Middle-level clouds are clouds that typically form between altitudes of 6,500 feet (2,000 meters) and 20,000 feet (6,000 meters). These clouds are composed of water droplets and can occasionally contain ice crystals. Middle-level clouds are often associated with a combination of vertical development and horizontal layering. They have a more substantial appearance compared to high-level clouds and can have a significant influence on weather conditions. The main types of middle-level clouds are:
- Altocumulus (Ac): Altocumulus clouds are characterized by their patchy or layered appearance. They often form as rounded or lumpy cloud masses with individual cloud elements called cloudlets. Altocumulus clouds are typically white or gray and can have a puffy or wavy texture. They are composed of water droplets and can occasionally indicate the approach of a cold front or a change in weather conditions. Altocumulus clouds are lower in altitude compared to high-level clouds, typically forming between 6,500 and 20,000 feet (2,000 to 6,000 meters).
- Altostratus (As): Altostratus clouds are thick, gray or blue-gray clouds that cover the sky in a uniform layer. They have a more solid and continuous appearance compared to altocumulus clouds. Altostratus clouds often block out the Sun or Moon, resulting in diffuse lighting. They are composed of water droplets and can occasionally contain ice crystals. Altostratus clouds can be associated with steady precipitation or the approach of a warm front. They typically form between 6,500 and 20,000 feet (2,000 to 6,000 meters) in altitude.
Middle-level clouds, particularly altocumulus and altostratus clouds, play a significant role in moderating surface temperatures by reflecting a portion of incoming solar radiation back into space. They also contribute to the overall cloud cover and can influence the atmospheric stability and moisture distribution. Observing and understanding middle-level clouds is important for weather forecasting and assessing atmospheric conditions.