We know that there is a constant change in the atmosphere. These climatic variations affect our lifestyle. It is beyond our ability to change the climate of a place. We can merely make our living conditions better by artificially heating or cooling the place where we live; or building dams or taking out canals to the areas which are dry; or grow crops with the help of irrigation.
Weather You must have noticed that generally mornings are pleasant but noons are warmer as the sun is overhead. On some days, there may be clouds in the atmosphere while on others, the weather may be clear. Weather is the condition of the atmosphere at a place over a short period of time. It may change from day-to-day and even from hour-to-hour. It affects our food habits. It also affects our clothing. Weather affects our daily activities.
Climate - Climate is the average weather condition of a place over a long period of time. It affects our lifestyle. It also influences our clothing, housing, transportation, etc.
There are five factors that determine the climate of a place:
- Distance from the equator
- Height above the sea level
- Distance from the sea
- Direction of winds
- Humidity
Distance from the Equator - The Earth gets heated by the sunrays. The rays of the sun fall vertically on the equator. This direct heat makes the area near the equator the hottest region in the world. As we move towards the poles, the rays of the sun fall slantingly on the Earth. These areas, therefore, have low temperatures. The sun's rays do not get to the Arctic and Antarctic easily. Hence, these areas remain cold throughout the year.
Height Above the Sea Level - The height of a place above the sea level is called its altitude. The temperature goes down with increasing height. The higher we go, the cooler it becomes. The temperature decreases at the rate of 1 °C for every 165 metres' ascent. This happens because of two reasons; firstly, at higher altitude, the air pressure is less which reduces the atmospheric temperature. Secondly, the atmosphere is mostly heated by the surface of the Earth below and not directly by the sun from above. The peaks of high mountains remain covered with snow as the temperature there is below 0°C. When the snow slides down from the mountains, it melts into water and reaches low altitudes where temperature is more.
Distance from the Sea - The places located near the sea are cooler in summers and warmer in winters. They have moderate climate. On the other hand, places away from the sea generally have hot weather in summers and cold weather in winters. They have extreme climate. Let us compare the climate of Mumbai and Bhopal. You will observe that Bhopal is hotter in summer and cooler in winter as compared to the climate of Mumbai, which is neither very hot in summer nor very cold in winter. This happens because Mumbai is near the sea and Bhopal is far away from the sea. Places close to the sea have a moderate climate because sea water heats and cools much slower than land. It is the property of water that it takes more time to absorb and lose heat while land absorbs and releases heat faster than water. During the day, the land near the sea absorbs more heat and becomes warmer than the sea. The air over the land gets heated up and rises over the land. To fill the space created by this hot air, the cool air from the nearby sea moves towards the land and makes it cooler. During the night, the opposite happens; cool air from the land moves towards the sea. Due to this continuous flow of breeze between the land and the sea, places near the sea have more or less equable climate. In coastal areas, during summer, the sea breeze keeps the nearby areas cool while in winter, it keeps these areas warm.
Direction of Winds - Winds are caused by the uneven heating of the air around the Earth. Warm air rises and is replaced by the cool air. Winds flowing from the sea bring cool and moist weather. Winds flowing from hot areas raise the temperature while those flowing from cold areas decrease the temperature. Sometimes, winds bring moisture-laden clouds with them, which results in rainfall. Besides the seasonal winds, there are various local winds which influence the climate. In some parts of the Northern Plains, a very hot and dry wind blows. It is called Loo. In some extremely cold regions, icy winds blow and make the climate very cold. Mistral is a cold northerly wind which blows from Central France and the Alps to the Mediterranean region.
Humidity - Humidity is the amount of moisture or water vapour present in the atmosphere. It affects the temperature and climate of a place. Winds blowing from the sea to the land make the weather humid as they contain a lot of moisture. Humid air can cause rainfall. The amount of rainfall is an important factor in deciding the climate of that area. Some places experience rainfall throughout the year. Some places have rainfall in summer while some others have it in winter. At some places, there is snowfall along with rainfall. Thus, distribution of rainfall plays an important role in deciding the nature of climate.
Climatic Zones - On the basis of temperature and rainfall, the Earth can be divided into three climatic zones.
The Torrid or Tropical Zone - This zone includes areas between the Tropic of Cancer (231/2° N) and the Tropic of Capricorn (231/2° S). These areas are very hot as they are situated closest to the equator. This region has a tropical climate. India is situated in the Tropical Zone. The Temperate Zone This zone includes areas between the Torrid Zone and the Frigid Zone. The region lying between the Tropic of Cancer (231/2° N) and the Arctic Circle (661/2° N) is called the North Temperate Zone and the region lying between the Tropic of Capricorn (23'/2° S) and the Antarctic Circle (661/2° S) is called the South Temperate Zone. As compared to the other two zones, the regions of Temperate Zone have a mild climate, which is neither too hot nor too cold.
The Frigid Zone or Polar Zone - It includes the regions around the North Pole and the South Pole. The area lying between the Arctic Circle (661/2° N) and the North Pole (90° N) is called the North Frigid Zone. The area lying between the Antarctic Circle (661/2° S) and the South Pole (90° S) is called the South Frigid Zone. Both these areas have a polar climate, which makes these areas very cold.
Measuring Climate - As we know, in order to determine the climate of a place, we have to take into account the temperature and pressure as well as the amount of rainfall received by the place. These things have to be measured and recorded scientifically. Different instruments are used to measure them.
Thermometer - A thermometer is used to measure temperature. It is measured in degrees. There are two different scales for measuring temperature— Celsius or Centigrade (°C) and Fahrenheit (°F).
Barometer - A barometer is used to measure the atmospheric pressure of an area. It can measure the pressure exerted by the atmosphere by using water, air, or mercury.
Rain Gauge - The rainfall of an area is measured with the help of a rain gauge. A rain gauge is also known as a udometer or a pluviometer. It is an instrument used by meteorologists to gather and measure the amount of rain over a set period of time.
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