Freshman Geography Lecture 5

## Course Overview
- Title: Geography of Ethiopia and the Horn
- Author: Belete Ejigu (PhD)
- Affiliation: Assistant Professor of Urban Planning and Development, Addis Ababa University
- Course Type: Freshman Course
- Date: January 2021

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## Chapter Five: The Climate of Ethiopia and the Horn

### Objectives
- Understand and distinguish between weather and climate.
- Identify spatiotemporal patterns of temperature and rainfall in Ethiopia.
- Analyze climate implications on biophysical and socioeconomic aspects.
- Comprehend the mechanisms of climate change impacts and responses.

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## Introduction
- Ethiopia's climate is influenced by:
- Variety in altitude and topography.
- Proximity to the equator and the Indian Ocean leads to pronounced weather and climate variations.
-Main controllers of climate include:
- Seasonal migration of the Inter Tropical Convergence Zone (ITCZ)
- Atmospheric circulations

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## Weather vs Climate
- **Weather**: Short-term atmospheric conditions.
- **Climate**: Long-term average of weather conditions (decades).
- Climate is established through composite of daily weather records over a long time.

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## Elements and Controls of Weather and Climate
- **Major Forces influencing weather**:
- Wind: large scale horizontal air movement.
- **Climate determined by**:
- Radiation (amount and distribution)
- Latitude, altitude, nearby water, ocean currents.

### Key Elements of Climate
1. Temperature
2. Precipitation
3. Humidity
4. Winds and air pressure
5. Ocean currents

### Controls of Weather and Climate
- **Latitude**: Distance from the equator affects solar exposure and temperature.
- **Inclination of Earth's Axis**: Influences seasons and daylight length.
- **Altitude**: Higher elevations usually mean cooler temperatures.

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## Detailed Examination of Climatic Controls
### A. Latitude
- Influences temperature patterns:
- Colder as you move from equator to poles.
- Ethiopia's location results in:
- High average temperatures.
- Small temperature variations seasonally.

### B. Inclination of the Earth's Axis
- Affects directness of sun's rays and seasonal changes.

### C. Equinoxes and Solstices
- **Equinoxes**: Equal day and night lengths.
- Vernal Equinox: March 21
- Autumn Equinox: September 23
- **Solstices**: Unequal day lengths.
- Summer Solstice: June 21 (longest day in the North)
- Winter Solstice: December 22 (shortest day in the North)

### D. Altitude
- **General Temperature Decline** with increased elevation.
- Lapse Rate: Average 6.5°C decrease per kilometer.

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## Types of Lapse Rate
1. **Dry Adiabatic Lapse Rate**: Temperature change due to expansion/compression without heat exchange.
- Approximately 10°C per 1,000 meters.
2. **Wet Adiabatic Lapse Rate**: Occurs when air condensation releases latent heat.
- Average cooling is around 5°C per 1,000 meters.
3. **Environmental Lapse Rate**: Actual temperature changes with altitude, around 6.5°C per 1,000 meters.

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## Spatiotemporal Patterns of Temperature and Rainfall in Ethiopia
### Temperature Distribution
- Altitude and latitude determine temperature distribution significantly.
- Mean annual temperatures range from >30°C in lowlands to