Abstract
This study describes a retrieval algorithm developed at the University of
Bremen to obtain vertical profiles of ozone from limb observations performed
by the Ozone Mapper and Profiler Suite (OMPS). This algorithm is based on the
technique originally developed for use with data from the SCanning Imaging
Absorption spectroMeter for Atmospheric CHartographY (SCIAMACHY) instrument.
As both instruments make limb measurements of the scattered solar radiation
in the ultraviolet (UV) and visible (Vis) spectral ranges, an underlying
objective of the study is to obtain consolidated and consistent ozone
profiles from the two satellites and to produce a combined data set. The
retrieval algorithm uses radiances in the UV and Vis wavelength ranges
normalized to the radiance at an upper tangent height to obtain ozone
concentrations in the altitude range of 12–60 km. Measurements at
altitudes contaminated by clouds in the instrument field of view are
identified and filtered out. An independent aerosol retrieval is performed
beforehand and its results are used to account for the stratospheric aerosol
load in the ozone inversion. The typical vertical resolution of the retrieved
profiles varies from ∼ 2.5 km at lower altitudes ( < 30 km) to ∼ 1.5 km (about 45 km) and becomes
coarser at upper altitudes. The retrieval errors resulting from the
measurement noise are estimated to be 1–4 % above 25 km,
increasing to 10–30 % in the upper troposphere. OMPS data are processed
for the whole of 2016. The results are compared with the NASA product and
validated against profiles derived from passive satellite observations or
measured in situ by balloon-borne sondes. Between 20 and 60 km, OMPS
ozone profiles typically agree with data from the Microwave Limb Sounder
(MLS) v4.2 within 5–10 %, whereas in the lower altitude range the bias
becomes larger, especially in the tropics. The comparison of OMPS profiles
with ozonesonde measurements shows differences within ±5 % between 13
and 30 km at northern middle and high latitudes. At southern middle and
high latitudes, an agreement within 5–7 % is also achieved in the same
altitude range. An unexpected bias of approximately 10–20 % is detected in
the lower tropical stratosphere. The processing of the 2013 data set using
the same retrieval settings and its validation against ozonesondes reveals a
much smaller bias; a possible reason for this behaviour is discussed.
Citation
ID:
195698
Ref Key:
arosio2018atmosphericretrieval