Thesis

Spatiotemporal Variability and Comparative trend Analysis of Rainfall in Western Aamhara, Ethiopia and its Implication on Development Sectors

2026-09-01T12:31:02Z

Spatiotemporal Variability and Comparative trend Analysis of Rainfall in Western Aamhara, Ethiopia and its Implication on Development Sectors SEWAGEGN, Tilahun Studying rainfall's spatial variations and temporal trends is crucial for assessing climaterelated changes and designing future water resource management strategies and agricultural planning. This study investigated the spatiotemporal variability and comparative trend analysis of rainfall and its implication on development sectors using time-series rainfall data from Enhancing National Climate Services (ENACTS) over western Amhara for the period 1991–2020. None of the past researchers has addressed the analysis of the spatiotemporal trend of seasonal and annual rainfall using ITA over western Amhara. Rainfall variability was assessed using the coefficient of variation, precipitation concentration index (PCI), and standardized anomaly index (SAI). Mann-Kendall and Sen's slope estimator tests were also used to assess spatiotemporal trends, and the low, medium, and high rainfall clusters were analyzed using the most recent innovative trend analysis (ITA) approach. The spatial distribution of annual rainfall was varied from 600 mm to 2300 mm. In most of the rainfall grid points, a high amount of annual rainfall happened in the Kiremt (JJAS) season, and high rainfall variability occurred during the Bega (October - January) season. SAI also witnessed the presence of inter-annual variability of rainfall with negative and positive anomalies in 46.7% and 53.3% of the reference years, respectively. The PCI result indicated that the distribution of rainfall in the area was strongly irregular. The result indicated that in most grid points, the MK test and SSE showed a statistically non-significant trend in annual rainfall. Most rainfall grid points displayed high clusters and increasing trends during the Kiremt and annual periods, but low rainfall was observed during the Bega season, indicating declining trends. The comparison results showed that the ITA approach is more reliable and superior to the MK test because it can identify both monotonic and non-monotonic trends that the MK method is unable to identify. The rainfall trend during the Kiremt and Bega seasons shows that it is increasing and decreasing, respectively. Therefore, I recommend planting drought-tolerant and early-maturing crops to cope with the risks associated with rainfall variability.

Characterizing the Past and Future Rainfall of the Main Rainy Season Over Western Amhara, Ethiopia

2026-09-01T12:04:30Z

Characterizing the Past and Future Rainfall of the Main Rainy Season Over Western Amhara, Ethiopia Tesema, Tewabech Rainfall is an important hydrological cycle and has major influence on the environment and agricultural productivity all over the world.Western Amhara,heavily relies on agriculture,making rainfall variability a critical concern.There is not recent study on characterization of past and future main rainy season (Kiremt/June September) over Western Amhara region,Ethiopia.Hence,this research investigates historical and projected changes in rainfall during Kiremt season (June-September) to understand the implications for water resources and agricultural productivity.We analyzed observational data from 1991-2020 and projected future rainfall (2021 2100) using Coupled Model Inter comparison Project phase 6 Global Climate Models (CMIP6 GCMs),by evaluating their performance against ground observations for the period 1995 2014.Applying appropriate statistical metrics for model performance evaluation,and the ensemble mean of top three best performing CMIP6 GCMs were selected separately for future daily,monthly ,and seasonal rainfall study under different Shared Socioeconomic Pathways (SSPs).Our findings reveal a statistically significant increase in the cessation date of the kiremt season during the past period.Future projections indicate that,under various SSP scenarios,the onset date of the kiremt season will be delayed,while the cessation date will advance,resulting in a shorter growing period.Interestingly,despite the shortened season,projections suggest an increase in total seasonal rainfall under most scenarios.These findings highlight the need for adaptation strategies to mitigate the potential impacts of changing rainfall patterns on agriculture and water resources in Western Amhara region,Ethiopia.

Assessment of CMIP6 Climate Model Performance and Projection of Climate Extreme Indices over the Upper Blue Nile Basin, Northwestern Ethiopia.

2026-09-01T11:56:01Z

Assessment of CMIP6 Climate Model Performance and Projection of Climate Extreme Indices over the Upper Blue Nile Basin, Northwestern Ethiopia. Bazie, Fekadie limate change is a worldwide concern that poses a treat of the century and has resulted in significant damages. Projection as well as identification of past and future changes in climatextremes is important. The study aimed to assess CMIP6 climate model performances and projections of climate extreme indices over the Upper Blue Nile Basin, Northwestern Ethiopia.Observed and future CMIP6 precipitation and temperature data under SSP1-2.6, SSP2-4.5, and SSP5-8.5 for near (2015-2044), mid (2045-2074) and far (2075-2100) periods were used. Thestudy was applied power transformation and distribution mapping for precipitation andtemperature bias correction methods to correct the bias of seven CMIP6 models, respectively. To alidate the performance of model data with observed data, the statistical evaluation techniques ere employed. Mann–Kendall (MK) and Sen’s slope tests were computed to detect the rainfalland temperature trends and magnitude of change, respectively. Furthermore, the spatiotemporadistribution and trends of 15 extreme indices from the ETCCDI list were computed. Theperformance evaluation result revealed that model INM-CM5-0 and INM-CM4-8 for precipitation and temperature were selected based on their highest performance, respectively. The precipitation projection in all agro-climatic zones under SSP1-2.6, SSP2-4.5, and SSP5-8.5 scenarios showsignificant (p<0.01) positive trend. The mean annual maximum temperature over UBNB isprojected to increase by 1.8°C, 2.1°C, and 2.8 °C under SSP1-2.6, SSP2-4.5, and SSP5-8.5 from 2015-2100, respectively. Similarly, the mean annual minimum temperature is estimated toincrease by 1.5°C, 2.1°C, and 3.1 °C under SSP1-2.6, SSP2-4.5, and SSP5-8.5, respectively. Thending also reveals that the onset and cessation of rainy seasons were vary in each SSPs. Themidland and highland part of the UBNB were characterized by a short length of rainy season (82130 days). Whereas, lowland part of basin was characterized by a longer length of rainy seaso140-150 days). Furthermore, extreme temperature indices showed a significant decrease in thenumber of cold days and nights, and an increase warm days and nights. Conversely, rainfallindices showed a decreasing trend. Therefore, it is critical to boost capacity and decreassusceptibility to extreme temperatures. Thus, this study will enable the development of effectivadaptation and mitigation measures for climate extreme hazards to combat the effects of excessivheat in the UBNB. In addition, the community in the study area should introduce quick-matureand drought-resistant crops.

Analysis of Climate Variables and Drought Characteristics in West Amhara, Ethiopia

2026-09-01T11:43:35Z

Analysis of Climate Variables and Drought Characteristics in West Amhara, Ethiopia Melsie, Nigatu Examining localised climate conditions can alert decision-makers, policymakers, and the community to potential risks and support proactive strategies to reduce impacts. The study analysed climate variables and drought characters in west Amhara, Ethiopia. Since 1992–2021the Ethiopian meteorological institute has provided historical meteorological data for twelve stations. The study utilised statistical tests, R software, and climate data tool software to analyse climate variables, detect trends, conduct homogeneity testing, and analyse droughtcharacteristics. Arc-Map 10.8 interpolated spatial variability of rainfall, temperature, and drought characteristics. The study showed a low variation in the spatial distribution of long-term annual and kiremt season rainfall across all stations, ranging between 990–1300 mm and 714944 mm, respectively. The standard rainfall anomaly showed negative trends in the 2000s an2010s, with an inconsistent rainfall distribution range between 13.1 and 35.4. The kiremt season showed uniform to moderate rainfall, with four stations showing statistically significantincreasing trends. Dangila, Motta, and Gonder showed positive trends with increasing rates of 76.0 mm, 72.0mm, and 60.0mm per decade. The temperature trend showed maximum and minimum temperatures ranging from 18.7 to 35.4 °C, with the highest and lowest at Metema and N/mewucha stations. The 2000s and 2020s were the coldest and warmest. Rate of change between 0.020°C and 0.1°C/year at D/tabour and Chagine stations. Seven stations showed statistically significant increase in mean minimum temperature (Zs> 1.96), with a slight decrease observed in Bahir dar station. The study indicates a decrease in drought frequency and duration in most stations, with moderate droughts being more frequent than severe and extreme droughts. Historical drought years (1992, 1997, 2002, 2004, 2009, 2012, and 2015) were welldocumented. The study showed statistically significant increases in meteorological drought trends in Dangila, Gonder, Metema, and Debark stations, while a decreasing trend was observed in layber stations, indicating decreasing and increasing drought tendencies respectively. The average meteorological and agricultural drought trends showed increasing trends, indicating decreasing drought tendencies in the main rainy season. The study enhances understanding of historical climate trends and drought characteristics, recommending better data sets like coordinated regional downscaling experiment models for future impact analysis.