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The global mean pressure at the surface of the Earth is PS = 984 hPa, slightly less than the mean sea-level pressure because of the elevation of land. We deduce the total mass of the atmosphere ma: (2.2) where R = 6400 km is the radius of the Earth. The total number of moles of air in the atmosphere is Na = ma/Ma = 1.8x10 20 moles. Exercise 2-1.
The air density at sea level does not vary much around the world; the sea-level pressure varies by at most 5%, and the temperature rarely departs by more than 15% from 273 K, so that na remains within 25% of the value calculated here. The number density of CO2 is derived from the mixing ratio CCO2 = 365 ppmv: M a = C N2M N2 ++C O2M O2 C ArM Ar
4 kwi 2020 · In this equation, p ( h) is the atmospheric pressure at altitude h, p0 is the atmospheric pressure at sea level, g is the gravitational acceleration, ρ0 is the mass density of air at sea level, R is the gas constant, T is the temperature, M is the (average) molar mass, m is the average mass of a gas molecule, and H is a composite parameter somet...
This is in contrast to mean sea-level pressure, which involves the extrapolation of pressure to sea level for locations above or below sea level. The average pressure at mean sea level in the International Standard Atmosphere is 1,013.25 hPa, or 1 atmosphere (atm), or 29.92 inches of mercury.
Surface Pressure vs. Sea Level Pressure • Sea Level Pressure – the pressure that would exist if the observation point were at sea level. • Surface Pressure – the pressure observed at a particular location ATMO 1300 Equation of State • Ideal gas law – P = pressure (Pa) – ρ= density (kg/m3) – T = temperature (K)
Atmospheric pressure is slightly dependent on weather conditions. On the graph below, we can see the decrease in atmospheric pressure as the altitude increases. At sea level, the atmospheric pressure would be a little over \(100 \: \text{kPa}\) (one atmosphere or \(760 \: \text{mm} \: \ce{Hg}\)).
Sea Level and Pressure Systems 2.2.1 Pressure at the Surface QFE The atmospheric pressure measured on a barometer at an airfield is known as the QFE or Aerodrome Pressure. The QFE varies widely, both from day to day and place to place, due to variations in the weight of the air column above the surface 2.2.2 Pressure at Mean Sea Level QFF
