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Significance and Use
Atmospheric pressure is one of the basic variables used by meteorologists to describe the state of the atmosphere.
The measurement of atmospheric pressure is needed when differences from “standard” pressure conditions must be accounted for in some scientific and engineering applications involving pressure dependent variables.
These methods provide a means of measuring atmospheric pressure with the accuracy and precision comparable to the accuracy and precision of measurements made by governmental meteorological agencies.
1.1 These methods cover the measurement of atmospheric pressure with two types of barometers: the Fortin-type mercurial barometer and the aneroid barometer.
1.2 In the absence of abnormal perturbations, atmospheric pressure measured by these methods at a point is valid everywhere within a horizontal distance of 100 m and a vertical distance of 0.5 m of the point.
1.3 Atmospheric pressure decreases with increasing height and varies with horizontal distance by 1 Pa/100 m or less except in the event of catastrophic phenomena (for example, tornadoes). Therefore, extension of a known barometric pressure to another site beyond the spatial limits stated in 1.2 can be accomplished by correction for height difference if the following criteria are met:
1.3.1 The new site is within 2000 m laterally and 500 m vertically.
1.3.2 The change of pressure during the previous 10 min has been less than 20 Pa.
The pressure, P2 at Site 2 is a function of the known pressure P1 at Site 1, the algebraic difference in height above sea level, h1 − h 2, and the average absolute temperature in the space between. The functional relationship between P1 and P2 is shown in 10.2. The difference between P1 and P2 for each 1 m of difference between h1 and h2 is given in Table 1 and 10.4 for selected values of P1 and average temperature.
1.4 Atmospheric pressure varies with time. These methods provide instantaneous values only.
1.5 The values stated in SI units are to be regarded as the standard.
1.6 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. Specific safety precautionary statements are given in Section 7.
|Pressure P1, Pa|
|110 000||100 000||90 000||80 000||70 000|
|Correction to P1, Pa/m, positive if h1 > h, negative if h1 < h2|
2. Referenced Documents (purchase separately) The documents listed below are referenced within the subject standard but are not provided as part of the standard.
D1356 Terminology Relating to Sampling and Analysis of Atmospheres
D3249 Practice for General Ambient Air Analyzer Procedures
ICS Number Code 07.060 (Geology. Meteorology. Hydrology)
UNSPSC Code 41114402(Barometers)