Theoretical and Applied Climatology

, Volume 124, Issue 1–2, pp 425–449 | Cite as

Search for an astronomical site in Kenya (SASKYA) using climate reanalyses and high-resolution meteorological model data

  • Edward GrahamEmail author
  • Richard Vaughan
  • David A. H. Buckley
  • Koi Tirima
Original Paper


The goal of the Search for an Astronomical Site in Kenya (SASKYA) project is to identify the best possible site(s) in Kenya for astronomical optical observation, using ERA-interim climate reanalyses and high-resolution UK Met Office Africa Limited Area meteorological model (Africa-LAM) data. This initial search focusses on a selection of 13 candidate mountain peaks across Kenya. A mixture of 30 years (1981–2010) of relatively coarse-grained ERA-interim reanalyses data and 12 months’ (2011–2012) of much higher resolution UK Met Office Africa-LAM data were used to determine the best possible sites. Cloud cover, precipitable water vapour (specific humidity), vertical velocity, aerosol loadings and wind data were analysed. The results confirm that many sites in Kenya are reasonably cloud free, with estimated photometric night fractions of possibly 50 % at the best sites. Significant seasonal inter-annual and inter-decadal variations in cloud cover can be expected, however. Average precipitable water vapour (PWV) values are uncomfortably high, but periods of much lower PWV can be expected during favourable conditions in the dry seasons. Long-term vertical velocities (as a proxy to determine areas of improved “seeing” conditions) indicate that good astronomical viewing conditions are likely to be dependent on the season and wind direction across Kenya. Finally, after full consideration of the climatological data, a trade-off is expected between the best possible site in climatological terms, and the practicalities of installing remote equipment in isolated, inaccessible areas with little or no infrastructure.


Cloud Cover Rift Valley Precipitable Water Vapour Candidate Site Total Cloud Cover 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.



The ECMWF ERA-interim data used in this study/project have been provided by ECMWF and have been obtained from the ECMWF data server. The UK Met Office (UKMO) Limited Area Model for Africa (Africa-LAM) was kindly made available by the UK Met Office, through the British Atmospheric Data Centre (BADC). This research was funded by the Kenya–South Africa Joint Science and Technology Research programme. A grant by the Carnegie Trust for the Universities of Scotland enabled Dr. E. Graham of the University of the Highlands and Islands to travel to South Africa in December 2012 and participate in discussions with the SASKYA team, leading to the decision to install astronomical site testing equipment at Warges and Mount Kulal. Dr. Graham is grateful for the support of the Carnegie Trust in this regard.


  1. Agabi A, Aristidi E, Azouit M, Fossat E, Martin F, Sadibekova T, Vernin J, Ziad A (2006) First whole atmosphere night-time seeing measurements at Dome C, Antarctica. Publ Astron Soc Pac 118(840):344–348CrossRefGoogle Scholar
  2. Anyah RO, Semazzi FH (2007) Variability of East African rainfall based on multiyear RegCM3 simulations. Int J Climatol 27(3):357–371CrossRefGoogle Scholar
  3. Casals P, Beniston M (2001) Climatological analysis of seeing conditions at the site of the European Southern Observatory (ESO) in Paranal, Chile. Report by the Department of Geosciences, University of Fribourg, Switzerland. Contract no. 61243/ODG/00/8543/GWI/LETGoogle Scholar
  4. Chevallier F, Kelly G, Simmons AJ, Uppala S, Hernandez A (2003) High clouds over oceans in the ECMWF 15-year and 45-year re-analyses. ERA-40 Project Report Series No.11. ECMWF, Shinfield Park, Reading, England. Available at: Accessed May2008
  5. Dee DP, Uppala SM, Simmons AJ, Berrisford P, Poli P, Kobayashi S, Vitart F (2011) The ERA-interim reanalysis: configuration and performance of the data assimilation system. Q J R Meteorol Soc 137(656):553–597CrossRefGoogle Scholar
  6. Ehgamberdiev SA, Baijumanov AK, Ilyasov SP, Sarazin M, Tillayev YA, Tokovinin AA, Ziad A (2000) The astroclimate of Maidanak Observatory in Uzbekistan. Astron. Astrophys. Suppl. Ser. 145, 293–304Google Scholar
  7. Environment Canada (2014) Seeing forecast for astronomical purposes [online]. Available at:  Accessed: 25 Jan 2015
  8. European Southern Observatory ESO (2007) OWL Concept design report: phase A design review (OWL-TRE-ESO-0000-0001 Issue 2: Chapter 14: site characterisation), Garching, GermanyGoogle Scholar
  9. European Southern Observatory ESO (2015) Astroclimatology [online], Available at: <>. Accessed 22 Jan 2015
  10. Giordano P, Sarazin M (1994) Survey of airborne particle density and the ageing of mirror coatings in the open air at the VLT Observatory. Proc Int Soc Opt Eng (SPIE) 2199:977–985, SPIE 2199–977Google Scholar
  11. Graham E, Sarazin M, Beniston M, Collet C, Hayoz M, Neun M, Casals P (2005) Climate-based site selection for a Very Large Telescope using GIS techniques. Meteorological Applications 12(01), 77-81Google Scholar
  12. Graham E (2008a) The FriOWL Guide: A site selection tool for extremely large telescopes using climate data. Forschungsbericht Nr. 2008-09-MW, Institut fur Angewandte Physik, Universitat Bern, 256pp.Google Scholar
  13. Graham (2008b) Applications of FriOWL: the Paranal and La Silla astroclimate report. IAP Research Report, No. 2008-08-MW, Institut für angewandte Physik, Universität Bern, 85ppGoogle Scholar
  14. Graham E, Sarazin M, Matzler C (2011) Using re-analysis model data (“FriOWL”) to analyse climate trends related to astroclimatology of Paranal and La Silla. Rev Mex Astron Astrofís (Ser Conf) 41:12–15Google Scholar
  15. Hastenrath S (1995) Glacier recession on Mount Kenya in the context of the global tropics. Bull Inst Fr Etudes Andines 24:633–638Google Scholar
  16. Hastenrath S, Kruss PD (1992) The dramatic retreat of Mount Kenya’s glaciers between 1963 and 1987: greenhouse forcing. Ann Glaciol 16:127–133Google Scholar
  17. Herman JR, Bhartia PK, Torres O, Hsu C, Seftor C, Celarier E (1997) Global distribution of UV-absorbing aerosols from Nimbus 7/TOMS data. J Geophys Res 102(D14):16911–16922CrossRefGoogle Scholar
  18. Janowiak JE (1988) An Investigation of Interannual Rainfall Variability in Africa. Journal of Climate 1(3):240-255Google Scholar
  19. Kalnay E, Kanamitsu M, Kistler R, Collins W, Deaven D, Gandin L, Iredell M, Saha S, White G, Woollen J, Zhu Y, Chelliah M, Ebisuzaki W, Higgins W, Janowiak J, Mo KC, Ropelewski C, Wang J, Leetmaa A, Reynolds R, Jenne R, Joseph D (1996) The NCEP/NCAR Reanalysis Project. Bull Am Meteorol Soc 77:437–471CrossRefGoogle Scholar
  20. Kaser G, Hardy DR, Mölg T, Bradley RS, Hyera TM (2004) Modern glacier retreat on Kilimanjaro as evidence of climate change: observations and facts. Int J Climatol 24(3):329–339CrossRefGoogle Scholar
  21. Koffi E, Graham E, Mätzler A (2013) The water vapour flux above Switzerland and its role in the August 2005 extreme precipitation and flooding. Meteorol Z 22(3):328–341CrossRefGoogle Scholar
  22. Lawrence JS, Ashley MCB, Tokovinin A, Travouillon T (2004) Exceptional astronomical seeing conditions above Dome C in Antarctica. Nature 431:278–281. doi: 10.1038/nature02929 CrossRefGoogle Scholar
  23. Lumb FE (1970) Topographic influences on thunderstorm activity near Lake Victoria. Weather 25(9):404–410CrossRefGoogle Scholar
  24. Marchant R, Mumbi C, Behera S, Yamagata T (2007) The Indian Ocean dipole—the unsung driver of climatic variability in East Africa. Afr J Ecol 45(1):4–16CrossRefGoogle Scholar
  25. Masciadri E, Egner SE (2004) First complete seasonal variation study of the 3D optical turbulence above San Pedro Mártir Observatory. Proc Int Soc Opt Eng (SPIE) 5490:818–829Google Scholar
  26. Mastny L (2000) Melting of earth's ice cover reaches new high. Worldwatch Institute News Brief (6), 5ppGoogle Scholar
  27. Maxwell D, Fitzpatrick M (2012) The 2011 Somalia famine: context, causes, and complications. Global Food Secur 1(1):5–12CrossRefGoogle Scholar
  28. Morland JC, Matzler C (2007) Spatial interpolation of GPS Precipitable water vapour measurements made in the Swiss Alps. Meteorol Appl 14:15–26CrossRefGoogle Scholar
  29. Nicholson SE (1996) A review of climate dynamics and climate variability in Eastern Africa. The limnology, climatology and paleoclimatology of the East African lakes. Gordon and Breach, Amsterdam, pp 25–56Google Scholar
  30. Sarazin M (1997) Characterisation of the optical properties of atmospheric turbulence: methods for the evaluation of an astronomical site. European Southern Observatory, internal document, 21 November 1997, Garching, Germany (revision of a partial translation from an original French PhD thesis, 1992) (online). Accessed 4 December 2013
  31. Siher EA, Ortolani S, Sarazin MS, Benkhaldoun Z (2004) Correlation between TOMS aerosol index and the astronomical extinction. Proc Int Soc Opt Eng (SPIE) 5489-13, 138–145Google Scholar
  32. Tapia M (1992) Ten years of weather and observing statistics in San Pedro Mártir, Baja California, Mexico. Rev Mex Astron Astrofis 24:179–186Google Scholar
  33. Torres O, Bhartia PK, Herman JR, Sinyuk A, Ginoux P, Holben B (2002) A long term record of aerosol optical thickness from TOMS observations and comparison to AERONET measurements. J Atmos Sci 59:398–413CrossRefGoogle Scholar
  34. Trenberth KE (1984) Signal versus noise in the Southern Oscillation. Mon Weather Rev 112(2):326–332CrossRefGoogle Scholar
  35. UK Meteorological Office UKMO (2012) Limited Area Model for Africa (Africa-LAM), NCAS British Atmospheric Data Centre (online). Accessed 29 October 2014
  36. Uppala SM, Kållberg PW, Simmons AJ, Andrae U, da Costa Bechtold V, Fiorino M, Gibson JK, Haseler J, Hernandez A, Kelly GA, Li X, Onogi K, Saarinen S, Sokka N, Allan RP, Andersson E, Arpe K, Balmaseda MA, Beljaars ACM, van de Berg L, Bidlot J, Bormann N, Caires S, Chevallier F, Dethof A, Dragosavac M, Fisher M, Fuentes M, Hagemann S, Hólm E, Hoskins BJ, Isaksen L, Janssen PAEM, Jenne R, McNally AP, Mahfouf J-F, Morcrette J-J, Rayner NA, Saunders RW, Simon P, Sterl A, Trenberth KE, Untch A, Vasiljevic D, Viterbo P, Woollen J (2005) The ERA-40 re-analysis. Q J R Meteorol Soc 131:2961–3012. doi: 10.1256/qj.04.176 CrossRefGoogle Scholar
  37. Wilks D (2005) Statistical methods in the atmospheric sciences, 2nd edn. International Geophysics. Academic Press, 648ppGoogle Scholar
  38. Yin X, Nicholson S, Ba MB (2000) On the diurnal cycle of cloudiness over Lake Victoria and its influence on evaporation from the lake. Hydrol Sci J 45(3):407–424. doi: 10.1080/02626660009492338 CrossRefGoogle Scholar
  39. Ziad A (2012) Astronomical observations through atmospheric turbulence. Adaptive Optics and the Atmosphere Summer School, Sutherland, South AfricaGoogle Scholar

Copyright information

© Springer-Verlag Wien 2015

Authors and Affiliations

  • Edward Graham
    • 1
    Email author
  • Richard Vaughan
    • 3
  • David A. H. Buckley
    • 2
  • Koi Tirima
    • 4
  1. 1.Lews Castle CollegeUniversity of the Highlands and IslandsStornowayScotland
  2. 2.South African Astronomical ObservatoryCape TownSouth Africa
  3. 3.InCA Nairobi LtdNairobiKenya
  4. 4.Inoorero CentreInoorero UniversityNairobiKenya

Personalised recommendations