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atmospheric pressure
atmospheric pressure n. Pressure caused by the weight of the atmosphere. It has a mean value of one atmosphere at sea level but reduces with increasing altitude. Also called barometric pressure. atmospheric pressure n (General Physics) the pressure exerted by the atmosphere at the earth's surface. It has an average value of 1 atmosphere at′mospher′ic pres′sure
n. 1. the pressure exerted by the earth's atmosphere at any given point. 2. a value of standard or normal atmospheric pressure, equivalent to the pressure exerted by a column of mercury 29.92 in. (760 mm) high, or 1013 millibars (101.3 kilopascals). Also called barometric pressure. [1655–65] at·mos·pher·ic pressure (ăt′mə-sfîr′ĭk) Pressure caused by the weight of the air. At sea level it has an average value of one atmosphere and gradually decreases as the altitude increases.Did You Know? The atmosphere that blankets the Earth gently presses down on us, and the subtle variations in this atmospheric pressure greatly affect the weather. For example, forecasters often talk of low pressure bringing rain. In areas of low air pressure, the air is less dense and relatively warm, which causes it to rise. The expanding and rising air naturally cools and the water vapor in the air condenses, forming clouds and the drops that fall as rain. In high pressure regions, on the other hand, the air is dense and relatively cool, which causes it to sink. The water vapor in the sinking air does not condense, leaving the skies sunny and clear. So if you're trying to hit a home run, would you prefer a beautiful, sunny day or one in which it looks like rain? On the overcast day, the ball has less air to push aside on its way out of the ballpark, making it easier to hit a homer.Thesaurus| Noun | 1. |  atmospheric pressure - the pressure exerted by the atmosphereair pressure, pressuregas pressure - the pressure exerted by a gasbarometric pressure - atmospheric pressure as indicated by a barometercompartment pressure - the air pressure maintained in an air-tight compartment (as in an aircraft)overpressure - a transient air pressure greater than the surrounding atmospheric pressure; "the overpressure of the blast kills by lethal concussion"sea-level pressure - the atmospheric pressure reduced by a formula to the pressure at sea level |
TranslationsLuftdruckpresión atmosféricapressione atmosfericaatmospheric pressure
atmospheric pressure The force per unit area (i.e. pressure) exerted by a column of atmosphere extending vertically upwards to the limit of the atmosphere. It is usually expressed in millibars (mb) or newtons per square meter (N m–2). The standard atmospheric pressure at the Earth's surface at sea level is 1013 mb or 101 325 N m–2. On the surface of Venus and Mars the atmospheric pressure is about 90 000 mb and 7.5 mb, respectively.Atmospheric Pressure the hydrostatic pressure exerted by the atmosphere on all objects in it. Atmospheric pressure is a fundamental characteristic of the atmosphere’s condition; at each point in the atmosphere it is determined by the weight of the overlying air. Atmospheric pressure decreases with height; its dependence on height is expressed by the barometric formula. Atmospheric pressure is measured by a barometer and is expressed in millibars (mbar), in newtons per sq m (N/m2), or by the height of a column of mercury in mm in a barometer brought to 0° C and normal gravity value (at sea level and 45° latitude). Normal atmospheric pressure is considered to be 760 mm Hg = 1,013.25 mbar = 101,325 N/m2. At a height of 5 km it is approximately half the value at the earth’s surface. Atmospheric pressure at the earth’s surface varies from place to place and with time. Of particular importance are the nonperiodic variations associated with the onset, development, and dissolution of slowly moving high-pressure regions called anticyclones and vast, relatively fast-moving vortices, or cyclones, in which low pressure prevails. The extreme values of atmospheric pressure observed so far (at sea level) are 808.7 and 684.0 mm Hg. However, despite the large variability, the distribution of average monthly values at the earth’s surface each year is approximately the same. The average annual atmospheric pressure is low at the equator and has a minimum at about 10° N lat. It then increases and reaches a maximum at 30°-35° north and south latitudes; again it decreases, reaching a minimum at 60°-65°, but at the poles it increases again. This latitudinal distribution of atmospheric pressure is considerably influenced by the time of the year and the nature of the continental and oceanic layout. In winter there is a high-pressure region over the cold continents. Thus, latitudinal distribution is disturbed, and the pressure field is divided into a series of high-and low-pressure regions called centers of atmospheric action. The horizontal distribution of pressure becomes simpler with height, approaching the latitudinal distribution. Starting at a height of approximately 5 km, the atmospheric pressure diminishes from the equator to the poles over the entire globe. Two maxima are observed in the diurnal variation—at 9–10 A.M. and at 9–10 P.M. Minima occur at 3–4 P.M. and 3–4 P.M. The diurnal variation is especially regular in tropical countries where the daytime variation reaches 2.4 mm Hg and nighttime 1.6 mm Hg. The amplitude of the pressure change decreases with increasing latitude, but at the same time the nonperiodic pressure variations become stronger. REFERENCESKhrgian, A. Kh. Fizika atmosfery, 2nd ed., ch. V. Moscow, 1958.
Burgess, E. K granitsam prostranstva. Moscow, 1957. (Translated from English.)atmospheric pressure[¦at·mə¦sfir·ik ′presh·ər] (physics) The pressure at any point in an atmosphere due solely to the weight of the atmospheric gases above the point concerned. Also known as barometric pressure. atmospheric pressure, barometric pressureThe pressure exerted by the earth’s atmosphere; under standard conditions equal to 14.7 lb per sq in. (1.01 × 106 pascals) equivalent to the pressure exerted by a column of mercury 29.9 in. (76.0 cm) high.atmospheric pressure
pressure (P) [presh´ur] force per unit area.arterial pressure (arterial blood pressure) blood pressure (def. 2).atmospheric pressure the pressure exerted by the atmosphere, usually considered as the downward pressure of air onto a unit of area of the earth's surface; the unit of pressure at sea level is one atmosphere. Pressure decreases with increasing altitude.barometric pressure atmospheric p.blood pressure 1. see blood pressure.2. pressure of blood on walls of any blood vessel.capillary pressure the blood pressure in the capillaries.central venous pressure see central venous pressure.cerebral perfusion pressure the mean arterial pressure minus the intracranial pressure; a measure of the adequacy of cerebral blood flow.cerebrospinal pressure the pressure of the cerebrospinal fluid, normally 100 to 150 mm Hg.continuous positive airway pressure see continuous positive airway pressure.filling pressure see pressure" >mean circulatory filling pressure.high blood pressure hypertension.intracranial pressure see intracranial pressure.intraocular pressure the pressure exerted against the outer coats by the contents of the eyeball.intrapleural pressure (intrathoracic pressure) pleural pressure.intrinsic positive end-expiratory pressure elevated pressure" >positive end-expiratory pressure and dynamic pulmonary hyperinflation caused by insufficient expiratory time or a limitation on expiratory flow. It cannot be routinely measured by a ventilator's pressure monitoring system but is measurable only using an expiratory hold maneuver done by the clinician. Its presence increases the work needed to trigger the ventilator, causes errors in the calculation of pulmonary compliance, may cause hemodynamic compromise, and complicates interpretation of hemodynamic measurements. Called also auto-PEEP and intrinsic PEEP.maximal expiratory pressure maximum expiratory pressure.maximal inspiratory pressure the pressure during inhalation against a completely occluded airway; used to evaluate inspiratory respiratory muscle strength and readiness for weaning from mechanical ventilation. A maximum inspiratory pressure above −25 cm H2O is associated with successful weaning.maximum expiratory pressure (MEP) a measure of the strength of respiratory muscles, obtained by having the patient exhale as strongly as possible against a mouthpiece; the maximum value is near capacity" >total lung capacity.maximum inspiratory pressure (MIP) the inspiratory pressure generated against a completely occluded airway; used to evaluate inspiratory respiratory muscle strength and readiness for weaning from mechanical ventilation. A maximum inspiratory pressure above −25 cm H2O is associated with successful weaning.mean airway pressure the average pressure generated during the respiratory cycle.mean circulatory filling pressure a measure of the average (arterial and venous) pressure necessary to cause filling of the circulation with blood; it varies with blood volume and is directly proportional to the rate of venous return and thus to cardiac output.negative pressure pressure less than that of the atmosphere.oncotic pressure the osmotic pressure of a colloid in solution.osmotic pressure the pressure required to stop osmosis through a semipermeable membrane between a solution and pure solvent; it is proportional to the osmolality of the solution. Symbol π.partial pressure the pressure exerted by each of the constituents of a mixture of gases.peak pressure in mechanical ventilation, the highest pressure that occurs during inhalation.plateau pressure in mechanical ventilation, the pressure measured at the proximal airway during an end-inspiratory pause; a reflection of alveolar pressure.pleural pressure the pressure between the visceral pleura and the thoracic pleura in the pleural cavity. Called also intrapleural or intrathoracic pressure.positive pressure pressure greater than that of the atmosphere.positive end-expiratory pressure (PEEP) a method of control mode ventilation in which positive pressure is maintained during expiration to increase the volume of gas remaining in the lungs at the end of expiration, thus reducing the shunting of blood through the lungs and improving gas exchange. A PEEP higher than the critical closing pressure prevents alveolar collapse and can markedly improve the arterial Po2 in patients with a lowered functional residual capacity, as in acute respiratory failure. Effects of the application of positive end-expiratory pressure (PEEP) on the alveoli. A, Atelectatic alveoli before PEEP application. B, Optimal PEEP application has reinflated alveoli to normal volume. C, Excessive PEEP application overdistends the alveoli and compresses adjacent pulmonary capillaries, creating dead space with its attendant hypercapnia. From Pierce, 1995.pulmonary artery wedge pressure (PAWP) (pulmonary capillary wedge pressure (PCWP)) intravascular pressure, reflecting the left ventricular end diastolic pressure, measured by a swan-ganz catheter wedged into a small pulmonary artery to block the flow from behind.pulse pressure the difference between the systolic and diastolic pressures. If the systolic pressure is 120 mm Hg and the diastolic pressure is 80 mm Hg, the pulse pressure is 40 mm Hg; the normal pulse pressure is between 30 and 40 mm Hg.urethral pressure the pressure inwards exerted by the walls of the urethra, which must be counteracted in order for urine to flow through; see also profile" >urethral pressure profile.venous pressure the blood pressure in the veins; see also central venous pressure" >central venous pressure.water vapor pressure the tension exerted by water vapor molecules, 47 mm Hg at normal body temperature.wedge pressure blood pressure measured by a small catheter wedged into a vessel, occluding it; see also pulmonary capillary wedge pressure and wedged hepatic vein pressure.wedged hepatic vein pressure the venous pressure measured with a catheter wedged into the hepatic vein. The difference between wedged and free hepatic vein pressures is used to locate the site of obstruction in portal hypertension; it is elevated in that due to cirrhosis, but low in cardiac ascites or portal vein thrombosis.bar·o·met·ric pres·sure (PB), the absolute pressure of the ambient atmosphere, varying with weather, altitude, etc.; expressed in millibars (meteorology) or mm Hg or torr (respiratory physiology); at sea level, 1 atmosphere (atm, 760 mm Hg or torr) is equivalent to: 14.69595 lb/in2, 1013.25 millibars, 1013.25 × 106 dynes/cm2, and, in SI units, 101,325 pascals (Pa). Synonym(s): atmospheric pressureSee PRES
See APatmospheric pressure
Related to atmospheric pressure: barometric pressure, Absolute pressure, Gauge pressureSynonyms for atmospheric pressurenoun the pressure exerted by the atmosphereSynonymsRelated Words- gas pressure
- barometric pressure
- compartment pressure
- overpressure
- sea-level pressure
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