Understanding Earth’s Atmosphere, Monsoons, and Global Warming

Posted on Sep 17, 2024 in Geology

Rocks

Types of Rocks in the Lithosphere

Rocks are naturally occurring, hard, consolidated inorganic materials composed of one or multiple minerals. Here are the three main types:

Igneous: Formed by the solidification of magma (interior) or lava (surface). Composed primarily of silicate minerals. Igneous rocks can sometimes overlap with sedimentary and metamorphic rocks.
Sedimentary: Formed by the precipitation from solutions and consolidation of remnants of biotic components like plants and animals. These rocks contain both primary and altered minerals, as well as newly synthesized secondary minerals.
Metamorphic: Also known as thermal rocks, these are formed from pre-existing rocks (igneous or sedimentary) due to changes in temperature and pressure. This occurs when magma intrudes through pre-existing rocks. Igneous and metamorphic rocks can weather to form sediments, which can then be deposited and lithified into sedimentary rocks.

Indian Monsoon

A monsoon is a regional wind that blows towards land during a certain season and reverses direction in another. While monsoons occur globally, they are prominent over India and Southeast Asia. The Indian subcontinent experiences two types:

South-West Monsoon

Originates from southeast trade winds in the Indian Ocean. Upon crossing the equator, the Coriolis force deflects them rightward, becoming southwest trade winds.
These winds gather moisture over the Indian Ocean.
Upon reaching India, the monsoon splits into the Arabian Sea Branch and the Bay of Bengal Branch.
The Arabian Sea branch, laden with moisture, encounters the Western Ghats and is forced to ascend. This cooling leads to cloud formation and precipitation.
Kerala receives the southwest monsoon around early June.
The winds then turn west, spreading rain over northern India.
Delhi typically experiences monsoon onset in the first week of July, lasting until September or early October.

North-East Monsoon

As the sun shifts to the southern hemisphere, the Inter-Tropical Convergent Zone (ITCZ) moves south of the equator, reversing wind directions. Winds now blow from the northeast towards the ITCZ.
Originating from landmasses, these winds are relatively dry.
Passing over the Bay of Bengal, they gather moisture, causing rainfall in parts of Odisha, Andhra Pradesh, and Tamil Nadu.
Cyclone formation is common during this period, bringing additional rainfall to Odisha, Andhra Pradesh, Telangana, and Tamil Nadu.

Layers of the Atmosphere

Based on temperature, the atmosphere is divided into four layers:

Troposphere: The densest layer, closest to the ground, containing 70% of the atmosphere’s mass. Extends up to 11 km.
Stratosphere: Extends from the tropopause (top of the troposphere) to about 50 km.
Mesosphere: Located above the stratosphere, between 50 km and 80 km.
Thermosphere: Extends from 80 km to about 60,000 km. Temperatures here can reach 2000°C.

Greenhouse Effect

Incoming Solar Radiation

The atmosphere acts like a giant heat engine, powered by incoming solar radiation (insolation).
Insolation drives various atmospheric processes, including air movements, evaporation, cloud formation, and precipitation.
Earth receives a tiny fraction of the sun’s energy, with only a small portion driving physical and biological processes.
Insolation comprises various electromagnetic radiation types, including X-rays, gamma rays, ultraviolet (UV) rays, visible light, infrared rays, microwaves, and radio waves.
UV, visible, and infrared radiation make up over 95% of the energy received by Earth.
The ozone layer protects Earth from harmful UV radiation.
Some long-wave radiation is absorbed in the troposphere.
Visible light, composed of seven colors, makes up the majority of radiation reaching Earth’s surface.
Clouds reflect a portion of radiation, while gases and particles scatter and absorb some.

Outgoing Radiation

Earth maintains a habitable temperature by radiating some absorbed energy back into space.
Heat is transferred from the surface to the atmosphere through conduction and convection.
This emitted energy, called outgoing radiation, is in the form of long-wave radiation.
Greenhouse Gases (GHGs) like carbon dioxide (CO2), carbon monoxide (CO), and water vapor absorb a portion of outgoing radiation.
The amount of radiation absorbed is directly proportional to the concentration of GHGs.
GHGs act like a blanket, trapping heat and regulating Earth’s temperature, a process known as the greenhouse effect.
The intensity of the greenhouse effect varies depending on GHG concentrations.

Global Warming

Earth receives and radiates solar energy. GHGs in the atmosphere trap some of the outgoing heat, contributing to the greenhouse effect, which is essential for life.
However, human activities have significantly increased GHG concentrations, leading to an enhanced greenhouse effect and global warming.
Burning fossil fuels, deforestation, mining, agriculture, and industrial activities all contribute to GHG emissions.
Reduced green coverage exacerbates the issue.
Natural processes like volcanic eruptions also release GHGs.
Chlorofluorocarbons (CFCs) and methane from various sources have depleted the ozone layer.
The abnormal increase in GHGs has led to a global temperature rise, though not uniformly distributed.
Over the past century, Earth’s average temperature has increased by about 0.6 degrees Celsius (1.3 degrees Fahrenheit).
This warming trend is accelerating compared to the past.
Evidence strongly suggests that human activities are the primary driver of this recent warming.
Continuing at this rate, global temperatures could rise by 1.5°C to 4.5°C by 2030.
The Intergovernmental Panel on Climate Change (IPCC) projects a temperature increase of 1.4°C to 5.8°C by 2100.
Signs of global warming are evident worldwide, including melting ice caps, shrinking glaciers, and more frequent extreme weather events.