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# Chapter 1-Weather and Climate Weather is the state of the atmosphere which can change day to day, time to time, and place to place. It cannot be generalized. Climate is the average weather condition of a place over a considerable period of time. A minimum period of 35 years is desirable to know...

# Chapter 1-Weather and Climate Weather is the state of the atmosphere which can change day to day, time to time, and place to place. It cannot be generalized. Climate is the average weather condition of a place over a considerable period of time. A minimum period of 35 years is desirable to know the climate of a place. For example: Equatorial Type, Tropical Monsoon Type, Tropical Desert Type, etc. ## Elements of Weather and Climate: 1. **Atmospheric Temperature**: Atmospheric temperature is the measure of its heat. It tells you how hot or cold the place is. It varies from place to place. 2. **Atmospheric Pressure**: Atmospheric Pressure is the force exerted by a column of air at any point on the Earth's surface. 3. **Winds**: It is the horizontal movement of air from areas of high atmospheric pressure to low atmospheric pressure. 4. **Rain**: It is the falling down of moisture in the form of water on the surface of the Earth. Let us study each of the above in detail: (This chapter focuses only on temperature and the factors affecting temperature of a place. In the subsequent chapters, we will learn about the other elements in detail.) ## 1-Temperature * **Solar Radiation**: It is the amount of heat given out by the Sun in the form of rays. We derive energy from the Sun for all the atmospheric processes (heating and cooling), atmospheric phenomena and life on Earth. Solar Energy controls our weather and climate and distribution of heat on the Earth. * **Insolation**: A very small fraction of the Sun's energy -the solar radiation- is intercepted by our Earth at the top of its atmosphere. As the Sun's energy in the form of rays enters the atmosphere, a part of it is reflected, some of it is refracted, a very small part of it is absorbed by water vapour and dust and some scattered before a little more than half reaches the Earth's surface. This incoming solar radiation which is received on the Earth's surface is called Insolation. Insolation is the most important factor deciding the climate. Temperature is not equally distributed over the Earth. * **Terrestrial Radiation**: The atmosphere is not directly heated by the Sun, but is directly heated by the heated Earth from below. The Earth being solid absorbs the insolation readily and in turn re-radiates this energy to heat up the layers of the atmosphere. This heat energy given out by the Earth is known as Terrestrial Radiation.