Which statement about cirrus clouds is true?

Which statement about cirrus clouds is true?

• A. They form at low altitudes and bring rain
• B. They are dense fogs near the ground
• C. They are high-altitude clouds made of ice crystals
• D. They are composed of water vapor in the air

Answer: (C)

Cirrus clouds are high-altitude clouds made of ice crystals. They form in the upper parts of the troposphere where temperatures are very cold, so water vapor deposits directly into tiny ice crystals rather than forming liquid droplets. That gives the thin, wispy, feathery appearance you see far overhead. Because they sit so high and are ice crystals, cirrus clouds don’t produce rain themselves. Fog near the ground is a different phenomenon, and water vapor by itself isn’t visible—clouds appear when vapor condenses into droplets or crystals. Cirrus typically occur from about 20,000 to 40,000 feet and can signal moisture up there and sometimes indicate an approaching weather change.

Cirrus clouds are high-altitude clouds made of ice crystals. They form in the upper parts of the troposphere where temperatures are very cold, so water vapor deposits directly into tiny ice crystals rather than forming liquid droplets. That gives the thin, wispy, feathery appearance you see far overhead. Because they sit so high and are ice crystals, cirrus clouds don’t produce rain themselves. Fog near the ground is a different phenomenon, and water vapor by itself isn’t visible—clouds appear when vapor condenses into droplets or crystals. Cirrus typically occur from about 20,000 to 40,000 feet and can signal moisture up there and sometimes indicate an approaching weather change.