Browsing by Author "Kelonye, Festus Beru"

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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.
Long-Term Assessment of the Spatial Temporal Trends in Selected Cloud Physical Properties over the Three Distinct Sites in Kenya
(Open Access Library Journal, 2022-12-30) Makokha, Sostine N.; Makokha, John Wanjala; Kelonye, Festus Beru
The presence of clouds in the Earth’s atmosphere plays a pivotal role in regulating the Earth’s energy budget. Increased anthropogenic activities and emissions can significantly lead to changes in cloud composition and cloud structure affecting the clouds physical characteristics, hence causing alterations in the climatic conditions over Kenya. Given this, the present study examined the spatial temporal physical properties of clouds over three study sites, by paying a special consideration on cloud parameters, such as: Cloud Effective Radius (CER), Cloud Top Pressure (CTP), Cloud Top Temperature (CTT) and the Cloud Fraction (CF). These cloud parameters were retrieved from the MODerate resolution Imaging Spectroradiometer (MODIS) sensor and the Modern Era Retrospective analysis for Research and Applications, version 2 (MERRA-2) model between January 2005 and December 2020. The data retrieved on clouds physical properties was utilized to estimate the trends and spatial variations and assess their statistical significance on climate over the study domain. The Spatial patterns of seasonal mean of cloud parameters from the sensors and the model were generally characterized with positive and negative trends over Kenya observed during the four seasons. Trends in CER were found as follows: Nairobi (0.04, 0, −0.04 and −0.01) for the four seasons respectively, Malindi (0.04, 0.01, 0.04 and 0.01) and lastly Mbita (−0.06, −0.06, 0.04 and −0.05); for CTT, Nairobi, −0.1, −0.2, −0.1 and −0.2, Malindi, 0.1, −0.2, 0.1 and 0.05 and Mbita, 0.2, 0.2, −0.2 and 0.15 respectively for every season. Trends in CTP were observed to vary seasonally as follows: Nairobi −0.5, −1, 0.5 and −0.5, Malindi −0.5, −3, 1, and 0.5 and lastly Mbita 0.5, 0, −1 and −1 respectively. And finally, the spatial trends in CF observed over the four seasons over the study domains were obtained a follows: Nairobi (0.3, 0, -0.002 and 0), Malindi (0.3, 0.002, 0 and 0.001) and lastly for Mbita (0.3, 0.003, 0.001 and 0.001) respectively for the four seasons of the study. Spatial trends in the selected cloud properties were determined and observed to vary both seasonally and regionally. The study revealed patterns of trends in physical cloud properties and formed a basis for further research on clouds over Kenya.
Projected rainfall and temperature changes over Bungoma County in western kenya by the year 2050 based on PRECIS modeling system
(Ajol: Ethiopian Journal of Environmental Studies & Management, 2016-06-19) shem, Godfrey Juma; Kelonye, Festus Beru
This study investigated projected changes in rainfall and temperature over Bungoma County by the year 2050 based on the Intergovernmental Panel on Climate Change (IPCC) Special Report on Emission Scenarios (SRES) A1B and A2B emission Scenarios (IPCC, 2007) using the Providing Regional Climates for Impacts Studies (PRECIS); (Giorgi, 2007). The PRECIS regional Climate Model (Hadley RM3P) was configured in 0.22°×0.22° horizontal grid resolution was forced at the lateral boundaries by the UKMO-HadAM3P and UKMOHadCM3 global Models. The future projection of temperature indicates warming over Bungoma County by the year 2050 coupled with reduced precipitation. Time series analysis revealed a cyclic and seasonal trend in rainfall and temperature over the area of study. Temporal characteristics revealed a warmer and colder September-October-November (SON) season under A1B and A2B scenarios respectively. The results also revealed increasing temperatures and reducing rainfall across all seasons under both scenarios except in March-April-May (MAM) season where rainfall amounts increased and temperature reduced. A two paired t-test for the two climate variables revealed a ρ value of less than 0.05 (ρ<0.05) suggesting a statistically significant relationship between each pair of the two variables. The study recommends further evaluation of the model performance in simulating the present day climate over the area of study.
Spatial-Temporal Assessment of Changes in Aerosol Optical Properties Pre, during, and Post COVID-19 Lockdowns over Kenya, East Africa
(Open Access Library Journal, 2024-04-26) Mutama, Peter M.; Makokha, John Wanjala; Kelonye, Festus Beru; Khamala, Geoffrey W.
In reference to the contribution of natural and anthropogenic activities to pollution levels over Kenya, investigation of the changes in aerosol optical properties during COVID-19 lockdowns was assessed. To achieve its objective the present study used aerosol Optical Depth (AOD), Angstrom exponent (AE) and Single Scattering Albedo (SSA) from Ozone Monitoring Instrument (OMI) and Moderate-resolution Imaging Spectroradiometer (MODIS) satellite sensors, to analyze the variations in aerosol properties for pre, during and post COVID-19 pandemic. This was achieved by doing a phase wise analysis of the spatial-temporal variation over Kenya during the lockdown phase. A comparison to reference period was done for the pre-lockdown, during lockdown and post lockdown phases. 24-hour mean value data retrieval over Kenya was obtained from the Modern-Era Retrospective analysis for Research and Applications (MERRA-2) model from 1st April to 30th June 2019 - 2021. It was evident that the emissions into the atmosphere over Kenya did not reduce relatively during the COVID-19 lockdowns. The spatial-temporal variability of the pollutants (AOD, AE AND SSA) did not depict a significant deviation from the normal in the lockdown phase as compared to the same season in the previous one year and a year after lockdowns. This was because of the migration of aerosols from regional sources, dominance of natural sources such as geothermal activities and low stringent levels on lockdown protocols. However meteorological factors have had great influence on the variability and seasonality of the aerosol optical properties over the sampled region, with the March-April-May (wet season) recording lower values of AOD and June-July-August (dry season) registering the highest values of AOD. In summary lockdowns did not alter values of aerosol optical properties over Kenya due to limited control of anthropogenic emissions. The findings of this proposed study can be utilized by the scientific community and regulators to strengthen the emergency response to check on high pollution in Kenya until cleaner technologies are put in place.