Towards a Better Tropospheric Ozone Data Product from SCIAMACHY: Improvements in High Latitude Stratospheric Ozone - Towards an Interdisciplinary Approach in Earth System Science - page 38

Fig. 3 Comparison of ozone vertical profiles from SCIAMACHY and from ozone sonde at station
Eureka. a SCIAMACHY limb retrieval version 2.9. b SCIAMACHY limb retrieval version 3.0

(e.g. Weber et al. 2011 ). After that the Brewer-Dobson circulation gets weaker,
leading to colder polar stratospheric temperatures, thus causes polar ozone loss.
Combining with the weaker Brewer-Dobson circulation and the increasing solar
shortwave radiation, stratospheric ozone concentration decreases after spring and
reaches its minimum in fall. The lower panel of Fig. 2 depicts the difference
between SPOs from SCIAMACHY and ozone sonde at Eureka. A severe under-
estimation by SCIAMACHY with a median difference of 19 DU is clearly seen.
The reasons for that can be identi ed by analysing the left panel of Fig. 3 . The left

panel of this figure shows a comparison of a single V2.9 SCIAMACHY ozone limb

pro le (black solid line

indicates the original data and red solid line sonde data smoothed to the vertical
resolution of SCIAMACHY) at Eureka for 22 March, 2006. The ozone concen-
tration peak near 17 km is not captured by data version 2.9. This is a typical
behaviour that explains the underestimation seen in Fig. 2 . This behaviour is
probably attributed to the instrumental

le (blue solid line) with a collocated ozone sonde pro

in fl uence to the SCIAMACHY V2.9

retrieval.

4 SCIAMACHY Limb Retrieval of Version 3.0
and Comparison Results

In the new SCIAMACHY limb retrieval (V3.0), extra-terrestrial solar spectrum is
used instead of the reference TH to normalize the measured limb radiance. A
drawback of this method is that the instrument calibration features are not fully
cancelled out any more since the optical paths for limb and solar measurements are
not identical anymore. This might have serious consequences for the ozone retrieval
quality because the short and long wavelength wings of the Chappuis absorption
band of ozone are measured in different spectral channels of the SCIAMACHY