Johannes W. Kaiser

The Ozone Hole Breakup in September 2002 as Seen by SCIAMACHY on ENVISAT

An unprecedented stratospheric warming in the Southern Hemisphere in September 2002 led to the breakup of the Antarctic ozone hole into two parts. The Scanning Imaging Absorption Spectrometer for Atmospheric Chartography (SCIAMACHY) on the European Environmental Satellite (ENVISAT ) performed continuous observations of limb-scattered solar radiance spectra throughout the stratospheric warming. Thereby, global measurements of vertical profiles of several important minor constituents are provided with a vertical resolution of about 3 km. In this study, stratospheric profiles of O3 ,N O 2, and BrO retrieved from SCIAMACHY limb-scattering observations together with polar stratospheric cloud (PSC) observations for selected days prior to (12 September), during (27 September), and after (2 October) the ozone hole split are employed to provide a picture of the temporal evolution of the Antarctic stratosphere’s three-dimensional structure.

Fast weighting functions for retrievals from limb scattering measurements

Abstract The satellite-borne UV-visible-NIR spectrometers SCIAMACHY and OSIRIS perform operational measurements of the Earths limb radiance with global coverage. The vertically resolved atmospheric composition is retrieved from the measurements. We have computed synthetic limb measurements and O 3 weighting functions (WFs) with several orders of scattering and surface reflection. Comparisons reveal the wavelength-dependent contributions of single scattering and the second orders of scattering and surface reflection. We have also performed test retrievals of the O 3 and NO 2 profiles with the program package SCIARAYS. They prove that the single scattering approximation is sufficient for the calculation of the WFs during the retrieval process. We conclude that algorithms for the analysis of limb scattering measurements can be accelerated by neglecting higher orders of scattering in the WF calculations.

Consistent interpretation of ground based and GOME BrO slant column data

Model computations of slant column densities (SCD) enable the comparison between ground based and satellite based absorption measurements of scattered light and are therefore a good basis to investigate the presence of tropospheric BrO amounts. In this study ground based zenith sky and GOME nadir measurements of BrO SCD are compared with simulations for the 19-21 March 1997 at Ny-Alesund. The vertical columns of tropospheric BrO amounts are estimated to be in the range 4 f 0.8 * 1Or3 [molecules/cm21 for the investigated period and location.

Theoretical precisions for sciamachy limb retrieval

The UV-vis-NIR spectrometer SCIAMACHY on ESAs Envisat will measure the back-scattered solar radiation from the Earths atmosphere in limb geometry. From these measurements atmospheric parameter profiles will be retrieved (T, p, trace gas abundances, and aerosol and cloud parameters). Theoretical precisions for retrievals from SCIAMACHYs limb measurements are calculated with a fully spherical radiative transfer model and a realistic instrument model. The retrievals can be performed for the atmospheric layers above the top of optically thick clouds. The vertical resolution of the retrieval parameter profiles is 3 km. O3 profiles can be measured with a theoretical precision of 1% throughout the stratosphere and in the upper troposphere. The retrievals of other trace gases (NO2, BrO, CH4, …) will have precisions between 2 and 100 % depending on retrieval altitude.

SCIAMACHY-a hyperspectral sensor for global atmospheric studies

The Scanning Imaging Absorption spectroMeter for Atmospheric CHartographY (SCIAMACHY) is a hyperspectral space-based spectrometer covering almost continuously the spectral range between 240 nm and 2380 nm. SCIAMACHY will measure both the extraterrestrial irradiance and the earthshine radiance, i.e., sunlight which is transmitted, reflected or scattered by the Earths atmosphere or surface. Measurements will be performed in nadir, limb, and both solar and lunar occultation geometry. Inversion of the SCIAMACHY measurements will provide the amount and distributions of a large number of atmospheric constituents in the stratosphere and troposphere (O/sub 3/, NO/sub 2,/ H/sub 2/O, CO/sub 2/, CH/sub 4/. N/sub 2/O, BrO, CO, O/sub 2/,NO, SO/sub 2/, H/sub 2/CO, OClO, and possibly ClO).

Precision estimates for SCIAMACHY limb retrievals

SCIAMACHY is a space-based hyper-spectral spectrometer for atmospheric research. It is recording Earth-shine spectra in the UV-visible and near infrared spectral range in nadir, limb and occultation geometries. Measurements of UV-VIS-NIR spectra in limb geometry are a new technique with high demands on the quality of radiative transfer and retrieval algorithms. Theoretical precisions for retrievals from SCIAMACHYs limb measurements are calculated with a fully spherical radiative transfer model. O/sub 3/ profiles will be measured with a precision of 1% throughout the stratosphere and in the UT/LS region. The retrievals of other trace gases will have precisions between 1 and 100% depending on retrieval altitude.