Clouds Formation & Types PDF

CLOUDS  Clouds come in many different types. Often the type of cloud can help us to understand what type of weather is moving in across an area. Clouds are categorised according to height and shape. The different categories of clouds are then given names based on latin words, e.g. Nim...

CLOUDS  Clouds come in many different types. Often the type of cloud can help us to understand what type of weather is moving in across an area. Clouds are categorised according to height and shape. The different categories of clouds are then given names based on latin words, e.g. Nimbus clouds bring rain, stratus clouds appear as layers.  Clouds only produce precipitation if they have enough water or ice particles that can collide and join together The particles will then grow too big and heavy to be supported in the air and will fall through the rising air. Cumulonimbus and stratus are the only clouds capable of producing precipitation Stratus clouds are just thick enough to produce drizzle Cumulonimbus clouds have strong rising air , vertical height and thickness Clouds consist of tiny water droplets or ice particles that are too light to fall to earth  Cloud cover is measured in units of oktas Each okta represents one eighth of the sky covered by cloud 0 oktas = clear sky, 8 oktas = total coverage In other words, cloud cover is the amount of clouds in the sky or the degree of cloud cover. This is one of the main weather elements. +.  CLASSIFICATION OF CLOUDS Clouds are classified according to their height above and appearance (texture) from the ground. The following cloud roots and translations summarize the components of this classification system: 1) cirro-: curl of hair, high; 2) alto-: mid; 3) strato-: layer; 4) nimbo-: rain, precipitation; And 5) cumulo-: heap.  HIGH-LEVEL CLOUDS: High-level clouds occur above about 20,000(6 km) feet and are given the prefix “cirro.” Due to cold temperatures at these levels, the clouds primarily are composed of ice crystals, and often appear thin, streaky, and white The three main types of high clouds are cirrus, cirrostratus, and cirrocumulus.  Cirrus clouds are wispy, feathery, and composed entirely of ice crystals. Unlike cirrus, cirrostratus clouds form more of a widespread, veil-like layer (similar to what stratus clouds do in low levels). When sunlight or moonlight passes through the hexagonal shaped ice crystals of cirrostratus clouds, the light is dispersed in such a way that a familiar ring or halo may form. As a warm air approaches, cirrus clouds tend to thicken into cirrostratus, which may, in turn, thicken and lower into altostratus, stratus, and even nimbostratus. Finally, cirrocumulus clouds are layered clouds with small lumpiness. They also may line up in “streets” or rows of clouds across the sky  MIDDLE LEVEL CLOUDS Altostratus clouds are "strato" type clouds) that possess a flat and uniform type texture in the mid levels. They frequently indicate the approach of a warm air and may thicken and lower into stratus, then nimbostratus resulting in rain or snow. However, altostratus clouds themselves do not produce significant precipitation at the surface, although sprinkles or occasionally light showers may occur from a thick alto-stratus deck. Altocumulus clouds exhibit "cumulo" type characteristics in mid levels, i.e., Heap-like clouds. Like cirrocumulus, altocumulus may align in rows or streets of clouds, with cloud axes indicating localized areas of rising, moist air.  The bases of clouds in the middle level given the prefix “alto,” appear between 6,500 and 20,000 feet. (2km-6km) The two main type of mid-level clouds are altostratus and altocumulus. Altostratus clouds are “strato” type clouds (see below) that possess a flat and uniform type texture in the mid levels. However, altostratus clouds themselves do not produce significant precipitation at the surface, although sprinkles or occasionally light showers  LOW LEVEL CLOUDS Low-level clouds are not given a prefix, although their names are derived from “strato” or “cumulo,” depending on their characteristics. Low clouds occur below 6500 feet, and normally consist of liquid water droplets , except during cold winter storms when ice crystals (and snow) comprise much of the clouds. the two main types of low clouds include stratus, which develop horizontally, and cumulus, which develop vertically. Stratus clouds are uniform and flat, producing a gray layer of cloud cover which may be precipitation-free or may cause periods of light precipitation or drizzle. Stratocumulus clouds are hybrids of layered stratus and cumulus which are characteristic of cumulo type clouds, clumped together in a continuous distribution and characteristic of strato type clouds.  Stratocumulus also can be thought of as a layer of cloud clumps with thick and thin areas. Thick, dense stratus or stratocumulus clouds producing steady rain or snow often are referred to as nimbostratus clouds. Cumulonimbus clouds are multi-level clouds, extending high into the sky in towers or plumes.x Height of base Is 1,100 - 6,500 feet(0,33km-1,82 km) More commonly known as thunderclouds, cumulonimbus is the only cloud type that can produce hail, thunder and lightning. The base of the cloud is often flat, with a very dark wall-like feature hanging underneath, and may only lie a few hundred feet above the earth's surface.  WHY ARE CLOUDS WHITE? Clouds are white because light from the sun is white. As light passes through a cloud, it interacts with the water droplets, which are much bigger than the atmospheric particles that exist in the sky. When sunlight reaches an atmospheric particle in the sky, blue light is scattered away more strongly than other colours, giving the impression that the sky is blue. But in a cloud, sunlight is scattered by much larger water droplets. These scatter all colours almost equally meaning that the sunlight continues to remain white and so making the clouds appear white against the background of the blue sky.  WHY ARE CLOUDS SOMETIMES GREY? Cloud bases are often grey as a result of the same scattering that makes them white. When light is scattered in a cloud it usually is sent back upwards, or out to the sides of the cloud, making the tops and sides of the cloud whiter than the base which receives less light. This is more prominent in rain clouds because the cloud droplets are bigger, thus scattering more light. This means that even less light from the sun reaches the bottom of the cloud, giving rain clouds their intimidating appearance.