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Dr. Eddy Graham UHI Research Conference Presentation Thursday 8 November 2012

SASKA: Search for an Astronomical Site in Kenya. Dr. Eddy Graham UHI Research Conference Presentation Thursday 8 November 2012. Why study Astronomy?. Aesthetic beauty! Unanswered questions about “ dark matter ” (83% of universe) and “ dark energy ” (73% of mass-energy universe)

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Dr. Eddy Graham UHI Research Conference Presentation Thursday 8 November 2012

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  1. SASKA: Search for an Astronomical Site in Kenya Dr. Eddy Graham UHI Research Conference Presentation Thursday 8 November 2012

  2. Why study Astronomy? • Aesthetic beauty! • Unanswered questions about “darkmatter” (83% of universe) and “dark energy” (73% of mass-energy universe) • “Are we alone?” .. Last count on exoplanet.eu = 843 • Humans want to “explore and extend beyond…”

  3. Why Astronomy, Weather and Climate? Weather and climate are vital for successful astronomical observations: • Clear skies (not even partial cloudiness) • Little atmospheric water vapour • Minimal turbulence… • Other variables: Gentle and consistent winds; few aerosols / dust; no extreme weather (snow, hail, lightning, etc..); low night-time relative humidity; low seismic risk; nearness to infrastructure.

  4. Twinkling stars and refraction of light Space Parallel wave front of stellar image gets distorted by atmosphere Atmosphere

  5. Where is Kenya?

  6. Kenya: Topography metres Semi-Arid / Desert More Humid R I f t V a l l e y Mt. Kenya Mt. Kilimanjaro

  7. Kenya: Identification of candidate sites Mount Kulal (2293m) Warges (2688m) Google Earth followed by site visits Mount Kenya (~4400m)

  8. Data Provenance: • ECMWF ERA-interim 1979-2012 “reanalysis” • 0.5 deglat/lon resolution (~50km), ~ 50 levels • 24 years of data, 6-hourly temporal resolution • Easy to use, small file sizes (kb to mb) • United Kingdom Met Office Africa Limited Area Model (“Africa-LAM”) output • Very high 12km resolution, 70 levels, night-time hourly resolution • run daily in real-time • archive 2010-2012 • large file sizes (2 GB per day!)

  9. Analyses and Results: Cloud cover & variability (Integrated)

  10. Analyses and Results: Integrated water vapour

  11. Vertical velocity and height of turbulent layers -> need to go as high as possible -> surface turbulent layer is deep (2,500 to 3,000m,or more)

  12. Interim decision soon, South Africa (Dec 2012): Mount Kulal (2293m) Monitoring conditions for two years. ~2017: begin construction of 1.5 to 2-metre telescope Warges (2688m) Mount Kenya (~4400m)

  13. Not quite ESO Paranal (Chile)… But a worthy project nonetheless: - Will provide a much-needed economic boost to Kenyan economy - Provide a dedicated research and training facility for African physics and astronomy students at home

  14. Thank you to sponsors! Spiral Galaxy, NGC 1232 21 Sep 1998, VLT Paranal (ESO) But 1017 times difference in scale!! Hurricane Epsilon, 3 Dec 2005, NASA

  15. Appendix 1: Seismic Risk

  16. Appendix 2: TOMS 20-year aerosol index

  17. Reanalysis Appendix 3: What are “Reanalyses” ? Re-analyses are reconstructed weather analyses (maps) for the past (~1950s onwards) using all available weather data for the past, but using a fixed numerical meteorological model of today (avoids inhomogenities)

  18. H H H H H H H H ERA40 mid-to-upper tropospheric (775 to 200 hPa) vertical velocities in range 2.5 < > 5.0 cm /sec (i.e. gently subsiding air, turbulence less likely) Appendix 4: Vertical velocities

  19. Appendix 5: Prevailing windspeeds

  20. Appendix 6: Global mean annual IWV

  21. Kenya: Identification of candidate sites Mount Kulal (2293m)

  22. Kenya: Identification of candidate sites OlDonyoNyiro (2752m)

  23. Kenya: Identification of candidate sites Mount Kenya (~4400m)

  24. Identification of candidate sites OlDonyoLenkiyo (2550m) Mount Kenya (~4400m) Loita Hills (2642m)

  25. Analyses and Results: Cloud cover & variability ERA: cloud cover data and variability More or less same results with UK Met Office African-LAM

  26. Analyses and Results: Integrated water vapour (IWV) IWV is extremely height dependent

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