ESS220
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)