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Seasonal variation of atmospheric nitric acid over the South Pole in 1992
Author(s) -
Van Allen Renate,
Liu Xu,
Murcray Frank J.
Publication year - 1995
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/94gl02794
Subject(s) - nitric acid , stratosphere , atmospheric sciences , polar vortex , polar , environmental science , chemistry , physics , inorganic chemistry , astronomy
We conducted year‐round measurements of mid infrared atmospheric emission over the South Pole in 1992. We were able to observe a large seasonal change of the total column of nitric acid (HNO 3 ) vapor. During the summer, the HNO 3 column abundance was about 2×10 16 molecules/cm². There was a small increase in the fall. A rapid decrease of 50% was observed in late June, soon after the stratospheric temperature reached the threshold for formation of type I polar stratospheric clouds (PSCs). By early July, the stratospheric temperature was cold enough to form type II PSCs, and the HNO 3 column decreased to 7×10 15 molecules/cm². Measured nitric acid values in the spring remained extremely low even after the stratosphere warmed well above PSC temperatures. This may indicate permanent removal of HNO 3 by gravitational settling, or long‐term sequestering in large particles. Normal summer values were not observed until the vortex dissipated and allowed the lateral transport of HNO 3 , to the south polar region.