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Atmospheric pressure, also known as air pressure or barometric pressure (after the barometer), is the pressure within the atmosphere of Earth. The standard atmosphere (symbol: atm) is a unit of pressure defined as 101,325 Pa (1,013.25 hPa ), which is equivalent to 1,013.25 millibars , [ 1 ] 760 mm Hg , 29.9212 inches Hg , or 14.696 psi . [ 2 ]
Air density, like air pressure, decreases with increasing altitude. It also changes with variations in atmospheric pressure, temperature and humidity . At 101.325 kPa (abs) and 20 °C (68 °F), air has a density of approximately 1.204 kg/m 3 (0.0752 lb/cu ft), according to the International Standard Atmosphere (ISA).
The current global average concentration of carbon dioxide (CO 2) in the atmosphere is 421 ppm (0.04%) as of May 2022. [ 1] This is an increase of 50% since the start of the Industrial Revolution, up from 280 ppm during the 10,000 years prior to the mid-18th century. [ 2][ 1][ 3] The increase is due to human activity.
Air mass. In meteorology, an air mass is a volume of air defined by its temperature and humidity. Air masses cover many hundreds or thousands of square miles, and adapt to the characteristics of the surface below them. They are classified according to latitude and their continental or maritime source regions.
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Air pressure actually decreases exponentially with altitude, dropping by half every 5.6 km (18,000 ft) or by a factor of 1/e (0.368) every 7.64 km (25,100 ft), (this is called the scale height) -- for altitudes out to around 70 km (43 mi; 230,000 ft). However, the atmosphere is more accurately modeled with a customized equation for each layer ...
An air quality index (AQI) is an indicator developed by government agencies [ 1 ] to communicate to the public how polluted the air currently is or how polluted it is forecast to become. [ 2 ][ 3 ] As air pollution levels rise, so does the AQI, along with the associated public health risk. Children, the elderly and individuals with respiratory ...
CSF: CSF alb = 30. CSF glu = 60. CSF/S alb = 7.5. CSF/S glu = 0.6. The Alveolar–arterial gradient (A- aO. 2, [ 1] or A–a gradient ), is a measure of the difference between the alveolar concentration ( A) of oxygen and the arterial ( a) concentration of oxygen. It is a useful parameter for narrowing the differential diagnosis of hypoxemia.