Fredrick Karanja | University of Nairobi, Kenya (original) (raw)

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Papers by Fredrick Karanja

Boundary-Layer Meteorology, 1989

Ground-based flux measurements of carbon dioxide and water vapor integrate physiological processe... more Ground-based flux measurements of carbon dioxide and water vapor integrate physiological processes taking place on a field scale. Aircraft flux measurements have recently been undertaken to attempt to widen the scope of applicability of such measurements. However, because of the intermittency of turbulent transfer, flux measurements must be averaged over long periods of time or long distances to give reproducible

University of Nairobi, 2006

The Policy Research Working Paper Series disseminates the findings of work in progress to encoura... more The Policy Research Working Paper Series disseminates the findings of work in progress to encourage the exchange of ideas about development issues. An objective of the series is to get the findings out quickly, even if the presentations are less than fully polished. The papers carry the names of the authors and should be cited accordingly. The findings, interpretations, and conclusions expressed in this paper are entirely those of the authors. They do not necessarily represent the views of the International Bank for Reconstruction and Development/World Bank and its affiliated organizations, or those of the Executive Directors of the World Bank or the governments they represent.

The importance of historical rainfall pattern in gaining a sound understanding of climate change ... more The importance of historical rainfall pattern in gaining a sound understanding of climate change in any particular region is paramount. This study investigated rainfall variability at Wiyumiririe location of Ngobit ward, Laikipia County Kenya. The study sought to gain insight into rainfall variability, intensity, and frequency of droughts and wet periods as a pointer to the distribution, reliability and total amount of rainfall received both for the long and short growing seasons. The study relied on historical rainfall data derived from the nearby Lamuria weather station (code: 9036213; 0o08’S 36o 52’E) operated by the Water Management Authority (WMA) for Kenya Meteorological Department (KMD), for the period between January 1958 and December 2017. The choice of the weather station was based on the fact that it was the only one of its kind within a radius of 100 kms from the study site and in the same Agro Climatic Zone V. Moreover, it contained credible historical weather data. ...

Proceedings of the Fourth Kenya Meteorological …, 1999

International Journal of Agriculture & Environmental Science

Bonorowo Wetlands

Wambui MB, Opere A, Githaiga MJ, Karanja FK. 2017. Assessing the impacts of climate variability a... more Wambui MB, Opere A, Githaiga MJ, Karanja FK. 2017. Assessing the impacts of climate variability and climate change on biodiversity in Lake Nakuru, Kenya. Bonorowo Wetlands 1: 13-24. This study evaluates the impacts of the raised water levels and the flooding of Lake Nakuru and its surrounding areas on biodiversity, specifically, the phytoplankton and lesser flamingo communities, due to climate change and climate variability. The study was to review and analyze noticed climatic records from 2000 to 2014. Several methods were used to ascertain the past and current trends of climatic parameters (temperature, rainfall and evaporation), and also the physicochemical characteristics of Lake Nakuru (conductivity, phytoplankton, lesser flamingos and the lake depth). These included time series analysis, and trend analysis, so the Pearson’s correlation analysis was used to show a relationship between the alterations in lake conductivity to alterations in population estimates of the lesser flam...

Advances in Agricultural Sciences, 2018

Climate variability and change are among the greatest hindrance to the realization of the Rio +20... more Climate variability and change are among the greatest hindrance to the realization of the Rio +20 declaration addressed by Sustainable Development Goals (SDGs), the New Partnership for Africa's Development (NEPAD's) Initiatives on "Food for All" and the planned Kenyan vision 2030 of transforming Kenya to self-reliance in food production since it directly influences agricultural production and community livelihoods. Knowledge of climate variability is currently of remarkable importance in Kenya, where agriculture is the driver of its economy contributing approximately 26 % of the Gross Domestic Product. This study investigated the extent of the temporal variability and trends of rainfall, temperature and their effect on crop production for the period (1981 to 2013) in Machakos County, Kenya. The findings show that the March to May (MAM) season is characterized by high variations seasonal rainfall compared to the October to December (OND) season in the study area, b...

Sustainable Food Production, Nov 1, 2018

Reduced agricultural production and food security continues to be pressing problems for the large... more Reduced agricultural production and food security continues to be pressing problems for the larger part of smallholder famers in Sub-Saharan Africa (SSA), as well as semi-arid Eastern Kenya. The main objective of this study was to assess the potential impacts of climate change on rain-fed sorghum production in the semi-arid environment of Machakos County. The APSIM model was calibrated and evaluated using field experimental data obtained from a two-year experiment (2014 to 2015) of sorghum parameters carried out at Kenya Agricultural and Livestock Research Organization (KALRO) in Katumani. The baseline simulation was based on daily observed climate data for the period 1976 to 2005. The future climate simulations data were derived by perturbing the observed climate data using deltas for the three GCMs and ensemble and were refered to Representative Concentration Pathways (RCPs): RCP 4.5 and RCP 8.5. Each GCMs and the ensemble and the two RCPs were run for three future periods (2010-2039, 2040-2069 and 2070-2099), thus 24 future simulations were run and compared to baseline simulations. Impact of climate change is projected to be more on sorghum under RCP8.5 than RCP4.5. Across all the GCMs projected mean changes on phenological dates (days to 50% flowering and physiological maturity) showed a consistent decline for both sorghum varieties during the long and short growing seasons with the application of different rates of fertilizer. These trends were more manifested in the RCP8.5 than RCP4.5 and in the end century (2071-2100) of the simulation. With the RCP8.5 flowering dates reduced by 24 and 28 days and the crop cycle duration shrinked by 35 and 38 days in the end century (2071-2100) for gadam and seredo, respectively. There was slight increase or decrease in biomass for both varieties under climate change with no fertilizer application. However, with application of 50kgha-1 N, there was a slight increase of biomass. It has been noted that under changing climate sorghum grain yields will constantly increase for both cultivars over the three future time periods with almost 85.3% increase as we approach the end of the century (2070-2099). The extent of yield change was higher for seredo than for gadam. APSIM model was capable of simulating the response of sorghum to climate change and, on the basis of the results obtained; some adaptation strategies could be proposed, such as: modifications of sowing dates or plant populations.

This research thesis attempts to determine the effects of climate variability and/or change on fo... more This research thesis attempts to determine the effects of climate variability and/or change on food utilization at the household level. Food utilization is one of the major pillars of food security. However, this pillar has so far received little attention from global research work. About 70% of the global research work on food security focuses mainly on availability and access pillars. In carrying out this work, the first tusk was to demonstrate that indeed climate change is taking place in Mwingi region of Kitui County manifesting itself in form of increasing trend of extreme climate events in form of drought. The second task was to investigate the influence of drought on household diets whereby two indicators were used for analysis i.e. Food Consumption Score (FCS) and Micro nutrient Intake (MNI).
.Examination of secondary climate data was used to demonstrate how Mwingi region is experiencing climate change and/or variability over the last 30 years. Data was also collected from the field through administration of household questionnaires to track household food consumption patterns for a period of seven days.
One of the key finding is that Mwingi region has been experiencing mild to severe drought events for the last 30 years. Majority of the households (over 70%) do not meet acceptable food consumption thresholds. This therefore implies that most of the population could be lacking important micronutrients needed for a healthy active life with the vulnerable population of children and women bearing the highest risk.
As a result of presence of climate change and/or variability, appropriate livelihood based intervention measures have been recommended with the intention of improving the overall food security situation in the County. This will ensure that incidents of malnutrition and disease prevalence associated with poor food utilization are minimized in the County of Kitui and the entire ASAL regions of Kenya.

Understanding the Earth System, 2001

The pilot quantified the socio-economic benefits of the meteorological information and services p... more The pilot quantified the socio-economic benefits of the meteorological information and services provided to the maize producers in two counties in Kenya using a Cost-Benefit Ratio (CBR) technique. The analysis indicated that the project posted an overall profit of 39% in Machakos county and 110% in Nakuru county. At the plot level, the Cost-Benefit Ratio values, representing the benefit of using weather information and services, were 1.64 for Machakos and 2.38 for Nakuru. This, in effect, indicates that for every shilling (Sh) invested, a return on investment of between Sh. 1.6 and 2.4 could be realized in maize farming in the study areas, implying that the use of weather information was beneficial to the project farmers. Studies in other countries have shown that the cost-benefit ratio of a national meteorological service is around 1:4 to 1:6. These results clearly indicate that there are socioeconomic benefits derived from using meteorological information and services in the agric...