Freshman Geography Lecture 5

Course Information

• Course Title: Geography of Ethiopia and the Horn

• Instructor: Belete Ejigu (PhD), Assistant Professor of Urban Planning and Development, Addis Ababa University, College of Natural and Computational Science

• Duration: Freshman Course, January 2021

Chapter Overview

• Chapter Five: The Climate of Ethiopia and the Horn

Objectives

• Upon completion of this chapter, students will be able to:

  • Distinguish between weather and climate.

  • Explain the spatiotemporal patterns and distribution of temperature and rainfall in Ethiopia.

  • Analyze the implications of climate on biophysical and socio-economic aspects.

  • Comprehend the causes, consequences, and response mechanisms of climate change.

Introduction

• Ethiopia's diverse climatic condition is influenced by:

  • A wide variety of altitudinal ranges.

  • Proximity to the equator and the Indian Ocean, resulting in spatial and temporal variations.

• Key Controlling Factors:

  • Seasonal migration of the Inter Tropical Convergence Zone (ITCZ).

  • Complex topography of the country.

Definitions

• Weather: Average atmospheric conditions over a short period.

• Climate: Composite of daily weather over long periods, usually decades or more.

Elements and Controls of Weather and Climate

• Elements:

  1. Temperature

  2. Precipitation and humidity

  3. Winds and air pressure

  4. Altitude and mountain barriers

  5. Ocean currents

• Controls:

  • Latitude: affects solar insolation and temperatures.

  • Proximity to land and water bodies.

  • Wind patterns and pressure systems, including annual fluctuations.

Climatic Controls

A. Latitude

• The distance from the equator affects solar energy received; Ethiopia's latitude leads to:

  • High average temperatures.

  • Small annual temperature variations.

  • Little fluctuation in day length between summer and winter.

B. Inclination of the Earth's Axis

• Earth’s axial tilt (23.5°) affects sunlight distribution and seasonal changes.

C. Temperature Lapse Rate

• Defined as the rate at which temperature decreases with altitude.

• Dry Adiabatic Lapse Rate: 10°C per 1000m change in elevation for unsaturated air.

• Wet Adiabatic Lapse Rate: Slower cooling rate for saturated air, approximately 5°C per 1000m.

• Environmental Lapse Rate: Actual observed decrease in temperature with altitude; typically 6.5°C per 1000m.

Spatiotemporal Patterns of Temperature and Rainfall in Ethiopia

I. Temperature Distribution

• Altitude & Temperature:

  • Major determinant of temperature; as altitude increases, temperature typically decreases.

• Variation:

  • Mean annual temperature ranges from over 30°C in lowlands to below 10°C in high altitudes.

  • Areas such as the Plateau and Bale Mountains witness extreme temperature variations.

II. Rainfall Distribution

• Complex Rainfall Systems:

  • Governed by ITCZ dynamics, pressure cells, and trade winds.

  • Seasonal variability in rainfall linked to the activities of the ITCZ.

  • Rainfall occurs in distinct seasons (e.g., summer main rainy season).

Agro-ecological Zones of Ethiopia

• Defined based on temperature and altitude:

  1. Bereha (Hot arid)

  2. Kolla (Warm semiarid)

  3. Woina Dega (Cool humid)

  4. Dega (Cool humid)

  5. Wurch (Cold to moist)

Climate Change

• Definition: Change in climatic patterns due to natural variability or human activity.

Causes of Climate Change

• Natural Causes:

  • Earth orbital changes, energy budget, volcanic eruptions.

• Anthropogenic Causes:

  • Greenhouse gas emissions from agriculture, land use, and industrial processes.

Consequences of Climate Change

• Significant impacts on:

  • Human health (increased diseases, mortality).

  • Water resources (melting glaciers, decreased water tables).

  • Agriculture (food security issues).

  • Ecosystems (species adaptation challenges).

Climate Response Mechanisms

1. Mitigation

• Strategies to reduce greenhouse gas emissions.

• Examples: Energy efficiency, renewable energy adoption.

2. Adaptation

• Adjusting practices to address climate change impacts.

• Includes infrastructure planning for flood defense, and water management.

3. Resilience

• Ability to recover from climate-related stressors.

• Emphasizes safety net programs to support affected populations.

Discussion Questions

1. Differentiate between weather and climate.

2. Identify which factors affect Ethiopian climate.

3. Discuss temperature and rainfall distribution in Ethiopia.

4. Analyze dynamics in temperature changes in Ethiopia. Is it warming or cooling?

5. Examine the causes of climate change.

6. Propose responses to climate change.