From: Dale 25/02/00 16:10:18 Subject: why is it colder at higher altitudes? post id: 41986 I know this should be simple, but can soem-on eplease explain to me why it is colder at higher altitudes? Aren't you closer to the sun's rays? From: Em 25/02/00 16:19:52 Subject: re: why is it colder at higher altitudes? post id: 41991 I'm no expert but isn't it something to do with this idea? The higher up you go in the atmosphere(higher altitude) the amount of atmospheric pressure is less and therefore the 'barrier', keeping heat in is weaker, thus letting more heat escape resulting in the air having a lower temp.... Or am I waxing lyrical... Em From: Martin B 25/02/00 17:20:14 Subject: re: why is it colder at higher altitudes? post id: 42004 Yes, that's about it. You live your life about 150 000 000 000 km away from the Sun. Getting 1 km closer ain't going to make a hoot of difference to the amount of sunlight you encounter. The reduced atmosphere is going to be important, in a number of ways. First there is less thermal energy in the air hanging around you, so you will feel colder. Second, more UV radiation will reach you, so will get sunburnt more quickly. From: bart 25/02/00 17:27:28 Subject: re: why is it colder at higher altitudes? post id: 42009 there is less air pressure. From: steve(primus) 25/02/00 18:35:34 Subject: re: why is it colder at higher altitudes? post id: 42036 Not quite right. Rather than looking at why it is colder higher in the atmosphere, it is better to consider the rays of the sun coming from the cold vastness of space into the atmosphere. The outer edges of the atmosphere are very warm, this is the thermosphere. As the very short wavelengths, x-rays and shorter reach the atmosphere, they break down any atmospheric molecules, such as water vapour, into ions and atoms. This process absorbs the radiation and heats up this part of the atmosphere. The atmosphere is very thin in any case up there so the atoms have more room to move. Greater movement means increased temperature. As we get lower in the atmosphere the x-rays etc are all absorbed and the temperature falls to the mesopause - the boundary between the mesosphere and the thermosphere. In the mesosphere, the ultraviolet radiation from the sun starts to break down the oxygen molecules into free atoms which then combine with other oxygen molecules producing ozone. The ozone is heavier than the oxygen molecules and sinks towards the earth. Lower down, the ozone(O3)is broken down by further UV radiation back into O2 and O. This process warms the atmosphere again. The peak of this activity occurs at the stratopause, the boundary beteen the stratosphere and the mesosphere. The temperature falls through the stratosphere to the tropopause, the boundary between the troposphere and the stratosphere. In the troposphere, the solar radiation heats the surface of the earth and also the clouds and dust particles in the air. These in turn heat the surrounding air with the greatest heating ocurring at the earth's surface. The troposphere warms as you descend to the surface. As you can see, the question should not be "why does it get colder as you get higher?" but "why does it get warmer as you get lower? From: Reverend 25/02/00 18:37:31 Subject: re: why is it colder at higher altitudes? post id: 42037 yeah..... if hot air rises, why is it so cold in the mountains? From: steve(primus) 25/02/00 18:48:11 Subject: re: why is it colder at higher altitudes? post id: 42039 if hot air rises, why is it so cold in the mountains? because rising air expands and becomes cooler. From: Martin B 28/02/00 9:35:20 Subject: re: why is it colder at higher altitudes? post id: 42420 Steve, if you were in the thermosphere, would you feel hot/warm? This forum is un-moderated. The views and opinions expressed are those of the individual poster and not the ABC. The ABC reserves the right to remove offensive or inappropriate messages.