INTRODUCTION (5:12 PM)

• Overview & doubts related to the previous class.

INSOLATION, HEAT BUDGET, AND ALBEDO (5:22 PM)

• The amount of incoming solar radiation is called insolation.
• The amount of insolation received by the Earth is 2 billionth of solar energy.
• The amount of insolation received on the surface= 1.92 calories per cm2 per minute called the Solar Constant.
• The incoming solar radiation is shorter in wavelength.
• This radiation is absorbed by the Earth's surface and is reemitted as long-wavelength Terrestrial Radiation.

GREEN HOUSE EFFECT (5:48 PM)

• The atmosphere is transparent to incoming solar radiation and opaque to outgoing terrestrial radiation.
• The warming of the Earth's atmosphere and its surface by the absorption of terrestrial radiation by some of the gases is called the Green House effect.
• The gases responsible are called Green House Gases, for example, CO2, CH4, N2O, HFCs (Hydro-fluro carbon), PFCs (Per-fluro carbon), SF6 (Sulphur hexafluoride), Water vapor, etc. 
• The Earth's surface absorbs incoming solar radiation and emits terrestrial radiation hence it acts as a source of heat for the atmosphere.
• Therefore, temperature decreases with height at the rate of 6.5 degrees celsius per km which is called the Normal Lapse Rate.

HEAT TRANSFER (5:56 PM)

• Methods of heat transfer:
• (1) Radiation 
• It involves the transfer of heat in the form of radiant energy.
• The incoming solar energy is in the form of electromagnetic radiation.
• (2) Conduction 
• It involves the transfer of heat through molecular activity at the zone of contact.
• It occurs at the zone of contact between the troposphere and the Earth's surface.
• (3) Convection
• Transfer of heat by vertical movement of the mass of air. 
• For Example, the convection of air along the equator.
• (4) Advection
• Transfer of heat by horizontal movement of mass.
• For Example, planetary winds and ocean currents.

FACTORS AFFECTING INSOLATION (6:16 PM)

• (1) Transparency of the atmosphere
• Cloud cover, dust particles, water vapor, etc. reduces the transparency of the atmosphere and reduces insolation received at the surface.
• (2) Latitude
• Latitude of a place decides the angle of incidence of insolation which affects insolation received per unit area of the surface.
• For Example, in tropical regions insolation falls vertically and is concentrated in a small area. Along temperate and polar regions angle of incidence is oblique and insolation is distributed over a larger area.
• (3) Length of the day
• Longer the day, the more the insolation received at the surface. The length of the day depends on the season.

HEAT BUDGET (6:29 PM)

• On the global scale the Earth must reradiate as much heat back to space as it receives from the sun.
• This is necessary in order to maintain a uniform temperature on the Earth.
• The gains and losses in heat by way of incoming solar radiation and outgoing terrestrial radiation are called Heat Budget.
   
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• Doubts related to heat budget (7:15 PM)

ALBEDO (7:24 PM)

• Albeo is the ratio between the reflected amount of solar radiation and the incoming solar radiation by the Earth as a whole.
• It is also called as Reflection Coefficient.
• The average albedo of the Earth = 35%.
• 

TEMPERATURE (7:42 PM)

• The degree of hotness or coldness of a surface is called temperature.

Factors affecting Temperature:

• (1) Insolation
• Insolation in turn depends upon the transparency of the atmosphere, latitude, and length of the day.
• Even though the sun's rays are vertical along the equator throughout the year, the equator will not have maximum temperature due to cloud cover.
• (2) Albedo
• Surface with higher albedo reflects back more insolation resulting in less absorption of heat causing lower temperature.
• (3) Nature of the surface
• Earth behaves differently depending upon the specific heat of the surface.
• The land surface with lower specific heat, heats up more rapidly and intensely than the water surface.
• Also, the land cools rapidly.
• (4) Distance from the sea or continentality
• The locations that are in the interior of the continent experience a higher range of temperatures than coastal locations.
• For Example, Delhi experiences hotter summers and colder winters than Mumbai.
• (5) Distribution of continents
• Northern Hemisphere with more proportion of land than oceans experience a higher range of temperature than the Southern Hemisphere with more water surface.
• (6) Altitude
• Temperature decreases with an increase in altitude.
• (7) Winds
• Air in motion is called Winds.
• They transport temperatures prevailing in one area to another. 
• For Example, planetary winds. 
• (8) Ocean currents
• Ocean currents are like rivers inside the oceans.
• They transport warm water from the tropics to polar regions and vice versa helping in the global distribution of temperatures.

TOPIC FOR THE NEXT CLASS: DISTRIBUTION OF TEMPERATURE ACROSS THE GLOBE