Temperature

The interaction between insolation, the atmosphere, and the Earth’s surface generates heat, which we measure in terms of temperature. While heat signifies the molecular movement of particles within a substance, temperature indicates the degree of hotness or coldness of a place or object.

Factors Controlling Temperature Distribution

Latitude

• The temperature at a location depends on the amount of insolation received.
• Insolation varies with latitude, hence temperature also varies with latitude.

Altitude

• The atmosphere is warmed from below by terrestrial radiation.
• Places at sea level record higher temperatures than places at higher elevations.
• Temperature generally decreases with increasing altitude, a phenomenon known as the normal lapse rate, which is 6.5°C per 1,000 meters.

Distance from the Sea

• The sea heats and cools more gradually than land.
• Land heats up and cools down rapidly.
• Temperature variation is less over the sea compared to land.
• Coastal areas experience moderate temperatures due to the influence of sea and land breezes.

Air Masses and Ocean Currents

• Warm air masses raise temperatures, while cold air masses result in lower temperatures.
• Coastal areas influenced by warm ocean currents have higher temperatures.
• Coastal areas influenced by cold ocean currents have lower temperatures.

Latitude

• Effect of Latitude:
  • Temperature distribution is heavily influenced by latitude.
  • Equatorial regions receive more direct sunlight and thus have higher temperatures.
  • Polar regions receive slanted sunlight, leading to cooler temperatures.

Altitude

• Effect of Altitude:
  • Temperature decreases with altitude due to the thinning atmosphere.
  • Higher altitudes are cooler than areas at sea level.

Horizontal Temperature Distribution

The horizontal distribution of temperature refers to the variation of temperature across different latitudes on the Earth’s surface.This is typically represented by isotherms, which are lines connecting locations with the same temperature on maps.

Horizontal Temperature Distribution in January

• In late December, the sun is directly overhead at the Tropic of Capricorn.
• Maximum average monthly temperatures are recorded in January, not December.
• The Southern Hemisphere experiences high temperatures due to increased insolation.
• In January, the Western Australian desert can reach temperatures of about 32 °C.
• Along 60° E longitude, mean temperatures in January can be as low as -20 °C at both 80° N and 50° N latitudes.
• Equatorial oceans have mean temperatures over 27 °C, while the Eurasian interior can have temperatures ranging from -18 °C to -48 °C.

Horizontal Temperature Distribution in July

• By the end of June, the sun is overhead at the Tropic of Cancer.
• Maximum average monthly temperatures are recorded in July, not June.
• The Northern Hemisphere experiences high temperatures due to increased insolation.
• The isotherm of 30 °C is found between 10° N and 40° N latitudes.
• Equatorial oceans record temperatures higher than 27 °C.
• Regions such as the Southwestern USA, Sahara, Arabia, Iraq, Iran, Afghanistan, and the desert regions of India and China record high temperatures.
• However, in central Greenland, temperatures can drop to as low as 0°C even in July.

Vertical Temperature Distribution

Temperature generally decreases with an increase in elevation, a phenomenon known as the normal lapse rate. The average decrease in temperature is about 6 °C per kilometer in the troposphere, extending to the tropopause.

Inversion of Temperature

• Normally, temperature decreases with altitude, known as the normal lapse rate.
• Sometimes, this rate is inverted, resulting in temperature inversion.
• Inversion is usually short-lived but common.
• Ideal conditions for inversion include long winter nights with clear skies and still air.
• During inversion, the Earth’s surface cools rapidly at night, leading to cooler air near the surface and warmer air above.
• Polar regions frequently undergo temperature inversion throughout the year.
• Inversion leads to stability in the lower atmosphere, trapping smoke and dust, and can cause dense fog in winter mornings.
• Air drainage in hills and mountains also causes inversion, as cold air flows downhill and accumulates in valleys, with warmer air above, protecting plants from frost damage.

Types of Inversions

1. Radiation Inversion:

Occurs during the night when the Earth’s surface loses heat through radiation, cooling the air close to the ground while the air above remains warmer.

2. Advection Inversion:

Happens when warm air moves over a cooler surface, such as when warm air from the ocean flows over cooler land, creating a layer of cooler air beneath warmer air.

1. Subsidence Inversion:

Forms when air in the upper atmosphere descends and compresses, heating up while the lower layers of air remain cooler, common in high-pressure areas.

2. Frontal Inversion:

Occurs when warm and cold air masses meet, with the warmer air mass rising above the cooler one, creating a temperature inversion along the front.

3. Turbulence Inversion:

Created by mixing layers of air, often caused by strong winds or turbulence, where cooler air becomes trapped below warmer air layers.

Solar Radiation Management (SRM)

Solar Radiation Management (SRM) is a form of climate engineering designed to reflect a portion of sunlight back into space to mitigate global warming. This strategy arises from the urgent need to address the accelerating climate crisis, which poses significant threats to human and planetary health.

Key SRM Methods

1.Stratospheric Aerosol Injection (SAI):

• Process: Reflective particles, like sulfate aerosols, are injected into the stratosphere.
• Mechanism: These particles scatter incoming solar radiation back into space, mimicking the cooling effect of volcanic eruptions.
• Benefits: Potentially effective in cooling the planet quickly.
• Challenges: Potential risks include stratospheric ozone depletion and uneven regional climate impacts.

2. Marine Cloud Brightening (MCB):

• Process: Fine droplets of seawater or other substances are sprayed into marine stratocumulus clouds.
• Mechanism: These droplets act as cloud condensation nuclei, increasing cloud reflectivity and persistence.
• Benefits: Enhanced cooling effect due to increased cloud albedo.
• Challenges: Localized and reversible but highly dependent on weather conditions and technically challenging.

3.Space Sunshades:

• Process: Large mirrors or screens are placed in orbit or at the Lagrange point 1 between Earth and the sun.
• Mechanism: These structures block or deflect incoming solar radiation, reducing solar energy reaching Earth.
• Benefits: Highly controllable and adjustable.
• Challenges: Extremely expensive and complex to deploy and maintain.

Recent Developments

A recent US government report underscores the need for comprehensive research and a governance framework to assess the risks and benefits associated with SRM. The report highlights the necessity for thorough examination and regulation to understand SRM’s potential impacts fully.

Considerations and Risks

• Environmental Impact: Potential unintended consequences, such as changes in precipitation patterns or disruptions to ecosystems.
• Governance: The need for international cooperation and regulation to manage SRM deployment responsibly.
• Ethical Issues: The moral implications of deliberately altering the Earth’s climate and the potential for unequal impacts across different regions.
• Technical Feasibility: Challenges related to the technical implementation and maintenance of SRM methods.

Prelims

Q. Different seasons are formed because

a) Sun is moving around the earth

b) Of revolution of the earth around the sun

on its orbit

c) Of rotation of the earth around its axis

d) All of the above

Q. Humidity of the air

a) Increases with the increase in atmospheric temperature

b) Decreases with the increase in atmospheric temperature

c) Is not affected by the change in atmospheric temperature

d) Does not show any consistent behavior with the change in atmospheric temperature

Q. Why is there a severe difference in the climates of the Northern and Southern Hemisphere?

a) Due to rotation of the earth around its axis

b) Due to revolution of the earth around the sun of its orbit

c) Both of the above

d) None of the above

Q. Arrange the following three atmospheric layers starting from the surface of the earth:

A. Stratosphere

B. Ionosphere

C. Troposphere

Codes:

a) A, B, C

b) C, A, B

c) A, C, B

d) C, B, A

Q. In the context of which of the following do some scientists suggest the use of cirrus cloud thinning technique and the injection of sulfate aerosol into the stratosphere? (2019)

(a) Creating the artificial rains in some regions
(b) Reducing the frequency and intensity of tropical cyclones
(c) Reducing the adverse effects of solar wind on the Earth
(d) Reducing the global warming

Ans: (d)

Q. A layer in the Earth’s atmosphere called Ionosphere facilitates radio communication. Why?

1. The presence of ozone causes the reflection of radio waves to Earth.
2. Radio waves have a very long wavelength.

Which of the statement(s) given above is/are correct?

(a) 1 only

(b) 2 only

(c) Both 1 and 2

(d) Neither 1 nor 2

Q. Normally, the temperature decreases with the increase in height from the Earth’s surface, because

1. the atmosphere can be heated upwards only from the Earth’s surface
2. there is more moisture in the upper atmosphere
3. the air is less dense in the upper atmosphere

Select the correct answer using the codes given below

(a) 1 only

(b) 2 and 3 only

(c) 1 and 2 only

(d) 1, 2 and 3

Q. With reference to the Earth’s atmosphere, which one of the following statements is correct?

(a) The total amount of insolation received at the equator is roughly about 10 times that received at the poles.

(b) Infrared rays constitute roughly two-thirds of insolation.

(c) Infrared waves are largely absorbed by water vapor that is concentrated in the lower atmosphere.

(d) Infrared waves are a part of the visible spectrum of electromagnetic waves of solar radiation.

Previous Year Mains Question

• • • 1. Troposphere is a very significant atmosphere layer that determines weather processes. How? (2022)

Ans:

Introduction	The troposphere, the lowest layer of the Earth’s atmosphere, extends from the Earth’s surface to an average altitude of about 12 km. It plays a crucial role in determining weather patterns and processes due to its composition, temperature variations, and interaction with other atmospheric layers. Understanding the significance of the troposphere is essential for grasping how weather and climate systems operate on a global scale.
Body	Concentration of Water Vapor The troposphere contains almost all the atmospheric water vapor, which is a fundamental element in the formation of clouds, precipitation, and other weather phenomena. Water vapor condenses to form clouds, leading to rainfall, thunderstorms, and snow, which are all integral to the Earth’s hydrological cycle. Temperature Gradients The troposphere shows a decline in temperature as altitude increases, creating a temperature gradient that drives the movement of air masses. This temperature variation generates convection currents, which are vital for the formation of winds, storms, and cyclones. The circulation of warm and cold air within this layer plays a significant role in shaping weather patterns. Interaction with Earth’s Surface The troposphere is heated from below by terrestrial radiation, which results in the formation of weather patterns. The uneven heating of the Earth’s surface causes differences in air pressure, leading to wind movements. The surface conditions, including ocean currents, landmass heat absorption, and urban heat islands, all interact with the troposphere to produce localized weather conditions such as monsoons, sea breezes, and heat waves. Role in Air Circulation The troposphere plays a key role in global air circulation patterns, including the Hadley, Ferrel, and Polar cells, which are responsible for distributing heat across the planet. These circulation cells ensure the redistribution of surplus heat from tropical regions to higher latitudes, balancing the global climate system and influencing weather phenomena such as trade winds, jet streams, and cyclones. Weather Events and Phenomena The troposphere is where all weather events occur, including storms, lightning, and hurricanes. These events are driven by the dynamics of the troposphere, which includes the rising of warm air, condensation, and the release of latent heat. Extreme weather events such as tropical cyclones and tornadoes are also products of tropospheric instability.
Conclusion	The troposphere is indispensable to weather processes due to its composition, interaction with Earth’s surface, and role in temperature gradients. It governs the daily weather that affects life on Earth, ranging from local weather systems to large-scale climatic patterns. Its dynamic nature, which includes constant interaction between air masses, water vapor, and solar energy, makes it a significant atmospheric layer for understanding weather and climate.

• • • 1. Bring out the causes for the formation of heat islands in the urban habitat of the world. 5 marks 100 words(2013)

Ans:

Introduction	Urban heat islands (UHIs) are areas in metropolitan regions that experience significantly higher temperatures than their rural surroundings. This phenomenon is a direct consequence of urbanization and has several environmental and health implications.
Body	Increased Surface Absorption Urban areas have extensive surfaces like roads, buildings, and pavements, which absorb and retain more heat than natural landscapes. Materials such as asphalt and concrete have high thermal mass and heat capacity, contributing to elevated temperatures. Reduced Vegetation The replacement of vegetation with impermeable surfaces reduces the natural cooling effect of transpiration and shade provided by trees and plants. This lack of green cover intensifies heat accumulation in urban areas. Heat Generation Cities generate significant heat from various sources, including industrial activities, transportation, and domestic energy consumption. Air conditioners, vehicles, and factories release heat, further contributing to the urban heat island effect. Altered Wind Patterns Tall buildings and dense infrastructure can disrupt natural wind flow, reducing the dispersion of heat. This trapping of warm air within the city limits exacerbates the UHI effect. Limited Evaporation The prevalence of impervious surfaces in urban areas limits water infiltration and evaporation, a natural cooling process. This leads to less moisture in the air and higher surface temperatures.
Conclusion	Urban heat islands are primarily caused by increased surface absorption, reduced vegetation, heat generation from human activities, altered wind patterns, and limited evaporation. Addressing these factors through urban planning and green infrastructure can mitigate the adverse effects of UHIs.

• • • 1. What do you understand about the phenomenon of temperature inversion in meteorology? How does it affect the weather and the habitants of the place? 5 marks 100 words(2013)

Ans:

Introduction	Temperature inversion is a weather phenomenon where the usual temperature gradient in the atmosphere is reversed. Instead of the air temperature decreasing with height, it increases.Instead of air temperature decreasing with altitude, it increases. This reversal can significantly impact weather patterns and living conditions in affected areas.
Body	Causes of Temperature Inversion Radiation Inversion: This occurs during clear, calm nights when the ground loses heat rapidly through radiation. The air near the ground cools down faster than the air above it, leading to an inversion. Subsidence Inversion: Associated with high-pressure systems, where descending air warms by compression, creating a layer of warm air above cooler air near the ground. Advection Inversion: Happens when warm air moves over a cold surface, cooling from below and creating an inversion layer. Frontal Inversion: Occurs along weather fronts where warm air overrides cooler air, leading to a temperature inversion. Effects on Weather Stability: Inversions create a stable atmosphere, preventing vertical air movement. This stability can suppress cloud formation and precipitation. Fog Formation: The cool, moist air trapped beneath the inversion layer often leads to fog, reducing visibility and impacting transportation. Pollution Accumulation: Temperature inversions trap pollutants close to the ground, leading to poor air quality and associated health problems. Frost Formation: Cold air trapped near the surface can lead to frost, affecting agriculture and damaging crops. Impact on Habitats Human Health: Increased levels of pollutants trapped by inversion layers can cause respiratory problems, cardiovascular issues, and exacerbate conditions like asthma. Agriculture: Frosts resulting from temperature inversions can damage crops, leading to economic losses for farmers. Transport: Reduced visibility due to fog can disrupt air, road, and sea transport, leading to delays and accidents. Ecosystem Balance: Prolonged temperature inversions can disrupt local ecosystems, affecting plant and animal life adapted to specific temperature conditions.
Conclusion	Temperature inversion is a significant meteorological phenomenon with far-reaching effects on weather patterns and living conditions. Understanding its causes and impacts can help in mitigating adverse effects, especially in urban planning and agricultural practices.

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