Desert - Definition


Deserts are part of a wide classification of regions that, on an average annual basis, have a moisture deficit (i.e. they lose more moisture than they receive). Measurement of rainfall alone cannot provide an accurate definition of what a desert is because being arid also depends on evaporation, which depends in part on temperature. For example, Phoenix, Arizona receives less than 250 millimeters (10 in) of precipitation per year, and is immediately recognized as being located in a desert due to its arid adapted plants. The North Slope of Alaska's Brooks Range also receives less than 250 millimeters (10 in) of precipitation per year and is often classified as a cold desert. Other regions of the world have cold deserts, including areas of the Himalayas and other high altitude areas in other parts of the world. Polar deserts cover much of the ice free areas of the arctic and Antarctic. An alternative definition describes deserts as parts of earth that don't have a sufficient vegetation cover to support human population.

Potential evapotranspiration supplements the measurement of rainfall in providing a scientific measurement-based definition of a desert. The water budget of an area can be calculated using the formula PPE ± S, wherein P is precipitation, PE is potential evapotranspiration rates and S is amount of surface storage of water. Evapotranspiration is the combination of water loss through atmospheric evaporation and through the life processes of plants. Potential evapotranspiration, then, is the amount of water that could evaporate in any given region. As an example, Tucson, Arizona receives about 300 millimeters (12 in) of rain per year, however about 2500 millimeters (100 in) of water could evaporate over the course of a year. In other words, about 8 times more water could evaporate from the region than actually falls. Rates of evapotranspiration in cold regions such as Alaska are much lower because of the lack of heat to aid in the evaporation process.

Read more about this topic:  Desert

Other articles related to "definitions, definition":

Pashtun People - Pashtuns Defined
... These three definitions may be described as the ethno-linguistic definition, the religious-cultural definition, and the patrilineal definition, respectively ...
Definition - In Medicine
... In medical dictionaries, definitions should to the greatest extent possible be simple and easy to understand, preferably even by the general public useful ...
Sustainable Development - Definition
... what is now one of the most widely recognised definitions "Sustainable development is development that meets the needs of the present without compromising the ability of future generations to meet their ... It offers an integrated vision and definition of strong sustainability ... It generates a more nuanced definition of sustainable development “the need to ensure a better quality of life for all, now and into the future, in a just and equitable manner, whilst living within the limits ...
Definition of Dietary Fiber
... the components of plants that resist human digestive enzymes, a definition that includes lignin and polysaccharides ... The definition was later changed to also include resistant starches, along with inulin and other oligosaccharides ... Official definition of dietary fiber differs a little among different institutions Organization (reference) Definition Institute of Medicine Dietary ...
ESPN - High Definition
... ESPN launched its 720p high-definition simulcast, originally branded as ESPNHD, on March 20, 2001 ... Live studio shows, along with most live events on ESPN, use high definition ... non-HD sources is presented in a standard definition, 43 format with stylized pillarboxes ...

Famous quotes containing the word definition:

    Beauty, like all other qualities presented to human experience, is relative; and the definition of it becomes unmeaning and useless in proportion to its abstractness. To define beauty not in the most abstract, but in the most concrete terms possible, not to find a universal formula for it, but the formula which expresses most adequately this or that special manifestation of it, is the aim of the true student of aesthetics.
    Walter Pater (1839–1894)

    The physicians say, they are not materialists; but they are:MSpirit is matter reduced to an extreme thinness: O so thin!—But the definition of spiritual should be, that which is its own evidence. What notions do they attach to love! what to religion! One would not willingly pronounce these words in their hearing, and give them the occasion to profane them.
    Ralph Waldo Emerson (1803–1882)

    No man, not even a doctor, ever gives any other definition of what a nurse should be than this—”devoted and obedient.” This definition would do just as well for a porter. It might even do for a horse. It would not do for a policeman.
    Florence Nightingale (1820–1910)