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Ozone heating the lower stratosphere.

  1. Feb 23, 2010 #1
    So, I'm a student working on a M.S. Environmental Science.

    I just took a test, the course is Mechanisms in the Environment, and got a question marked wrong that I believe is a correct answer.

    The question was, paraphrased, Can ozone formation in the mid to upper stratosphere heat up the lower atmosphere? true/false and explain your answer.

    My answer was true, basically because heat transfers from a hot medium to cold medium due to excited particles bumping into one another and transferring energy to the lower energy (colder particles) in the form of heat. I guess in physics terminology I was arguing that conduction causes this, although after some background reading it could be more of a convection transfer.

    Some basic information

    -Ozone formation is Exothermic

    -Temperature decreases as you travel from the ground towards the stratosphere once you enter the stratosphere temperature increases until you enter the mesosphere

    -Ozone formation occurs predominantly in the mid to upper stratosphere

    during our discussion he argued that air cannot transfer heat down (to a lower elevation) citing the example of heat in a house (near the ceiling is warmer than near the ground.

    I do not have a good answer for this question, however I would venture to guess that this could be due to convection forces or due to higher energy particles moving faster and thus being more able to reach higher elevations despite gravity's pull.

    I still maintain that Ozone formation releasing energy has to transfer heat to the lower atmosphere. Part of my logic is that the temperature increases as you approach the reaction area and then decreases as you leave it traveling farther into the mesosphere. So in effect as you travel away from the exothermically active reaction temperature cools.

    If his argument were correct wouldn't temperature decrease until you reach the energy source, then jump to the temperature of that source and the only temperature changes occur above the said heat source?

    Anyways what I need to know is am I correct and why or is he correct and why?

    P.S. Not sure if I posted this in the correct forum, I apologize if it is in the wrong location, I don't think this fit the qualifications for homework and I didn't see a heat area. Also if some of my physics terms are slightly misused I apologize, I'm sure someone will correct me. Finally, I hope that I have described the problem clearly.
     
  2. jcsd
  3. Feb 23, 2010 #2
    Ok some more thoughts of my own on this.

    After posting I kept trying to figure out: If the heat energy moves like I predict, then why does the lower stratosphere not heat up to the same temperature as the reaction over time (thinking on the time-scale of how long the stratosphere has been there.

    My answer thus far:

    UV radiation strikes the surface of the earth producing IR radiation which heats up molecules that absorbs these frequencies. The heat from the ground moves upward towards the cooler air in the atmosphere. Simultaneously the exothermic ozone creation process (O2 + O -> 03) creates heat warming the mid and upper stratosphere which has net movement both up and down.

    So ground heat and ozone creation heat is being moved via conduction towards a colder band between the two heat sources. One would initially think that the heat from the two sources would eventually heat up the cold band in between and then continue to have net heat movement upwards in elevation. However in real application the cold band does exist and is not being heated up. This is because there is a heat sink that removes heat from the cold band. This cold band is a temperature equivalent to:

    (Heat from surface + Heat From Upper stratosphere) - heat removed from Mechanism X = Temp. experienced in said cold band

    An easy Mechanism X is precipitation since cloud formations stop at this boundary the water is able to absorb energy from both sides and then precipitate back to the earth thereby preventing the heating of this cold band.
     
  4. Feb 23, 2010 #3
    Ok some more thoughts of my own on this.

    After posting I kept trying to figure out: If the heat energy moves like I predict, then why does the lower stratosphere not heat up to the same temperature as the reaction over time (thinking on the time-scale of how long the stratosphere has been there.

    My answer thus far:

    UV radiation strikes the surface of the earth producing IR radiation which heats up molecules that absorbs these frequencies. The heat from the ground moves upward towards the cooler air in the atmosphere. Simultaneously the exothermic ozone creation process (O2 + O -> 03) creates heat warming the mid and upper stratosphere which has net movement both up and down.

    So ground heat and ozone creation heat is being moved via conduction towards a colder band between the two heat sources. One would initially think that the heat from the two sources would eventually heat up the cold band in between and then continue to have net heat movement upwards in elevation. However in real application the cold band does exist and is not being heated up. This is because there is a heat sink that removes heat from the cold band. This cold band is a temperature equivalent to:

    (Heat from surface + Heat From Upper stratosphere) - heat removed from Mechanism X = Temp. experienced in said cold band

    An easy Mechanism X is precipitation since cloud formations stop at this boundary the water is able to absorb energy from both sides and then precipitate back to the earth thereby preventing the heating of this cold band.
     
  5. Feb 24, 2010 #4
    Don't you have a textbook for this course?

    Because the top op the stratosphere is warmer than the bottom there is no convection in the stratosphere. The heating at the top of the stratosphere is not because of the formation of ozone, but because of the fact that it intercepts ultraviolet rays of the sun.
    You seem to be ignoring heat transport by radiation.
     
  6. Feb 24, 2010 #5
    The question specifically refers to the production of ozone (which is an exothermic reaction) the uv radiation only causes heat when a molecule can absorb the radiation (ozone can absorb UVB so this does occur) generally this enery ends up breaking the bonds forming O2 + O (also an exothermic reaction but not the reaction that the question focused on) which would also generate heat and undergo the same heat transfer that I ascert is occuring above.
     
  7. Feb 24, 2010 #6
    The complete reaction from O2 to O3 is NOT an exothermic reaction. The energy comes from ultraviolet light.

    you have O2 + UV foton -> 2O

    and then O2 + O -> O3 this pis exothermic, but the energy comes from the first reaction.

    most of the UV light is absorbed by O3 + foton => O2 + O

    The only energy produced here comes from the sun. If the ozone layer didn't catch those
    photons, they would be caught lower down in the atmosphere or on the ground, and they would warm the atmosphere there as well.
     
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