Error Analysis And Validation Of Stratospheric Ozone Profiles

Abstract

From 1993 to 2000, the Institute for Environmental Studies (IEMA) depending of
the University of Mendoza, carried out ground-based stratospheric ozone measurements by
means of millimetre wave radiometry (Project TROPWA). In this paper we present a
complete theoretical study necessary to qualify the uncertainties in the retrieval process. This
type of error analysis is often used to characterize any remote sensing experiment. To
evaluate and validate the quality of the obtained TROPWA stratospheric ozone profiles, we
also performed a comparative study using the ozone profiles measured by the HALOE
experiment. This study includes a comparison of individual profiles and of seasonal averages
from 1993 to 2000. Given the coarser height resolution of the retrieved ozone profiles from
microwave ground based instrument, compared to those obtained from the solar occultation
technique, the HALOE profiles were averaged by convolving them with the averaging kernels
of the TROPWA retrieval process. This error analysis and the comparison tests allowed us to
evaluate and characterize the retrieval of our instrument. It can be seen that from 20 to 40 km
the TROPWA instrument is able to retrieve ozone profiles with absolute errors varying from
10 to 20 %, and relative errors less than 5%, with a height resolution (FWHM) that varies
from 5 to 11 km depending on the altitude. The seasonal variations show consistent patterns
but having TROPWA measurements a systematic lower peak value of about 0.5 to 0.7 ppmv.
The mayor discrepancies between both set of profiles occurs in the period of May-June with
values varying around +8 to –10% (+0.4 to –0.8 ppmv). This difference is partially due to the
coarser height resolution of our instrument.