Large-scale atmospheric circulations produce polar weather systems that result in spring thaws, sea ice movement, and severe winter storms. Changes in storm frequency and intensity accelerate erosion of polar coastlines. Long-range atmospheric transport processes deliver pollutants to Arctic and Antarctic environments. Transport of remote aerosols and local emissions from open ocean leads play major roles in polar cloud formation and in polar precipitation. Peak atmospheric concentrations of man-made ozone-depleting substances will occur approximately during the IPY time span, and because changes in stratospheric temperature, moisture, or circulation might develop during that same period, IPY researchers will give careful attention to polar stratospheric clouds, to ozone loss, and to damaging UV-B radiation penetrating the polar atmosphere.