What is the standard temperature and pressure at sea level?
Standard temperature is defined as zero degrees Celsius (0 0C), which translates to 32 degrees Fahrenheit (32 0F) or 273.15 degrees kelvin (273.15 0K). This is essentially the freezing point of pure water at sea level, in air at standard pressure.
The mean sea-level pressure (MSLP) is the average atmospheric pressure at sea level. When barometers in the home are set to match the local weather reports, they measure pressure adjusted to sea level, not the actual local atmospheric pressure. The altimeter setting in aviation is an atmospheric pressure adjustment.
- Barometric pressure (also known as atmospheric pressure) is the force exerted by the atmosphere at a given point. It is known as the "weight of the air". A barometer measures barometric pressure. Measurement of barometric pressure can be expressed in millibars(mb) or in inches or millimeters of mercury (Hg).
- 14.70 pounds per square inch
- Key idea: Atmospheric pressure is caused by the weight of the atmosphere pushing down on itself and on the surface below it. Pressure is defined as the force acting on an object divided by the area upon which the force is acting.
1000 hPa are equal to 1000 mbar, which is equal to 750 mm of mercury in a barometric column, which is 0.987 of the average atmospheric pressure, which on global average is 1013 millibars or hectopascals. While hPa is used in meteorology most weatherforecasts quote atmospheric pressure in millibar.
- The altimeter setting in aviation is an atmospheric pressure adjustment. Average sea-level pressure is 1013.25 mbar (101.325 kPa; 29.921 inHg; 760.00 mmHg). However, in Canada's public weather reports, sea level pressure is instead reported in kilopascals.
- Air pressure is caused by the weight of the air molecules above. Even tiny air molecules have some weight, and the huge numbers of air molecules that make up the layers of our atmosphere collectively have a great deal of weight, which presses down on whatever is below.
- That is, as the altitude increases, atmospheric pressure decreases. This is due to the fact that air molecules are constantly being pulled downwards (towards the center of the Earth) by Gravity. So, air molecules are tightly packed near the surface of the earth, compared to some higher altitude.
At sea level, the weight of the air above this unit area would (on average) weigh 14.7 pounds! That means pressure applied by this air on the unit area would be 14.7 pounds per square inch. Meteorologists use a metric unit for pressure called a millibar and the average pressure at sea level is 1013.25 millibars.
- Human bodies are used to air pressure. The air pressure in our lungs, ears and stomachs is the same as the air pressure outside of our bodies, which ensures that we don't get crushed. Our bodies are also flexible enough to cope when the internal and external pressures aren't exactly the same.
- In physiology, intrapleural pressure (also called intrathoracic pressure) refers to the pressure within the pleural cavity. Normally, the pressure within the pleural cavity is slightly less than the atmospheric pressure, in what is known as negative pressure.
- The molecules making up a gas, such as the gases in our atmosphere, are not bound to each other at all. They are free to move about, bumping into each other as well as into liquids and solids. At sea level, the amount of pressure exerted by our atmosphere is about 14.7 pounds per square inch.
Updated: 16th October 2019