Browsing by Author "Shem, Godfrey Juma"

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    Hybrid single particle simulation of atmospheric pollutants over Bungoma County in Kenya
    (Ethiopian Journal of Environmental Studies and Management (EJESM), 2018-12-20) Shem, Godfrey Juma; Makokha, John Wanjala; Kelonye, Festus Beru
    Microscale dispersion models with different levels of complexity may be used to assess urban air quality and support decision making for pollution control. Mathematical models calculate pollutant concentrations by solving either analytically a simplified set of parametric equations or numerically a set of differential equations that describe in detail wind flow and pollutant dispersion. Air pollution has been evident at Webuye town in Bungoma Kenya and this may be attributable to the current and residual effect of the pan paper and heavy chemical processing plants. A Lagrangian trajectory modeling system for urban air pollution was used to model the flow of atmospheric pollutants in Bungoma County with emphasis to Webuye, an industrial town within the County. Results of the study reveal that pollutants from the area of study exhibit a seasonal dispersion trend over Lake Victoria and surroundings to the Eastern part of Uganda. An investigation of factors that influence this trend is recommended.
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    Long term assessment of aerosol radiative forcing over selected sites of East Africa
    (Scientific Research Publishing Inc., 2018-04-02) Makokha, John W.; Odhiambo, Jared O.; Shem, Godfrey Juma
    Atmospheric aerosols have contributed to radiative forcing through direct and indirect mechanisms. Aerosol effects are important in computing radiative forcing estimates for the past, current and future climate. In this study, a comprehensive assessment of regional aerosol radiative forcing, Optical Properties of Aerosol and Clouds (OPAC) model (wavelength range of 0.25 - 4.0 μm) over selected sites in East Africa was done. Aerosol optical properties constituted the inputs of a Radiative Transfer Model (RTM). Optical properties investigated included Aerosol Optical Depth (AOD), Single Scattering Albedo (SSA) and Asymmetry Parameter (AP). Aerosol Radiative Forcing (ARF) during the study period at the surface (SFC), top of the atmosphere (TOA) and the atmosphere (ATM) was estimated to be –18.4 ± 1.4 W∙m−2 , +1.1 ± 0.3 W∙m−2 and +19.5 ± 2.5 W∙m−2 , respectively. This corresponds to an increment in net atmospheric forcing at a heating rate of about 0.55 ± 0.05 K/day (0.41 ± 0.03 to 0.78 ± 0.03 K/day) in the lower troposphere. The study points out the significant role played by atmospheric aerosols in climate modification over the area of study. It is recommended that a further assessment be done in view of uncertainties that may impact on the findings and which were not within the scope of this research.