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What Are Two Characteristics of a Cloud?

Clouds are classified according to various characteristics such as altitude, origin and appearance. The process of condensation (in which gas or vapor turns to liquid) results in the formation of a cloud. According to the Plymouth State University Meteorology Program, the two most important characteristics used to accurately classify a cloud are altitude and appearance. Clouds may form near the ground or up to an altitude of 50,000 feet and vary in appearance from thin or wispy, to thick or puffy. Depending on the cloud that forms, precipitation may or may not result.

Altitude
- Clouds form at various altitudes in the atmosphere and are classified according the level at which the base of the cloud forms. High-level clouds form above 20,000 feet and are labeled with the prefix "cirro". Mid-level clouds form around the middle of the troposphere, forming between 6,500 and 20,000 feet and are assigned the prefix of "alto". Low-level clouds on the other hand are formed below 6,500 feet and are not assigned a specific prefix, but are usually described with the prefixes of "strato" or "cumulo" depending on appearance.
Appearance
- There are three main types of high-level clouds: cirrus, cirrostratus, and cirrocumulus. Made up of mainly ice crystals, cirrus clouds appear wispy or feathery. Cirrostratus clouds occur with a warm front move in on cirrus clouds and they thicken, giving a veil-like appearance. Cirrocumulus clouds on the other hand are distinguished by layers punctuated by a lumpiness that is cumulus in appearance.
  
  Mid-level clouds are mainly classified as either altostratus or altocumulus. Altostratus clouds have a flat, but uniform texture while altocumulus clouds are heaped on top of one another creating a "cumulo" visual.
  
  The two main types of low-level clouds are stratus, which form horizontally; and cumulus, which form vertically. While stratus clouds are flat and uniform producing a gray cloud cover, cumulus clouds at the low level form a flat base, growing vertically with a rounded top. Fog is also another common low level cloud that comes in contact with the ground, but when rises will form stratus clouds.
Multi-Layer Clouds
- Multi-layer clouds usually bring heavy forms of precipitation. Nimbostratus clouds, while at times seen as low-level clouds, are considered multilayer because they extend into the mid-level region. They are dark in appearance, creating an overcast effect bringing continued precipitation.
  
  Cumulonimbus clouds on the other hand are considered "dangerous" clouds, producing such weather phenomena as lighting, hail, tornados and thunderstorms. These clouds can span all layers of the atmosphere up to 60,000 feet with large anvil-shaped tops.
Orographic Clouds
- Orographic clouds form when flowing air interacts with mountainous terrain. There are two main types of orographic clouds, cap clouds and lenticular clouds. Cap clouds form from air containing water vapor that is uplifted on the windward side of the slope . Once the air reaches saturation, it produces liquid water in the form of droplets and a cloud which appears to "cap" the summit of the mountain.
  
  Lenticular clouds form a bit differently. They are lens-shaped clouds resulting from strong winds flowing up and over rugged terrain. The strong flow results in vertical wavelike patterns on the side of a mountain, creating lenticular clouds that form at the peaks of these waves. They appear round and the edges sharply defined, resembling flying saucers. Lenticular clouds are often categorized as mid-level clouds, which is where they are commonly found.

Nature