en>Monkbot: /* References */Fix CS1 deprecated date parameter errors

2014-01-18T05:43:56Z

References: Fix CS1 deprecated date parameter errors

← Older revision		Revision as of 07:43, 18 January 2014
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	~~Greetings! I am Marvella and I feel comfy when people use~~ the ~~full name~~. He used to be ~~unemployed but now he~~ is a ~~meter reader~~. ~~California~~ is ~~our birth location~~. ~~To play baseball~~ is [~~http~~://~~203~~.~~250~~.78.~~160~~/~~zbxe~~/~~?document_srl~~=~~810524&mid~~=~~gallery&sort_index~~=~~regdate&order_type~~=~~desc over the counter std test~~] ~~hobby he will by no means quit performing~~.		The '''potential density''' of a fluid parcel at [[pressure]] <math>P</math> is the [[density]] that the parcel would acquire if [[adiabatic process\|adiabatically]] brought to a reference pressure <math>P_{0}</math>, often 1 [[bar (unit)\|bar]] (100 [[kilopascal\|kPa]]). Whereas density changes with changing pressure, potential density of a fluid parcel is [[conservation law\|conserved]] as the pressure experienced by the parcel changes (provided no mixing with other parcels or net heat flux occurs). The concept is used in [[oceanography]][http://oceanworld.tamu.edu/resources/ocng_textbook/contents.html] and (to a lesser extent) [[atmospheric science]].

			Potential density is a dynamically important property: for static stability potential density must decrease upward. If it doesn't, a fluid parcel displaced upward finds itself lighter than its neighbors, and continues to move upward; similarly, a fluid parcel displaced downward would be heavier than its neighbors. This is true even if the density of the fluid decreases upward. In stable conditions (potential density decreasing upward) motion along surfaces of constant potential density ([[isopycnal]]s) is energetically favored over flow across these surfaces (diapycnal flow), so most of the motion within a 3-D geophysical fluid takes place along these 2-D surfaces.

			In oceanography, the symbol <math>\rho_\theta</math> is used to denote ''potential density'', with the reference pressure <math>P_0</math> taken to be the pressure at the ocean surface. The corresponding ''potential density anomaly'' is denoted by <math>\sigma_\theta = \rho_\theta - 1000 </math> [[kilogram\|kg]]/m<math>^3</math>. Because the [[compressibility]] of [[seawater]] varies with [[salinity]] and [[temperature]], the reference pressure must chosen to be near the actual pressure to keep the definition of potential density dynamically meaningful. Reference pressures are often chosen as a whole multiple of 100 bar; for water near a pressure of 400 bar (40 [[megapascal\|MPa]]), say, the reference pressure 400 bar would be used, and the potential density anomaly symbol would be written <math>\sigma_4</math>.
			Using these reference pressures can be defined the potential density surfaces, used in the analyses of ocean data and to construct models of the [[ocean circulation\|ocean current]]. [[Neutral density]] surfaces, defined using another variable called [[neutral density]] ( <math> \gamma^n\, </math> ), can be considered the continuous analog of these potential density surfaces.

			Potential density adjusts for the effect of [[Compressibility\|compression]] in two ways:
			*The effect of a parcel's change in volume due to a change in pressure (as pressure increases, volume decreases).
			*The effect of the parcel's change in temperature due to adiabatic change in pressure (as pressure increases, temperature increases).

			A parcel's density may be calculated from an [[equation of state]]:
			:<math>\rho = \rho(P,T,S_1,S_2,...) </math>
			where <math>T</math> is temperature, <math>P</math> is pressure and <math>S_n</math> are other [[Flow tracer\|tracer]]s that affect density (e.g. [[salinity]] of [[seawater]]). The potential density would then be calculated as:
			:<math>\rho_\theta = \rho(P_0,\theta,S_1,S_2,...) </math>
			where <math>\theta</math> is the [[potential temperature]] of the fluid parcel for the same reference pressure <math>P_0</math>.

			==See also==
			[[Potential energy]]
			==References==
			*{{cite book \| author=John M. Wallace and Peter V. Hobbs \| title=Atmospheric Science, An Introductory Survey, Second Edition \| publisher=Academic Press \| year=2006 \| isbn=0-12-732950-1}}
			*{{cite book \| author=Robert H. Stewart \| title=Introduction to Physical Oceanography \| year=2002 \| unused_data=\|url=http://oceanworld.tamu.edu/resources/ocng_textbook/chapter06/chapter06_05.htm}}

			[[Category:Density]]

79.173.96.2: /* Finding all solutions */

2012-05-10T15:43:16Z

Finding all solutions

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Greetings! I am Marvella and I feel comfy when people use the full name. He used to be unemployed but now he is a meter reader. California is our birth location. To play baseball is [http://203.250.78.160/zbxe/?document_srl=810524&mid=gallery&sort_index=regdate&order_type=desc over the counter std test] hobby he will by no means quit performing.

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en>Monkbot: /* References */Fix CS1 deprecated date parameter errors

79.173.96.2: /* Finding all solutions */