Atmosphere & Weather — Set 3

Correct Answer: A. Low Pressure

• **Low Pressure** = the defining characteristic of a cyclone's center, where winds blow inward and converge toward the pressure minimum. • **Eye** — in tropical cyclones, the calm center area with low pressure is called the 'Eye', surrounded by the eyewall with most severe weather. • 💡 Wrong-option analysis: High Wind Speed: found in the eyewall surrounding the eye, not in the center; Dense Clouds: also in the eyewall, not the calm eye; High Pressure: characteristic of anticyclones, not cyclones.

Correct Answer: A. Clear and stable

• **Anticyclone (Clear and stable)** = a high-pressure system where winds blow outward from the center, bringing fair weather, clear skies, and stable conditions. • **Outward wind flow** — diverging from the high-pressure center suppresses cloud formation and precipitation, leading to dry and calm weather. • 💡 Wrong-option analysis: Heavy snowfall: associated with cold cyclonic systems, not anticyclones; Stormy and wet: characteristic of low-pressure cyclones; Violent winds: occur in cyclones and frontal systems, not anticyclones.

Correct Answer: D. Willy-Willies

• **Willy-Willies** = the local Australian name for tropical cyclones, which are the same phenomenon as Hurricanes in the Atlantic and Typhoons in the Pacific. • **Same phenomenon, different names** — tropical cyclones are called Hurricanes (Atlantic/E. Pacific), Typhoons (W. Pacific), and Willy-Willies (Australia). • 💡 Wrong-option analysis: Tornadoes: small-scale violent land storms, not tropical cyclones; Hurricanes: Atlantic/East Pacific term; Typhoons: Western Pacific term used around China, Japan, Philippines.

Correct Answer: C. Fujita Scale

• **Fujita Scale (F0-F5)** = the scale used to rate tornado intensity by estimating wind speeds based on the damage caused to structures and vegetation. • **F0 to F5** — the range of the Fujita Scale; F5 represents the most catastrophic tornadoes with winds exceeding 320 km/h. • 💡 Wrong-option analysis: Richter Scale: measures earthquake magnitude; Saffir-Simpson Scale: rates hurricane/cyclone intensity (Category 1-5); Beaufort Scale: measures general wind force at sea (0-12).

Correct Answer: D. Air Mass

• **Air Mass** = a large volume of air covering thousands of square miles with relatively uniform temperature and humidity throughout its extent. • **Source region** — the surface over which an air mass forms determines its properties: continental air masses are dry, maritime ones are moist. • 💡 Wrong-option analysis: Jet Stream: fast-flowing air current at high altitudes; Front: boundary between two different air masses; Cyclone: rotating low-pressure weather system.

Correct Answer: A. Frontolysis

• **Frontolysis** = the process where a weather front dissipates or dies out, as the temperature contrast between adjacent air masses diminishes. • **Frontogenesis (opposite)** — is the creation or intensification of a front when air masses with contrasting properties come together. • 💡 Wrong-option analysis: Occlusion: process where a fast cold front overtakes a warm front; Cyclogenesis: formation and development of a cyclone; Frontogenesis: opposite of frontolysis, formation of a new front.

Correct Answer: D. Temperature and Precipitation

• **Koeppen Climate Classification** = the world's most widely used climate system based on average monthly temperature and precipitation patterns. • **5 main climate groups** — A (Tropical), B (Dry), C (Temperate), D (Continental), E (Polar); each identified by corresponding vegetation zones. • 💡 Wrong-option analysis: Vegetation and Soil: used in Thornthwaite classification; Latitude and Longitude: geographic coordinates, not climate variables; Wind and Pressure: used in synoptic meteorology, not Koeppen classification.

Correct Answer: C. Carbon Dioxide

• **Carbon Dioxide (CO2)** = the primary greenhouse gas driving global warming by trapping infrared heat radiated from Earth's surface. • **Human activities** — burning fossil fuels and deforestation have significantly increased CO2 concentration, from 280 ppm pre-industrial to over 420 ppm today. • 💡 Wrong-option analysis: Oxygen: vital for life and combustion but not a greenhouse gas; Nitrogen: most abundant atmospheric gas (78%) but transparent to infrared radiation; Argon: inert noble gas with no greenhouse properties.

Correct Answer: D. El Nino

• **El Nino** = the warm phase of the ENSO cycle, involving unusual warming of the central and eastern tropical Pacific Ocean surface. • **ENSO cycle** — El Nino-Southern Oscillation; El Nino (warm phase) and La Nina (cool phase) together drive global weather variability. • 💡 Wrong-option analysis: Monsoon: seasonal wind reversal driven by land-sea temperature differences; La Nina: opposite of El Nino, cooling of Pacific surface; Jet Stream: fast upper-atmosphere wind current, separate from ocean temperature.

Correct Answer: D. Calm and clear skies

• **Eye of cyclone (Calm and clear skies)** = the calm central region of a tropical cyclone with light winds and clear skies, surrounded by the violent eyewall. • **Eyewall** — the ring of intense thunderstorms surrounding the eye, where the most severe winds and heaviest rainfall occur. • 💡 Wrong-option analysis: Heavy lightning: found in the eyewall and outer bands, not in the eye; Violent winds: maximum wind speeds in the eyewall; Torrential rain: also in the eyewall and spiral bands, not in the calm eye.