ARCTIC NRT SERVICE 2002/2003
|Mirror sites also at Uni-Bremen and DLR Oberpfaffenhofen|
|H o m e||O v e r v i e w A r c h i v e|
OClO is produced by the reaction of BrO and ClO
it can be used as an indicator for chlorine activation of the stratosphere. Thus
daily OClO maps of the polar region can provide unique information about the
status of the stratospheric chemistry. In particular they might be used for the
planning of stratospheric balloon launches and aircraft campaigns for the
scientific community. The University of Heidelberg in co-operation with the
University of Bremen developed and validated an algorithm for the detection of
the atmospheric OClO absorption from GOME. The level 1 GOME data is transferred
from the ESA satellite receiving station in Kiruna, Sweden to the NADIR data
base at NILU (Norwegian Institute for Air Research) where the daily spectral
analysis of the OClO is carried out. The produced GOME OClO maps show the
so-called slant column density (SCD) of OClO for each single GOME measurement.
The SCD is the integrated atmospheric OClO concentration along the light path of
a GOME observation. Thus it depends strongly on the length of the light path
through the atmosphere which is a function of the solar zenith
angle (SZA) at the observation site, which in turn largely depends on the
latitude. Enhanced OClO absorption is generally only detected when the
stratospheric temperatures inside within the polar vortex below ca. 200K.
Occasionally, 'apparent' OClO absorption may appear outside of the polar vortex
on the maps. This should be regarded as an artifact in the NRT analysis program.
Please note: Since for GOME measurements the SZA changes with latitude,
different OClO SCDs for different latitudes do not necessarily represent
different degrees of chlorine activation. In addition, OClO is rapidly
photolysed at increasing SZA. Thus we recommend using these maps for a
qualitative indication of stratospheric chlorine activation.
More information about the GOME OClO products
can be found in the following References
Wittrock, F., A. Richter, J.P. Burrows,
Validation of GOME BrO and OClO observations in the northern hemisphere,
Proceedings of the European Symposium on Atmospheric Measurements from Space
(ESAMS 99), Jan. 18-22, ESTEC, Noordwijk, Netherlands, WPP-161, Eur. Space
Agency, Noordwijk, Netherlands, pp.
Wagner, T, F. Wittrock, A. Richter, M. Wenig,
J.P. Burrows, and U. Platt, Continuos monitoring of the high and persistent
chlorine activation during the Arctic winter 1999/2000 by the GOME instrument on
ERS-2, J. Geophys. Res., 0.1029/2001JD000466, 21 September 2002.