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Earth’s Climate System

by | Feb 7, 2022 | Climate Change


You have been asked many times how the climate of your city is? A region’s or city’s climate refers to its usual or average weather. Let’s say the climate of Mumbai is hot and humid. At the same time, the climate of Antarctica is cold and freezing. So we can say that the average weather conditions for a certain region and over a long period are described as climate. Therefore Earth’s climate is the average of all the world’s regional climates.

The conditions of the earth are always changing. Hence, climate change is defined as a shift in the normal weather of an area or city. This might be a shift in the average annual rainfall of a region. It might also represent a shift in a city’s average temperature for a specific month or season. The shift in Earth’s climate system has been happening for the past millions of years. Then, why is Climate & Climate Change a concern now? This article will assist you in understanding how to effectively adapt to a changing climate. Why do we research the climate, its changes, and extremes? Its impacts on a variety of activities such as human health and safety. And how climate change is going to be a threat to the survival of life.


Climate Classification

Climate classification is a method of classifying the world’s climates. Life in a location is highly impacted by the climate; hence a climate classification may be closely related to a biome category.

There are several systems of climatic classification:

  • Aridity index
  • Alisov climate classification
  • Berg climate classification
  • Köppen climate classification
  • Holdridge life zone classification
  • Lauer climate classification
  • Strahler climate classification
  • Thornthwaite climate classification
  • Trewartha climate classification
  • Troll climate classification
  • Vahl climate classification

Koppen climate classification is the most acceptable system of classification. The Köppen categorization is based on the average monthly temperature and precipitation data.

The Köppen classification contains five major kinds designated A to E.

  • Tropical
  • Dry
  • Mild mid-latitude
  • Cold mid-latitude
  • Polar.

And then to subsidiary classes: Rainforest, monsoon, tropical savanna, humid subtropical, humid continental, oceanic climate, Mediterranean climate, desert, steppe, subarctic climate, tundra, and polar ice cap.

In the middle of the 1960s, the Köppen climate classification system was further updated as part of the Trewartha climatic classification system (revised in 1980). This attempted to construct a more defined middle latitude climatic zone. Which was one of the back draws of the Köppen system.

Global Wind Systems

What is wind?

The wind is defined as the movement of air from a high-pressure area to a low-pressure area. As we know, pressure is force per unit area. If we apply the same relation with air, Air pressure is just the weight (force) of the column of air over a specific location per unit area.

The unequal heating of the surface of the earth creates large global wind systems. The surface currents of the seas are driven by the global wind systems. For the majority of the year, the sun is nearly directly above the equatorial region. At the equator, hot air rises vertically up and flows in the direction of the poles. Colder air sinks close to the poles and travels back in the direction of the equator.

Trade winds

The trade winds are formed as air moves back toward the equator and generates warm, continuous breezes. The warm, wet air that ascended vertically cools and sinks at 30° north and south of the equator. The sky is clear here. There are no strong winds. These are known as horse latitudes.

At 30°N and 30°S, deserts such as the Sahara in Africa are frequent. Some of the dipping air comes back to the equator in the horse latitudes.

Prevailing westerlies: some of the cold, sinking air move north and south. The westerlies are the winds that lie between 40° and 60° latitudes in both hemispheres.

Polar easterlies– As they approach the poles, the westerlies in both hemispheres begin to rise and cool between 50° and 60° latitude. The polar easterlies are formed when they collide with extremely cold air traveling toward the equator from the poles.

Hadley cells – The rising air forms a Hadley Cell, in which air rises and cools at high elevations, flows outward (towards the poles), and finally descends back to the surface.

Global Wind System

Cloud Formation and Monsoon Rains

Clouds are formed when warm air rises and becomes saturated due to adiabatic cooling. When water vapor present in the air condenses into visible water droplets or ice crystals, they form clouds. Water vapor is always present around us in the form of microscopic gas particles. Aerosols are microscopic particles that float around in the air, such as salt and dust.

Water vapor and aerosols are continually colliding with one another. Condensation occurs when the air is cooled, and part of the water vapor adheres to the aerosols when they meet.

Larger water droplets eventually develop surrounding the aerosol particles, and these droplets begin to clump together with other droplets to form clouds.

Monsoon System

Winds shift from NE to SW in the winter and from SW to NE in the summer. It is responsible for 90% of the precipitation, and we refer to that as monsoon rains.

Two types of monsoon systems –

  • Southwest monsoon season – Rainfall from the southwest monsoons is seasonal, falling between June and September.
  • The retreating monsoon season – The retreating monsoon season occurs in October and November.

The region creates low pressure as a result of the high temperature above the Tropic of Cancer. High-pressure water-belt winds, such as those from the Bay of Bengal, Arabian Sea, and the Indian Ocean, begin to move towards low-pressure belts. While crossing the equator, they change direction and begin blowing from the southwest. While traveling over these waves, the wind becomes wet. This moisture-laden breeze brings heavy rain to India’s varied regions.

Storms and Hurricanes

Storms are a type of violent atmospheric disturbance marked by cloud cover, low barometric pressure, precipitation, and strong winds. They’re also accompanied by lightning and thunder.

Storms form when a low-pressure core develops in conjunction with the high-pressure system that surrounds it. These opposing forces can also produce winds, resulting in the creation of cumulonimbus clouds. Heated air rising off the hot earth may also cause localized pockets of low pressure, resulting in minor disturbances such as dust devils and whirlwinds.

The wind may travel faster than 64 to 72 miles per hour (103 to 117 kilometers per hour) during a storm. These violent, gusty storms have the potential to endanger people’s lives and property. It also creates rain or snow, which can result in flooding or road closures, as well as lightning and wildfires. Wind shear can also occur as a result of this.

Cyclones – Cyclones are among the most powerful storms on the planet. In the Northern Hemisphere, a cyclone is a system of winds revolving counterclockwise around a low-pressure point. Clouds and precipitation form when the spinning air rises and cools.

Tropical cyclones and medium latitude (mid-latitude) cyclones are the two types of cyclones. Winter storms in the middle latitudes are mostly due to mid-latitude cyclones.


Tropical cyclones are also referred to as Hurricanes. Tropical storms that originate in the regions such as the Gulf of Mexico, the southern Atlantic Ocean, the eastern Pacific Ocean, and the Caribbean Sea are known as hurricanes.

Hurricanes cause damage due to high winds, rain, and storm surge. As the storm’s low-pressure core approaches the shore, a storm surge develops, forcing the water level to rise extremely high.

The hurricane’s powerful winds often exacerbate a storm surge by driving saltwater across the ocean and onto the beach. Flooding, particularly in low-lying beaches like the Atlantic and Gulf Coasts, may be deadly.


The Hydrological Cycle

The hydrologic cycle, sometimes referred to as the water cycle, is the process of how water moves through the Earth’s atmosphere in various forms. How water flows throughout the Earth and changes form are described in a sequence of processes. Water is circulated between seas, the atmosphere, and the land as a response to these precise stages.

Evaporation, transpiration, condensation, precipitation, and runoff are some of the most essential of the numerous processes involved in the water cycle. Although the overall amount of water in the cycle remains relatively constant, the distribution of that water across these multiple processes changes with time.


Evaporation, in general, is the transformation of a liquid state to a gaseous form. Liquid water (from the ocean, lakes, or rivers) evaporates and turns into water vapor in the water cycle. Solar energy heats the water of the water bodies. This energy from the sun energizes water molecules on the surface of oceans, lakes, rivers, ponds, and other water bodies surfaces.

Because the ocean contains 97.5 percent of the earth’s water, a considerable amount of water evaporates at the ocean’s surface and enters the atmosphere.


Condensation is the transformation of a gas into a liquid. Water vapor in the atmosphere condenses and becomes liquid throughout the water cycle. When water vapor rises, it cools and condenses somewhat.

In most cases, water condenses on dust particles in the air and condenses into liquid. Water can sometimes bypass the liquid phase and convert straight into a solid, such as ice, hail, or snow. Particles accumulate in liquid form and create clouds.


Rain, snow, and hail are just a few of the diverse types of precipitation that fall from the sky. Clouds, which are free to travel throughout the earth and are driven by air currents, are the source of this precipitation. Water may readily migrate throughout the world as a result of this.

The hydrological Cycle


Global Ocean Circulation

The large-scale flow of waters in ocean basins is known as ocean circulation. Surface circulation is driven by winds, while deep circulation is driven by the cooling and sinking of waters in the polar regions.

Ocean currents have a significant influence on the global climate by dispersing heat around the world. They are responsible for the relative mildness of the climate in Western Europe, for example. A linked dynamic system is formed by the ocean and air currents.

Instabilities in this system, particularly the El Nino Southern Oscillation (ENSO), cause significant climatic variations. Ocean currents not only carry heat but also store CO2 and recycle nutrients, making them vital to the global ecology.

Ocean currents are divided into two categories: Wind-driven Ocean currents and Deep Ocean circulation.

Wind-driven Ocean currents

Wind stress causes each ocean to have a similar circulation pattern. In either condition, the wind-driven ocean circulation is differentiated into gyres that cover the whole ocean: Subtropical and Subpolar gyres.

Deep ocean Circulation

Density differences are the primary driving force behind deep ocean circulation. Temperature and salinity generate density changes, which is why it’s termed thermohaline circulation.


Solar Radiation

The electromagnetic radiation released by the sun is known as solar radiation, sometimes known as the solar resource or just sunshine. The light of the Sun is the ultimate energy source for the biosphere of the Earth, as well as the ultimate driving force for atmospheric and oceanic circulations.

With the use of several technologies, solar radiation may be absorbed and converted into usable forms of energy such as heat and electricity. The Sun is a massive energy source, and the sunlight is by far the most abundant source of energy that Earth receives.

Solar energy has huge potential, as Earth receives nearly 200,000 times the world’s entire daily electric-generating capacity in the form of solar energy every day. Unfortunately, even though solar energy is free, the high cost of collecting, converting, and storing it restricts its use in many regions. Solar radiation can be turned into thermal energy (heat) or electrical energy.




  • The author has done a master's in Environmental science and is currently working as chief Environmental Advisor with New Delhi State Government.


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