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| | | Richard Daniel chairs the interactive environmental programme in which he and his guests deal with listener's questions and concerns.
Call 03700 100 400
home.planet@bbc.co.uk
91热爆 Planet, PO Box 3096, Brighton BN1 1PL | | | | | LISTEN AGAIN 30 min | | | |
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| "91热爆 Planet is the environmental programme for which you set the agenda. We tackle your questions and concerns and try and make some sense out of the conflicting opinions which make up the environmental debate."
Richard Daniel | |
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Panel
University of Essex
Dr Nick Riley
Bio-geographer, University of London
TOPICS
Can we use disused North Sea oil wells to store our waste?
What is the impact of acid rain on seas?
How heavy are clouds?
The panel discussed the mass of clouds and not their weight. Here are Professor Stott's calculations:
Mass = volume x density.
Thus we need to know the volume of a
cloud (near a sphere) and its density.
The density is primarily governed
by its water content, which can vary from 0.1g to a whopping 15g
per m3, as follows:
small cumulus cloud: 0.2-0.5 g /m3
large cumulus cloud: 0.5-1.0 g/m3
stratus cloud: 0.1-0.5 g/m3
cumulonimbus cloud: 5-15 g/m3
Thus a very large cumulus cloud forming an approximate sphere of 1km
radius would contain 4 billion m3 at c.1 g/m3, which gives a "weight" of 4 billion g or 4 million kg.
How much ozone is there in the ozone layer?
Here are Professor Stotts' calculations:
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We should note that we are measuring stratospheric ozone, not ozone
in the troposphere near to ground-level. Only about eight percent of atmospheric
ozone occurs in the troposphere;
- Ozone is measured in Dobson Units (DU) with each DU = 2.7 x 1016
ozone molecules per cm2. At standard temperature and pressure (STP),
one Dobson Unit is defined as corresponding to 0.001cm thickness. An
undepleted ozone layer is usually c.300DUs, which gives a thickness, at
STP, of c.3mm. In a depleted ozone layer, the DUs can fall to as little
as 117DUs, ie 117 x 0.01~1mm;
- Now for the weight calculation. For a cm2 of the Earth's surface
at STP:
The molecular weight of ozone is 47.9982 atomic mass units (amu);
One atomic mass unit (amu) = 1.660538 x 10-27 kg;
One Dobson Unit contains 2.7 x 1016 molecules per cm2;
There are, in an undepleted ozone layer, 300 DUs;
Thus: the weight of ozone per cm2 at STP is:
(1.660538 x (10-27)) x 47.9982 x (2.7 x (1016)) x 300
Which equals: 6.45592964 x 10-07 kg per cm2.
If we take the area of the surface of the Earth to be 5.112 x 1018
cm2, then the final figure for the weight of ozone in the stratosphere
(at STP) is:
3.300 x 1012kg.
Jellyfish
Looking after our soil
Contact 91热爆 Planet
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91热爆 Planet
91热爆 Radio 4
PO Box 3096
Brighton BN1 1PL
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