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

2 Why study Astronomy? 1.Aesthetic beauty! 2.Unanswered questions about “dark matter” (83% of universe) and “dark energy” (73% of mass-energy universe) 3.“Are we alone?”.. Last count on exoplanet.eu = Humans want to “explore and extend beyond…”

3 Why Astronomy, Weather and Climate? 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. Weather and climate are vital for successful astronomical observations:

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

5 Where is Kenya?

6 Kenya: Topography metres R I F T V A L L E Y Semi- Arid / Desert More Humid Mt. Kenya Mt. Kilimanjaro

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

Data Provenance: ECMWF ERA-interim “reanalysis” 0.5 deg lat/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 large file sizes (2 GB per day!)

Analyses and Results: Cloud cover & variability (Integrated)

Analyses and Results: Integrated water vapour

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) Warges (2688m) Mount Kenya (~4400m) Monitoring conditions for two years. ~2017: begin construction of 1.5 to 2- metre telescope

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 Sep 1998, VLT Paranal (ESO) Hurricane Epsilon, 3 Dec 2005, NASA But times difference in scale!!

Appendix 1: Seismic Risk

Appendix 2: TOMS 20-year aerosol index

17 Appendix 3: What are “Reanalyses” ? Reanalysis 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)

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

19 Appendix 5: Prevailing windspeeds

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)

ERA: cloud cover data and variability Mt_Kulal OlDonyoN yiro Mt_Marsa bit Kapchol ioNdotoWargesLoita_HillsMtelo CC St.dev Mt_FurroliOlDonyoLenkyoSololoMt_KenyaCherangany3350m_ODY CC St.dev More or less same results with UK Met Office African-LAM Analyses and Results: Cloud cover & variability

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