Towards a Better Tropospheric Ozone Data Product from SCIAMACHY: Improvements in High Latitude Stratospheric Ozone - Towards an Interdisciplinary Approach in Earth System Science - page 36

Fig. 1 Ozone sonde stations from WOUDC used for the comparisons. They are: Alert (82.5 ° N,
62.3 ° W), Eureka (80.1 ° N, 85.9 ° W), Ny-Alesund (78.9 ° N, 11.9 ° W), Sodankyla (67.4 ° N, 26.6 ° E),
Lerwick (60.1 ° N, 1.2 ° W) and Resolute (74.7 ° N, 94.9 ° W)

where N z le in number density units (molecules per

cm 2 per km), z i represents the altitude in km and i is the layer index. SPO time
series are analyzed for the period from January 2003 to December 2012.

ðÞ is the stratospheric ozone pro

3 SCIAMACHY Limb Retrieval of Version 2.9

The current SCIAMACHY limb retrieval (V2.9) uses combined spectral informa-
tion from the UV and visible spectral ranges to obtain vertical pro

les of ozone.
The limb radiances measured in the visible spectral range are processed as sug-
gested by Flittner et al. ( 2000 ). At the le is

normalized with a limb measurement at an upper TH (often referred to as the
reference TH): I n k ;

first step, the entire limb radiance pro

denoting wavelength and
TH i the tangent height at elevation step i. The normalization removes the solar
Fraunhofer structures and reduces the in

ð TH i Þ ¼ I ð

k ;

TH i Þ= I ð

k ;

TH ref Þ , with

k

fl uence of the lower atmosphere, e.g. due to

multiple scattering and re ection from the surface. Furthermore, it provides a kind

of self-calibration of the instrument since the instrument calibration parameters do
not differ much for different THs. Subsequently, to minimize the in

fl

uence of the
broad-band spectral features, e.g. Rayleigh and aerosol scattering, the so called
triplet method is used. Thereby the measurement vector, y, is obtained from the
normalized radiances at 525, 589 and 675 nm as follows:

fl