A cloud is a visible mass of condensation droplets or ice crystals suspended in the atmosphere above the surface of the Earth or another planetary body.
On Earth, the condensing substance is water vapor, which forms small droplets of water (typically 0.01 mm or ice crystals that, when surrounded with billions of other droplets or crystals, are visible as clouds. Clouds reflect all visible wavelengths of light equally and are usually white, but they can appear grey or even black if they are so thick or dense that sunlight cannot pass through.
Cloud formation and properties
 
A variety of cloud formations.
 
Global scheme of cloud optical thickness.
Clouds form when the invisible water vapour in the air condenses into visible water droplets or ice crystals. This can happen in two ways.
1. The air is cooled to its saturation point. This happens when the air comes in contact with a cold surface or a surface that is cooling by radiation, or the air is cooled by adiabatic expansion (rising). This can happen
along warm and cold fronts (Frontal lift),
where air flows up the side of a mountain and cools as it rises higher into the atmosphere (orographic lift),
by the convection caused by the warming of a surface by insolation (diurnal heating),
when warm air blows over a colder surface such as a cool body of water.
2. The air stays the same temperature but absorbs more water vapour into it until it reaches saturation.
Clouds are quite heavy. The water in a typical cloud can have a mass of up to several million tonnes. However, the volume of a cloud is correspondingly high, and the net density of water vapor is actually low enough that air currents below and within the cloud are capable of keeping small droplets suspended. As well, conditions inside a cloud are not static: water droplets are constantly forming and re-evaporating. A typical cloud droplet has a radius on the order of 1 x 10-5 m and a terminal velocity of about 1-2 cm/s. This give these droplets plenty of time to re-evaporate as they fall into in the warmer air beneath the cloud.
Most water droplets are formed when water vapor condenses around a condensation nucleus, a tiny particle of smoke, dust, ash, or salt. In supersaturated conditions, water droplets may act as condensation nuclei.
Water droplets large enough to fall to the ground are produced in two ways. The most important is through the Bergeron Process, theorized by Tor Bergeron, in which supercooled water droplets and ice crystals in a cloud interact to produce the rapid growth of ice crystals, which precipitate from the cloud and melt as they fall. This process typically takes place in clouds with tops cooler than -15°C. The second most important process is the collision and wake capture process, occurring in clouds with warmer tops, in which the collision of rising and falling water droplets produces larger and larger droplets, which are eventually heavy enough to overcome air currents in the cloud and the updraft beneath it and fall as rain. As a droplet falls through the smaller droplets which surround it, it produces a "wake" which draws some of the smaller droplets into collisions, thus perpetuating the process. This method of raindrop production is the primary mechanism in low stratiform clouds and small cumulus clouds in tropical regions. It typically produces smaller raindrops and drizzle.
The actual form of cloud created depends on the strength of the uplift and on air stability. In unstable conditions convection dominates, creating vertically developed clouds. Stable air produces horizontally homogeneous clouds. Frontal uplift creates various cloud forms depending on the composition of the front (ana-type or kata-type warm or cold front). Orographic uplift also creates variable cloud forms depending on air stability, although cap cloud and wave clouds are specific to orographic clouds.

Cloud Classification
 
Cloud Classification by altitude of occurrenceClouds are divided into two general categories: layered and convective. These are named stratus clouds (or stratiform, the Latin stratus means layer) and cumulus clouds (or cumiloform, cumulus means piled up). These two cloud types are divided into four more groups that distinguish the cloud's altitude. Clouds are classified by the cloud base height, not the cloud top. This system was proposed by Luke Howard in 1802 in a presentation to the Askesian Society.

High clouds (Family A)
These generally form above 16,500 feet (5,000 m), in the cold region of the troposphere. However, in Polar regions they may form as low as 10,000 ft (3,048 m). They are denoted by the prefix cirro- or cirrus. At this altitude water almost always freezes so clouds are composed of ice crystals. The clouds tend to be wispy, and are often transparent.

Rain is a form of precipitation, other forms of which include snow, sleet, hail, and dew. Rain forms when separate drops of water fall to the Earth's surface from clouds. Not all rain reaches the surface, however; some evaporates while falling through dry air. When none of it reaches the ground, it is a precipitation called virga.

Rain in nature
Rain plays a major role in the hydrologic cycle in which moisture from the oceans evaporates, condenses into clouds, precipitates back to earth, and eventually returns to the ocean via streams and rivers to repeat the cycle again. There is also a small amount of water vapor that respires from plants and evaporates to join other water molecules in condensing into clouds.
The amount of rainfall is measured using a rain gauge. It is expressed as the depth of water that collects on a flat surface, and can be measured to the nearest 0.25 mm or 0.01 in. It is sometimes expressed in litres per square metre (1 L/m² = 1 mm).
Rain drops on grassFalling raindrops are often depicted in cartoons or anime as "tear-shaped", round at the bottom and narrowing towards the top, but this is incorrect (only drops of water dripping from some sources are tear-shaped at the moment of formation). Small raindrops are nearly spherical. Larger ones become increasingly flattened, like hamburger buns; very large ones are shaped like parachutes. [1] On average, raindrops are 1 to 2 mm in diameter. The biggest raindrops on Earth were recorded over Brazil and the Marshall Islands in 2004 - some of them were as large as 10 mm. The large size is explained by condensation on large smoke particles or by collisions between drops in small regions with particularly high content of liquid water.
Generally, rain has a pH slightly under 6, simply from absorption of atmospheric carbon dioxide, which dissociates in the droplet to form minute quantities of carbonic acid. In some desert areas, airborne dust contains enough calcium carbonate to counter the natural acidity of precipitation, and rainfall can be neutral or even alkaline. Rain below pH 5.6 is considered acid rain.
Rain is said to be heavier immediately after a bolt of lightning. The cause of this phenomenon is traceable to the bipolar aspect of the water molecule. The intense electric and magnetic field generated by a lightning bolt forces many of the water molecules in the air surrounding the stroke to line up. These molecules then spontaneously create localized chains of water (similar to nylon or other 'poly' molecules). These chains then form water droplets when the electric/magnetic field is removed. These drops then fall as intensified rain.

Culture
 
Rain on an umbrellaCultural attitudes towards rain differ across the world. In the largely temperate Western world, rain traditionally has a sad and negative connotation - reflected in children's rhymes like Rain Rain Go Away - in contrast to the bright and happy sun. In dry places such as India, the rain is greeted with euphoria.
Several cultures have developed means of dealing with rain and have developed numerous protection devices such as umbrellas and raincoats, and diversion devices such as gutters and storm drains. Many people also prefer to stay inside on rainy days, especially in tropical climates where rain is usually accompanied by thunderstorms or rain is extremely heavy (monsoon). Rain may be collected for drinking water, or used as greywater. Excessive rain, particularly after a dry period has hardened the soil so that it cannot absorb water, can cause floods.
Many people find the scent smelt during and immediately after rain especially pleasant or distinctive. The source of this smell is petrichor, an oil produced by plants, then absorbed by rocks and soil, and later released into the air during rainfall.

A rainforest is a forested biome with high annual rainfall due to the Intertropical convergence zone.
As well as prodigious rainfall, many rainforests are characterised by a high number of resident species and tremendous biodiversity.
The largest tropical rainforests exist in the Amazon basin (the Amazon Rainforest), in the equatorial portions of Africa from Cameroon to the Democratic Republic of Congo; in much of southeastern Asia from Myanmar to Indonesia and Papua New Guinea; and also eastern Queensland, Australia.
It has been estimated that rainforests provide up to 40% of the oxygen found in the atmosphere and that the vegetation acts as an important consumer of atmospheric carbon. As such, many scientists feel that the rainforests are of vital importance within the global climate system.

Characteristics
Rainforests are characterised by high rainfall, with definitions setting minimum normal annual rainfall between 2,000 mm (about 100 inches or 200 centimetres) and 1700 mm (about 67 inches). The soil can be poor because high rainfall tends to leach out soluble nutrients.
Rain forests are home to two-thirds of all the living animal and plant species on the planet. It has been estimated that many hundreds of millions of new species of plants, insects, and microorganisms are still undiscovered and as yet unnamed by science. Tropical rain forests are called the "jewel of the earth", the "Earth's lungs", and the "world's largest pharmacy" because of the large amount of natural medicines discovered there
Despite the growth of flora in a rainforest, the actual quality of the soil is quite poor. Oxisols, infertile, deeply weathered and severely leached, have developed on the ancient Gondwanan shields. Rapid bacterial decay prevents the accumulation of humus. The concentration of iron and aluminium oxides by the laterization process gives the oxisols a bright red color and sometimes produces minable deposits (e.g. bauxite). On younger substrates, especially of volcanic origin, tropical soils may be quite fertile.
The undergrowth in a rainforest is restricted in many areas by the lack of sunlight at ground level. This makes it possible for people and other animals to walk through the forest. If the leaf canopy is destroyed or thinned for any reason, the ground beneath is soon colonised by a dense tangled growth of vines, shrubs and small trees called jungle.

Trees
There are several common characteristics of tropical trees. Tropical species frequently possess one or more of the following attributes not commonly seen in trees of higher latitudes.
Many species have broad, woody flanges (buttresses) at the base of the trunk. Originally believed to help support the tree, now it is believed that the buttresses channel stem flow and its dissolved nutrients to the roots.
Large leaves are common among trees of the C layer. Young individuals of trees destined for the B and A layers may also have large leaves. When they reach the canopy new leaves will be smaller. The large leaf surface helps intercept light in the sun-dappled lower strata of the forest. Drip tips facilitate drainage of precipitation off the leaf to promote transpiration. They occur in the lower layers and among the saplings of species of the emergent layer (A layer).
Trees are often well connected in the canopy layer especially by the growth of woody climbers or lianas. Plants with epiphytic adaptations, allowing them to grow on top of existing trees in the competition for sunlight.
Other characteristics that distinguish tropical species of trees from those of temperate forests include:
Exceptionally thin bark, often only 1-2 mm thick. Usually very smooth, although sometimes armed with spines or thorns.
Cauliflory, the development of flowers (and hence fruits) directly from the trunk, rather than at the tips of branches.
Large fleshy fruits attract birds, mammals, and even fish as dispersal agents.

The canopy
Away from river banks, swamps and clearings where dense undergrowth is found, the forest floor is relatively clear of vegetation, as little sunlight penetrates to ground level. The densest areas of biodiversity are found in the forest canopy, a more or less continuous cover of foliage formed by adjacent treetops.
The canopy, by some estimates, is home to 40% of all plant species, suggesting that perhaps half of all life on Earth could be found there. A quarter of all insect species are believed to exist in the rainforest canopy.
Scientists have long suspected the richness of the canopy as a habitat, but have only recently developed practical methods of exploring it. As long ago as 1917, US naturalist, William Beebe declared that "another continent of life remains to be discovered, not upon the Earth, but one to two hundred feet above it, extending over thousands of square miles".
True exploration of this habitat only began in the 1980's, when scientists developed methods to reach the canopy, such as firing ropes into the trees using crossbows. Exploration of the canopy is still in it's infancy, but other methods include the use of balloons and airships to float above the highest branches and the building of cranes and walkways planted on the forest floor.

The rainforest as a source of drugs
Tropical rain forests are called the 'world's largest pharmacy' because the large amount of natural medicines discovered there. Nearly half of the medicines that we use come from the rainforests. For example, rain forests are responsible for containing the "basic ingredients of birth control hormones, stimulants, and tranquilizing drugs" (Banks 36). Scientists believe that the cures for many more diseases will be discovered there in the future.

Degradation of the rainforests
Tropical and temperate rain forests have been subjected to heavy logging and agricultural clearance throughout the 20th century and the area covered by rainforest around the world is rapidly shrinking. It is estimated that the rainforest was reduced by about 58,000 km² annually in the 1990s. Rainforests used to cover 14% of the Earth's surface. This percentage is now down to 6% and it is estimated by some that the remaining natural rainforests could disappear within 40 years (mid-21st century). Biologists have estimated that large numbers of species are being driven to extinction, possibly more than 50,000 a year, due to the removal of habitat with destruction of the rain forests. Protection and regeneration of the rainforests is a key goal of many environmental charities and organisations.

Jungle boots are a type of combat boot that is designed for use in jungle warfare or hot, wet and humid environments where a standard leather combat boot would be uncomfortable or unsuitable to wear due to these conditions. Jungle boots have two vent holes on the leather located on the inner side of the boot near the middle of the boot to aid in ventilation.

The most well-known type of jungle boot are the ones that the US Armed Forces issued to their personnel during the Vietnam War in which the boot's upper was a mixture of leather for the toe, heel and eyelets and cotton/nylon for the neck of the boot.

The jungle boots that were made for the US armed forces during the Vietnam War sported a direct molded rubber sole (in either a Vibram style tread or a Panama-style tread) which also has a stainless steel plate installed inside the boot's sole to protect the wearer from punji stake traps.

The US military jungle boot helped design the famed desert combat boot which many American soldiers wore during Operation Desert Storm in 1991, Operation Enduring Freedom in Afghanistan in 2001 and Operation Iraqi Freedom in 2003. Despite the introduction of the desert boot at the time of Operation Desert Storm, many American military personnel were still issued jungle boots because there were not enough desert boots to issue to all the personnel in the Middle East at the time.

There are two American combat boot companies who manufacture the US military jungle boot in both its original Vietnam War configuration with the green cotton/nylon upper and conventional eyelets and in an updated version with a black cotton/nylon/Cordura upper and a hook and eyelet lacing system as well as the desert boot of Desert Storm, Enduring Freedom and Iraqi Freedom fame.

Jungle ist ein Stil der elektronischen Musik, der sich durch schnelle gebrochene Rhythmen, sogenannten Breakbeats, auszeichnet. In Deutschland und England werden damit verwandte, aber nicht identische Genres bezeichnet.
Der Stil entstand über den Umweg des Hardcore Techno und unter starken Einflüssen der Tradition von Raggamuffin und Dancehall aus dem House. Jungle gilt als Vorläufer des stark von synthetischer Klangfarbe und Rhythmen (Breakbeat) geprägten Musikstils Drum and Bass.

Zur Bezeichnung "Jungle"
Die Bezeichnung Jungle leitet sich ab von einer als Concrete Jungle bezeichneten Gegend in Kingston, Jamaika. Zudem kommt allerdings die Tatsache, dass eines der ersten Jungle-Stücke ein Sample enthielt, in dem ein jamaikanischer Soundsystem-Toaster zu "Maxiumum respect to all the junglists" aufrief. Dies bezog sich auf eine Clique von Jamaikanern, welche viel in einem öffentlichen Park in Kingston chillten, der von den Locals "the Jungle" genannt wurde. Der Name blieb hängen. Das Sample kam übrigens von einem "Yard Tape" (live Mitschnitt von einer Soundsystem Session) aus den 70er Jahren.

Beschreibung
Jungle besteht aus elektronisch beschleunigten und zerhackten Beats. Vor allem die Breaks alter Funk-Stücke wurden dazu eingesetzt. Besonders beliebt ist dabei der so genannte Amen-Break aus dem Stück "Amen my Brother" von The Winstons. Ein weiterer gern benutzter Break ist das des Stückes "Apache" der Michael Viner's Incredible Bongo Band. Als Kontrast zu den schnellen Beats wird meist eine halb so schnelle, also in Half Time gespielte Bassline eingesetzt. Im Vergleich zum heutigen Drum'n'Bass hatten die Breakbeats einen metallisch scheppernden, sich überschlagenden Klang.
Jungletracks sind allgemein in einem Tempo von rund 170 BPM gehalten. Diese Geschwindigkeit ist so gewählt, dass das menschliche Gehör bereits stark versucht ist, die schweren Zählzeiten in halbierter Geschwindigkeit zu hören. Dieser Kontrast wird durch schnelle Drums und langsamen Bass noch weiter hervorgehoben und macht einen Gutteil des Reizes dieser Stilrichtung aus. Der selbe Effekt kommt auch im Drum'n'Bass zum tragen, der allerdings, der ständigen Beschleunigung der modernen Tanzmusik angepasst, noch um einiges schneller gespielt wird. Die meisten der in der ersten Hälfte der 1990er entstandenen Jungletracks wurden von einem toastenden MC begleitet. Auch in den Texten waren die Anknüpfungspunkte zu Jamaikas Raggamuffin sehr stark.

Entwicklung
Jungle wurde in der ersten Hälfte der 1990er Jahre in England von Musikern westindischer Herkunft entwickelt und produziert. Dort erreichte er eine derartige Popularität, dass zeitweise mehrere Jungletracks gleichzeitig in den britischen Charts verteten waren. Viele der ersten Jungletunes wurde mit primitivsten Mitteln produziert, so zum Beispiel Some Justice von Aphrodite und Mickey Finn, das auf zwei Amiga 500 mit Hilfe eines Trackers produziert wurde.
In England wird die Bezeichnung Jungle heute meist gleichbedeutend mit Drum'n'Bass verwendet. Dies kommt in erster Linie von der langen Jungletradition und dem großen damaligen Erfolg. Der Ur-Jungle der Produzenten westindischer Herkunft wird deshalb zur Abgrenzung oft als Ragga Jungle bezeichnet.
Simultan mit dem Erfolg des Ur-Jungles hatten Produzenten den Jungle bereits stilistisch weiterentwickelt. Die Musik wurde minimalistischer, insbesondere die Ragga-Elemente verschwanden fast vollständig. Darkside, ein Subgenre des Jungle, setzte beispielsweise auf eine sehr düstere Atmosphäre. 1993 produzierte Goldie den Track "Terminator". Er gilt als Blaupause eines neuen Stils, der Mitte der 1990er Jahre Jungle ablösen sollte: Drum'n'Bass.