The figure shows the sudden appearance of Polar Stratospheric Clouds composed of nitric acit trihydrate (NAT) on June 11, 2003 explained by a strong mountain wave event over the Antarctic Peninsula.
Höpfner et al. (2006) discovered the sudden onset of Polar Stratospheric Clouds (PSCs) composed of small nitric acid trihydrate (NAT) particles forming a belt-like structure around the cold region in the stratosphere on June 11, 2003. This type of PSCs appeared several weeks after the first PSCs formed over Antarctica in mid-May. Model results have explained these to be formed by heterogeneous nucleation on ice in the cooling phases of large-amplitude stratospheric mountain waves over the Antarctic Peninsula. The presence of such waves has been confirmed recently through independent observations (Eckermann et al., 2009).