15 20 25 0 5 10 15 20 Mean vertical profiles of temperature and wind speed above Dome C for 47 winter nights. RS = radiosoundings ; ANA = ECMWF Analyses ; MM = Meso-NH monomodel simulation ; GN = Meso-NH grid-nested simulation.

  5. Optical Turbulence – Meso-NH V (wind intensity) + P (pressure) + T (temperature) + Lo (dynamical outer scale) Refractive index structure parameter From the Cn2 field we can deduce all the astroclimatic parameters that depend on it. -Especially the seeing: Best possible angular resolution, in arcsec (“) With λ=0,5.10-6 m -But also the surface layer thickness (Hsl), with the criteria used in Trinquet et al. 2008 (15 winter nights observed): FA (Free Atmosphere) Hsl SL (Surface Layer) Ground

  6. TEMPORAL EVOLUTION OF Cn² PROFILES • 15 nights between 21 June 2005 and 21 September 2005 (winter) have been observed by Trinquet et al. (2008). We simulated these nights using the astro-meso-nh package developed by the team. • - Examples of simulations for 3 nights: monomodel (left) and grid-nested (right) Hsl = 25.3 m Hsl = 38.2 m Hsl = 18.2 m Taken from Lascaux et al. 2009

  7. MEDIAN Cn² VERTICAL PROFILE AVERAGE Hsl,obs = 35,3m Hsl,mnh = 48,5m MEDIAN εobs,FA = 0,3” εmnh,FA = 0,45” εobs,TOT = 1,6” εmnh,TOT = 3,1” Medians of the simulated mean vertical profile of Cn² (between 12 UT and 17 UT) for the 15 nights observed in Trinquet et al. (2008), above Dome C.

  8. CORRELATION PLOTS SimulatedJ SimulatedJ SimulatedJ Observed J Observed J Observed J Total J Surface Layer J Free Atmosphere J J = Cn2(h).dh MEDIAN ε εobs,FA = 0,3” εmnh,FA = 0,45” AVERAGE Hsl Hsl,obs = 35,3m Hsl,mnh = 48,5m εobs,TOT = 1,6” εmnh,TOT = 3,1”

  9. CALIBRATION AT DOME C USING OBSERVATIONS Goal: -to adjust the total intensity of the optical turbulence, especially inside the surface layer where it is too strong. Method: -first step: modification of a coefficient in the Meso-NH turbulence scheme. For this, we change XCTP in ini_cturb.f90: from 4 to 4.88 (computed from the ratio between observed and simulated Hsl) -> Change of XCSHF coefficient in the w’v’ term. => Hsl and ε -second step: correction in the optical turbulence package in the CT2 computations, from which is deduced the Cn2. From CT2 as 0.598 x 3 x LM4/3 x ( /  Z)2 to CT2 as 0.210 x 3 x LM4/3 x ( /  Z)2 (deduced from the ratio between observed and simulated median J=Cn2.dh) => ~Hsl and ε -third step: correction of the TKEmin, in order to have a model more active in altitude. No impact near the surface. TKEmin (new) = TKEmin (old) x 1.74

  10. AFTER CALIBRATION Radiosoundings ECMWF analyses M-NH before calibration M-NH after calibration Potential temperature profiles, some examples: 150 m AGL 0 m Average (only 8 days)

  11. AFTER CALIBRATION Simulations of the same sample of nights. Configuration 2. Median vertical Cn2 profiles: Observations M-NH, before calibration M-NH, after complete calibration

  12. AFTER CALIBRATION Seeing and surface layer thickness correlation plots: Total Seeing Free Atmosphere Seeing Surface Layer Thickness M-NH, before calibration εtot,before = 2.90” εFA,before = 0.45” Hsl,before = 44.4 m εtot,after = 1.70” εFA,after = 0.30” Hsl,after= 44.2 m εtot,OBS = 1.6” εFA,OBS = 0.3” Hsl,OBS = 36.4 m M-NH, after complete calibration

  13. CONCLUSIONS -We presented here a detailed study of the wintertime optical turbulence at Dome C, Antarctica, with Meso-NH in which our team included an astronomical package allowing for the forecasting of optical turbulence (the astro-meso-nh package, only available at the Osservatorio Astrofisico di Arcetri). -Configuration used: o Masdev 4.7 bug 4 + Surfex 4.7 + LDOMEC=T + LDEEPSOIL=T o Use of the “Radarsat Antarctic Mapping Project Digital Elevation Model version 2” for the description of the orography (GTOPO30 unreliable in the Plateau). oX = 25, 5, and 1 km. o Vertical grid: first point at 2 m, 12 points in the first 100 m, 55 levels up to 22 km. Acknowledgements: This work has been funded by the Marie Curie Excellence Grant (FOROT) – MEXT-CT-2005-023878 Data set from the MARS Catalog (ECMWF) are used in this presentation. Access to the MARS Catalog is authorized by the Servizio Meteorologico dell’Aeronautica Militare Italiana.

  14. εtot,before = 2.90” εFA,before = 0.45” Hsl,before = 44.4 m εtot,after = 1.70” εFA,after = 0.30” Hsl,after= 44.2 m εtot,OBS = 1.6” εFA,OBS = 0.3” Hsl,OBS = 36.4 m CONCLUSIONS -Optical Turbulence results: o Before calibration with available observations, winter simulations with the astro-mnh package generate too much optical turbulence and a slightly too high surface layer thickness. o After a calibration process (adaption of surface fluxes, CT2 coefficient, and modification of TKEmin), results are more satisfying. o Next step: looking at other sites in Antarctica (Dome A, South Pole...) Acknowledgements: This work has been funded by the Marie Curie Excellence Grant (FOROT) – MEXT-CT-2005-023878 Data set from the MARS Catalog (ECMWF) are used in this presentation. Access to the MARS Catalog is authorized by the Servizio Meteorologico dell’Aeronautica Militare Italiana.

  15. AFTER CALIBRATION Simulations of the same sample of nights. Some examples of Cn2 profiles: 04/07/2005 07/09/2005 21/09/2005 Fisrt 300 m Zoom up to 50m Reference simulations Simulations using calibration 04/07: Hsl from 31.3m to 30.4m εtot from 4.05” to 2.28” εFA from 0.32” to 0.22”

  16. Exemple initialisation (ECMWF + MESO-NH après real step – basse et haute résolution verticale)

  17. SIMULATED VERTICAL PROFILES ABOVE DOME C Meteorological parameters (2) - At the surface: Radiosondes ECMWF Monomodel Grid-nesting Wind speed (m/s) 4.02 ± 2.55 6.51 ± 2.51 4.23 ± 1.77 3.98 ± 1.95 Temperature (K) 212.90 ± 7.64 216.64 ± 5.83 214.92 ± 4.64 214.50 ± 4.97 Mean values of temperature and wind speed at the surface above Dome C for the 47 winter nights. -> Meso-NH better reproduces the surface temperature and wind speed at Dome C than the ECMWF analyses. -> The grid-nested high horizontal resolution configuration gives results closer to the observations than the low horizontal configuration.

  18. TEMPORAL EVOLUTION OF Cn² PROFILES • 16 nights between 16 June 2005 and 21 September 2005 (winter) have been observed by Trinquet et al. (2008). We simulated these nights using the astro-meso-nh package developed by the team. • - Examples of simulations for 3 of these nights: monomodel (top row) and grid-nested (bottom row) H (m AGL) Log(Cn²) Log(Cn²) Log(Cn²) -12 -12 300 -12 Night 1 Night 2 Night 3 -13 -13 -13 200 -14 -14 -14 -15 -15 -15 100 -16 -16 -16 0 H (m AGL) -12 -12 300 -12 Night 1 Night 2 Night 3 -13 -13 -13 200 -14 -14 -14 -15 -15 -15 100 -16 -16 -16 0 00 06 12 18 (UTC) 00 06 12 18 (UTC) 00 06 12 18 (UTC)

  19. SIMULATED VERTICAL PROFILES ABOVE DOME C Examples We show here the results for two different nights in winter 2005. Vertical profiles at 12 UT, after 12 hours of simulation 300 Temporal evolutions of Cn² profiles H (m AGL) Log(Cn²) (m AGL) 300 -12 Night 1 Potential temperature 200 -13 200 -14 100 -15 100 -16 0 00 06 12 18 (UTC) 235 240 245 250 255 260 265 270 (K) H (m AGL) 300 -12 300 (m AGL) Night 2 -13 200 200 -14 -15 100 100 -16 0 00 06 12 18 (UTC) Wind speed 0 2 4 6 8 10 12 14 (m/s)

  20. MEDIAN Cn² VERTICAL PROFILE 20km 300m Measurements 15 Monomodel 200 Grid-nested 10 100 5 0 0 -19 -18 -17 -16 -15 -14 -13 -18 -17 -16 -15 -14 -13 Log(Cn²) Medians of the mean vertical profiles of Cn² (between 11 UT and 17 UT) over the 16 nights observed in Trinquet et al. (2008), above Dome C.  For each night, using the Cn² vertical profile, we deduce the surface layer thickness of the Dome C site.

  21. SURFACE LAYER THICKNESS AT DOME C Mean values of Hsl: Observations: 34.2 m (Eq. 1) Monomodel (Eq. 1):60.7 m / Monomodel (Eq.2): 72.1 m Grid-nested (Eq. 1): 46.8 m / Grid-nested (Eq. 2): 60 m Hsl (m) Surface Layer Thickness (m) Winter Nights

  22. SEEING Computed seeing (mean between 11 UT and 17 UT) for the same 16 nights. FA= free atmosphere, starts at: -33 m in the observations; -46.8 m in the simulations Median values of the FA seeing: Observations: 0.3” Simulated (top 13 km): 0.46” Simulated (top 20 km): 0.53”

More Related