A COMPARATIVE-STUDY OF POAM-II AND ELECTROCHEMICAL CONCENTRATION CELLOZONESONDE MEASUREMENTS OBTAINED OVER NORTHERN EUROPE

Ozone profiles measured by the Polar Ozone and Aerosol Measurement (FO AM II) instrument (version 5 retrievals) flown on the SPOT 3 spacecraf t are compared with coincident electrochemical concentration cell (ECC ) ozonesonde profiles at 11 stations over polar northern regions. The comparison study extends from December 1993 to March 1996 and contains about 500 coincidences. The satellite and ozonesonde profile coincide nces are averaged separately for winter and nonwinter periods and for winter coincidences occurring inside and outside of the polar vortex. The mean differences versus altitude show a dependence on the latitude separation between the sondes and the FOAM II measurements. The best estimate of the biases between the FOAM II and the ECC ozone measureme nts is obtained after removal of the latitudinal gradient effect on th e relative mean differences for the dynamically quiet nonwinter period s. The biases are negative at all altitudes indicating that the FOAM v ersion 5 retrievals are low relative to the ECC sondes. The magnitude of this bias ranges from 2-3% near the lowest and highest altitudes of profile overlap (17 and 30 km) to 7.6% from 21 to 24 km, which is com parable to the evaluated errors of both instruments.