What altitudes are considered high clouds?

High clouds are generally categorized as those that form at altitudes exceeding 20,000 feet above ground level (AGL). This classification stems from meteorological standards, which specify that high clouds typically include cirrus, cirrostratus, and cirrocumulus types. These clouds form in the upper troposphere where the temperature is very low, leading to the formation of ice crystals, which is characteristic of high-altitude cloud formations.

Choosing 20,000 feet AGL as the threshold for high clouds is consistent with the standard meteorological definitions, and it allows for differentiation from mid-level clouds, which are found between approximately 6,500 and 20,000 feet AGL, and low clouds, which are generally below 6,500 feet AGL.

Therefore, the correct identification of high clouds reinforces the understanding of cloud classification and the atmospheric layers.