College of Biological and Physical Sciences

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The aim of this study was to determine suitability zones of future banana growth under a changing climate to guide the design of future adaptation options in the banana sub-sector of Uganda. The study used high resolution (~1 km) data on combined bioclimatic variables (rainfall and temperature) to map suitability zones of the banana crop while the Providing Regional Climate for Impacts Studies (PRECIS) regional climate model temperature simulations were used to estimate the effect of rising temperature on banana growth assuming other factors constant. The downscaled future climate projections were based on the Intergovernmental Panel on Climate Change (IPCC) Representative Concentration Pathways (RCPs, 2.6, 4.5, 6.0 and 8.5) and Special Report on Emission Scenarios (SRES, A1B and A2) across the period 2011–2090. The methodology involved identification of banana-climate growth thresholds and developing suitability indices for banana production under the high mitigation (RCP 2.6, less adaptation), medium mitigation (RCP 4.5 and RCP 6.0, medium adaptation), no mitigation (RCP 8.5, very high adaptation) scenarios, SRES A1B and A2 scenarios. The FAO ECO-Crop tool was used to determine and map future suitability of banana growth. Banana production indices were determined using a suitability model in the Geographical Information System (GIS) spatial analyst tool. The non-linear banana-temperature regression model was used to assess the impact of future changes in temperature on banana growth. The results revealed unique and distinct banana production suitability and growth patterns for each climate scenario in the sub-periods. RCPs 2.6 and 6.5 are likely to be associated with higher levels of banana production than RCPs 4.5 and 8.5. The results further showed that projected temperature increase under SRES A1B will promote banana growth. In contrast, expected increases in temperatures under SRES A2 are likely to retard banana growth due to high moisture deficits. There is need to develop adaptation option for farming communities to maximize their agricultural production and incomes. The effectiveness of adaptation options needed to combat the impacts will be influenced by the magnitude of the expected climatic changes associated with each scenario, the timing of expected climate change extremes and sensitivity of the crop to climate. This study has provided critical information that will be useful for planning integrated adaptation practices in the banana farming subsector to promote productivity.

This study examined the spatial and temporal variability of the onset and cessation of long rains (MAM). The daily rainfall data used in the study was obtained from the Kenya Meteorological Department (KMD. Both graphical and statistical methods were applied in the analyses. Most of the stations indicated the onset month to be March. However, a few stations indicated February as their onset month while a few others had April as the onset month. Further analysis indicated a link between performance of the seasonal rainfall and the onset date. Thus positive (negative) rainfall anomaly was associated with early (late) onset. The results from the analysis showed that over most stations, the mean onset is the 74th day (14th march) with an average standard deviation of 24 days.

The mean cessation day was day 150 (29th of May) with an average standard deviation of 21 days.
The highest variability was observed in dry areas.
The study showed that over most parts of the country there is very high likelihood of below normal rainfall when the onset is late. However, over the north western part of the country (region 1) which receive it seasonal rainfall over a short period, the rainfall performance may not be affected by the late the onset It was also noted that over most regions there is high chances of near normal rainfall occurring when the onset is normal. The chances of below normal rainfall occurring when the onset is normal are low. It was noted that whereas the chances of below normal rainfall occurring when there is an early onset were minimal, The western region (region 12) represented by Elgon had substantive chance of having below normal rainfall even with early onset. The onset over this region is associated with the low level westerlies from Congo, while the performance of the seasonal rainfall over this region is largely linked with the characteristics of the ITCZ.

: Variations in weather and climate have a significant impact on rain-fed banana yields in East Africa. This study examined empirical linkages between banana yields and variations in rainfall and temperature over Uganda for the historical period (1971-2009) using time series moments, correlation and regression analysis. The Food and Agriculture Organization (FAO) Crop Water Assessment Tool (CROPWAT) was used to estimate banana crop water requirements, soil moisture deficits and their effects on banana yield levels under rain-fed conditions for different regions. The study observed high comparability in moment indices with some significant differences reflected in the values of the banana yields and rainfall and temperature moment indices. The cumulative effect of rainfall and temperature variations on banana yields was discernible from strong correlation coefficients of up to 78%. The CROPWAT simulations indicated up to 46% reductions in optimal banana yields due to soil moisture deficits within banana plantations. In conclusion, the study observed stronger linkages between banana yields and temperature variations than rainfall. In addition, temperature manifests both direct and indirect effects on banana growth while rainfall exhibits comparatively high intra-seasonal and intra-annual variability with lag effects on banana yields. The study provides a strong scientific basis for the development of coping, adaptation and mitigation strategies in the banana farming subsector in the region due to the anticipated shifts in rainfall and
temperature extremes and changes across Uganda and neighbouring regions.

Deep convective clouds (DCCs) associated with tropical convection, are significant sources of precipitation in Equatorial East Africa. The DCCs play a fundamental role in hydrological and energy cycle. Weather Research and Forecasting (WRF) model with detailed bin-resolved microphysics are used to explore the diurnal variation of DCCs under maritime/clean and continental/polluted conditions. The sign and magnitude of the Twomey effect, droplet dispersion effect, cloud thickness effect, Cloud Optical Depth (COD) susceptibility to aerosol perturbations, and aerosol effects on clouds and precipitation is evaluated. Twomey effect emerges as dominant in total COD susceptibility to aerosol perturbations. The dispersion effect is positive and accounts for 3-10% of the total COD susceptibility at nighttime, with greater influence on heavier drizzling clouds. The cloud thickness effect is positive (negative) for a moderate/heavy drizzling (light thickness) clouds. The cloud thickness effect results in 5-22% of the nighttime total cloud susceptibility. Cloud microphysical properties and accumulated total precipitation show a complex relationship under varied aerosol conditions. The mean of core updraft and maximal vertical velocity increased (decreased) under low (high) CCN scenarios. Overall, the total COD susceptibility ranges from 0.28-0.53 at night; an increase in aerosol concentration enhances COD, especially with heavier precipitation and in a clean environment. During the daytime, the range of magnitude of each effect is more variable owing to cloud thinning and decoupling. The ratio of the magnitude of cloud thickness effect to that of the Twomey effect depends on cloud thickness and base height in unperturbed clouds while the response of precipitation to increase in aerosol concentration was non-monotonic

The study investigated potential of enhancing precipitation through cloud seeding during October-November-December (OND) season. Rainfall, cloud top temperature (CTT), aerosol optical depth (AOD) and wind data were used. Short-Cut Bartlett correlation, composite wind and time series analysis, and HYSPLIT backward trajectory analysis were used to achieve the objectives of study. Precipitation showed decreasing patterns with peaks between pentad 65 and 68. Delineated dry years (18) exceeded wet years (9). Low level winds were predominantly north-easterly during dry years characterized by continental trajectory. AOD values iincreased in all stations during dry year with aerosol load being higher in areas characterized by depressed rainfall. Pollutants suspended 1000 above mean sea level (AMSL) originated from Arabian and India subcontinent and pollutants suspended below 1000 AMSL were predominantly south easterly during wet years originated from Western Indian Ocean and characterized by maritime trajectory. Mean CTT during dry/wet years were positve over coastal areas while central, Rift-valley and Lake Victoria basin showed negative values, indicating presence of seedable conditions and thus potential cloud seeding to enhance rainfall and alleviate existing water stress.

Most urban areas in Kenya are facing water crisis due to rapid population growth, industrialization and climate change. This study investigates potential of harvesting water from fog and air humidity over urban cities in Kenya. Daily air temperature, dew point temperature, wind direction and speed were used. Parameters including atmospheric water vapor pressure, saturated vapor pressure and the absolute and relative humidity of the atmosphere were derived. Air temperatures ranged between 18.2 and 27.6°C in urban areas. Mean annual foggy days was higher at Jomo Kenyatta International Airport (JKIA) with a maximum of 17 foggy days compared to other stations. However, mean annual harvesting days was higher at Moi International Airport (MIA) with a maximum of 350 days. Based on device efficiency of 10%, stations in Nairobi city (JKIA/Dagorretti Corner/Wilson Airport) indicated maximum water harvesting potential of 3.2/1.4/2.9 litres/m2 /day in direction d6 (225 -270°) while Kisumu station showed highest potential of harvesting water (2.2 litres/m2 /day) in direction d5 (180-225°). In Mombasa, the MIA and Lamu stations showed potential of harvesting 4.4 litres/m2 /day and 3.9 litres/m2 /day in direction d6 and d5 respectively. Based on monthly distribution of potential monthly water, harvesting from fog and air humidity was classified into either coastal or non-coastal/continental regions. The urban cities in Kenya have high potential of water harvesting from fog and air humidity presenting an alternative sustainable low cost approach to augmenting available fresh water sources and alleviating existing water stress. This will enable achievement of Kenya’s long term development footprint (Vision 2030) and Millennium Development Goals.

Key words: Vision 2030, urbanization, water stress, fog water harvesting.

This study sought to investigate the spatial and temporal variations of aerosols over Kenya based on
Moderate Resolution Imaging Spectroradiometer (MODIS) satellite sensor Aerosol Optical Depth (AOD) data
for the period between 2001 and 2012. A Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT)
model was used for trajectory analysis in order to reconstruct the origins of air masses and understand the
Spatial and temporal variability of aerosol concentrations. Validation of MODIS AOD using Aerosol Robotic
Network (AERONET) indicated that MODIS overestimated the aerosol loading over the study region. Space
time variability of MODIS AOD measurements over Kenya showed a decreasing trend in aerosol loading with a
long term mean of between 0.02 and 0.56. Mean monthly AOD values showed two peaks during the months
of July and December while seasonal variations indicated high aerosol loading during the December –
January –February (DJF) and June –July –August (JJA) season. Back trajectory analyses showed that aerosols
mainly dust and sea salt reaching Kenya were transported from either Arabian or Indian sub continent or
western parts of the Indian Ocean respectively. Therefore, long term and more comprehensive satellite AOD
retrievals are necessary in order to achieve a better understanding of spatial and temporal variations in
aerosols over Kenya

Key Words: Aerosol Optical Depth, MODIS, Kenya

Linkages between dominant spatio-temporal decadal rainfall variability modes and the global sea surface temperature (SST) modes are investigated over East Africa region for the period 1950–2008. Singular value decomposition (SVD)and canonical correlation analysis (CCA) techniques are employed to examine potential linkages and predictability of decadal rainfall variability over the region. When the ten-year periodicity is filtered out from the observed monthly rainfall data, distinct decadal rainfall regimes are exhibited in the time series of mean seasonal rainfall anomalies. Spectral density analysis of rainfall time series showed dominance of a ten-year periodicity, significant at 95% confidence level.The Principal Component Analysis (PCA) results yielded nine and seven homogeneous decadal rainfall zones for long rains; March–May (MAM), and the short rains: October–December (OND) seasons, respectively. The third season of June–August (JJA) which is mainly experienced in western and coastal sub-regions had eight homogenous zones delineated. Results show that
the leading three SVD-coupled modes explain greater than 75% of the squared co variance between the two fields. The first SVD mode for Indian, Atlantic and Pacific Oceans contributed to 50, 43 and 38% of the total square covariance for MAM season, respectively. The same mode accounted for 65, 48 and 40% for OND rainfall season, respectively. For the JJA season, mode one contributed to about 61, 39 and 42% of the variance. The study showed that forcing of decadal rainfall over the region is associated with El Ni˜no mode that is prominent over the Pacific Ocean, while Indian Ocean dipole is the leading mode over the Indian Ocean basin. An inter-hemispheric dipole mode that is common during ENSO was a prominent feature in the Atlantic Ocean forcing regional decadal rainfall. The high variability of these modes highlighted the significant roles of all the global oceans in forcing decadal rainfall variability over the region. In addition, results from multiple linear regression model showed substantial variation of the model prediction skill of the decadal rainfall variability
modes within various homogenous zones and for different seasons. Copyright© 2012 Royal Meteorological Society.

KEY WORDS decadal rainfall variability; Eastern Africa; decadal modes of variability; global oceans SSTs

Influence of low frequency global Sea Surface Temperatures (SSTs) modes on decadal rainfall modes over Eastern Africa region is investigated. Fore-knowledge of rainfall distribution at decadal time scale in specific zones is critical for planning purposes. Both rainfall and SST data that covers a period of 1950–2008 were subjected to a ‘low-pass filter’ in order to suppress the high frequency oscillations. VARIMAX-Rotated Principal Component Analysis (RPCA) was employed to delineate the region into decadal rainfall zones while Singular Value Decomposition (SVD) techniques was used to examine potential linkages of these zones to various areas of the tropical global oceans. Ten-year distinct decadal signals, significant at 95% confidence level, are dominant when observed in-situ rainfall time series are subjected to spectral analysis. The presence of variability at El Niño Southern Oscillation (ENSO)-related timescales, combined with influences in the 10–12 year and 16–20 year bands were also prevalent. Nine and seven homogeneous decadal rainfall zones for long rainfall season i.e. March-May (MAM) and the short rainfall season i.e. October-December (OND), respectively, are delineated. The third season of June–August (JJA), which is mainly experienced in western and Coastal sub-regions had eight homogenous zones delineated. The forcing of decadal rainfall in the region is linked to the equatorial central Pacific Ocean, the tropical and South Atlantic Oceans, and the Southwest Indian Ocean. The high variability of these modes highlighted the significant roles of all the global oceans in forcing decadal rainfall variability over the region.

Welcome to Oceanography (SMR 411). This course is offered to both Meteorology students and atmospheric students. While this course does not require pre-requisites, a basic knowledge on climate and atmospheric circulation will enable the leaner to comprehend the concepts presented in the course.

Oceanography is the study of the physical, chemical, and biological aspects of the world ocean. All the global oceans together with the seas cover nearly three-quarters of the surface of the earth. The major goals of oceanography are to understand the geologic and geochemical processes involved in the evolution and alteration of the ocean and its basin, to evaluate the interaction of the ocean and the atmosphere so that greater knowledge of climatic variations can be attained, and to describe how the biological productivity in the sea is controlled.

Oceans play an important role on weather and climate. Have you ever heard of El Niño, tropical cyclones, the Atlantic hurricane season and storm surges? How does the oceans contribute to these phenomena? These and many other interesting features will be learnt in this course.

Over the past four decades, Lake Victoria basin has experienced drastic environmental changes on account of both natural and anthropogenic factors. The natural factors include prolonged droughts and the recent emergence of water hyacinth in the Lake, while anthropogenic factors include the deforestation rates, poor agricultural practices, and destruction of critical wetlands. This study examines the potential impact of deforestation on the rainfall over the lake Victoria basin. To assess the potential impact of deforestation on rainfall over the region, the General Circulation Model (GCM) ECHAM5 was applied. ECHAM5 was used to predict the possible impact of land cover and land use changes on rainfall using land cover and land use scenarios based on the Integrated Model to Assess Global Environment (IMAGE). The projected vegetation cover for 2050 was used to model the impact of deforestation, which indicated a general decrease in the canopy. The results from the model indicate a decrease in rainfall over many parts, although some areas showed increased rainfall. From the study we conclude that while deforestation has an impact on climate, there seem to be a complex interaction between forest and the rainfall generation mechanism.

Extreme wet spells affect the East Africa Coast (EAC) during March to June (long rains) and October to December (short rains). While these spells are less frequent during the short rains, some of the most extreme wet spells occur at this time of the year. The present study examined the general characteristics of the wet spells during the short rains. A detailed study of the anomalous wet spell event of October 1997, with record rainfall around Mombasa (4.0°S, 39.6°E), was also carried out.
Daily rainfall for 1962-1997 and NCEP2 reanalysis data for 1979-1997 were used to study the characteristics of the wet events. A high spatial coherence is found in the rainfall over the EAC. The circulation features that were common during most of the wet events were: weakening or reversal of the east-west (Walker type) circulation over the Indian Ocean, enhanced convergence between the northern and southern hemisphere trade winds and westward-moving disturbances in the low-level equatorial wind field. During the 1997 wet event, it is shown that prior to the heavy rainfall event a ridge of high pressure, on the eastern coast of southern Africa, intensified and propagated eastwards leading to the strengthening of moist easterlies reaching the EAC. The zonal wind component along longitude 40°E showed shears in the flows that were associated with the development of the Mozambique Channel low/trough in the lower troposphere round which southerlies surged northwards. These southerlies converged with the easterlies near the EAC. Thus, the warm and wet air from the east interacted with the relatively cold and mainly continental air from the south generating instability at the EAC.

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Maize Streak virus (MSV) disease is a major disease in many parts of Africa, and is the most important viral pathogen of maize in Kenya. A study was conducted in 2004 to evaluate the agronomic performance and maize streak virus (MSV) resistance of maize ( Zea mays check for this species in other resources L.) three-way crosses developed in Kenya. Twenty hybrids and one check were grown under normal conditions in a randomized complete block design, in two replications at Embu, 1540 masl; and Muguga, 2093 masl). In a parallel trial in Muguga, hybrids were also evaluated in two replications under artificial inoculation with MSV. The analyses of variance combined across environments showed significant differences (P<0.05) among genotypes for grain yield, days to 50% pollen shed, days to mid-silk and ear height. Genotype x environment interaction was significant (P<0.01) for grain yield and days to mid-silk, indicating some hybrids were more adapted in some environments. Grain yield for MU03-025 (10.04 t ha-1) was significantly better (P<0.05) than the check, H513 (7.53t ha-1). In the disease inoculated experiment, the best hybrids for disease resistance were MU03-012 and MU03-006 (score of 1.75), while H513 had a mean score of >3.0. The highest yielding hybrid under disease inoculation, MU03-026 showed yield gain of 5.2 t ha-1 above that of H513. The results indicate adoption of disease resistant hybrids would result in a higher maize yields in the mid-altitude areas of Kenya.

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This course is a continuation of Dynamic Meteorology I (SMR401). If you studied SMR301 a long while ago, it
may be advisable to review it once more before you embark on this course. As you worked through SMR301, you may have been introduced to several equations and may be wondering why this course appear to be mathematical. Well, as you may have already found out, there are many processes that take place in the atmosphere, dynamic meteorology will seek not only to explain how this comes about, but also to express the relationship between the forces involved in a mathematical form.

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