Freshman Geography Lecture 5

## Course Title and Author - **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 - **Course Period**: Freshman Course, January 2021 ## Chapter Overview - **Chapter Title**: The Climate of Ethiopia and the Horn ## Objectives of the Chapter - Students will achieve the following upon completion: - Differentiate between weather and climate. - Explain the spatial and temporal patterns of temperature and rainfall in Ethiopia. - Analyze climate and its socio-economic implications. - Understand the causes, consequences, and response mechanisms of climate change. ## Introduction to Ethiopia’s Climate - Ethiopia, a large country in the Horn of Africa, has: - A variety of altitudinal ranges - Diverse climatic conditions - Influences on climate: - Major temporal and spatial variations due to proximity to the equator and Indian Ocean - Controlled mainly by: - Seasonal migration of the Inter Tropical Convergence Zone (ITCZ) - Atmospheric circulations and complex topography ## Definitions - **Weather**: Average atmospheric conditions over a short period - **Climate**: Long-term average of atmospheric conditions over decades ## Elements and Controls of Weather and Climate - **Changes in weather** often result from wind, defined as large-scale horizontal motion of air. - **Key climatic elements**: 1. Temperature 2. Precipitation and humidity 3. Winds and air pressure 4. Altitude and mountain barriers 5. Ocean currents - **Climate controls**: - Latitude - Land and water distribution - Winds and air pressure ## Factors Influencing Weather and Climate ### A. Latitude - Distance from the equator affects solar insolation: - Moving from equator to poles decreases temperature - Ethiopia’s latitude influences high average temperatures and minimal seasonal variations ### B. Inclination of the Earth's Axis - The earth’s 23.5° axial tilt changes the directness of the sun’s rays - This results in varying daylight and seasonal changes ### C. Equinoxes and Solstices #### Equinoxes - Day and night lengths equal due to parallelism of the Earth's rotation axis - Occur twice a year - **Vernal Equinox**: Marks the beginning of Spring, around March 21 - **Autumn Equinox**: Marks the start of Autumn, around September 23 #### Solstices - Distinctions in day and night length - **Summer Solstice**: June 21, longest day in Northern Hemisphere - **Winter Solstice**: December 22, longest night in Northern Hemisphere ## Temperature and Altitude Effects ### A. Altitude - Higher altitudes correlate with lower temperatures - The normal lapse rate is 6.5°C per kilometer rise in altitude ### B. Types of Lapse Rate 1. **Dry Adiabatic Lapse Rate**: Temperature changes during air mass expansion/compression. 2. **Wet Adiabatic Lapse Rate**: Changes during condensation affecting cooling rates. 3. **Environmental Lapse Rate**: Represents actual observed temperature changes with altitude. ## Spatiotemporal Patterns of Temperature in Ethiopia - **Altitude and Temperature**: Higher altitudes lead to lower temperatures. - Tropical temperatures limited to lowland peripheries due to Ethiopia's highland nature. - The mean annual temperature varies across the country, with extremes in the Bale Mountains and Afar Depression. ## Spatiotemporal Patterns of Rainfall in Ethiopia - Rainfall distribution is complex, influenced by the ITCZ, pressure cells, and Trade Winds. - **Seasonal Variability**: - Influenced primarily by the position of the ITCZ, which shifts seasonally, impacting rainfall amounts. - Rainfall is irregular both spatially and temporally, with significant variability across regions. ## Agro-Ecological Zones of Ethiopia - **Divisions by Altitude**: - **Wurch**: >3,200m, Cold (<10°C) - **Dega**: 2,300-3,200m, Cool (11.5-17.5°C) - **Weyna Dega**: 1,500-2,300m, Warm (17.5-20°C) - **Kolla**: 500-1,500m, Warm semiarid (20-27.5°C) - **Bereha**: <500m, Hot arid (>27.5°C) ## Climate Change: Causes and Effects - **Definition**: Changes in climate identified by mean and variability over extended periods. - **Natural Causes**: Earth orbital changes, volcanic eruptions affecting climate. - **Human Causes**: Greenhouse gas emissions primarily from activities such as agriculture and industrial processes. - **Consequences**: Impacts on health, water resources, agriculture, and ecosystems. ## Response Mechanisms to Climate Change ### A. Mitigation - Reducing greenhouse gases by energy efficiency, using renewable sources. ### B. Adaptation - Adjusting to a changing climate to lessen harmful impacts and utilize beneficial opportunities. ### C. Resilience - Building capacity to recover from climate-related challenges. ## Conclusion - **Chapter Wrap-Up**: Summary of the key findings regarding Ethiopia's climatic characteristics and response strategies.