how does atmospheric pressure change with altitude?
486747
There are basically two things happening in regards to atmospheric pressure, both caused by the same thing.\n\n1.Pull from below-Gravity is pulling on all of the molecules so the heavier a molecule is, the closer to the surface of the earth it wants to be as a result of gravity.\n\n2. Push from above-Because gravity is pulling on all of the atmosphere's molecules, all of them "want" to be at the earth's surface. If you were to remove all of the most dense air at the surface, all of the less dense molecules above would simply be pulled down to take the place of the removed ones. This results in the molecules above pushing down on those below, adding to the force that gravity is exerting on them. (more pressure)\n\n\nThe atmosphere is basically arranged most dense (closest to the earth's surface) to least dense (outermost region of the atmosphere) according to the atomic weight of the molecules.\n\nSo the further you go upward into the atmosphere, the less molecules there are that "want" to be at the earth's surface, and therefore the less atmospheric pressure there is.\n\nHope this helps
948748
Because within the troposphere, temperature decreases with altitude.
126339
actually you should phrase it "why does pressure decrease when temperature is reduced?" because a rise or fall in temperature affects air pressure (not the other way around).  the higher temperature is, the faster molecules in the air are moving and therefore they increase the space they take up.  if temperature is lower, molecules move around less and require less space.
836671
At an atmosheric pressure of 101.3 KPa (14.7 psi), the usual pressure at sea-level (it DOES vary a bit with the weather), water boils at 212 deg.F or 100 deg.C.  However, the boiling point goes down as the atmospheric pressure goes down, which is what happens when you go up in elevation.  Where I live, the elevation is about 4600 ft.  In a physics lab I took here, one of the experiments was to measure the B.P. of water.  It turned out to be 92 deg.C.
105710
To expand on Valentin's answer:\n\nFirst, realize that most atmospheric heating comes from the surface of the earth; the atmosphere itself is transparent to most frequencies of light energy coming from the Sun.  It's when that radiation hits the surface of the Earth and gets converted to infrared, i.e. heat, radiation that the atmosphere gets heated.\n\nNow, the "physics problem":  Pressure, density and temperature are all related by gas laws.  As the warm air rises, it expands, without taking on heat from its environment, and thus cools.  \n\nNext, add the "natural phenomenon".  Higher altitude air is generally drier than lower altitude air; water vapor helps lock in the heat radiating from the surface; hence higher altitude air locks in less heat than lower altitude air.  And, it's true that high altitude winds result in the air absorbing less heat from the surface.
37068
The air gets less dense, not lighter as elevation increases because there is less air on top to push down on the air beneath it you as you go up.  It would be like diving to the bottom of a swimming pool.  Whenever you go so deep, your ears start to hurt because the pressure of the water on you.  It's like that, but we're used to the pressure of the air.  \n\nTall people don't breathe easier, there isn't that much of a difference in pressure.  But actually, the higher you go, the harder it is to breathe.  There is less oxygen as you go up (that's why mountain climbers have to wear oxygen masks when climbing tall mountains like Everest!)
495221
Barometric pressure is the measure of how dense the air around you is. It is measured in inches or millibars.  The reason for this type of measurement is that early barometers were constructed using a tube of mercury.  it was discovered that a tube containing mercury sitting in a pool of mercury varied with the air pressure.  Scientists noted that this device gave a higher reading at the bottom of a mountain where the air is more dense than at the top where there is less air pressure to support that column of mercury.( if you could keep going higher you would get to a place where there is no air to support your column of mercury.  That is outer space. Say you took an inflated balloon with you on your journey to outer space.  It would explode because there are air molecules inside the balloon pushing outward, and no air pressure outside the balloon to keep it in check. The same with your body.). The average reading at sea level is around 30 inches of mercury.  If you live in a place where there are mountains you can test this for yourself. Most barometers now days do not use mercury, but instead are operated using a spring. Take your barometer with you when you travel up a mountain.  As you get higher you will see the reading decrease. As you travel up or down a mountain, your ears might "pop".  This is due to the change in air pressure. Have you noticed the weatherman talking about areas of low preassure and areas of high presure? The barometric pressure is what they are talking about.  In general the higher the air pressure the less likely there will be a storm. In tornados and hurricanes air pressure is very low. This lower air pressure is what causes some people with arthritus to complain of their aches and pains and causes your headaches. \nSandy Claws
218879
It seeks its equilibrium, meaning that it rises to the altitude at which the air within and without are at equal pressure.  Volume does not change.
404726
First, a high elevation on Earth is not that much closer to the sun than sea level is when you consider the great distance from Earth to the sun.\n\nThe temperature changes have to do with air pressure... there is less of an atmosphere to hold in the heat at a high elevation than there is at sea level.  You might notice that cities at high elevation also have widely varying temperatures between day and night.  Here it will warm up in the day easily without much atmosphere to reflect energy from the sun, but at night it's like just having a sheet over you--the heat escapes easily.  At sea level you will warm up more slowly but hold that heat in much longer because you have a giant blanket of atmosphere over you, and higher air pressure to maintain the heat.  \n\nAlso at sea level, if you are by the sea, you have the added effect of the ocean or sea keeping the air temperate (around the same temperature all the time) since water maintains it temperature better than the air.
1014941
The air gets thinner with altitude and with that so does the temperature. \n\nBesides, to say that you're approaching the sun when you've not even left earth's atmosphere is like saying you're approaching New York when you've only checked in your luggage at Heathrow.
856212
There is a standard model of the atmosphere which is used for calibrating instruments such as aircraft altimeters.  The standard sea level pressure is 1.01325 bars, or about 760 mm Hg.  In a vacuum, the pressure is reduced sufficiently to facilitate whatever process the vacuum was intended to enable; in laboratories, vacuums of 1E-8 bar or lower are attainable.
148133
ok, the relationship between altitude and temperature is not constant.  at sea level it is on avg 288.26 kelvin.  the temperature falls as you get higher until you are at about 11 km at which point the temperature remains constant.  the temperature fromm 11 km through 25 km from sea level is 216.66 Kelvin.  and then after 25km it starts getting warmer as you get higher until you reach 47 km and then it again becomes constant, this time at 282.66 kelvin and stays constant until 53 km.  after 53 km it continously gets colder again.  And if you go really high, it just keeps getting warmer again after 90km as you leave earth and enter space because then there is nothing between you and the the full force of the suns energy.  So if you go high enough, between 47 and 53 km, it is actually not that much colder than on the ground.  these temperatures and altitudes are based on standardized data, meaning that it is not going to be exactly the temperature everywhere at a given altitude, just like it is not 288.66 kelvin everywhere on earth, they are standardized avgs., but when engineers design airplanes, these are the numbers they use.  \n\nthe reasoning for all this is a combination of what everyone else has already mentioned.  it is the result of density, distance from the earth, radiation, etc.  See, at sea level it is warmer b/c the atmosphere traps the suns energy.  as you get higher, you get further away and it gets colder since the atmosphere it thinner(less dense) and doesnt trap as much heat.  then it levels off and starts getting warmer because the atmosphere is thinner.  this time the thinner atmosphere doesnt block as much of the suns energy and radiation, causeing it to get warmer again.  then once you get really high, it just keeps getting warmer as you enter space.  other factors are that the composition of the air changes with altitude, like the o-zone layer for example, is different from the air at sea level.\n\nhttp://mintaka.sdsu.edu/GF/explain/thermal/std_atm.html\nhere's a link to a graph showing how the temperature changes with altitude.  you can find tables with the exact values used to create the graph in engineering textbook or the internet as they are very common
132266
Ignore harsha.  A 1 atm decrease in pressure would mean zero pressure at 100 meters above sea level, which is absurd.\n\nPressure decreases as you rise because the total mass of the atmosphere weighing down on you decreases.  High pressure means you need more energy to make water boil, so at sea level the boiling point will be higher than it will be on a mountain top.
19016
Can you be more specific?  The earth's atmosphere has many gases in it, one being oxygen.  Dry air and humid air will have little difference in oxygen levels.  Altitude, however, does affect oxygen.  The higher you are, the less air, and less oxygen.  I hope this helped.
634368
Low pressure develops when pockets of warm air rise.\n\nHigh pressure develops when air sinks. It is literally pushing down.\n\nAir pressure in general changes due to elevation. The higher up you go, the less air. In turn, there is less air pressure. This is due to the forces of gravity.
601836
1)typical atmospheric pressure is 1atmosphere or 10^2kilopascals or 760mmHg.\n2)Atmospheric pressure decreases with altitude.So external pressure decreases.As preessure decreases volume increases(if the temperature change is insignificant)\n3)Water pressure increases with depth (P=h*density*g).So as external pressure increases the volumme decreases.\n4)Here we assume that the temperature doesn't change in the process.Use Boyle's law PV=P'V'\nso 760*V=1.30*0.21\nwhich gives V=3.59*10^-4L
141597
If there was no sunshine and no vertical air motion, cold air would settle to the surface, and temperature would increase going up in the atmosphere (and we'd all be dead soon ;) ). Because the ground is always radiating away heat (though often receiving more during daytime from the sun), there is a tendency for that to occur. Note the polar regions for example - during winter there is a semi-permanent temperature inversion (increase of temperature with altitude).\n\n2 things which counter the tendency for inversion are solar heating and vertical air motion.\n\nSunshine heats the ground, heat is conducted to air directly above the ground, and convection transports it up into the atmosphere. Cooling/heating of air by radiation is a slower process, so heat builds as spring and summer progress (at mid & high latitiudes) - especially in the lower atmosphere.\n\nAir moving vertically in the atmosphere (up or down) does so at the adiabatic lapse rate, which is 10 °C per km for dry air and less for saturated air (varies depending with temperature - averages about 6-7°C per km). Rising air cools at that rate, and subsiding air heats at the rate. Thus vertical air motions act to heat the lower atmosphere and cool the higher.\n\nThe combined effect of those, as a few people mentioned, is that temperature on the average decreases with altitude in the troposphere - at a rate of 6.5 °C per km (3.6 °F per 1000 ft.). Yet the lapse rate varies depending on conditions. Air during a clear night normally increases directly above the surface, strong inversions may occur during winter and ahead of warm fronts, and air can decrease at the dry adiabatic rate or briefly greater during a warm, sunny spring day. Etc.