• Anyah, R. O., 2005: Modeling the variability of the climate system over Lake Victoria Basin. Ph.D. dissertation, North Carolina State University, 287 pp. [Available online at http://www.lib.ncsu.edu/theses/available/etd-07202005-123806/.].

  • Anyah, R. O., , and F. H. M. Semazzi, 2004: Simulation of the response of Lake Victoria basin climate to lake surface temperatures. Theor. Appl. Climatol., 79 , 5569.

    • Search Google Scholar
    • Export Citation
  • Anyamba, E. K., 1984: Some aspects of the origin of rainfall deficiency in East Africa. Proc. Regional Scientific Conf. on GATE, WAMEX and Tropical Meteorology, Dakar, Senegal, WMO, 110–112.

  • Asnani, G. C., 1993: Tropical Meteorology. Vols. 1 and 2. Indian Institute of Tropical Meteorology, 1012 pp.

  • Ba, M. B., , and S. E. Nicholson, 1998: Analysis of convective activity and its relationship to rainfall over the Rift Valley Lakes of East Africa during 1983–90 using the meteosat infrared channel. J. Appl. Meteor., 37 , 12501264.

    • Search Google Scholar
    • Export Citation
  • Blumberg, A. F., , and G. L. Mellor, 1987: A description of a three-dimensional coastal ocean model. Three-Dimensional Coastal Ocean Models, N. Heaps, Ed., Amer. Geophys. Union, 1–16.

    • Search Google Scholar
    • Export Citation
  • Datta, R. R., 1981: Certain aspects of monsoonal precipitation dynamics over Lake Victoria. Monsoon Dynamics, J. Lighthill and R. P. Pearce, Eds., Cambridge University Press, 333–349.

    • Search Google Scholar
    • Export Citation
  • Dickinson, R. E., , A. Henderson-Sellers, , and P. J. Kennedy, 1993: Biosphere–Atmosphere Transfer Scheme (BATS) version 1e as coupled to the NCAR Community Model. NCAR Tech. Note NCAR/TN-387+STR, 72 pp.

  • Fraedrich, K., 1972: A simple climatological model of the dynamics and energetics of the nocturnal circulation at Lake Victoria. Quart. J. Roy. Meteor. Soc., 98 , 332335.

    • Search Google Scholar
    • Export Citation
  • Giorgi, F., , M. R. Marinucci, , and G. T. Bates, 1993a: Development of a second-generation regional climate model (RegCM2). Part I: Boundary-layer and radiative transfer processes. Mon. Wea. Rev., 121 , 27942813.

    • Search Google Scholar
    • Export Citation
  • Giorgi, F., , M. R. Marinucci, , G. T. Bates, , and G. De Canio, 1993b: Development of a second-generation regional climate model (RegCM2). Part II: Convective processes and assimilation of lateral boundary conditions. Mon. Wea. Rev., 121 , 28142832.

    • Search Google Scholar
    • Export Citation
  • Hostetler, S., , and F. Giorgi, 1992: Use of a regional atmospheric model to simulate lake-atmosphere feedbacks associated with Pleistocene Lakes Lahontan and Bonnevile. Climate Dyn., 7 , 3944.

    • Search Google Scholar
    • Export Citation
  • Hostetler, S., , G. T. Bates, , and F. Giorgi, 1993: Interactive nesting of a lake thermal model within a regional climate model for climate studies. J. Geophys. Res., 98 , 50455057.

    • Search Google Scholar
    • Export Citation
  • Kalnay, E., and Coauthors, 1996: The NCEP/NCAR 40-Year Reanalysis Project. Bull. Amer. Meteor. Soc., 77 , 437471.

  • Kiehl, J. T., , J. J. Hack, , G. B. Bonan, , B. A. Boville, , B. P. Briegleb, , D. L. Williamson, , and P. J. Rasch, 1996: Description of the NCAR Community Climate Model (CCM3). NCAR Tech. Note NCAR/TN-420+STR, 152 pp.

  • Kummerow, C., and Coauthors, 2000: The status of the Tropical Rainfall Measuring Mission (TRMM) after two years in orbit. J. Appl. Meteor., 39 , 19651982.

    • Search Google Scholar
    • Export Citation
  • Laird, N. F., , D. A. R. Kristovich, , and J. E. Walsh, 2003a: Idealized model simulations examining the mesoscale structure of winter lake-effect circulations. Mon. Wea. Rev., 131 , 206221.

    • Search Google Scholar
    • Export Citation
  • Laird, N. F., , J. E. Walsh, , and D. A. R. Kristovich, 2003b: Model simulations examining the relationships of lake-effect morphology to lake shape, wind direction, and wind speed. Mon. Wea. Rev., 131 , 21022111.

    • Search Google Scholar
    • Export Citation
  • McPherson, R. D., 1970: A numerical study of the effect of a coastal irregularity on a sea breeze. J. Appl. Meteor., 9 , 767777.

  • Mellor, G. L., 1991: An equation of state for numerical models of oceans and estuaries. J. Atmos. Oceanic Technol., 8 , 609611.

  • Mellor, G. L., , and T. Yamada, 1974: A hierarchy of turbulence closure models for planetary boundary layers. J. Atmos. Sci., 31 , 17911806.

    • Search Google Scholar
    • Export Citation
  • Mistry, V. V., , and D. Conway, 2003: Remote forcing of East African rainfall and relationships with fluctuations in levels of Lake Victoria. Int. J. Climatol., 23 , 6789.

    • Search Google Scholar
    • Export Citation
  • Mukabana, J. R., , and R. A. Pielke, 1996: Investigating the influence of synoptic-scale monsoonal winds and mesoscale circulations on diurnal weather patterns over Kenya using a mesoscale numerical model. Mon. Wea. Rev., 124 , 224244.

    • Search Google Scholar
    • Export Citation
  • Mutai, C. C., , and M. N. Ward, 2000: East African rainfall and the tropical circulation/convection on intraseasonal to interannual time scales. J. Climate, 13 , 39153939.

    • Search Google Scholar
    • Export Citation
  • Nicholson, S. E., 1996: A review of climate dynamics and climate variability in eastern Africa. The Limnology, Climatology and Paleoclimatology of the East African Lakes, T. C. Johnson and E. Odada, Eds., Gordon and Breach, 25–56.

    • Search Google Scholar
    • Export Citation
  • Nicholson, S. E., 1998: Historical fluctuations of Lake Victoria and other lakes in the northern Rift Valley of East Africa. Environmental Change and Response in East African Lakes, J. T. Lehman, Ed., Kluwer, 7–35.

    • Search Google Scholar
    • Export Citation
  • Ogallo, L. A., 1988: Relationship between seasonal rainfall in East Africa and Southern Oscillation. Int. J. Climatol., 8 , 3143.

  • Okeyo, A. E., 1987: The influence of Lake Victoria on the convective activities over the Kenya Highlands. J. Meteor. Soc. Japan, 65 , 689695.

    • Search Google Scholar
    • Export Citation
  • Pal, J. S., , E. E. Small, , and E. A. B. Eltahir, 2000: Simulation of regional-scale energy and water budgets: Representation of sub-grid scale cloud and precipitation processes in RegCM. J. Geophys. Res., 105 , 2957929594.

    • Search Google Scholar
    • Export Citation
  • Saji, N. H., , B. N. Goswami, , P. N. Vinayachandran, , and T. Yamagata, 1999: A dipole mode in the tropical Indian Ocean. Nature, 401 , 360363.

    • Search Google Scholar
    • Export Citation
  • Song, Y., , F. H. M. Semazzi, , and L. Xie, 2002: Development of a coupled regional climate simulation model for the Lake Victoria Basin. The East African Great Lakes, Limnology, Paleolimnology and Biodiversity, E. Odada and G. Olago, Eds., Gordon and Breach, 141–154.

    • Search Google Scholar
    • Export Citation
  • Song, Y., , F. H. M. Semazzi, , L. Xie, , and L. J. Ogallo, 2004: A coupled regional climate model for Lake Victoria basin of East Africa. Int. J. Climatol., 24 , 5775.

    • Search Google Scholar
    • Export Citation
  • Sun, L., , F. H. M. Semazzi, , F. Giorgi, , and L. A. Ogallo, 1999a: Application of the NCAR Regional Climate model to Eastern Africa. Part 1: Simulation of the short rains of 1988. J. Geophys. Res., 104 , 65296548.

    • Search Google Scholar
    • Export Citation
  • Sun, L., , F. H. M. Semazzi, , F. Giorgi, , and L. A. Ogallo, 1999b: Application of the NCAR Regional Climate model to Eastern Africa. Part 2: Simulation of interannual variability of short rains. J. Geophys. Res., 104 , 65496562.

    • Search Google Scholar
    • Export Citation
  • Sundqvist, H., , E. Berge, , and J. E. Krisjansson, 1989: Condensation and cloud parameterization studies with a mesoscale numerical weather prediction model. Mon. Wea. Rev., 117 , 16411657.

    • Search Google Scholar
    • Export Citation
All Time Past Year Past 30 Days
Abstract Views 0 0 0
Full Text Views 113 113 20
PDF Downloads 106 106 17

Simulated Physical Mechanisms Associated with Climate Variability over Lake Victoria Basin in East Africa

View More View Less
  • 1 Center for Environmental Prediction, Department of Environmental Sciences, Rutgers, The State University of New Jersey, New Brunswick, New Jersey
  • | 2 Department of Marine, Earth and Atmospheric Sciences, and Department of Mathematics, North Carolina State University, Raleigh, North Carolina
  • | 3 Department of Marine, Earth and Atmospheric Sciences, North Carolina State University, Raleigh, North Carolina
© Get Permissions
Restricted access

Abstract

A fully coupled regional climate, 3D lake modeling system is used to investigate the physical mechanisms associated with the multiscale variability of the Lake Victoria basin climate. To examine the relative influence of different processes on the lake basin climate, a suite of model experiments were performed by smoothing topography around the lake basin, altering lake surface characteristics, and reducing or increasing the amount of large-scale moisture advected into the lake region through the four lateral boundaries of the model domain. Simulated monthly mean rainfall over the basin is comparable to the satellite (Tropical Rainfall Measuring Mission) estimates. Peaks between midnight and early morning hours characterize the simulated diurnal variability of rainfall over the four quadrants of the lake, consistent with satellite estimates, although the simulated peaks occur a little earlier. It is evident in the simulations with smoothed topography that the upslope/downslope flow generated by the mountains east of the lake and the land–lake breeze circulations play important roles in influencing the intensity, the location of lake/land breeze fronts, and the horizontal extent of the land–lake breeze circulation, as well as lake basin precipitation. When the lake surface is replaced with marsh (water hyacinth), the late night and early morning rainfall maximum located over the western sector of the lake is dramatically reduced. Our simulations also indicate that large-scale moisture transported via the prevailing easterly trades enhances lake basin precipitation significantly. This is in contrast to the notion advanced in some of the previous studies that Lake Victoria generates its own climate (rainfall) through precipitation–evaporation–reprecipitation recycling only.

Corresponding author address: Dr. Richard Anyah, Center for Environmental Prediction, Department of Environmental Sciences, Rutgers, The State University of New Jersey, New Brunswick, NJ 08901. Email: anyah@cep.rutgers.edu

Abstract

A fully coupled regional climate, 3D lake modeling system is used to investigate the physical mechanisms associated with the multiscale variability of the Lake Victoria basin climate. To examine the relative influence of different processes on the lake basin climate, a suite of model experiments were performed by smoothing topography around the lake basin, altering lake surface characteristics, and reducing or increasing the amount of large-scale moisture advected into the lake region through the four lateral boundaries of the model domain. Simulated monthly mean rainfall over the basin is comparable to the satellite (Tropical Rainfall Measuring Mission) estimates. Peaks between midnight and early morning hours characterize the simulated diurnal variability of rainfall over the four quadrants of the lake, consistent with satellite estimates, although the simulated peaks occur a little earlier. It is evident in the simulations with smoothed topography that the upslope/downslope flow generated by the mountains east of the lake and the land–lake breeze circulations play important roles in influencing the intensity, the location of lake/land breeze fronts, and the horizontal extent of the land–lake breeze circulation, as well as lake basin precipitation. When the lake surface is replaced with marsh (water hyacinth), the late night and early morning rainfall maximum located over the western sector of the lake is dramatically reduced. Our simulations also indicate that large-scale moisture transported via the prevailing easterly trades enhances lake basin precipitation significantly. This is in contrast to the notion advanced in some of the previous studies that Lake Victoria generates its own climate (rainfall) through precipitation–evaporation–reprecipitation recycling only.

Corresponding author address: Dr. Richard Anyah, Center for Environmental Prediction, Department of Environmental Sciences, Rutgers, The State University of New Jersey, New Brunswick, NJ 08901. Email: anyah@cep.rutgers.edu

Save