The barometric pressure is the reading given by a barometer. A barometer is used for determining atmospheric air pressure. The pressure is not constant; it will change depending on the altitude and the weather.

How Air Pressured is Measured

The units of measurement used are inches of millibars and mercury. Inches of mercury are used by meteorologists to make weather reports. The millibars are used to evaluate the pressure aloft and assessing the weather. The standard pressure in millibars is 1013.2. In inches of mercury the average is 29.92.

Aneroid and Mercury Barometers

These are the instruments used to measure air pressure. A mercury barometer has a vacuum tube in a mercury dish. When the atmospheric pressure goes up, air is pushed downward in the dish.

From the tube the mercury goes into the dish. This makes the mercury rise. When air pressure goes down, the air is carried off the mercury. It departs the vacuum tube and goes back to the dish. The height is gauged in inches.

An aneroid barometer is configured differently. A thin metal cell is set up around a vacuum. One of the metal sides is connected to the device. The other is hooked up to levers and gears. These can move the pointer. When air pressure pushes the cell, the needle starts to move.

How Altitude Affects Barometric Pressure

At sea level, the atmosphere is greater over you compared to a higher altitude. Pressure is very strong at sea level and goes down as the altitude goes up. The pressure goes down an inch of mercury for every 1,000 feet increase in altitude. This equals to about 1 millibar of pressure for every 8 meters of increase in altitude.

Density and Temperature

Air mass density influences the atmospheric pressure. If the air mass is dense, the pressure is higher. If the air is not dense, the air pressure is lower. Warm air is not as dense as cool air. That is the reason why warm air goes up and cool air does not. Altitude and temperature interact, and so they affect air pressure.

Facts about High Pressure Systems

In a high pressure system, air sinks and goes down in an area. As the air goes down, warming occurs just over the dew point. In high pressure systems, clouds rarely form. High pressure moves counterclockwise in the southern hemisphere and clockwise in the northern hemisphere.

Facts about Low Pressure Systems

Low pressure systems usually herald a storm. Air goes up in a low pressure system, taking evaporated moisture from the ground. As air goes up, the air cools, reaching the dew point.

The air is condensed and turns into clouds. The clouds get heavy and become storms. They can also turn into hurricanes. Low pressure systems run clockwise in the southern hemisphere and counterclockwise in the northern hemisphere.

Barometric pressure is affected by several factors, from the weather to altitude levels. Although it is something people can take for granted, it has a direct influence on life, as it can determine whether the climate will be sunny or stormy.