Earth's Temperature & Energy Balance

• Earth's temperature varies due to solar radiation, atmospheric conditions, and geographical factors.
• The sun is the primary source of heat for Earth.

Heat and Heat Zones

• Heat on Earth mainly comes from solar radiation, with minor contributions from geothermal heat and human activities.
• The amount of heat a place receives depends on latitude, altitude, land-water contrast, and atmospheric conditions

Heat Zones

• Earth is divided into three major heat zones based on solar radiation intensity at different latitudes.

Torrid Zone (Tropical Zone) [0° – 23.5° N/S]

• Located between the Tropic of Cancer (23.5° N) and Tropic of Capricorn (23.5° S).
• Receives direct sunlight throughout the year
• It is the hottest zone on Earth.
• Examples include the Amazon Basin, Sahara Desert, South Asia, and Central Africa.

Temperate Zones [23.5° – 66.5° N/S]

• Located between the Tropics and the Polar Circles.
• Receives slanting rays of the Sun, resulting in moderate temperatures.
• Experiences four distinct seasons: summer, winter, spring, and autumn.
• Examples include the USA, Europe, China, and Argentina.

Frigid Zones (Polar Zones) [66.5° – 90° N/S]

• Located beyond the Arctic Circle (66.5° N) and Antarctic Circle (66.5° S).
• Receives minimal or no sunlight during winter.
• Extremely cold throughout the year, with permafrost in some areas.
• Examples include Greenland, Antarctica, Siberia, and Canada.

Factors Affecting Temperature Distribution

• Several factors influence temperature distribution on Earth.

Latitude

• Areas near the Equator receive direct sunlight, making them warmer.
• As latitude increases, sunlight becomes more slanting, reducing heat intensity.

Altitude (Elevation)

• Temperature decreases with altitude at a rate of 6.5°C per 1000m.
• Higher altitudes are colder because of thinner air and lower heat retention.

Land and Water Distribution

• Land heats and cools quickly, causing inland areas to experience extreme temperatures.
• Oceans heat and cool slowly, moderating coastal climates through maritime influence.

Ocean Currents

• Warm currents, such as the Gulf Stream, raise temperatures of nearby land.
• Cold currents, such as the Labrador Current, lower the temperatures of coastal regions.

Winds and Pressure Systems

• Winds transfer heat; warm winds increase temperature, while cold winds reduce it.
• High-pressure zones trap heat, while low-pressure zones promote cloud cover and cooling.

Cloud Cover and Albedo

• Clouds trap heat at night, causing a warming effect, but reflect sunlight during the day, causing a cooling effect.
• Snow-covered areas have high albedo, reflecting most sunlight and staying cold.

Seasonal Changes

• Earth’s tilt (23.5°) causes seasons by changing the angle of sunlight received at different latitudes.
• During the Summer Solstice (June 21), the Northern Hemisphere receives maximum heat.
• During the Winter Solstice (December 21), the Northern Hemisphere receives the least heat.

Isotherms

• Isotherms are imaginary lines on a map that connect places with the same temperature at a given time.
• Used to study global temperature distribution.

General Characteristics of Isotherms

• Isotherms run roughly parallel to latitude lines since temperature varies mainly by latitude.
• Over oceans, isotherms remain stable due to water's high heat capacity.
• Isotherms bend over land due to rapid heating/cooling effects.
• Closer spacing indicates rapid temperature change in deserts and polar regions.
• In oceans and equatorial areas, isotherms are more spaced out due to stable temperatures.
• Warm currents shift isotherms poleward.
• Cold currents shift isotherms equatorward.

Shifting of Isotherms

• Isotherms shift seasonally.

Summer Shifts

• During summer (June-July in the Northern Hemisphere, December-January in the Southern Hemisphere), isotherms shift poleward.
• Continental regions experience higher temperature rises than oceans.

Winter Shifts

• During winter (December-January in the Northern Hemisphere, June-July in the Southern Hemisphere), isotherms shift equatorward.
• Oceans retain heat longer, causing milder coastal winters.

Key Observations in Isotherm Shifting

• Over land, isotherms shift more due to quick heating and cooling.
• Over oceans, isotherms shift less because of water’s heat retention.
• In the Southern Hemisphere, isotherms are more stable because oceans dominate.
• Near the poles, seasonal shifts are strongest due to extreme temperature variations.

Explore factors influencing Earth's temperature, including clouds, pressure zones, albedo, and solar energy distribution. Understand seasonal changes, isotherm behavior, and the effect of land/water masses on temperature variations. Also learn about the environmental lapse rate.