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Information about Arid

In general terms, the climate of a locale or region is said to be arid when it is characterized by a severe lack of available water, to the extent of hindering or even preventing the growth and development of plant and animal life. As a result, environments subject to arid climates tend to lack vegetation and are called xeric or desertic.

Concepts

The expression 'available water' refers to water in the soil in excess to the wilting point. The air over a hot desert may actually contain substantial amounts of water vapor but that water may not be generally accessible to plants, except for very specialized organisms (such as some species of lichen). 'Lack of water' refers to use by plants. The water that is actually present in the environment may be sufficient for some species or usages (such as climax vegetation), and grossly insufficient for others. Aridity, the characteristic nature of arid climates, may thus depend on the use of the land. Regards to the presence of life, what is more important than the degree of rainfall is the fraction of precipitation that is not quickly lost through evaporation or runoff. Attempts to quantitatively describe the degree of aridity of a place has often led to the development of aridity indexes. There is no universal agreement on the precise boundaries between classes such as 'hyper-arid', 'arid', 'semi-arid', etc.

Geographical distribution

If different classification schemes and maps differ in their details, there is a general agreement about the fact that large areas of the Earth are considered arid. These include the hot deserts located broadly in sub-tropical regions, where the accumulation of water is largely prevented by either low precipitations, or high evaporation, or both, as well as cold deserts near the poles, where water may be permanently locked in solid forms (snow and ice). Other arid regions include areas located in the rain shadows of major mountain ranges or along coastal regions affected by significant upwelling (such as the Atacama Desert).

Change over time

The distribution of aridity observed at any one point in time is largely the result of the general circulation of the atmosphere. The latter does change significantly over time through climate change. In addition, changes in land use can result in greater demands on soil water and induce a higher degree of aridity.

See also

References

  • Griffiths, J. F. (1985) 'Climatology', Chapter 2 in Handbook of Applied Meteorology, Edited by David D. Houghton, John Wiley and Sons, ISBN 0-471-08404-2.
  • Durrenberger, R. W. (1987) 'Arid Climates', article in The Encyclopedia of Climatology, p. 92-101, Edited by J. E. Oliver and R. W. Fairbridge, Van Nostrand Reinhold Company, New York, ISBN 0-87933-009-0.
  • Stadler, S. J (1987) 'Aridity Indexes', article in The Encyclopedia of Climatology, p. 102-107, Edited by J. E. Oliver and R. W. Fairbridge, Van Nostrand Reinhld Company, New York, ISBN 0-87933-009-0.
Climate is the average and variations of weather over long periods of time. Climate zones can be defined using parameters such as temperature and rainfall.
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Water is a common chemical substance that is essential to all known forms of life.[1] In typical usage, water refers only to its liquid form or state, but the substance also has a solid state, ice, and a gaseous state, water vapor.
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Individual growth is the increase in structural mass of an individual organism, in the context of the Dynamic Energy Budget theory. This frequently (but not always) goes with an increase in weight.
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Morphogenesis (from the Greek morphê shape and genesis creation) is one of three fundamental aspects of developmental biology along with the control of cell growth and cellular differentiation.
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Plantae
Haeckel, 1866[1]

Divisions

Green algae
  • Chlorophyta
  • Charophyta
Land plants (embryophytes)
  • Non-vascular land plants (bryophytes)

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Deserts and xeric shrublands is a biome characterized by a dry climate. Deserts and xeric shrublands receive an annual average rainfall of ten inches or less, and have an arid or hyperarid climate, characterized by a strong moisture deficit, where annual potential loss of moisture
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desert is a landscape form or region that receives very little precipitation. Deserts are defined as areas that receive an average annual precipitation of less than 250 mm (10 in). In the Köppen climate classification system, deserts are classed as (BW).
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Permanent wilting point (PWP) or wilting point (WP) is defined as the minimum soil moisture at which a plant wilts and can no longer recover its turgidity when placed in a saturated atmosphere for 12 hours.
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Water vapor or water vapour (see spelling differences), also aqueous vapor, is the gas phase of water. Water vapor is one state of the water cycle within the hydrosphere.
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Lichens (IPA: /ˈlaɪkən/)[1] are symbiotic associations of a fungus (the mycobiont) with a photosynthetic partner (the photobiont also known as the phycobiont) that can produce food for the lichen from
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Climax vegetation is the vegetation which establishes itself on a given site for given climatic conditions in the absence of anthropic action after a long time (it is the asymptotic or quasi-equilibrium state of the local ecosystem).
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'Land use' is also often used to refer to the distinct land use types in Zoning.

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precipitation (also known as hydrometeor) is any product of the condensation of atmospheric water vapor that is deposited on the earth's surface. It occurs when the atmosphere (being a large gaseous solution) becomes saturated with water vapour and the water condenses and
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Evaporation is the process by which molecules in a liquid state (e.g. water) spontaneously become gaseous (e.g. water vapor), without being heated to boiling point. It is the opposite of condensation.
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Surface runoff is a term used to describe the flow of water, from rain, snowmelt, or other sources, over the land surface, and is a major component of the water cycle.
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An aridity index (AI) is a numerical indicator of the degree of dryness of the climate at a given location. A number of aridity indices have been proposed (see below); these indicators serve to identify, locate or delimit regions that suffer from a deficit of available water, a
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A Semi-arid climate or steppe climate generally describes climatic regions that receive low annual rainfall (250-500 mm or 10-20 in). A more precise definition is given by the Köppen climate classification that treats steppe climates (BS) as intermediates between the desert
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Atacama Desert is a virtually rainless plateau in South America, extending 966 km (600 mi) between the Andes mountains and the Pacific Ocean. It is created by the rain shadow of the Andes east of the desert.
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atmosphere is a layer of gases that may surround a material body of sufficient mass.[1] The gases are attracted by the gravity of the body, and are retained for a longer duration if gravity is high and the atmosphere's temperature is low.
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Climate change refers to the variation in the Earth's global climate or in regional climates over time. It describes changes in the variability or average state of the atmosphere over time scales ranging from decades to millions of years.
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drought is an extended period of months or years when a region notes a deficiency in its water supply. Generally, this occurs when a region receives consistently below average precipitation. It can have a substantial impact on the ecosystem and agriculture of the affected region.
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Relative humidity is a term used to describe the amount of water vapor that exists in a gaseous mixture of air and water.

Definition

The relative humidity of an air-water mixture is defined as the ratio of the partial pressure of water vapor in the mixture to the
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The saturation vapor pressure is the static pressure of a vapor when the vapor phase of some material is in equilibrium with the liquid phase of that same material. The saturation vapor pressure of any material is solely dependent on the temperature of that material.
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