Assessing Seasonal and Annual Trend of Extreme Precipitation Indices and the Influence of Climate Modes in the Northern Coast of Tanzania under Climate Conditions = 기후 조건하에서 탄자니아 북부 해안 지역의 극한 강수 지수의 계절별 및 연간 경향과 기후 모드의 영향

다국어 초록 (Multilingual Abstract)

Climate Change evidenced as the most pressing global challenges, with substantial evidence demonstrating its influence on rainfall patterns worldwide. Global warming is expected to enhance the frequency and intensity of extreme rainfall events, where a warmer atmosphere allows greater moisture retention, thereby strengthening the hydrological cycle in the globe. The study aims to provide a comprehensive trend analysis of the annual and seasonal extreme precipitation indices and the influence of Climate Modes: ENSO and IOD in the Northern Coast (NC) region of Tanzania from 1982 to 2024. The study analyzed six (6) precipitation extreme indices as defined by ETCCDI based on daily precipitation at four (4) stations scattered across the north coast region of Tanzania where its average represent summary for the whole NC region. The trends were seasonally and annually evaluated through the nonparametric Mann–Kendall test and the Sen’s slope estimator. The averages for Annual precipitation total (PRCPTOT), Intensity of 1-day precipitation amount (RX1day), Intensity of consecutive 5-day precipitation amount (RX5day), Frequency of heavy rainfall (R20mm) and frequency of very heavy rainfall (R50mm) in region revealed a positive trend with statistically significant at 95% confidence level (p<0.05). The study also examined the shift toward extreme wet anomalies relative to the long-term trend, and also revealed that from 2017 onward, there has been a notable increase in extreme wet anomalies at both annual and seasonal scales in the region. Concerning the influence of Climate Modes patterns, the findings showed that both ENSO and IOD are the major external drivers that modulating the extreme precipitation events in the north coast region in annual and seasonal scales especially during the OND “short rain” season where during positive IOD and El Nino phases, most extreme precipitation indices tend to increase, reflecting enhanced rainfall intensity and frequency of extreme events. Moreover, the IOD exhibits a stronger and more statistically significant correlation with extreme precipitation indices than ENSO in the region. The findings of this study contribute to a deeper understanding of the variability of extreme precipitation events in the northern coastal region of Tanzania as the observed shift toward more frequent extreme wet anomalies underscores the need for strengthening early warning systems to minimize risks from intense rainfall events. Integrating climate information into infrastructure design and expanding urban water discharge systems enhance resilience against flooding. These findings are directly relevant to water resource management, agricultural planning, and disaster risk reduction efforts in the region.

목차 (Table of Contents)

• ABSTRACT i
• LIST OF TABLES vi
• LIST OF FIGURES vii
• LIST OF ABBREVIATION ix
• CHAPTER 1. INTRODUCTION 1
• 1.1 Background 1
• 1.2 Statement of the problem 2
• 1.3 Significance of the study 5
• 1.4 Objectives of the Research 7
• 1.4.1 Specific Objectives 7
• 1.4.2 Research questions of the Study 7
• 1.4.3 Hypothesis 8
• CHAPTER 2: LITERATURE REVIEW 9
• 2.1 Global and Climatic Drivers of Precipitation Variability 9
• 2.2 Climate Change and Intensification of Extreme Rainfall 10
• 2.3 Rainfall Patterns and Climate Drivers Across Africa 11
• 2.4 Rainfall Variability and Climate Modes in East Africa 12
• 2.5 Rainfall Characteristics and Extremes in Tanzania 13
• CHAPTER 3. METHODOLOGY 15
• 3.1 Study Area 15
• 3.2 Dataset Sources 17
• 3.2.1 Precipitation 17
• 3.2.2 Sea Surface Temperature (SST) Data 19
• 3.3 Methodology 19
• 3.3.1 Extreme Precipitation Indices 19
• 3.3.2 Trend analysis and Statistical Tests 21
• 3.3.3 Standardized Anomaly Index (SAI) 24
• 3.3.4 Oceanic Climate Indices 25
• 3.3.5 Correlation Analysis 26
• 3.3.6 Composite Mean Analysis 28
• CHAPTER 4: RESULTS 29
• 4.1 Analysis of long-term Trends of Extreme Precipitation Indices in the Northern Coast of Tanzania from 1982 to 2024 29
• 4.1.1 Trend Analysis of Extreme Precipitation Indices by Annual 29
• 4.1.2 Trend Analysis of Extreme Precipitation Indices by Seasonal 32
• 4.2 Standardized Anomaly Index (SAI) Analysis for PRCPTOT Index 37
• 4.2.1 Standardized Anomaly Index (SAI) of the PRCPTOT by Annual 37
• 4.2.2 Standardized Anomaly Index (SAI) of the PRCPTOT by MAM 40
• 4.2.3 Standardized Anomaly Index (SAI) of the PRCPTOT by OND 43
• 4.3 The influence of Climate mode in extreme precipitation indices in the North Coast region of Tanzania 45
• 4.3.1 The Correlation Analysis on Extreme Precipitation Indices with Climate modes 48
• 4.3.2 Composite analysis of Extreme Precipitation Indices and Climate Modes in north coast region of Tanzania 56
• 4.3.2. Composite analysis of Extreme Precipitation Indices by ENSO phases 56
• 4.3.2.2 Composite analysis of Extreme Precipitation Indices by DMI phases 60
• CHAPTER 5. DISCUSSION AND CONCLUSION 66
• 5.1 Discussion 66
• 5.2 Conclusion 77
• 5.3 Limitation and Suggestion of the study 78
• 5.3.1 Limitation of the study 78
• 5.3.2 Recommendation of the Study 79
• ACKNOWLEDGEMENT 81
• References 82
• 국문초록 91