MEV 012: Unit 07 - Meteorology

-

UNIT 7: METEOROLOGY

7.0 Introduction

Meteorology is the scientific study of the atmosphere and weather processes. This unit covers essential meteorological concepts such as atmospheric composition, layering, moisture variables, greenhouse effects, energy balance, stability, and interpretation tools like thermodynamic diagrams.

7.1 Objectives

By the end of this unit, you should be able to:

  • Understand the composition and structure of the atmosphere.
  • Explain key moisture variables and their role in weather phenomena.
  • Describe the greenhouse effect and Earth's radiation balance.
  • Understand atmospheric stability and related processes.
  • Interpret basic thermodynamic diagrams used in weather forecasting.

7.2 Composition of Atmosphere

The Earth's atmosphere is composed of:

  • Permanent gases:
    • Nitrogen (78.08%)
    • Oxygen (20.95%)
    • Argon (0.93%)
  • Variable gases:
    • Carbon dioxide (~0.04%), Water vapor (0–4%), Ozone, Methane, etc.

Aerosols, dust, and pollutants also affect atmospheric properties and play a role in cloud formation and climate.

7.3 Stratification of Atmosphere

The atmosphere is stratified into layers based on temperature gradients:

  1. Troposphere (0–12 km): Weather occurs here; temperature decreases with altitude.
  2. Stratosphere (12–50 km): Contains ozone layer; temperature increases with altitude.
  3. Mesosphere (50–85 km): Coldest layer; meteors burn here.
  4. Thermosphere (85–500 km): High temperatures; auroras occur.
  5. Exosphere (above 500 km): Transition to outer space.

The tropopause is the boundary between the troposphere and stratosphere.

7.4 Moisture Variables

Moisture in the atmosphere is critical for cloud formation and precipitation. Key variables include:

  • Humidity: Amount of water vapor in air.
  • Relative Humidity: Percentage of moisture compared to saturation.
  • Dew Point: Temperature at which air becomes saturated.
  • Vapor Pressure: Partial pressure exerted by water vapor.
  • Specific and Absolute Humidity: Measure of water vapor mass per unit of air.

These variables affect cloud formation, fog, rainfall, and evaporation processes.

7.5 Greenhouse Effect

The greenhouse effect refers to the trapping of Earth's infrared radiation by atmospheric gases like CO₂, CH₄, N₂O, and water vapor.

  • Natural Greenhouse Effect keeps Earth warm (~15°C).
  • Enhanced Greenhouse Effect from anthropogenic emissions leads to global warming.

Major greenhouse gases:

  • Carbon dioxide (CO₂)
  • Methane (CH₄)
  • Nitrous oxide (N₂O)
  • Water vapor (H₂O)
  • Ozone (O₃)

7.6 Earth’s Radiation Budget

The radiation budget is the balance between incoming solar radiation and outgoing terrestrial radiation:

  • Incoming: Shortwave radiation from the Sun (~340 W/m²).
  • Reflected: ~30% reflected back (albedo).
  • Absorbed by atmosphere and surface: ~70%.
  • Outgoing: Longwave infrared radiation emitted by Earth.

Imbalance in this budget (due to greenhouse gases or aerosols) leads to climate change or global cooling/warming.

7.7 Atmospheric Stability

Stability determines whether air parcels rise, sink, or remain stationary when displaced.

  • Stable atmosphere: Resists vertical motion (e.g., temperature inversion).
  • Unstable atmosphere: Encourages convection, cloud development, storms.
  • Neutral atmosphere: No tendency to rise or sink.

Lapse rates (rate of temperature decrease with height):

  • Environmental Lapse Rate (ELR)
  • Dry Adiabatic Lapse Rate (DALR)
  • Moist Adiabatic Lapse Rate (MALR)

These are used to analyze vertical air motion.

7.8 Thermodynamic Diagrams

Thermodynamic diagrams help visualize atmospheric conditions and forecast weather. Key types:

  • Skew-T Log-P Diagram
  • Emagram
  • Tephigram (T–phi gram)

These graphs plot pressure, temperature, dew point, and lapse rates—used in radiosonde analysis.

7.9 T-Phigram and Mixing Height

T–Phigram (Tephigram):

  • A thermodynamic diagram that plots temperature vs. entropy.
  • Used to identify stability, cloud base, and potential for convection.

Mixing Height:

  • The vertical extent of turbulent mixing in the atmosphere.
  • Important in pollution dispersion and air quality studies.
  • Varies with time of day, surface heating, and weather.

7.10 Let Us Sum Up

This unit provided an overview of key meteorological concepts. You learned about the atmosphere's structure, moisture variables, and energy balance. You also explored atmospheric stability, the role of greenhouse gases, and how thermodynamic diagrams help analyze and forecast weather conditions.

7.11 Keywords

  • Atmosphere-A layer of gases surrounding the Earth, vital for weather and life.
  • Troposphere-Lowest atmospheric layer where weather occurs.
  • Humidity-Amount of water vapor present in the air.
  • Dew Point-Temperature at which air becomes saturated with moisture.
  • Greenhouse Effect-Trapping of Earth’s heat by atmospheric gases.
  • Radiation Budget-Balance between incoming solar and outgoing terrestrial radiation.
  • Atmospheric Stability-Tendency of the atmosphere to resist or support vertical motion.
  • Lapse Rate-Rate at which air temperature decreases with altitude.
  • Tephigram-Diagram used in meteorology to plot temperature and pressure.
  • Mixing Height-Height up to which atmospheric mixing occurs.
  • Jet Stream-High-altitude wind that influences weather patterns.
  • Thermosphere-Hot upper layer of atmosphere where auroras occur.
  • Albedo-Reflectivity of Earth’s surface to incoming solar radiation.
  • Cloud Formation-Process by which rising moist air cools and condenses.
  • Specific Humidity-Mass of water vapor per unit mass of air.
  • Skew-T Diagram-A graphical tool to analyze vertical profiles of the atmosphere.

 


Comments

Post a Comment

Popular Posts

Jcert Class 8 Daffodil Chapter 1a: The Naive Friends Solutions

-
Chapter 1a : The Naive Friends Answer the following questions: 1. Which questions made Keshav and Shyama curious about the egg? Ans.         How did the chick come out? How big would the eggs? How many? What colours would they? What did they eat? Such types of questions made Keshav and Shyama curious about the egg. 2. What three things did the children do to protect the eggs? Ans.         The children done three things are: (i)          Adjustment of food. (ii)        Adjustment of water. (iii)      Adjustment of roof. 3. Why did Keshav think of making a cushion for the eggs? Ans.         When Keshav saw the egg on direct sun light, he thaught making a cushion for the eggs. 4. What excuse did Keshav give for not showing the eggs to Shyama? Ans.     ...
Read more

Jcert Class 8 भाषा मंजरी Chapter 3 मित्रता Solutions

-
अध्याय - 3 : मित्रता 1. आप किस प्रकार कह सकते हैं कि मित्रों के चुनाव की उपयुक्तता पर हमारे जीवन की सफलता निर्भर करती है? उ. मित्रों के चुनाव की उपयुक्तता पर हमारे जीवन की सफलता निर्भर करती है क्योंकि संगति का गुप्त प्रभाव हमारे आचरण पर पड़ता है और यदि हमें अच्छी संगति, अच्छे मित्र मिलते हैं तो वे हमें सफलता की ओर ले जाते हैं जबकि बुरी संगति हमारे जीवन को खाक में मिला देती है।  2. 'विश्वासपात्र मित्र जीवन की एक औषध है।' आशय स्पष्ट कीजिए। उ. 'विश्वासपात्र मित्र जीवन की एक औषध है'- ऐसा इसलिए कहा गया है कि यदि हमें विश्वासी मित्र मिल गया तो हम अपने जीवन में चाहे जैसा भी कदम उठाएँ, उस कदम की आलोचना करके वह हमें सही दिशा की ओर उन्मुख करेगा। हम अपनी गलती रूपी बीमारी को उसकी आलोचना रूपी औषधि से दूर कर सकेंगे।  3. मित्र का चुनाव करते समय हमें किन बातों का ध्यान रखना चाहिए? उ. मित्र का चुनाव करते समय हमें निम्नलिखित बातों का ध्यान रखना चाहिए हमारे अच्छे विचारों (संकल्पों) को दृढ़ करने वाला हो। हमें दोषों और त्रुटियों से बचाए। हमारे सत्य, पवित्रता ...
Read more

Jcert Class 8 भाषा मंजरी Chapter 8 अमरूद का पेड Solutions

-
अध्याय - 8 : अमरूद का पेड 1. लेखक को क्यों लगता है कि इन सब पिछड़े खयालातों का हमारे घर में गुजर नहीं हो सकेगा। उ. अमरूद के पेड़ को देखकर सबसे पहले बाबू कन्हैयालाल की बूढ़ी पत्नी ने एक दिन टोका कि पश्चिम की तरफ अगर मकान का मुखड़ा हो और सामने ही अमरूद का पेड़ तो 'राम-राम बड़ा अशुभ होता है और माँ के चेहरे पर थोड़ा-सा भय दिखा पर लेखक को विश्वास था कि इन सब पिछड़े खयालातों का हमारे घर में गुजर नहीं हो सकेगा क्योंकि उसके घर के लोग आधुनिक विचारधारा के थे उसकी माँ सत्याग्रह के दिनों में अजमेर में लम्बा जेल कर चुकी है। पिताजी खुद राजनैतिक सामाजिक उदारता वाले आदमी थे। बुआ ने विवाह नहीं किया था, पढ़ने-लिखने में ही अपनी सम्पूर्ण जिन्दगी लगा दी और समाज कोई चुनौती देने का साहस नहीं कर सका। साथ ही परिवार के सभी लोगों में पिछड़ेपन के प्रति भर्त्सना का भाव था। 2. अमरूद के पेड़ की छाया किस प्रकार लेखक को उनके भाई-बहनों के साथ जोड़ती है ? उ. अमरूद के पेड़ की छाया लेखक को उसके भाई-बहनों के साथ जोड़ती है। वे सभी अमरूद की छाया में बेंत की कुर्सियों पर बैठ चर्चाएँ करते थे जिससे उनके बीच...
Read more