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well in aerosol the physical definition

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of it it's a small particle which is

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suspended in the air can be suspended at

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any altitude but our main interest is in

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tropospheric aerosols which are

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suspended at altitudes from essentially

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from the ground to about eight

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kilometers in the atmosphere

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the total number of aerosols in the

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atmosphere is extremely large it's like

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the number of stars in a

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galaxy those are tiny particles most of

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them are invisible to a naked eye

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aerosol particles can be natural and can

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be created as a result of human

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activities and so those particles are

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natural aerosols can come from

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all places for example desert dust is

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blown off the surface of the sahara

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desert the asian deserts the australian

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deserts

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sea salt particles are produced when

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ocean waves break they produce a lot of

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essentially all kind of

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volcanoes they throw out a lot of

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volcanic ash and those are also natural

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all kinds of human activities produce

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different kinds of aerosols and the most

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typical example would be sulfate

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particles the result of

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combustion or soot particles

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on average an aerosol particle is

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estimated to to leave for about a week

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air sources are produced

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they're transported

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and eventually they disappear because

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aerosol particles can differ by their

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size and by their chemical composition

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and by their shape

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and all these inequalities can be mixed

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together and that's what makes aerosols

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so difficult to study at any given

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location particles of different types

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and of different origins can co-exist if

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a particle is for example generated some

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way in china it can be transported to

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the united states of america so this

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transport from different places makes

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their solar population at any given

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they have several roles in affecting

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climate for once they simply reflect

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sunlight back to space and this effect

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amounts to cooling of the atmosphere and

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on the surface

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but the same particles can also absorb

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light

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warmer and they warm the surrounding ear

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so this effect is to warm the atmosphere

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and how much light is reflected and how

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much is absorbed depends on the chemical

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composition of the particles on their

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size even on their shape

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there's another effect that aerosols

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exude on climate because they affect the

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properties of clouds

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and clouds are a major modulator of the

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amount of energy that reaches the

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surface and warms it

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and so by changing the properties of

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clouds and precipitation their soils can

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the most important knowledge that we

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have is that aerosol particles are

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extremely complex

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so we need to study the distribution of

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particles globally and the only way to

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do that is from satellites

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the knowledge about aerosols that we

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have tells us that the instrumentation

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on this satellite must also be very

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complicated and with this

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instrumentation we must be able to infer

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00:04:02,229 --> 00:03:59,280
many properties of the aerosol particles

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and that's the purpose of the air soil

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00:04:09,190 --> 00:04:05,920
polarimetry sensor which will fly as

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00:04:13,910 --> 00:04:11,110
we are not interested so much in their

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total number as how they are distributed

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00:04:18,150 --> 00:04:16,079
because their distribution affects local

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climate and that's why we need to know