Brief Summary
This YouTube video by The Unstoppable is an educational lecture on the atmosphere and water within it. The lecture covers the composition and evolution of the atmosphere, its various layers (troposphere, stratosphere, mesosphere, and thermosphere), and the hydrological cycle. It also discusses concepts like insulation, terrestrial radiation, greenhouse effect, temperature inversion, humidity, condensation, and precipitation, including different types of rainfall.
- Atmosphere composition, evolution and layers
- Hydrological cycle and it's components
- Types of rainfall
Introduction
The lecture will cover the atmosphere and the water present within it. The lecture will cover the different layers of the atmosphere, the percentage of water present in the atmosphere, and the hydrological cycle, including evaporation, condensation, and precipitation. The lecture is important for students preparing for exams like CDS, CPF, and SSC.
Atmosphere Composition and Evolution
The atmosphere is an envelope of gases and aerosols held in place by Earth's gravity, which is essential for a habitable planet. The evolution of the atmosphere occurred in three stages: loss of the primordium sphere due to solar flares, degassing from volcanic activity, and modification by the living world through photosynthesis.
Layers of the Atmosphere
The Earth's atmosphere consists of several layers: the troposphere, stratosphere, mesosphere, thermosphere (also known as the ionosphere), and exosphere. The troposphere is the most important layer because it is where we live and where all weather phenomena occur. Its thickness varies from 8 km at the poles to 18 km at the equator. The temperature in the troposphere decreases with height due to terrestrial radiation.
Troposphere and Temperature
The temperature decreases with height in the troposphere because the atmosphere is primarily heated by terrestrial radiation, not direct solar insulation. Greenhouse gases like carbon dioxide and water vapor trap long-wave radiation, warming the atmosphere. The amount of insulation depends on factors like atmospheric transparency, length of day, Earth's tilt, and the Earth's position relative to the Sun.
Insulation and Earth's Surface
The amount of insulation received depends on the transparency of the atmosphere, the length of the day, the tilt of the Earth, and the Earth's position relative to the sun. The Earth's surface is not uniform, and different surfaces have different reflecting powers, known as albedo. Fresh snow has a high albedo, while asphalt has a low albedo.
Greenhouse Effect and Temperature Inversion
The greenhouse effect is a phenomenon where greenhouse gases trap heat, making Earth habitable. However, excessive emissions of CO2 are causing global warming. Temperature inversion is when temperature increases with height in the troposphere, usually occurring in polar areas during long winter nights with stable air and cloudless skies.
Stratosphere and Ozone Layer
The stratosphere lies above the tropopause and extends up to 50 km. The temperature increases with height due to the presence of the ozone layer, which protects the Earth from harmful ultraviolet rays. Airplanes fly in the stratosphere because it is free from weather phenomena.
Mesosphere and Thermosphere
In the mesosphere, temperature decreases with height, and meteorites burn up. The thermosphere, also known as the ionosphere, contains ions that reflect radio waves, making communication possible. The thermosphere is the warmest layer. The Karman line marks the boundary where the atmosphere ends and outer space begins.
Earth's Water Distribution
97.2% of Earth's water is salt water, while 2.8% is fresh water. Of the fresh water, 68.7% is in glaciers and ice caps, 30.1% is in ground water, and 1.2% is in surface water and other sources. Water continuously circulates through the atmosphere, lithosphere, and hydrosphere via evaporation, condensation, and precipitation.
Evaporation and Humidity
Evaporation is the process where water turns into water vapor. The rate of evaporation is high when there is a lot of heat, wind, and surface area. Humidity is the amount of water vapor present in the atmosphere. Absolute humidity is the weight of water vapor per unit volume of air, while relative humidity is the percentage of moisture present compared to its full capacity.
Condensation and Forms of Condensation
Condensation is when water vapor converts into water. It requires loss of heat and hygroscopic nuclei (particles for water to condense on). Forms of condensation include fog, mist, dew, and clouds. Smog is a combination of smoke and fog. Cloud seeding involves adding particles like silver iodide to clouds to promote rain.
Types of Clouds
Clouds are divided into low-level, middle-level, and high-level clouds. Nimbus clouds are rain-bearing and opaque. Cumulus clouds are wool-shaped with flat bases. Cirrus clouds are feather-shaped and made of ice crystals. The study of clouds is called nephology.
Cloud Classification and Cyclone Formation
Clouds are further classified based on altitude and characteristics. Stratus clouds are low-level and layered. Nimbostratus clouds are middle-level and rain-bearing. Cumulonimbus clouds are associated with cyclones and have an anvil-shaped top.
Precipitation and Types of Rainfall
Precipitation occurs when air can no longer hold moisture. It includes rain, snowfall, sleet, and hail. Sleet is frozen and refrozen raindrops, while hail is larger. There are three types of rainfall: conventional, orographic (relief), and cyclonic.
Orographic and Cyclonic Rainfall
Orographic rainfall occurs when moist air is forced to rise over mountains, causing condensation and precipitation on the windward side, while the leeward side remains in a rain shadow. Cyclonic rainfall is associated with cyclones and involves cumulonimbus clouds with extensive vertical development. Cloud bursts are characterized by heavy rainfall in a short area and time, common in hilly regions.
