Upslope flow of warm, moist air leads to which cloud type?

• A. Stratus type clouds
• B. Cumulonimbus
• C. Cirrus
• D. Altostratus

Answer: (A)

When warm, moist air is forced to rise up a slope, it expands and cools. If the air is moist enough, it reaches its dew point and condenses into a widespread, flat layer—typical of low-level stratus clouds. The lifting is usually gentle and the atmosphere stable, so you get a horizontal, sheet-like cloud deck rather than tall, vertical development. Cumulonimbus requires strong convection and vertical growth, cirrus forms high and ice-crystal clouds, and altostratus sits at mid levels without the characteristic upslope-driven low deck. So the result of upslope flow of warm, moist air is stratus clouds.