Chapter 5 Climate Vs Weather
Page 1: Introduction to Ethiopia's Climate
Overview of Ethiopia's Climate
Ethiopia has varied altitudinal ranges and diverse climatic conditions.
The country’s location near the equator and the Indian Ocean results in significant temporal and spatial weather variations.
The seasonal migration of the Intertropical Convergence Zone (ITCZ) and its atmospheric circulations, along with complex topography, primarily control Ethiopia's climate.
The ITCZ is formed by the convergence of Northeast Trade winds, creating a low-pressure zone.
Page 2: Characteristics of the ITCZ
ITCZ Details
The ITCZ circles the Earth near the equator where the Northern and Southern Hemispheres' trade winds meet.
Characterized by convective activity leading to vigorous thunderstorms over large areas.
Most active over continental land masses during the day, less so over oceans.
Page 3: Pressure Systems and Climate
Global Climate Influences
Diagram depicting key climatic features, including:
High Pressure Zones: 30° and 60° latitude.
Low Pressure Zones: ITCZ at 0° and Doldrums.
Wind Patterns associated with Hadley, Ferrel, and Polar Cells.
Page 4: Polar Climate Influence
Atmospheric Dynamics
Detailed outline of atmospheric circulation patterns:
Polar Vortex and Jet Streams: Influence on weather systems.
Impacts of westerlies and trade winds on Ethiopia's climate dynamics.
Page 5: Weather vs Climate
Definitions and Differences
Weather: The current state of the atmosphere at a certain time (temperature, pressure, humidity, wind, cloudiness, precipitation).
Climate: Average atmospheric conditions over long periods (decades).
Both definitions underscore the interplay between daily weather patterns and long-term climatic conditions.
Elements and Controls of Weather and Climate
Weather conditions stem from the sun's impact on Earth, emphasizing the importance of:
Latitude
Altitude
Water Distribution
Winds and Pressure Systems
Page 6: Elements and Controls Table
Major Elements and Controls
Elements | Controls |
|---|---|
1. Temperature | 1. Latitude/Angle of the Sun |
2. Precipitation & Humidity | 2. Land & Water Distribution |
3. Winds & Air Pressure | 3. Winds & Air Pressure |
4. Altitude & Mountain Barriers | 4. Ocean Currents |
Page 7: Factors Affecting Climate
Climate Influences
Multiple interacting factors determine the climate of a location:
Latitude
Elevation
Nearby Water
Ocean Currents
Topography
Vegetation
Prevailing Winds
The global climate system and changes within it also affect local climates.
Page 8: Latitude's Influence
Latitude Effects
Latitude defines a location's distance from the equator:
More solar insolation at the equator means higher temperatures.
As you move toward poles, solar insolation declines.
Ethiopia’s latitude results in consistent high temperatures and minimal seasonal daylight variation.
Page 9: Earth's Axis and Climate
Axis Inclination
The Earth's axis is tilted at approximately 23.5°, affecting sun ray directness and seasonal changes:
Significant in determining Tropics of Cancer/Capricorn and the Arctic/Antarctic Circles.
Page 10: Solstices and Equinoxes
Seasonal Changes
Significant dates related to solstices and equinoxes that influence climate:
Winter Solstice: December 21-22
Autumnal Equinox: September 22-23
Vernal Equinox: March 20-21
Summer Solstice: June 20-22
Page 11: Equinox Definition
Equinox Characteristics
Equinox: Time when sun's rays strike the equator, resulting in equal day and night.
There are two equinoxes each year, marking seasonal shifts due to Earth's axial revolution.
Page 12: Vernal and Autumn Equinoxes
Specific Equinox Events
Vernal Equinox (March 21): Marks spring's start, equal day/night lengths in the Northern Hemisphere.
Autumn Equinox (September 23): Equal day/night, marks the onset of autumn.
Page 13: Solstice Events
Solstice Impact
Solstices determine daylight length and season commencement:
Summer Solstice (June 21): Longest daylight in Northern Hemisphere.
Winter Solstice (December 22): Longest night in Northern Hemisphere, sun directly over Tropic of Capricorn.
Page 14: Impact of Altitude on Climate
Altitude Overview
Altitude: Higher locations generally experience lower temperatures due to the lapse rate.
Effects of elevation on temperature and climate conditions are critical in Ethiopia.
Page 15: Lapse Rate Explained
Temperature Changes with Elevation
Normal Lapse Rate: 6.5°C decrease per kilometer rise.
Types of lapse rates:
Dry Adiabatic Lapse Rate: Temperature drops 10°C per 1000m for unsaturated air.
Page 16: Wet Adiabatic Lapse Rate
Saturated Air Dynamics
Wet Adiabatic Lapse Rate: Saturated air cools at a slower rate than unsaturated air.
Cooling rate approximately 5°C per 1000m.
Page 17: Environmental Lapse Rate
Observed Temperature Changes
Environmental Lapse Rate: Actual observed temperature changes with altitude.
Normal decrease in temperature from low to high elevations in the troposphere.
Page 18: Spatio-temporal Temperature Distribution
Factors Influencing Temperature
Temperature distribution in Ethiopia influenced by:
Altitude
Latitude
Highlands exhibit cooler temperatures than lowlands, with mean annual temperature ranging from 30°C to below 10°C.
Page 19: Temperature Variation Insights
Altitudinal Temperature Trends
Temperature decreases with elevation, mean annual temperatures vary significantly across regions:
Lowlands exceed 30°C; high altitudes like the Bale Mountains experience lower averages.
Page 20: Local Temperature Expressions
Temperature Zones Classification
Local temperature expressions in Ethiopia:
Altitude (m)
Mean Annual Temp (°C)
Description
Local Equivalent
3300 and above
10 or less
Cool
Wurch
2300 - 3300
10 – 15
Cool
Temperate Dega
1500 - 2300
15 – 20
Temperate
Woina Dega
500 - 1500
20 – 25
Warm Temperate
Kola
Below 500
25 and above
Hot
Bereha
Page 21: Temporal Temperature Distribution
Temperature Extremes in Ethiopia
Monthly and seasonal temperature variations in Ethiopia:
Higher daily ranges in tropics with lower annual variability.
Typical temperature trends indicate high summer temperatures and lower values from November to February.
Page 22: Seasonal Temperature Observations
Seasonal Temperature Characteristics
Daily maximum temperatures can vary from over 37°C in lowlands to 10-15°C in highlands.
Seasonal temperature shifts observed, with slight increases noted in summer.
Page 23: Regional Temperature Differences
Northern vs Southern Temperature Profiles
Southern Ethiopia has higher temperatures recorded during Autumn and Spring, while the North sees increased temperatures in summer.
Unique local climatic variations exist in southern and southwestern highlands.
Page 24: Rainfall Influences
Rainfall and ITCZ Interaction
Rainfall patterns in Ethiopia greatly influenced by the ITCZ:
Northeast Trade winds and equatorial westerlies interact to form a low-pressure system.
Page 25: Seasonal Rainfall Dynamics
ITCZ Seasonal Shifts
The ITCZ shifts north and south with overhead sun position, creating distinct rainy seasons across regions:
January: ITCZ shifts South, decreasing rainfall; Afar region experiences some rains.
March-September: Central and southeastern highlands receive significant rains from southeasterly winds.
Page 26: Seasonal Rainfall Breakdown
Annual Rainfall Patterns
Summer Season (June-September): Predominant rainfall coinciding with ITCZ position northwards.
Autumn Season (September-November): ITCZ retreats to the equator; lowlands receive rains from south easterlies.
Page 27: Winter and Spring Rainfall
Winter and Spring Season Characteristics
Winter Season (December-February): Northeasterly winds dominate but bring little moisture to most areas.
Spring Season (March-May): Increased rainfall as the sun shifts; southeasterly winds interact with highlands.
Page 28: Rainfall Regions Categorization
Regional Rainfall Classification
Four key regions based on rainfall distributions:
Summer Rainfall Region: Majority of the country except certain lowlands.
All Year-round Rainfall Region: Southwestern Ethiopia with significant rain year-round.
Page 29: Rainfall Regions Continued
Additional Rainfall Regions
Autumn and Spring Rainfall Regions: Lowlands receiving rains from weak north easterly and equatorial winds;
Winter Rainfall Region: Mainly influenced by northeasterly winds.
Page 30: Agro-ecological Zones of Ethiopia
Diversity in Agro-climatic Zones
Ethiopia features five agro-climatic zones due to varied altitude/climate:
Wurch: High altitude with low temperature.
Dega: High humidity and reliability for agriculture.
Page 31: Description of Agro-ecological Zones
Specific Zones Descriptions
Wurch Zone: Altitude > 3,200m, mean annual temp < 10°C.
Dega Zone: Higher temperatures than Wurch, suitable for settlements and agriculture.
Page 32: Weyna Dega and Kolla Zones
Key Agro-ecological Zones
Weyna Dega Zone: Altitude 1,500-2,300m, favorable for crops, covers 26% of Ethiopia.
Kolla Zone: Most extensive, hot climate, altitude 500-1,500m, average temperatures 20°C-30°C.
Page 33: Bereha Zone Characteristics
Lowland Climate Types
Bereha Zone: Arid climate, low altitude < 500m; average annual rainfall < 200mm, high temperatures.
Page 34: Climate Change Overview
Climate Change Definitions
Climate change entails long-term changes in climate properties impacting weather variables.
Page 35: Current Climate Trends
Extreme Weather Events
Notable increases in frequency of extreme weather events:
Droughts ranked high in risk, with historical data showing impacts on food security.
Page 36: Drought Trends
Historical Drought Impact
12 significant drought events recorded since 1900; majority post-1980.
The 2015-2016 drought correlated with El Niño-related conditions.
Page 37: Temperature Trends in Ethiopia
Rising Temperatures
Mean yearly temperature has risen 0.2-0.28°C per decade over recent decades.
Page 38: Specific Temperature Changes
Observational Data
Observed temperature increase of 1.3°C from 1960 to 2006, particularly in arid regions.
Page 39: Rainfall Variability Trends
changes in Rainfall Patterns
Rainfall remains stable nationally but varies regionally, with some areas reporting declines.
Page 40: Natural Climate Change Causes
Mechanisms Behind Change
Earth Orbital Changes: Affect seasonal climate variations.
Volcanic Eruptions: Influence atmospheric conditions through gas emissions.
Page 41: Anthropogenic Effects
Human-Induced Climate Changes
Industrial activities significantly raise greenhouse gas concentrations in the atmosphere.
Page 42: Consequences of Climate Change
Impacts on Environments and Populations
Climate change leads to health, agricultural, and ecological challenges, most hard hit in low-income countries.
Page 43: Climate Change Response Strategies
Mitigation and Adaptation Approaches
Major response mechanisms focus on:
Mitigation: Reducing greenhouse gas emissions.
Adaptation: Adjusting lifestyles and infrastructure to health impacts.
Page 44: Specific Mitigation Strategies
Practical Actions for Climate Control
Implementing renewable energy, promoting energy efficiency, and improving transportation methods.
Page 45: Adaptation Strategies
Resilience Building Approaches
Strategies for adapting include restoring landscapes, enhancing water conservation methods, and preparing for natural disasters.