Weather and Climate

SECTION A: BASIC CONCEPTS

Q1. What is the difference between weather and climate?

Answer:

• Weather: Atmospheric conditions such as temperature, pressure, wind, humidity and precipitation for a shorter period of time.
• Climate: The average weather condition experienced for a longer period (35-40 years) over a larger area.

Q2. What are the elements of weather?

Answer: The elements of weather are:

• Temperature
• Pressure
• Wind
• Humidity
• Precipitation

Q3. What is the Indian Meteorological Department (IMD)?

Answer: IMD is the agency functioning under the Ministry of Earth Sciences, Government of India. It is the principal agency responsible for weather observations and weather forecasting in the country. Its headquarters is in Delhi, with hundreds of observation stations across India and Antarctica.

SECTION B: ATMOSPHERIC TEMPERATURE

Q4. What is insolation?

Answer: The amount of sun's rays reaching the earth's surface is called insolation. Only a small amount of energy radiated from the sun reaches the earth's surface (approximately one part of 200 million).

Q5. Explain the processes of heat transfer in the atmosphere.

Answer: The four major processes are:

1. Conduction: Heat is transferred to the lower atmosphere directly in contact with earth's surface
2. Convection: Heated air expands and rises up, transferring heat to higher reaches
3. Advection: Heat is transferred horizontally through wind
4. Radiation: Emission of energy in the form of long waves after earth's surface gets heated

Q6. What is the Green House Effect?

Answer: The absorption of terrestrial radiation (long waves re-radiated from earth's surface) by atmospheric gases such as carbon dioxide heats up the atmosphere. This phenomenon is called the Green House Effect.

Q7. What is the Heat Budget of the Earth?

Answer: The process of heat balancing where almost entire energy reaching earth as insolation is radiated back every day, keeping the surface temperature balanced without becoming extremely hot or cold.

Q8. How do you calculate diurnal range and daily mean temperature?

Answer:

• Diurnal Range = Maximum Temperature - Minimum Temperature
• Daily Mean Temperature = (Maximum Temperature + Minimum Temperature) ÷ 2

Example: If max temp = 36°C and min temp = 28°C

• Diurnal Range = 36 - 28 = 8°C
• Daily Mean = (36 + 28) ÷ 2 = 32°C

Q9. What are isotherms?

Answer: Isotherms are imaginary lines drawn on maps connecting places having equal temperature. They are very useful for analyzing temperature distribution patterns.

Q10. What is the Normal Lapse Rate?

Answer: The phenomenon of gradual decrease in atmospheric temperature at the rate of 6.4°C per kilometer of altitude is called Normal Lapse Rate.

SECTION C: FACTORS AFFECTING TEMPERATURE

Q11. List the factors influencing temperature distribution.

Answer:

1. Latitude: Temperature decreases towards poles due to spherical shape of earth
2. Altitude: Temperature decreases with height
3. Distance from sea: Maritime influence moderates temperature
4. Ocean currents: Warm currents raise temperature, cold currents lower it
5. Relief: Mountain slopes facing sun experience higher temperature

Q12. What is the Thermal Equator?

Answer: The imaginary line connecting places with highest mean annual temperature along every longitude is called the Thermal Equator.

Q13. Name the temperature zones of the Earth.

Answer:

1. Torrid Zone: Between 23½°N and 23½°S
2. North Temperate Zone: Between 23½°N and 66½°N
3. South Temperate Zone: Between 23½°S and 66½°S
4. North Frigid Zone: Between 66½°N and 90°N
5. South Frigid Zone: Between 66½°S and 90°S

SECTION D: ATMOSPHERIC PRESSURE AND WINDS

Q14. What is atmospheric pressure?

Answer: The weight exerted by atmospheric air over the earth's surface is called atmospheric pressure. Average atmospheric pressure at sea level is 1013.2 mb or hpa.

Q15. What factors affect atmospheric pressure?

Answer:

1. Temperature: Hot air rises creating low pressure; cold air sinks creating high pressure
2. Altitude: Pressure decreases at rate of 1mb per 10 meters
3. Humidity: Humid air is lighter, creating lower pressure than dry air

Q16. What are isobars?

Answer: Isobars are imaginary lines drawn on maps connecting places having equal atmospheric pressure.

Q17. Name the Global Pressure Belts.

Answer:

1. Equatorial Low Pressure Belt (Doldrums): Around 0°
2. Sub-tropical High Pressure Belts: Around 30°N and 30°S
3. Sub-polar Low Pressure Belts: Around 60°N and 60°S
4. Polar High Pressure Belts: Around 90°N and 90°S

Q18. What is Coriolis Force?

Answer: Due to earth's rotation, winds deflect towards the right in the Northern Hemisphere and towards the left in the Southern Hemisphere. This deflecting force is called Coriolis Force.

Q19. What factors influence wind speed and intensity?

Answer:

1. Pressure Gradient Force: High pressure gradient creates strong winds
2. Frictional Force: Hills, mountains, forests obstruct wind flow

SECTION E: TYPES OF WINDS

Q20. Classify different types of winds.

Answer:

1. Permanent Winds: Trade winds, Westerlies, Polar winds
2. Periodic Winds: Monsoons, Land-sea breezes, Mountain-valley breezes
3. Local Winds: Loo, Chinook, Foehn, Harmattan
4. Variable Winds: Cyclones, Anticyclones

Q21. What is ITCZ?

Answer: Inter Tropical Convergence Zone (ITCZ) is the equatorial low pressure region where trade winds from Northern and Southern Hemispheres converge. It shifts with the apparent movement of the sun.

Q22. Explain monsoon winds.

Answer: Monsoon implies seasonal reversal in wind pattern:

• Southwest Monsoon: Summer winds from Indian Ocean to heated landmass, bringing rainfall
• Northeast Monsoon: Winter winds from cooled landmass to ocean, generally dry

Q23. What are cyclones and anticyclones?

Answer:

• Cyclones: Low pressure systems with inward spiraling winds (anticlockwise in NH, clockwise in SH)
• Anticyclones: High pressure systems with outward spiraling winds (clockwise in NH, anticlockwise in SH)

SECTION F: HUMIDITY AND PRECIPITATION

Q24. What is humidity?

Answer: The invisible water content in the atmosphere is called humidity. It reaches the atmosphere through evaporation from water bodies, transpiration from plants, etc.

Q25. Distinguish between absolute and relative humidity.

Answer:

• Absolute Humidity: Actual amount of water vapor per unit volume of atmosphere
• Relative Humidity: Ratio of actual water vapor to total water-holding capacity at that temperature, expressed in percentage

Formula: Relative Humidity = (Absolute Humidity ÷ Total water holding capacity) × 100

Q26. What is condensation? Name its forms.

Answer: The process by which water vapor turns into tiny water droplets when atmosphere reaches saturation point.

Forms:

1. Dew: Water droplets on grass, leaves during night cooling
2. Frost: Ice crystals when temperature falls below 0°C
3. Mist and Fog: Suspended water droplets in lower atmosphere
4. Clouds: Condensation around dust particles at various heights

Q27. Classify clouds based on their characteristics.

Answer:

1. Cirrus: Thin, feather-like clouds at high altitudes
2. Cumulus: Cotton wool-like clouds with vertical development
3. Stratus: Thick-layered clouds in lower atmosphere
4. Nimbus: Dark, rain-bearing clouds in lower atmosphere

Q28. What is precipitation? Name its types.

Answer: When water droplets in clouds become too heavy and fall to earth, it's called precipitation.

Types:

1. Rainfall: Water droplets
2. Snowfall: Ice crystals in cold regions
3. Hailstones: Layered ice pellets

Q29. Explain the types of rainfall.

Answer:

1. Orographic/Relief Rainfall: Moisture-laden winds rise along mountain slopes, causing condensation and rainfall on windward side
2. Convectional Rainfall: Due to heating and convection, common in afternoons (4 O'Clock rains)
3. Cyclonic/Frontal Rainfall: When warm and cold air masses meet in cyclonic systems

Q30. What are rain shadow regions?

Answer: Areas on the leeward side of mountains that receive very little rainfall because the windward side receives most of the moisture, leaving dry air to descend on the leeward side.

SECTION G: APPLICATION QUESTIONS

Q31. Why do coastal regions have moderate climate?

Answer: Due to differential heating of land and sea. Land heats and cools faster than sea, so sea breezes and land breezes help moderate the temperature in coastal areas.

Q32. Why is the diurnal range of temperature low in Kerala?

Answer: Kerala is a coastal state surrounded by water bodies. The maritime influence and high humidity moderate the temperature variations, resulting in low diurnal range.

Q33. Why do we experience low temperature at hill stations like Ooty and Munnar?

Answer: Due to the Normal Lapse Rate - temperature decreases at the rate of 6.4°C per kilometer of altitude. Higher elevations receive less atmospheric heating.

Q34. Why are westerlies stronger in the Southern Hemisphere?

Answer: The Southern Hemisphere has more oceanic area and less landmass compared to the Northern Hemisphere, so there's less friction to obstruct wind flow.

Q35. Why does Kerala receive southwest monsoon rains while western Tamil Nadu receives little rainfall?

Answer: Kerala lies on the windward side of the Western Ghats, receiving orographic rainfall from southwest monsoon. Western Tamil Nadu lies in the rain shadow region of the Western Ghats.

SECTION H: INSTRUMENTS AND MEASUREMENTS

Q36. Name the instruments used to measure weather elements.

Answer:

• Thermometer/Max-Min Thermometer: Temperature
• Barometer: Atmospheric pressure
• Anemometer: Wind speed
• Wind Vane: Wind direction
• Hygrometer: Humidity
• Rain Gauge: Rainfall

Q37. Convert 86°F to Celsius.

Answer: Using formula: °C = (°F - 32) × 5/9 °C = (86 - 32) × 5/9 = 54 × 5/9 = 30°C

IMPORTANT TERMS TO REMEMBER

• Insolation, Terrestrial Radiation, Green House Effect
• Heat Budget, Normal Lapse Rate, Thermal Equator
• Doldrums, ITCZ, Coriolis Force
• Orographic Rainfall, Rain Shadow, Convectional Rainfall
• Absolute Humidity, Relative Humidity, Condensation
• Cyclones, Anticyclones, Monsoons

Note: Practice drawing and labeling diagrams for global pressure belts, wind patterns, types of rainfall, and cloud formations for complete understanding.