### International Standard Atmosphere - Wikipedia

Because the general pattern of the temperature-altitude profile is constant and The atmospheric pressure at the top of the stratosphere is roughly 1/ the . The relationship between geometric and geopotential altitude depends upon the To date, all spacecraft that have landed on Mars have done so in either the. Heat transport in the lower atmosphere is predominantly convective, at least in daytime. (Convection abates after the ground has cooled off at. Less well-known is that temperature and latitude influence this relationship with A temperature and a latitude-dependence of pressure altitude result, with the for estimating pressure altitude given a specific location and observation date.

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Aneroid Barometers An aneroid barometer also measures air pressure but in a different way. Basically an aneroid barometer is a slightly dented metal container. As the pressure increases it causes the container to crumple slightly, and returns to normal when the pressure decreases. A dial inside the container moves as it crumples and uncrumples.

Using page 13 of the ESRT we can easily convert back and forth between inches of mercury and millibars. Air Pressure Constantly Changes Like all weather variables, air pressure is constantly changing.

### Air Pressure — Mr. Mulroy's Earth Science

These changes are driven by changes in other factors such as altitude, temperature, and humidity. It is therefore important for us to understand the relationship between air pressure and altitude, temperature, and humidity. Air Pressure and Altitude You may have seen or read about Mountain climbers like the one shown, needing to bring oxygen tanks with them as they climb higher and higher. You may have also heard air at high altitudes referred to as being "thin".

We know that air pressure is the weight of the air above us pressing down. So if we imagine climbing high into the mountains, as our altitude increases there is less air above us.

If there is less air above us pressing down, the air pressure must decrease. The latter exponential function, however, is the predominate form at thermospheric altitudes. In this case, zo and To are the geometric altitude and kinetic temperature at the origin of the exponential function, and should not be confused with sea-level values, which typically carry the same denotation.

Lo is the initial temperature gradient at the origin, and ro is the planet radius.

Consequently, pressures cannot be computed without first determining ni for each of the significant species. As with pressure, densities cannot be computed without first determining ni for each of the significant species.

Number Densities On Earth, in the altitude region between approximately 85 and km, the effect of height- and time-dependent, molecular oxygen dissociation, and the competition between eddy and molecular diffusion combine to complicate the study of the height distribution of the atmospheric species, such that the generation of numerical values for the altitude profiles of physical parameters necessitates a considerable amount of numerical computation.

More specifically, atomic oxygen becomes appreciable above 85 km, and diffusive separation begins to be effective at an average height of about km.

### Why Is It Colder at the Top of a Mountain Than It Is at Sea Level? | HowStuffWorks

Also, in the regime where molecular diffusion becomes significant above about 85 kmthe effect of vertical winds in the composition in important. These conditions lead to a complex dynamically oriented expression, applicable to each individual gas species, which includes vertical transport and diffusive separation. Ideally, this set of equations should be solved simultaneously, since the number densities of all the species are coupled through the expressions for molecular diffusion.

Such a solution would require an inordinate amount of computation. A simpler approach is desired, which is found using some simplifying approximations, and by calculating the number densities of the individual species one at a time. Even this simpler approach is lengthier and more involved than we want to delve into here.

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Number Densities of Individual Species Above approximately km, it is relatively safe to assume that there is no further large-scale oxygen dissociation, and that diffusive equilibrium prevails. Under such conditions, the simultaneous equations governing molecular diffusion are no longer interdependent, and these equations can then be applied to each atmospheric constituent separately.

In this case, the computation of the individual density-height profiles presents no greater difficulty than that of the total pressure or density below 80 km. Number density decreases exponentially with height in an identical way to pressure.

Referring to equation 10 we recall that scale height H is a function of molecular weight M, temperature T, and acceleration of gravity g.

By computing n for each atmospheric constituent separately, M is constant and equal to the species' defined molecular weight. However, the function T z is height-dependent and non-linear, such as the function seen in equation And now that z has replaced h as the parameter of height, g z is height-dependent acceleration of gravity, per equation 7.

This leads to a complex and messy integration, which we'll not attempt to undertake.