Atmosphere & Weather — Set 4

Correct Answer: B. Isotherms

• **Isotherms** = lines on a map connecting all points having the same temperature at a given time, used to visualize temperature distribution. • **Temperature gradient** — the spacing of isotherms indicates how quickly temperature changes; closely spaced isotherms show steep gradients. • 💡 Wrong-option analysis: Isohyets: lines connecting equal rainfall amounts; Isohalines: lines connecting equal ocean salinity; Isobars: lines connecting equal atmospheric pressure.

Correct Answer: B. Barometer

• **Barometer** = the instrument used to measure atmospheric pressure, available as mercury barometer or aneroid barometer types. • **Rapid pressure drop** — a sudden fall in barometric pressure indicates an approaching storm or low-pressure system. • 💡 Wrong-option analysis: Anemometer: measures wind speed; Hygrometer: measures relative humidity; Thermometer: measures temperature.

Correct Answer: A. The Southern Hemisphere

• **Roaring Forties (Southern Hemisphere)** = strong westerly winds between 40° and 50° south latitude, unimpeded by landmasses, making them exceptionally powerful. • **40°-50° south** — the latitude band with minimal continental landmass allowing these winds to blow continuously around the globe. • 💡 Wrong-option analysis: Northern Hemisphere: equivalent latitudes have landmasses that break wind continuity; Equatorial Region: Doldrums area with calm winds; Polar Region: polar easterlies, not westerlies.

Correct Answer: B. Northern India

• **Loo** = a strong, hot, and dry summer wind that blows over the western Indo-Gangetic Plain of Northern India and Pakistan. • **Heatstroke risk** — exposure to Loo during peak summer afternoons can cause severe heatstroke, making it a dangerous local wind. • 💡 Wrong-option analysis: Western Europe: Mistral and Foehn are local winds here; North America: Chinook is the famous warm dry local wind; South Africa: Berg wind is the hot dry local wind.

Correct Answer: A. Cumulus

• **Cumulus** = fluffy, white clouds with flat bases and distinct outlines resembling cotton wool or cauliflower, typically indicating fair weather. • **Vertical growth** — when cumulus clouds grow vertically into cumulonimbus, they can produce thunderstorms and heavy rainfall. • 💡 Wrong-option analysis: Stratus: flat, gray, uniform layer clouds covering the sky like a blanket; Cirrus: wispy, feathery high-altitude ice-crystal clouds; Nimbus: dark rain-bearing clouds, includes nimbostratus.

Correct Answer: D. 6.5°C per km

• **Normal Lapse Rate = 6.5°C per km** = the standard rate at which temperature decreases with altitude in the troposphere. • **6.5°C/km** — equivalent to approximately 1°C per 165 meters; this occurs because the troposphere is heated from the ground upward. • 💡 Wrong-option analysis: 2°C per km: too low, significantly below the actual lapse rate; 10°C per km: the dry adiabatic lapse rate for unsaturated air, higher than normal; 1°C per 165 meters: equivalent to the correct answer (6.5°C/km), but listed as a separate option.

Correct Answer: A. Lower Stratosphere

• **Lower Stratosphere** = the atmospheric layer where jet aircraft cruise to avoid turbulence and weather found in the troposphere, offering smooth flying conditions. • **10-12 km altitude** — typical cruising altitude for commercial jets, just above the tropopause, in the calm, cloud-free lower stratosphere. • 💡 Wrong-option analysis: Exosphere: outermost layer, too thin for jet engines; Upper Mesosphere: extremely cold and too high for commercial aircraft; Lower Troposphere: full of weather disturbances, not suitable for smooth flight.

Correct Answer: C. Rainfall

• **Isohyet** = a line on a map connecting all points that receive equal amounts of rainfall during a specified period. • **Rainfall analysis** — isohyet maps are essential for agricultural planning, flood forecasting, and water resource management. • 💡 Wrong-option analysis: Sunshine: isohels connect places of equal sunshine duration; Snowfall: no specific standard term, but isohyets can include solid precipitation; Cloudiness: isonephs connect places of equal cloud cover.

Correct Answer: C. Sea Breeze

• **Sea Breeze** = a local coastal wind blowing from sea to land during the day, as land heats faster creating low pressure that draws in cooler sea air. • **Daytime** — land heats up faster than the sea, creating a low-pressure zone over land that pulls cool moist air in from the sea. • 💡 Wrong-option analysis: Land Breeze: opposite direction, blows from land to sea at night; Mountain Breeze: blows down mountain slopes at night; Valley Breeze: blows up valleys during the day due to slope heating.

Correct Answer: C. Earth's rotation

• **Earth's rotation** = the primary cause of the Coriolis force, an inertial deflection force that affects the direction of winds and ocean currents. • **Zero at equator, maximum at poles** — the Coriolis effect is weakest at the equator (0°) and strongest at the poles (90°), proportional to the sine of latitude. • 💡 Wrong-option analysis: Lunar attraction: causes tides, not Coriolis force; Solar radiation: drives temperature differences and air circulation, not Coriolis; Gravitational pull: keeps atmosphere bound to Earth, not responsible for Coriolis deflection.