19 February 2014

Weather and Climate : Science

Weather and Climate : Science NCERT Notes


The day-to-day conditions of the atmosphere at a place with respect to elements like temperature, humidity, rainfall, wind speed, etc. is called the weather of that place.
The atmosphere is all around us – we cannot see it, but it keeps us warm. Without it, the earth would be a lifeless ice ball.
In addition, the atmosphere absorbs or deflects incoming ultraviolet rays and other charged particles. The temperature is low early in the morning, and increases by noon. It decreases again towards the evening, and the cycle continues

Similarly, rain, snow, thunder and lightning are constituents of weather. Sometimes, the weather isviolent, and sometimes, peaceful and quiet.
The sun is responsible for all the changes in the weather. We know that the sun is a huge sphere of hot gases and has a very high temperature. The distance between the sun and us is very large. The sun is the chief source of light and heat for the earth. It is also the primary source of energy, and causes changes in the weather.
The energy absorbed and reflected by the earth’s surface, the oceans and the atmosphere play an important role in determining the weather at any place. Also, gases like carbon dioxidemethane and water vapour play a role in determining the weather.
The weather in coastal areas is very different than that in a desert or hilly areas.
The maximum temperature of the day is recorded during the afternoon, while the minimum temperature is recorded early in the morning.

Weather and Climate , Class 7 Science, NCERT Notes, CBSE Notes

In winters, it gets dark early and you don’t get much time to play with your friends.
Meteorologists record the weather every day. The records of the weather are preserved for several decades. These records help us determine the pattern of the weather at a place.
The average weather pattern taken over a long time, say, 25 years, is called the climate of the place.
The mean temperature for a given month is found in two steps. First, we find the average of the temperatures recorded during the month. Next, we calculate the average of such temperatures over many years. The result is the mean temperature.
Mean temperature helps compare the weather at two different places. 
For example, if we compare the temperatures of Thiruvananthapuram in Kerala and Srinagar in Jammu and Kashmir, we can conclude that Thiruvananthapuram is very hot and wet than Srinagar, which is moderately hot and wet for some parts of the year.
Let’s consider another place like Rajasthan, which has high temperatures during most parts of the year, but very low temperatures in winter, which lasts for a few months. The region receives scanty rainfall. Therefore, it is known as typical desert climate.
North-eastern India receives rain for a major part of the year. Hence, we can say that the climate of the region is wet.

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