• Asnani, G. C., 1993: Tropical Meteorology. Vol. 1. Noble, 603 pp.

  • Atlas, E. L., and B. A. Ridley, 1996: The Mauna Loa observatory photochemistry experiment: Introduction. J. Geophys. Res., 101 , 1453114541.

    • Search Google Scholar
    • Export Citation
  • Brenninkmeijer, C. A. M., 1996: Global Atmosphere Watch adds six new stations. Eos, Trans. Amer. Geophys. Union, 77 , 109.

  • Davies, T. D., P. Brimblecombe, and C. E. Vincent, 1977: The daily cycle of weather on Mount Kenya. Weather, 32 , 406417.

  • Davies, T. D., C. E. Vincent, and P. Brimblecombe, 1979: Condensation nuclei and weather on Mount Kenya. J. Appl. Meteor., 18 , 12391243.

    • Search Google Scholar
    • Export Citation
  • Diab, R. D., A. M. Thompson, K. Mari, L. Ramsay, and G. J. R. Coetzee, 2004: Tropospheric ozone climatology over Irene, South Africa, from 1990 to 1994 and 1998 to 2002. J. Geophys. Res., 109 .D20301, doi:10.1029/2004JD004793.

    • Search Google Scholar
    • Export Citation
  • Findlater, J., 1969a: A major low-level air current near Indian Ocean during northern summer. Quart. J. Roy. Meteor. Soc., 95 , 362380.

    • Search Google Scholar
    • Export Citation
  • Findlater, J., 1969b: Interhemispheric transport of air in lower troposphere over western Indian Ocean. Quart. J. Roy. Meteor. Soc., 95 , 400403.

    • Search Google Scholar
    • Export Citation
  • Forrer, J., R. Ruttimann, D. Schneiter, A. Fischer, B. Buchmann, and P. Hofer, 2000: Variability of trace gases at the high-Alpine site Jungfraujoch caused by meteorological transport processes. J. Geophys. Res., 105 , 1224112251.

    • Search Google Scholar
    • Export Citation
  • Gatebe, C. K., P. D. Tyson, H. Annegarn, S. Piketh, and G. Helas, 1999: A seasonal air transport climatology for Kenya. J. Geophys. Res., 104 , 1423714244.

    • Search Google Scholar
    • Export Citation
  • Henne, S., M. Furger, and A. S. H. Prévôt, 2005: Climatology of mountain venting–induced moisture layers in the lee of the Alps. J. Appl. Meteor., 44 , 620633.

    • Search Google Scholar
    • Export Citation
  • Henne, S., J. Klausen, W. Junkermann, J. M. Kariuki, J. O. Aseyo, and B. Buchmann, 2008: Representativeness and climatology of carbon monoxide and ozone at the global GAW station Mt. Kenya in equatorial Africa. Atmos. Chem. Phys., 8 , 31193139.

    • Search Google Scholar
    • Export Citation
  • Hulme, M., R. Doherty, T. Ngara, M. New, and D. Lister, 2001: African climate change: 1900–2100. Climate Res., 17 , 145168.

  • Leroux, M., 2001: The Meteorology and Climate of Tropical Africa. Springer, 548 pp.

  • Ma, J. Z., J. Tang, X. J. Zhou, and X. S. Zhang, 2002: Estimates of the chemical budget for ozone at Waliguan Observatory. J. Atmos. Chem., 41 , 2148.

    • Search Google Scholar
    • Export Citation
  • Madden, R. A., and P. R. Julian, 1994: Observations of the 40–50-day tropical oscillation—A review. Mon. Wea. Rev., 122 , 814837.

  • Madronich, S., and S. Flocke, 1999: The role of solar radiation in atmospheric chemistry. The Handbook of Environmental Chemistry: Part L Environmental Photochemistry, Vol. 2, P. Boule, Ed., Springer, 1–26.

    • Search Google Scholar
    • Export Citation
  • Mendonca, B. G., 1969: Local wind circulation on the slopes of Mauna Loa. J. Appl. Meteor., 8 , 533541.

  • Nyeki, S., F. Li, E. Weingartner, N. Streit, I. Colbeck, H. W. Gaggeler, and U. Baltensperger, 1998: The background aerosol size distribution in the free troposphere: An analysis of the annual cycle at a high-alpine site. J. Geophys. Res., 103 , 3174931761.

    • Search Google Scholar
    • Export Citation
  • Schnell, R. C., 1978a: Some size and composition characteristics of aerosols at Mount Kenya, East Africa. Bull. Amer. Meteor. Soc., 59 , 1519.

    • Search Google Scholar
    • Export Citation
  • Schnell, R. C., 1978b: Report on the Mount Kenya Baseline Station Feasibility Study. Rep., World Meteorological Organization, 171 pp.

  • Seibert, P., F. Beyrich, S. E. Gryning, S. Joffre, A. Rasmussen, and P. Tercier, 2000: Review and intercomparison of operational methods for the determination of the mixing height. Atmos. Environ., 34 , 10011027.

    • Search Google Scholar
    • Export Citation
  • Singer, I. A., 1967: Steadiness of the wind. J. Appl. Meteor., 6 , 10331038.

  • Slingo, J., H. Spencer, B. Hoskins, P. Berrisford, and E. Black, 2005: The meteorology of the western Indian Ocean, and the influence of the East African highlands. Philos. Trans. Roy. Soc. London, A363 , 2542.

    • Search Google Scholar
    • Export Citation
  • Stohl, A., C. Forster, A. Frank, P. Seibert, and G. Wotawa, 2005: Technical note: The Lagrangian particle dispersion model FLEXPART version 6.2. Atmos. Chem. Phys., 5 , 24612474.

    • Search Google Scholar
    • Export Citation
  • Stull, R. B., 1988: An Introduction to Boundary Layer Meteorology. Kluwer Academic, 666 pp.

  • Thompson, A. M., and Coauthors, 2003: Southern Hemisphere Additional Ozonesondes (SHADOZ) 1998–2000 tropical ozone climatology 1. Comparison with Total Ozone Mapping Spectrometer (TOMS) and ground-based measurements. J. Geophys. Res., 108 .8238, doi:10.1029/2001JD000967.

    • Search Google Scholar
    • Export Citation
  • Thompson, A. M., J. C. Witte, S. J. Oltmans, and F. J. Schmidlin, 2004: SHADOZ—A tropical ozonesonde–radiosonde network for the atmospheric community. Bull. Amer. Meteor. Soc., 85 , 15491564.

    • Search Google Scholar
    • Export Citation
  • Vergeiner, I., and E. Dreiseitl, 1987: Valley winds and slope winds—Observations and elementary thoughts. Meteor. Atmos. Phys., 36 , 264286.

    • Search Google Scholar
    • Export Citation
  • Wang, T., H. L. A. Wong, J. Tang, A. Ding, W. S. Wu, and X. C. Zhang, 2006: On the origin of surface ozone and reactive nitrogen observed at a remote mountain site in the northeastern Qinghai-Tibetan Plateau, western China. J. Geophys. Res., 111 .D08303, doi:10.1029/2005JD006527.

    • Search Google Scholar
    • Export Citation
  • Whiteman, C. D., 1990: Observation of thermally developed wind systems in mountainous terrain. Atmospheric Processes over Complex Terrain, W. Blumen, Ed., Amer. Meteor. Soc., 5–42.

    • Search Google Scholar
    • Export Citation
  • Whittlestone, S., S. D. Schery, and Y. Li, 1996: Pb-212 as a tracer for local influence on air samples at Mauna Loa Observatory, Hawaii. J. Geophys. Res., 101 , 1477714785.

    • Search Google Scholar
    • Export Citation
  • World Meteorological Organization, 2001: Global Atmosphere Watch measurements guide. GAW Rep. 143/WMO Tech. Doc. 1073, 84 pp. [Available online at http://www.wmo.int/pages/prog/arep/gaw/documents/gaw143.pdf.].

  • World Meteorological Organization, 2007: WMO Global Atmosphere Watch (GAW) strategic plan: 2008–2015—A contribution to the implementation of the WMO strategic plan: 2008–2011. GAW Rep. 172/WMO Tech. Doc. 1384, 62 pp. [Available online at http://www.wmo.int/pages/prog/arep/gaw/documents/gaw172-26sept07.pdf.].

  • Zellweger, C., J. Forrer, P. Hofer, S. Nyeki, B. Schwarzenbach, E. Weingartner, M. Ammann, and U. Baltensperger, 2003: Partitioning of reactive nitrogen (NOy) and dependence on meteorological conditions in the lower free troposphere. Atmos. Chem. Phys., 3 , 779796.

    • Search Google Scholar
    • Export Citation
All Time Past Year Past 30 Days
Abstract Views 0 0 0
Full Text Views 363 199 5
PDF Downloads 222 115 7

Mount Kenya Global Atmosphere Watch Station (MKN): Installation and Meteorological Characterization

View More View Less
  • 1 Swiss Federal Institute for Materials Science and Technology (Empa), Dübendorf, Switzerland
  • | 2 Forschungszentrum Karlsruhe, Institut für Meteorologie und Klimaforschung IFU, Garmisch-Partenkirchen, Germany
  • | 3 Kenya Meteorological Department, Nairobi, Kenya
  • | 4 Swiss Federal Institute for Materials Science and Technology (Empa), Dübendorf, Switzerland
Restricted access

Abstract

The meteorological conditions at the Mount Kenya (station identifier MKN) tropical Global Atmosphere Watch Programme station are described. Like other stations in mountainous terrain, the site experiences thermally induced wind systems that disturb free tropospheric conditions. Therefore, the adequacy of the site for long-term background atmospheric composition measurements needs to be evaluated. Meteorological parameters for the period June 2002–June 2006 were analyzed, focusing on the development of thermally induced wind systems and boundary layer influence. Filters based on the local wind and day–night differences in specific humidity were developed for selection of times representative of undisturbed free tropospheric conditions. In addition, the convective boundary layer depth was evaluated. Throughout the whole year the station is influenced by thermally induced wind systems and the atmospheric boundary layer. The filters distinguished between thermally and synoptically influenced days. Thermally influenced days (86%) dominated. However, maxima in specific humidity were also reached in the afternoon on synoptically influenced days and were attributed to mixing in the convective boundary layer. During nighttime, downslope wind dominated that carries undisturbed free tropospheric air masses. Nevertheless, during 24% of all nights the specific humidity was also elevated, possibly indicating the presence of residual layers. It is recommended that nighttime data only (2100–0400 UTC) be used for analysis of long-term trends of the free tropospheric background while the remaining data can be used to characterize composition and trends of the regional atmospheric boundary layer. Further exclusion of apparent pollution events and residual layer influence should be considered. With these constraints, the Mount Kenya Global Atmosphere Watch site is adequate for the study of trends and budgets of background atmospheric composition.

Corresponding author address: Dr. Stephan Henne, Laboratory for Air Pollution/Environmental Technology, Swiss Federal Institute for Materials Science and Technology (Empa), 8600 Dübendorf, Switzerland. Email: stephan.henne@empa.ch

Abstract

The meteorological conditions at the Mount Kenya (station identifier MKN) tropical Global Atmosphere Watch Programme station are described. Like other stations in mountainous terrain, the site experiences thermally induced wind systems that disturb free tropospheric conditions. Therefore, the adequacy of the site for long-term background atmospheric composition measurements needs to be evaluated. Meteorological parameters for the period June 2002–June 2006 were analyzed, focusing on the development of thermally induced wind systems and boundary layer influence. Filters based on the local wind and day–night differences in specific humidity were developed for selection of times representative of undisturbed free tropospheric conditions. In addition, the convective boundary layer depth was evaluated. Throughout the whole year the station is influenced by thermally induced wind systems and the atmospheric boundary layer. The filters distinguished between thermally and synoptically influenced days. Thermally influenced days (86%) dominated. However, maxima in specific humidity were also reached in the afternoon on synoptically influenced days and were attributed to mixing in the convective boundary layer. During nighttime, downslope wind dominated that carries undisturbed free tropospheric air masses. Nevertheless, during 24% of all nights the specific humidity was also elevated, possibly indicating the presence of residual layers. It is recommended that nighttime data only (2100–0400 UTC) be used for analysis of long-term trends of the free tropospheric background while the remaining data can be used to characterize composition and trends of the regional atmospheric boundary layer. Further exclusion of apparent pollution events and residual layer influence should be considered. With these constraints, the Mount Kenya Global Atmosphere Watch site is adequate for the study of trends and budgets of background atmospheric composition.

Corresponding author address: Dr. Stephan Henne, Laboratory for Air Pollution/Environmental Technology, Swiss Federal Institute for Materials Science and Technology (Empa), 8600 Dübendorf, Switzerland. Email: stephan.henne@empa.ch

Save