A barometer is a scientific instrument applied in meteorology to measure atmospheric pressure. Pressure tendency can forecast short term alterations in the weather. A lot of measurements of air pressure are used within surface weather analysis to aid find surface troughs, high pressure systems, and frontal boundaries which bear on shipping. Meteorology is the interdisciplinary scientific analysis of the atmosphere . Studies in the field of study stretch back millennia, though important advancement in meteorology did not come about until the 18th century. The 19th century saw breakthroughs occur after observing networks evolved across several countries. Later on the development of the computer in the latter half of the 20th century, breakthroughs in weather forecasting were achieved.

Meteorological phenomena are observable weather events which illuminate, and are explained by the science of meteorology. Those results are bound by the variables that exist in Earth's atmosphere; temperature  air pressure , water vapor , and the gradients and interactions of each variable, and how they change in time. Different spatial scales  are analyzed to determine how systems on local, regional, and global levels bear upon weather and climatology.

Weather forecasting, climatology , atmospheric physics, and atmospheric chemistry are sub-disciplines of the atmospheric sciences  Meteorology and hydrology  compose the interdisciplinary area of hydrometeorology . Interactions between Earth's atmosphere and the seas are part of coupled ocean-atmosphere analyses. Meteorology has practical application in many diverse fields such as the armed forces, Energy Department production, transport, Department of Agriculture and construction. The barometer is just one of the tools used in this analysis.

The word "meteorology is from Greek µet metéoros "lofty; high (in the sky)" (from µeta-meta-  "above" and  eor "to lift up") and a -logia  "-(o)logy 

Atmospherical pressure makes up the force per unit area exerted upon a surface by the weight of air above that surface in the atmosphere of Earth (or that of a different planet). In most contexts atmospheric pressure is closely gauged by the hydro static pressure made by the mass  of air above the measurement point. Low-pressure areas have lower atmospheric mass above their position, whereas high-pressure areas have more atmospheric mass above their position. As well, as elevation increases, there's lower overlying atmospheric mass, so that atmospheric pressure drop-offs with rising elevation. On average, a column of air one square cm in cross-section, measured from sea level of about 10.1 N (2.28 lbf  (A column one square inch in cross-section would make a weight of about 14.7 lbs, or about 65.4 N). Across the area of your body, there's almost 1,000 kg of air; this is close to the same as having a small car bear down on you. The barometer really is a useful tool even when off the ship to forecast the weather.

 Barometer Standard Atmospheric Pressure

The standard atmosphere  (symbol: atm) is a unit of pressure  ("kiloPascals") or 1013.25 milli bars or hectopascals . It is equal to 760 mmHg  (torr , 29.92 inHg , 14.696 psi  One standard is standard pressure used for pneumatic liquid power (ISO R554), and in the aerospace (ISO 2533) and petroleum (ISO 5024) industries. In 1971, the International Union of Pure and Applied Chemistry (IUPAC) said that for the intentions of determining the properties of substances, "the standard pressure" should be defined as precisely 100 kPa (˜750.01 torr) or 29.53 inHg rather than the 101.325 kPa value of "one standard atmosphere".

This value is used as the standard pressure for the compressor and the pneumatic tool industries (ISO 2787).Standard temperature and pressure ) In the United States, compressed air flow is frequently calculated in "standard cubic feet" per unit of time, where the "standard" means the equal quantity of air at standard temperature and pressure.

Since every 300 meters (˜1,000 feet) one ascends, the atmospheric pressure drop-offs by about 4%. However, this standard atmosphere is specified slightly differently: temperature = 20 °C(68 °F), air density = 1.225 kg/m³ (0.0765 lb/cu ft), altitude = sea level, and relative humidity = 20%. In the air conditioning industry, the standard is frequently temperature = 0 °C (32 °F) instead.

For natural gas, the Gas Processors Association (GPA) defines a standard temperature of 60 °F (15.6 °C), but allows for a variety of "base" pressures, including 14.65 psi (101.0 kPa), 14.656 psi (101.05 kPa), 14.73 psi (101.6 kPa) and 15.025 psi (103.59 kPa).For a given "base" pressure, the higher the air pressure, the colder it is; the lower the air pressure, the warmer it is.

Atmospheric pressure-action=Mean sea level pressure

Kollsman-type barometric aircraft altimeter  as used in North America displaying an altitude of 80 ft (24 m).

The mean sea level pressure (MSLP) is the atmospheric pressure at sea level or (once measured at a given elevation on land) the station pressure reduced to sea level assuming that the temperature declines at a lapse rate  of 6.5 K per km in the fictive layer of air between the station and sea level.

This is the atmospheric pressure commonly given in weather reports on radio, television, and newspapers or on the World Wide Web . When barometers  in the home are set to match the local weather reports, they measure pressure reduced to sea level, not the actual local atmospheric pressure. See Altimeter (barometer vs. absolute) .

The reduction to sea level means that the standard range of fluctuations in atmospheric pressure is the same for everybody. The pressures that are considered high pressure or low pressure do not depend on geographical location. This forms isobars on a weather chart important and valuable tools.

The barometer nautical gift is a scientific instrument that will give the mariner many useful observations that they have the knowledge to apply and appreciate.

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