Which conditions are likely to be found on the poleward edge of a cirrus cloud shield?

• A. Heavy precipitation
• B. Stable atmospheric conditions
• C. High turbulence
• D. Enhanced divergence

Answer: (D)

On the poleward edge of a cirrus cloud shield, enhanced divergence is a key characteristic. Cirrus clouds are typically associated with the upper levels of the atmosphere and often form as part of a larger weather system, such as a warm front or an upper-level jet stream. These clouds indicate that air is rising, and as the air rises, it cools and expands, leading to the formation of cirrus clouds composed of ice crystals.

The concept of enhanced divergence pertains to the horizontal outflow of air that occurs at the top of these cloud formations. As air rises and expands, it creates an area with lower pressure above the clouds, allowing air to flow away from the cloud shield. This divergence at high altitudes often signals that the atmosphere is conducive to further development of weather systems, such as storm systems, while also indicating that the conditions can remain stable in the lower levels of the atmosphere as the high cirrus clouds often indicate the presence of warmer air aloft.

In contrast, conditions like heavy precipitation and high turbulence are typically not present at the poleward edge of a cirrus cloud shield; these conditions are more commonly associated with lower, denser clouds such as cumulonimbus or nimbostratus which signify active weather features. Stable