The three Global Ozone Monitoring Experiment-2 instruments will provide unique and long data sets for atmospheric research and applications. The complete time period will be 2007–2022, including the period of ozone depletion as well as the beginning of ozone layer recovery. Besides ozone chemistry, the GOME-2 (Global Ozone Monitoring Experiment-2) products are important e.g. for air quality studies, climate modelling, policy monitoring and hazard warnings. The heritage for GOME-2 is in the ERS/GOME and Envisat/SCIAMACHY instruments. The current Level 2 (L2) data cover a wide range of products such as ozone and minor trace gas columns (NO2, BrO, HCHO, H2O, SO2), vertical ozone profiles in high and low spatial resolution, absorbing aerosol indices, surface Lambertian-equivalent reflectivity database, clear-sky and cloud-corrected UV indices and surface UV fields with different weightings and photolysis rates. The Satellite Application Facility on Ozone and Atmospheric Chemistry Monitoring (O3M SAF) processes and disseminates data 24/7. Data quality is guaranteed by the detailed review processes for the algorithms, validation of the products as well as by a continuous quality monitoring of the products and processing. This paper provides an overview of the O3M SAF project background, current status and future plans for the utilisation of the GOME-2 data. An important focus is the provision of summaries of the GOME-2 products including product principles and validation examples together with sample images. Furthermore, this paper collects references to the detailed product algorithm and validation papers.

Abstract. Mineral particles, in general, are not spheres and so the assumption of spherical particles, instead of more realistic shapes, has significant effects on modeled optical properties and therefore on remote-sensing procedures for desert aerosol and the derived radiative forcing. Thus, in a new version of the database OPAC (Optical Properties of Aerosols and Clouds; Hess et al., 1998), the optical properties of the mineral particles are modeled describing the particles as spheroids with size dependent aspect ratio distributions, but with the size distributions and the spectral refractive indices not changed against the previous version of OPAC. The spheroid assumption is known to substantially improve the scattering functions but pays regard to the limited knowledge on particle shapes in an actual case. The relative deviations of the optical properties of non-spherical mineral particles from those of spherical particles are for the phase function in the solar spectral range up to +60% at scattering angles of about 130° and up to −60% in the backscatter region, but less than 2% for the asymmetry parameter. The deviations are generally small in the thermal infrared and for optical properties that are independent of the scattering angle. The improved version of OPAC (4.0) is freely available at www.rascin.net .

A suite of programs for high resolution infrared-microwave atmospheric radiative transfer modeling has been developed with emphasis on efficient and reliable numerical algorithms and a modular approach appropriate for simulation and/or retrieval in a variety of applications. The Generic Atmospheric Radiation Line-by-line Infrared Code - GARLIC - is suitable for arbitrary observation geometry, instrumental field-of-view, and line shape. The core of GARLIC's subroutines constitutes the basis of forward models used to implement inversion codes to retrieve atmospheric state parameters from limb and nadir sounding instruments.This paper briefly introduces the physical and mathematical basics of GARLIC and its descendants and continues with an in-depth presentation of various implementation aspects: An optimized Voigt function algorithm combined with a two-grid approach is used to accelerate the line-by-line modeling of molecular cross sections; various quadrature methods are implemented to evaluate the Schwarzschild and Beer integrals; and Jacobians, i.e. derivatives with respect to the unknowns of the atmospheric inverse problem, are implemented by means of automatic differentiation. For an assessment of GARLIC's performance, a comparison of the quadrature methods for solution of the path integral is provided. Verification and validation are demonstrated using intercomparisons with other line-by-line codes and comparisons of synthetic spectra with spectra observed on Earth and from Venus. (C) 2013 The Authors. Published by Elsevier Ltd. All rights reserved.

The SCIAMACHY instrument on-board ENVISAT measures since 2002 trace gas constituents of the atmosphere in nadir, limb and occultation configuration. It is an imaging spectrometer with q spectral range from the UV/VIS to SWIR (212 nm 2384 nm). In this paper we describe shortly the current status of the operational processing chains from Level 0-Ib and Level 1b-2 that deliver Earth radiances, solar irradiance, trace gas total columns and profiles as well as cloud characteristics on an orbital basis. An outlook for future operational products is also given.

Nadir infrared (IR) sounding can be used to derive information on trace gases relevant for climate and air quality. For vertical column density retrievals using SCIAMACHY near IR nadir observations, the BIRRA (Beer InfraRed Retrieval Algorithm) code has recently been implemented in the operational level 1 ‐ 2 processor. For analysis of thermal IR nadir observations of AIRS, GOSAT, IASI, or TES, a closely related code CERVISA (Column EstimatoR Vertical Infrared Sounding of the Atmosphere) has been developed. Both codes share a large portion of modules, e.g., for line-by-line absorption and the nonlinear least squares solver. The essential difference is the part of the forward model devoted to radiative transfer through the atmosphere, i.e., Beer’s law for the near IR versus Schwarzschild’s equation for the thermal IR. For the ongoing validation of the BIRRA carbon monoxide CO and methane CH4 products intercomparisons with thermal IR sounding data are performed. CERVISA retrieval results are compared both to the operational products of the IR sounder considered and to SCIAMACHY products retrieved with BIRRA.

In this study, we present an error analysis for Tikhonov regularization in a semi-stochastic setting. The analysis is carried out in such a way that it can be applied to any kind of inverse problem in atmospheric remote sensing. A method for selecting the optimal regularization parameter relying on the minimization of an estimator of the bound of the error between the first iterate and the exact solution is also discussed. Numerical simulations are performed for NO"2 retrieval from SCIAMACHY limb scatter measurements.

In this paper we present a retrieval algorithm for atmospheric remote sensing. The algorithm combines Tikhonov regularization and the iteratively regularized Gauss–Newton method and is devoted to the solution of multi-parameter inverse problems with simple bounds on the variables. The basic features of the algorithm: the solution of the bound-constrained minimization problem, the selection of the optimal regularization parameter, the derivation of the global regularization matrix and the characterization of the solution (error analysis) are discussed in detailed. The inversion algorithm is applied to ozone retrieval from SCIAMACHY limb scatter measurements in the ultraviolet spectral range.

Recently, the operational data processor chain for SCIAMACHY from Level 0 to Level 2 was subject to major revisions in each part including not only the Level 0-1b and Level 1b-2 data processing but also the IECF. In this contribution, we present the revisions and upgrades of the algorithms for the Level 1b-2 Off-line processing which had been applied to the derivation of products for Nadir and Limb back-scattered light observations as well. The results will be discussed briefly. In particular, the derivation of products from Nadir back-scattered light observations in the UV/VIS spectral region has been established by integration of most recently developments of state-of-the-art algorithms: The SDOAS algorithm of BIRA-IASB for the retrieval of column densities and the SACURA algorithm for the derivation of cloud-top height and cloud optical thickness based on cloud fraction provided by the DLR-IMF's OCRA algorithm. The combination of all three provides now the vertical column densities for Ozone and NO2. It is worth to note, that the product list for cloud parameters is now substantially extended due to SACURA. The derivation of Ozone and NO2 profiles from Limb back-scattered has been substituted by DLR-IMF's DRACULA retrieval package. Those in combination with optimised settings provide substantial improvements in profile information which are in very good agreement with scientific implementations of IFE Bremen. Additionally we present an overview about developments for future implementations. Beside an evolution scheme for the future, this holds for the evolution of the DRACULA package and for the retrieval of BrO profiles from Limb observations.

The near infrared channels of SCIAMACHY onboard ENVISAT can be used to derive information on CO, CH4, N2O, and H2O. A core element of the current operational level 2 data processor for nadir observations is the BIAS (Basic Infrared Absorption Spectroscopy) algorithm using a DOAS–type approach with a standard nonlinear least squares fit. Here we present work on recent advances towards a “Better InfraRed Retrieval Algorithm”, covering both the forward modelling and inversion aspect, nb. • Nonlinear least squares exploiting special structure of the forward model • Flexible choice of additional fit parameters besides molecular columns • Option for ’online’ line-by-line absorption cross section computation and continua First results of the improved algorithm for SCIAMACHY near infrared nadir processing are presented.

In this paper we present a retrieval algorithm for at- mospheric remote sensing. The algorithm combines the Tikhonov regularization and the iteratively Gauss-Newton method and is devoted to the solution of multi-parameter inverse problems with simple bounds on the variables. The basic features of the algorithm: the solution of the bound- constrained minimization problem, the selection of the op- timal regularization parameter, the derivation of the global regularization matrix and the characterization of the solu- tion (error analysis) are presented in detailed. Numeri- cal simulations are performed for O3 retrieval from SCIA- MACHY limb scatter measurements.