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# Heat Budget and Global Heat Balance A heat budget is a perfect balance between incoming heat (insolation) absorbed by the earth and outgoing heat (terrestrial radiation) escaping it in the form of radiation. If the incoming heat and the outgoing heat are not balanced, then Earth would get either...

# Heat Budget and Global Heat Balance A heat budget is a perfect balance between incoming heat (insolation) absorbed by the earth and outgoing heat (terrestrial radiation) escaping it in the form of radiation. If the incoming heat and the outgoing heat are not balanced, then Earth would get either too warm or too cold. The balance between the incoming and outgoing heat energy is called the Global Heat Balance. ### Draw a diagram to illustrate how the air is warmed: - A diagram of the sun with rays extending out to a circle labelled "Earth's surface" - 40% of the rays are reflected back to space by the atmosphere - 15% of the rays are absorbed by the upper layer of the atmosphere - 45% of the rays reach the earth's surface # Terrestrial Heat Radiation Terrestrial heat radiation is the heat waves sent out by the Earth's surface. # Conduction Conduction is the passing of heat by contact. # Convection Convection is the passing of heat by air currents. # Factors affecting the distribution of temperature ## Major factors 1. **Latitude (Distance from the Equator)** ### Near the Equator - At the Equator, the variation in the angle of the Sun's rays is between 66 1/2º and 90º. - Vertical rays heat the surface of the Earth to a greater extent than the inclined/slant/oblique rays. - This is because, in case of the vertical rays, the energy is concentrated on a smaller area resulting in intense heat and also the distance the rays have to travel through the atmosphere is shorter. ### Near the Poles - Higher the latitude of a place, the less is the angle the sunrays make with the surface of the Earth resulting in slant rays. - The slant rays have to travel a greater distance through the atmosphere and cover a larger area. - Therefore, the energy is distributed over a large area resulting in less intense heat. **Example:** Mumbai is warmer than New York because Mumbai is closer to the Equator than New York. Remember both these places are close to mean sea level. ## Latitude and temperature - Latitude is the distance in degrees from the equator. - A diagram of the Earth showing lines of latitude. The equator is highlighted. A circle showing a gradient from blue to red to blue is shown alongside, labelled "cold", "hot", and "cold". - What is the connection between latitude and temperature? - **Answer:** As latitude increases, the temperature decreases. [Picture courtesy: Slide Player]