POAM Trace Gas Retrievals

The POAM II and POAM III instruments have provided a unique database of important trace gases in the high latitude stratosphere. The gases measured by POAM include ozone (O₃), water vapor (H₂O) and nitrogen dioxide (NO₂). POAM II compiled a three-year record of O₃ and NO₂ between 1993 and 1996. This has allowed POAM to document the timing of the ozone depletion, and to estimate ozone loss as a function of altitude at high vertical resolution. The following plot shows the POAM II Southern Hemisphere ozone measurements over the three-year mission. Note the occurrence of the ozone hole each spring (September through October).

The following plot demonstrates the vertical structure of the ozone hole as it evolves through the month of September 1994.

The water vapor measurement is new to POAM III (POAM II had unresolved problems with its water vapor channel and therefore never produced a water vapor product). Measurements of H₂O in the winter polar vortex are of great scientific interest because they can be used to study stratospheric dehydration caused by the subsidence of large ice particles from Type II polar stratospheric clouds. The following plot shows the POAM III measurements of H₂O in the Southern Hemisphere winter of 1998. Note the region of severe dehydration that begins in late July, leading to extremely low values of stratospheric water vapor (approximately one part per million by volume).