The Polar Ozone and Aerosol Measurement (POAM) III instrument and early validation results

Polar Ozone and Aerosol Measurement (POAM) III, a follow-on to the successf ul POAM II, is a spaceborne experiment designed to measure the vertical pro files of ozone, water vapor, nitrogen dioxide, and aerosol extinction in th e polar stratosphere and upper troposphere with a vertical resolution of 1- 2 km. Measurements are made by the solar occultation technique. POAM III, n ow in polar orbit aboard the SPOT 4 satellite, is providing data on north- and south-polar ozone phenomena, including the south-polar ozone hole, and on the spatial and temporal variability of stratospheric aerosols, polar st ratospheric clouds, and polar mesospheric clouds. Differences between the P OAM III and POAM II instruments are described. First validations of POAM II I data products by comparison with Halogen Occultation Experiment and ozone sonde data are presented.