ESS200A
Prof. Jin-Yi Yu
Polar Stratospheric Clouds (PSCs)
qIn winter the
polar stratosphere is so cold (-80°C or below) that
certain trace atmospheric constituents can condense.
qThese clouds are
called “polar stratospheric clouds” (PSCs).
qThe particles that
form typically consist of a mixture of water and nitric acid
(HNO3).
qThe PSCs alter the
chemistry of the lower stratosphere in two ways:
(1) by coupling between the odd nitrogen and
chlorine cycles
(2) by providing surfaces on which heterogeneous
reactions can occur.
(Sweden, January 2000; from
NASA website)