CLIMATE AND WEATHER
In the last two chapters you have read about the landforms and the drainage of our country. These are two of the three basic elements that one learns about the natural environment of any area. In this chapter you will learn about the third, that is, the atmospheric conditions that prevail over our country. Why do we wear woollens in December or why it is hot and uncomfortable in the month of May, and why it rains in June - July? The answers to all these questions can be found out by studying about the climate of India.
Climate refers to the sum total of weather conditions and variations over a large area for a long period of time (more than thirty years). Weather refers to the state of the atmosphere over an area at any point of time. The elements of weather and climate are the same, i.e. temperature, atmospheric pressure, wind, humidity and precipitation. You may have observed that the weather conditions fluctuate very often even within a day. But there is some common pattern over a few weeks or months, i.e. days are cool or hot, windy or calm, cloudy or bright, and wet or dry. On the basis of the generalised monthly atmospheric conditions, the year is divided into seasons such as winter, summer or rainy seasons.
The world is divided into a number of climatic regions. Do you know what type of climate India has and why it is so? We will learn about it in this chapter.
The climate of India is described as the ‘monsoon’ type. In Asia, this type of climate is found mainly in the south and the southeast. Despite an overall unity in the general pattern, there are perceptible regional variations in climatic conditions within the country. Let us take two important elements – temperature and precipitation, and examine how they vary from place to place and season to season.
In summer, the mercury occasionally touches 50°C in some parts of the Rajasthan desert, whereas it may be around 20°C in Pahalgam in Jammu and Kashmir. On a winter night, the temperature at Drass in Jammu and Kashmir may be as low as minus 45°C. Thiruvananthapuram, on the other hand, may have a temperature of 22°C.'
Let us now look at precipitation. There are variations not only in the form and types of precipitation but also in its amount and seasonal distribution. While precipitation is mostly in the form of snowfall in the upper parts of Himalayas, it rains over the rest of the country. The annual precipitation varies from over 400 cm in Meghalaya to less than 10 cm in Ladakh and western Rajasthan. Most parts of the country receive rainfall from June to September. But some parts like the Tamil Nadu coast gets a large portion of its rain during October and November.
In general, coastal areas experience less contrasts in temperature conditions. Seasonal contrasts are more in the interior of the country. There is a decrease in rainfall generally from east to west in the Northern Plains. These variations have given rise to variety in lives of people – in terms of the food they eat, the clothes they wear, and also the kind of houses they live in.
More to know
* The word monsoon is derived from the Arabic word ‘mausim’ which literally means season.
* ‘Monsoon’ refers to the seasonal reversal in the wind direction during a year.
* In certain places, there is a wide difference between day and night temperatures. In the Thar Desert the day temperature may rise to 50°C, and drop down to near 15°C the same night. On the other hand, there is hardly any difference in day and night temperatures in the Andaman and Nicobar islands or in Kerala.
Let’s find out
1. Why the houses in Rajasthan have thick walls and flat roofs?
2. Why is it that the houses in the Tarai region and in Goa and Mangalore have sloping roofs?
3. Why houses in Assam are built on stilts?
Source: This topic is taken from NCERT TEXTBOOK