I am getting relatively lower downward diffuse flux when I increase the ozone concentration in lower atmosphere at around 40 degree of solar zenith angle. Can we define this effects in terms of multiple scattering ? How?
Dear Bikas,
I presume (1) you mean "lower downward diffuse solar radiation flux", and (2) you are working with a model of radiation transfer in the atmosphere, where you can modify the vertical profile of ozone concentration. Please confirm this.
Unless you are running your simulations for a region affected by a decrease in the stratospheric ozone (the so-called "ozone hole"), solar radiation is significantly absorbed in the relevant spectral bands (in particular in the UV) within that upper layer. Adding more ozone in the troposphere will have a limited impact in terms of absorption on the total downward irradiance at the planetary surface. However, please indicate how large an increase you are considering.
It is not clear to me that a marginally higher concentration of ozone in the troposphere will significantly change its scattering properties. However, if your model allows for a variety of chemical reactions and interactions between atmospheric gases and pollutants, it is possible that it predicts the formation of other airborne compounds which may result in additional absorption in other spectral bands or in a higher scattering, for instance if this results in the formation of particulates (aerosols).
Please provide additional information on your problem to solicit further ideas and perhaps more appropriate responses. Regards, Michel.
Dear Michel,
Thank you for your detail explanation. Exactly, I am running simple Radiation transfer model where I can change the vertical profile of ozone concentration. In this model chemical reaction is not allowed.
When I run model with normal ozone distribution (at 300 DB) with 40 degree of zenith angle, I got lower downward diffuse flux of 0.18 w/m2 (at wavelength of 305 nm). Then I Moved 10 DU from the layer between 14 and 15 km to the bottom layer (0-1 km), so that the total ozone column amount is unchanged, at that condition, I got lower downward diffuse flux of 0.021. So I am thinking how this redistribution of ozone affect the downward diffuse flux.
Thank you
Bikas
Dear Harry, total of 1000 ..? of what ..sorry I did not understand.
-Bikas
at a given wavelength you have to give the flux per unit of wavelength
Dear Bikas,
I still don't understand where Harry got his 1000 from. Is it 1000 W m-2 ? That is hardly a realistic flux per wavelength.
As well as absorbing UV in the stratosphere, ozone also absorbs infrared radiation. In other words is is another greenhouse gas. So moving ozone into the troposphere will cause outgoing longwave radiation there to be absorbed, if your model recognizes O3 as a greenhouse gas. Putting O3 at the base of the atmosphere will not increase shortwave radiation there but will increase downward longwave radiation since the ozone acting as a greenhouse gas produces back radiation.
HTH
Cheers, Alastair.
Alistair is completely right: ozone in the lower troposphere acts as an IR-greenhouse gas. As for solar influx: virtually all of the ozone is in the stratosphere: so why do you want to transfer that ozone to the troposphere?
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