Climate part 1

 

       Climate 

We are going to post a series of climate related blogs. This is gonna help you with providing knowledge about upsc climatology basics. 

Introduction:-

Climate- The sum total of atmospheric conditions and variations of a large area over a long period of time usually 30 years. When we say climate of India is monsoon type, we refer to India as a whole (large area) recorded over long time period.

Weather- Weather refers to atmospheric conditions and variations of a particular area at a point of time. Weather may fluctuate every hour. It may be sunny in the morning and turns cloudy in mid afternoon.

 

The elements of climate and weather are temperature, atmospheric pressure, humidity, wind and precipitation.

Seasons are divided on the basis of generalized weather conditions or climatic conditions of months of a year.

The world is divided into different climatic regions. India has ‘monsoon’ type of climate. This type of climate is mainly found in the areas of South Asia and Southeast Asia.

 

Fun fact:- Some places have a very high variation in day and night temperatures while some places barely experience any temperature changes between day and night. The example of former is desert areas and that of latter is islands or coastal areas. Clouds and humidity play a major role in determining temperature of a place. The drier the air, the more easily and quickly it cools down and warms up. In desert areas the air is dry and sun shines very brightly in such areas as a result of which the air warms up fast during the day and cools down during night. In desert areas the temperature may rise to 50 degrees during day and may drop to 15 degrees during night.

 

Precipitation is a principle factor affecting climatic conditions of a place. Like resources, the precipitation pattern is unevenly distributed in India. Precipitation occurs in the form of snowfall in upper reaches of Himalayas while it rains in rest of the country. Annual precipitation varies from 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 while coastal part of Tamil Nadu receives major portion of rain in October-November. Longitudinally, the rainfall increases from west to east in India.

 

Climate controls:-

There are six major controls of climate:-

1.  Latitude

2.  Altitude

3.  Pressure and wind system

4.  Distance from the sea

5.  Ocean currents

6.  Relief features

 

Now we will learn how these factors affect climate in general and India in particular.

The Earth’s curvature is such that it bulges from centre and flattens at the poles so the solar energy received varies according to latitude. As a result air temperature decreases from the equator towards the poles.

Density of atmosphere decreases with increasing height as a result of which temperature decreases. That is why places at higher altitude are cooler.

Further latitude and altitude of a place affect the pressure and wind system of an area that influences the temperature and rainfall pattern of an area.

Seas cause a moderating affect i.e. keeping the climatic conditions neither too hot nor too cold. As distance from the sea increases, the moderating effect decreases. This condition is known as continentality i.e. very hot during summers and very cold during winters.

Ocean currents along with onshore winds affect the climate. Both warm and cool winds and currents arise in coastal areas and temperature changes accordingly.

Relief plays a major role in determining climate of a place. For e.g.:- High mountains act as barriers for cold and hot winds. They can even cause precipitation if they are high enough and lie in the path of rain bearing winds.

How these Factor affect India’s climate:-

Latitude: - It refers to the angular distance of a place north or south of the earth’s equator expressed in degree and minutes. The latitudinal extent of India is 37°6' N and 8°4' N. Tropic of Cancer passes through the middle of India running from Rann of Kuchchh in west to Mizoram in east. Area lying north to tropic of cancer belongs to the subtropical area and experiences extreme climate and area lying to south of it belongs to tropical area and experiences moderate climate.

Altitude: - Every part of central Asia experiences very harsh winters but India doesn’t. This is because of the Great Himalayas that elevate up to a height of 6000 m which prevents the chilly winds from central Asia.

 Pressure and winds: - India lies in the region of north easterly winds. These winds originate from northern hemisphere in the parts of high pressure. These winds blow south and eventually get deflected to right due to Coriolis force. These winds bear little or no moisture. So technically India should be a dry land but is not. Here pressure and wind conditions in India are somewhat unique.

Let’s compare and contrast these wind and pressure conditions of India to understand India’s climate better. We know that pressure winds move from the areas of high pressure to the areas of low pressure. The difference in the pressures causes a force called pressure gradient. Greater the pressure difference, greater will be the force. This force tends to move things from area of higher pressure to the areas of lower pressure. More will be the pressure gradient, stronger will the wind move. In the month of January, there is a high pressure area north of the Himalayas and there is a low pressure in the southern part of India. Winds from these high pressure areas blow towards the south of India. These are usually dry. While reverse is the case in summers and there is a reversal of wind direction as well. During summers, there is a low pressure in interior of Asia and northern India. High pressure winds blow towards these areas from the south of India. Since these winds come covering the vast Indian ocean, these bear moisture and hence cause precipitation in large part of India. These winds blow in a north-easterly direction and are called southwest monsoon winds.

           The arrows indicate the direction of wind during winters.

The arrows indicate the direction of winds during summers.

Fun fact: - Most of the world’s deserts are located in the western margins of continents because the winds that blow in the tropics are easterly winds. By the point these winds reach the western margins of the continents, they become dry and hence bring no rain.