2
$\begingroup$

Why does temperature increase as height increases in the stratosphere (15 km - 60 km above earth), when the ozone molecules are most concentrated at about 25 km? ozone concentration through stratosphere

$\endgroup$

migrated from physics.stackexchange.com Mar 10 at 3:13

This question came from our site for active researchers, academics and students of physics.

  • $\begingroup$ Why do you think that ozone concentration and temperature are connected? $\endgroup$ – Jon Custer Feb 11 at 18:34
  • $\begingroup$ UCAR Center for Science Education: "Ozone, an unusual type of oxygen molecule that is relatively abundant in the stratosphere, heats this layer as it absorbs energy from incoming ultraviolet radiation from the Sun." Clearly, I am wrong in some regard. I just don't understand why highest temperature is in molecules significantly above the ozone layer, when the most electromagnetic radiation is being absorbed at the level of the ozone. $\endgroup$ – Ken Kutcel Feb 12 at 18:20
2
$\begingroup$

There are two main points to make here.

The first point is that UV radiation is entering the stratosphere from above (ignoring angular dependencies and scattering), so is preferentially absorbed by ozone higher in the stratosphere. This is a form of the Beer-Lambert law, which leads to greater absorption higher in the stratosphere.

The second point is that the Dobson Units used in your plot standardize for (partial) pressure and temperature differences between different heights in the stratosphere, so that you can compare the mass or number density of ozone at different levels. But it doesn't tell you how much ozone there is relative to all the other gases making up the air at a particular height. A common way to look at this is the mole mixing ratio:

enter image description here

A height–latitude cross section of annual average ozone mixing ratio (ppmv) from the climatology.

Source: McPeters et al (2005), Ozone climatological profiles for satellite retrieval algorithms, GRL.

While the ozone concentration peaks around 20 km, the mixing ratio peaks around 30 to 40 km and doesn’t decline so abruptly with height. Where the mixing ratio is greater, absorption of a particular amount of UV radiation can have a greater effect on the overall air temperature at that height.

The net effect of these two properties is that heating of the stratosphere by UV absorption (see plot below) peaks in the upper stratosphere around 50 km. This is why the greatest temperatures are found in the upper stratosphere.

enter image description here

Heating from absorption of UV radiation (K/day)

Source: Haigh (1984) Radiative heating in the lower stratosphere and the distribution of ozone in a two‐dimensional model, QJRMS.

$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.