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q |
In winter the polar stratosphere is so
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cold (-80°C
or below) that certain
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trace atmospheric constituents can
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condense.
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q |
These clouds are called “polar
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stratospheric clouds” (PSCs).
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q |
The particles that form typically
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consist of a mixture of water and
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nitric acid (HNO3).
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q |
The PSCs alter the chemistry of the
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lower stratosphere in two ways:
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(1) by slow down the
coupling
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between the odd nitrogen and
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chlorine cycles
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(2) by
providing surfaces on which
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heterogeneous reactions can occur.
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