Historical Variability of Rainfall in the African East Sahel of Sudan: Implications for Development

1 Introduction

1.1 Water Availability in Sub-Saharan Africa

1.2 Refocusing Climate and Water Policy from Regional to Local Scales

1.3 Scope of the Discussion

1.4 Long Term Precipitation Patterns South of the Sahara

1.5 Hydroclimate Setting of the Study Area

1.6 Interseasonal Variability of Rainfall

1.7 Precipitation Patterns for the Sahel of East Sudan: Annual Expected Totals

1.8 Annual Precipitation Patterns in the Study Area

References

2 Analysis of Long Term (100 yr) Patterns of Rainfall Variability

2.1 Study Area in East Sahel

2.2 Constructing Time Series of Annual Precipitation Totals

2.3 Spatial Differences in Annual Precipitation Totals

2.4 Expected Range of Annual Precipitation Totals

2.4.1 Gedaref (Median Annual Prcp = 600 mm)

2.4.2 Kassala (Median Annual Prcp = 280 mm)

2.4.3 Khartoum (Median Annual Prcp = 130 mm)

2.5 Normalized Precipitation Metrics to describe Interannual Variability

2.5.1 The Standardized Precipitation Index (SPI)

2.5.2 Percent (%) of Expected Annual Precipitation

2.5.3 Percent (%) Departure from Expected Annual Total

2.6 Variability and Synchrony of Annual Rainfall in Space & Time

References

3 Interannual and Interseasonal Variations in Monthly Rainfall

3.1 General Patterns

3.2 Longer Term Patterns of Interannual Variations in Monthly Precipitation

3.3 Statistics of Seasonal Behaviors of Monthly Precipitation

3.4 Statistics for the Month of Annual Maximum Monthly Totals

3.5 Statistics for the Month of Maximum Variability

References

4 Intra-Seasonal Patterns of Rainfall from Daily Values

4.1 General Patterns of Daily Precipitation

4.2 Daily Precipitation Records of Opportunity

4.3 An Overview of Daily Precipitation Patterns

4.4 Statistics of Daily Rainfall Intensities

4.5 Extreme Daily Precipitation

4.6 Seasonal (Annual) Patterns of Daily Precipitation

4.7 Seasonal Accumulation of Annual Precipitation

4.8 Seasonal Models for Percent of Annual Precipitation based on Daily Data

References

5 Analysis of Storm Events (& Interstorm Dry Periods)

5.1 Statistics of Storm Events

5.1.1 Defining Storm "Events"

5.1.2 Partitioning Storm Event Totals as a Percentage of Occurrence

5.1.3 Partitioning Storm Event Totals by Duration

5.1.4 Partitioning Storm Event Totals as a Percentage of Annual Rainfall

5.1.5 Essential Characteristics of Storm Events in the East Sahel

5.2 Time Interval between Storms: Dry Periods

5.2.1 Statistics of interstorm intervals

5.2.2 Classification of Interstorm Intervals by Duration

5.2.3 Statistics for Dry Periods in the Wet Season

5.2.4 Statistics on the Interannual Dry Period

References

6 Overview and Conclusions

6.1 General Patterns of Spatial Variability

6.2 Multi-Station versus Single Station Metrics

6.2.1 Un-normalized versus Normalized Metrics

6.2.2 Interannual Patterns of Rainfall Variability for the East Sahel

6.3 Interannual and Interseasonal Variations in Monthly Rainfall

6.4 Months of Maximum Precipitation and Greatest Variability

6.5 Statistics of Storms: Duration, Frequency and Total Rainfall

6.5.1 Importance of Daily Rainfall Data for Water Management

6.5.2 Spatial and Temporal Character of Storm Days

6.5.3 Duration and Frequency of Storm Events

6.6 Interannual Variability in Seasonal Rainfall Patterns

6.7 A View of Climate Change

6.8 Conclusions

References