Cloud Development, Clouds and Their Formation - Essay Example

Cloud Development: Introduction: Water is necessary for existence and it acts as a vital function in atmospheric processes. The Earth and its different structures are significantly prejudiced by water. Since water molecules' movement cycles itself through different forms of atmosphere and hydrosphere, it can easily be stored in its various forms in atmosphere in various forms. Water on the earth evaporates when it is heated by the sun. Some of the water molecules in different water reservoirs put on enough liveliness to break free of the surface and disperse in to the atmospheric air. Some of these lively water molecules then rise higher in the atmosphere, where the air is cooler. As the temperature decreases the molecules lose some of their energy, and compress onto particles in the atmosphere, shaping clouds. Water molecules are stored in the atmosphere in all three states of matter. Water vapor in the atmosphere is commonly referred to as humidity. If liquid and solid forms of water can overcome atmospheric updrafts they can fall to the Earth's surface as precipitation. The formation of ice crystals and water droplets occurs when the atmosphere is cooled to a temperature that causes condensation or deposition. Four processes that can trigger such atmospheric cooling are oro-graphic uplift; convectional uplift; air mass convergence; and energy loss. [01] Precipitation can be defined as any aqueous deposit, in liquid or solid form, that develops in a saturated atmospheric environment and generally falls from clouds. A number of different precipitation types have been classified by meteorologists including rain, freezing rain, snow, ice pellets, snow pellets, and hail. Fog represents the saturation of air near the ground surface. Classification of fog types is accomplished by the identification of the mechanism that caused the air to become saturated. [01] The distribution of precipitation on the Earth's surface is generally controlled by the absence or presence of mechanisms that lift air masses to cause saturation. It is also controlled by the amount of water vapor held in the air, which is a function of air temperature. A figure is presented that illustrates global precipitation patterns. Clouds and Their Formation: A cloud can be defined as a visible mass of condensed droplets, frozen crystals suspended in the atmosphere above the surface of the Earth. More importantly, these clouds can also occur as masses of material in interstellar space, where they are called interstellar clouds and nebulae. [02] On Earth the condensing substance is typically water vapor, which forms small droplets or ice crystals, typically 0.01 mm in diameter. [02] When surrounded by billions of other droplets or crystals they become visible as clouds. Dense deep clouds exhibit a high reflectance (70% to 95%) throughout the visible range of wavelengths: they thus appear white, at least from the top. Cloud droplets tend to scatter light efficiently, so that the intensity of the solar radiation decreases with depth into the cloud, hence the gray or even sometimes dark appearance of the clouds at their base. [02] Thin clouds may appear to have acquired the color of their environment or background, and clouds illuminated by non-white light, such as during sunrise or sunset, may be colored accordingly. In the near-infrared range, clouds would appear darker because the water that constitutes the cloud droplets strongly absorbs solar radiation at those wavelengths. [02] Types of Clouds: Although there are many types of clouds with respect to their different characteristics, clouds are mainly divided into three major classifications. These are as under, Cirrus Clouds: The name originates from the Latin word meaning "curl of hair". These feathery clouds form very high up in the sky (at altitudes between 5 km and 14 km) where it is very cold. [03] They are therefore made up of tiny ice crystals rather than water droplets. Cirrus clouds occur in warm air which is being slowly lifted over a large area by an approaching cold front, and they are therefore often the signal of bad weather. Cirrus clouds are often called mare's tails. This is because strong winds high in the air blow them into wispy curls like the tail of a horse. [03] Cumulus: These are the most familiar clouds and look like heaps of cotton wool or large cauliflower's. Cumulus clouds are found at a height of about 500 meters and are composed of tiny water droplets. [03] They form when sunshine warms pockets of moist air and causes them to rise quickly. As they get higher, the pocket of air billows out and forms the familiar fluffy shape as the moist air cools and condenses into water droplets. These clouds are usually seen in fine weather, when the sky is blue. Stratus: The name "stratus" means "layers" in Latin, although you in fact rarely see the layers in stratus clouds. Instead they appear as a grey, shapeless sheet of cloud extending in all directions across the sky. [03] They are usually only about 1 km thick, but can be as much as 1000 km wide. Stratus clouds build up when a layer of warm, moist air rises slowly over a mass of colder air. These clouds are often dark and gloomy, and are associated with rain and drizzle. Stratus clouds can sometimes rest on the ground or sea instead of up in the air, and they are then called 'fog'. [03] Cloud Development & Important Characteristics: Color of Clouds: Clouds are white because they reflect the light of the sun. Light is made up of colors of the rainbow and when you add them all together you get white. The sun appears a yellow color because it sends out more yellow light than any other color. Clouds reflect all the colors the exact same amount so they look white. Clouds are made up of tiny water droplets or ice crystals, usually a mixture of both. The water and ice scatter all light, making clouds appear white. If the clouds get thick enough or high enough all the light above does not make it through, hence the gray or dark look. Also, if there are lots of other clouds around, their shadow can add to the gray or multicolored gray appearance. [04] A cloud forms when air heated by the sun. As it rises, it slowly cools it reaches the saturation point and water condenses, forming a cloud. As long as the cloud and the air, that it is made of becomes warmer than the outside air around it, cloud starts floating around. Clouds move with the wind. High cirrus clouds are pushed along by the jet stream, sometimes traveling at more than 100 miles-per-hour. When clouds are part of a thunderstorm they usually travel at 30 to 40 mph. [04] Process of Cloud Development: Since condensation or deposition of water above the Earth's surface creates clouds, they develop in any air mass that becomes saturated. Saturation can occur by way of atmospheric mechanisms that cause the temperature of an air mass to be cooled to its dew point or frost point. The following mechanisms or processes can achieve this outcome causing clouds to develop: 1. Oro-graphic uplift occurs when air is forced to rise because of the physical presence of elevated land. As the parcel rises it cools as a result of adiabatic expansion at a rate of approximately 10 Celsius per 1000 meters until saturation. The development of clouds and resulting heavy quantities of precipitation along the west coast of Canada are mainly due to this process. 2. Convectional lifting is associated with surface heating of the air at the ground surface. If enough heating occurs, the mass of air becomes warmer and lighter than the air in the surrounding environment, and just like a hot air balloon it begins to rise, expand, and cool. When sufficient cooling has taken place saturation occurs forming clouds. This process is active in the interior of continents and near the equator forming cumulus clouds and or cumulonimbus clouds (thunderstorms). The rain that is associated with the development of thunderstorm clouds is delivered in large amounts over short periods of time in extremely localized areas. 3. Convergence or frontal lifting takes place when two masses of air come together. In most cases, the two air masses have different temperature and moisture characteristics. One of the air masses is usually warm and moist, while the other is cold and dry. The leading edge of the latter air mass acts as an inclined wall or front causing the moist warm air to be lifted. Of course the lifting causes the warm moist air mass to cool due to expansion resulting in saturation. This cloud formation mechanism is common at the mid-latitudes where cyclones form along the polar front and near the equator where the trade winds meet at the intertropical convergence zone. 4. Radiative cooling occurs when the Sun is no longer supplying the ground and overlying air with energy derived from solar. Instead, the surface of the Earth now begins to lose energy in the form of long wave radiation which causes the ground and air above it to cool. The clouds that result from this type of cooling take the form of surface fog. Of course these causes of cloud development do not always act in a singular fashion. It is possible to get combinations of all four types, such as when convection and oro-graphic uplift cause summer afternoon cloud development and showers in the mountains. Conclusion: Although clouds are created and are themselves part of a natural phenomenon, the technological and scientific researches of late have proved the fact that clouds can also be created upon human will. Hence, climate can thus be controlled by humans. This interesting research can be found out in the book 'Human Impacts on Weather and Climate' by Cotton and Pielke (1995). Pielke refers this phenomenon to as Cloud Seeding. The foremost purpose of the cloud seeding is to augment the competence of rainfall formation by introducing a concentration of ice crystals in super cooled clouds. It was originally thought that clouds were deficient in ice nuclei and therefore additions of modest concentrations of ice nuclei should result in a more efficient precipitation-producing cloud system. [05] All that was needed was to introduce seeding material from the ground or at the base of clouds which would then enhance ice crystal concentrations and thereby increase rainfall. Pielke, in his book, also defines that physical studies and inferences drawn from statistical seeding experiments over the last 50 years suggests that there exists a much more limited window of opportunity for precipitation enhancement. [05] Works Cited Page: [01] Physical Geography.Net, Introduction to the Hydrosphere - Chapter 8; by Dr. Michael Pidwirny. Available at June 30, 2007 [02] Clouds, Wikipedia - the free encyclopedia. Available at June 30, 2007 [03] CloudsRUs.com, Water Cycle-Clouds. Available at June 30, 2007 [04] Crystal Wicker, Cloud Development. Available at June 30, 2007 [05] Human Impacts on Weather and Climate' by Cotton and Pielke (1995). Read More