Atmospheric ozone is the only abundant atmospheric component that absorbs

UV $(290$ to $320nm.$ Its abundance is measured in Dobson Units $($DU$)$ defined

as a layer $10m$ thick at $1$atm and $0C.$ One DU contains $2\mathrm{.}69{10}^{16}$ ozone

molecules per $c{m}^2$ that is $10m$ tall $($thick$).$ Ozone absorbs at $300nm,$ with

${}_{300}=477Lmo{l}^{-1}c{m}^{-1}.[25]$

a$)$ A typical value for the ozone layer over antarctica, pre$-1975$ was $250DU,$ with

little variation. How thick would the ozone layer be at $250DU($maintaining $1$

atm and $\{$:$0C)?$

$($ atm and $0C]$

ticlevess $=250{10}^{-6}m=$

$($b$)$ What concentration of ozone would this correspend to$,$ in molt

$[0_3]=\frac{n}{r}=\frac{p}{RT}=\frac{1}{0\mathrm{.}0821273\mathrm{.}16}$

$($c$)$ What is the absorbance of $300nm$ UV $8$ radiation by atmospherior ofone over

the path length from part $a,$ at this concentration?

$A=lc=477250{10}^{-6}3{10}^{-8}A$

$=35\mathrm{.}775{10}^{-6}$

$($d$)$ The solar spectrum irradiates the Earth's atmosphere with $150W{m}^{-2}$ at $300$

$nm.$ What percent $(\%)$ of this is absorbed by ozone, based on your answer

from part $c?$

$1w=13s^{-1}$

will.

$($e$)$ In the late $1970$s$,$ this value began to show seasonal fluctuations that persist

to the present day, with levels dropping typically as low as $100DU$ in the

Antarctic summer. How does this change your answer to part d$?$