Stefan Noel

SCIAMACHY: Mission Objectives and Measurement Modes

Abstract SCIAMACHY (Scanning Imaging Absorption Spectrometer for Atmospheric Chartography) is a spectrometer designed to measure sunlight transmitted, reflected, and scattered by the earth’s atmosphere or surface in the ultraviolet, visible, and near-infrared wavelength region (240–2380 nm) at moderate spectral resolution (0.2–1.5 nm, λ/Δλ ≈ 1000–10 000). SCIAMACHY will measure the earthshine radiance in limb and nadir viewing geometries and solar or lunar light transmitted through the atmosphere observed in occultation. The extraterrestrial solar irradiance and lunar radiance will be determined from observations of the sun and the moon above the atmosphere. The absorption, reflection, and scattering behavior of the atmosphere and the earth’s surface is determined from comparison of earthshine radiance and solar irradiance. Inversion of the ratio of earthshine radiance and solar irradiance yields information about the amounts and distribution of important atmospheric constituents and the spectral reflecta...

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.

Atmospheric water vapor amounts retrieved from GOME satellite data

A new method for the retrieval of global atmospheric vertical column amounts of water vapor from measurements of the Global Ozone Monitoring Experiment (GOME) is presented. The method is based on a modified Differential Optical Absorption Spectroscopy (DOAS) approach, taking into account the effects arising from strong wavelength dependent absorptions. In this paper the feasibility of this approach is demonstrated and first estimates on the retrieval precision and the accuracy of the H 2 O data product are given by comparison with selected Special Sensor Microwave Imager (SSM/I) data.

Retrieval of total water vapour column amounts from GOME/ERS-2 data

Abstract A method for the retrieval of vertical column amounts of atmospheric water vapour from measurements of the Global Ozone Monitoring Experiment (GOME) in the visible spectral region is presented. Originally developed for the determination of global ozone concentrations, the GOME instrument is operating successfully on ERS-2 since 1995, providing information also on several other atmospheric constituents like NO 2 , BrO, OClO, H 2 CO, SO 2 , and recently also H 2 O. The method for the derivation of water vapour amounts is based on the Differential Optical Absorption Spectroscopy (DOAS) approach, which has been extended to take into account effects arising from a strongly wavelength dependent absorption. Further improvements of the algorithm now allow to retrieve water vapour column densities under all cloud conditions. First results show an acceptable agreement between total water vapour columns derived from GOME measurements and H 2 O columns obtained from the Special Sensor Microwave Imager SSM/I data, although the scatter of the GOME data is high, which needs to be further investigated.

Global atmospheric monitoring with SCIAMACHY

Abstract SCIAMACHY (SCanning Imaging Absorption spectrometer for Atmospheric CHartographY) is a space based spectrometer designed to measure sunlight transmitted, reflected and scattered by the Earth atmosphere or surface. It is a contribution to the Envisat-1 satellite to be launched in late 1999. SCIAMACHY measurements will provide amounts and distribution of 0 3 , BrO, OCl0, ClO, S0 2 , H 2 CO, N0 2 , CO, CO 2 , CH 4 , H 2 O, N 2 0, pressure, temperature, aerosol, radiation, cloud cover and cloud top height from atmospheric measurements in nadir, limb and occultation geometry. By the combination of the near simultaneous limb and nadir observations SCIAMACHY is one of a limited number of instruments which is able to detect tropospheric column amounts of 0 3 , N0 2 , CO, CH 4 , H 2 O, N 2 0, S0 2 , H 2 CO, and BrO down to the planetary boundary layer under cloud free conditions.

SCIAMACHY on ENVISAT: in-flight optical performance and first results

The Scanning Imaging Absorption spectroMeter for Atmospheric CHartographY (SCIAMACHY) is a contribution to the ENVISAT-1 satellite, which has been launched in March 2002. The SCIAMACHY instrument measures sunlight transmitted, reflected and scattered by the Earths atmosphere or surface simultaneously from the UV to the SWIR spectral region (214 - 2380 nm) in nadir, limb, and occultation viewing geometry. SCIAMACHY allows the characterisation of the composition of the Earth atmosphere from the ground to the mesosphere. This paper gives an overview of the SCIAMACHY instrument and its in-flight detector, spectral and radiometric performance. Furthermore first results on trace gas retrieval from limb and nadir measurement mode will be summarised.

Nadir, limb, and occultation measurements with SCIAMACHY

Abstract The Scanning Imaging Absorption spectroMeter for Atmospheric CHartographY (SCIAMACHY) is a contribution to the ENVISAT-1 satellite, which is to be launched in mid 2001. The SCIAMACHY instrument is designed to measure sunlight transmitted, reflected and scattered by the Earths atmosphere or surface simultaneously from the UV to the NIR spectral spectral region (240 – 2380 nm) in various viewing geometries. Inversion of the SCIAMACHY measurements will provide the amount and distributions of a large number of atmospheric constituents in the stratosphere and troposphere (O 3 , NO 2 , H 2 O, CO 2 , CH 4 , N 2 O, BrO, CO, O 2 , O 2 ( 1 Δ g ), NO, SO 2 , H 2 CO, (ClO,) and OClO). This paper concentrates on the characteristics of the SCIAMACHY mission. In particular, the measurement strategies for the different observational modes — nadir, limb, and both solar and lunar occultation — and their operational implementation are described.

Comparison of decadal global water vapor changes derived from independent satellite time series

We analyze trends in total column water vapor (TCWV) retrieved from independent satellite observations and retrieval schemes. GOME-SCIAMACHY (Global Ozone Monitoring Experiment-SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY) measurements are carried out in the visible part of the solar spectrum and present a partly cloud-corrected climatology that is available over land and ocean. The HOAPS (Hamburg Ocean Atmosphere Parameters and Fluxes from Satellite Data) product, provided by EUMETSATs Satellite Application Facility on Climate Monitoring is based on passive microwave observations from the Special Sensor Microwave/Imager. It also includes the TCWV from cloudy pixels but is only available over oceans. The common observation time period is between 1996 and 2005. Due to the relatively short length of the period, the strong interannual variability with strong contributions from El Nino and La Nina events and the strong anomaly at the start of the common period, caused by the 1997/1998 El Nino, the observed trends should not be interpreted as long-term climate trends. After subtraction of average seasonality from monthly gridded data, a linear model and a level shift model have been fitted to the HOAPS and GOME-SCIAMACHY data, respectively. Autocorrelation and cross correlation of fit residuals are accounted for in assessing uncertainties in trends. The trends observed in both time series agree within uncertainty margins. This agreement holds true for spatial patterns, magnitudes, and global averages. The consistency increases confidence in the reliability of the trends because the methods, spectral range, and observation technique as well as the satellites and their orbits are completely independent of each other. The similarity of the trends in both data sets is an indication of sufficient stability in the observations for the time period of ≈ 10 years.

The SCIAMACHY Calibration/Monitoring Concept and First Results

The Scanning Imaging Absorption Spectrometer for Atmospheric Chartography (SCIAMACHY) is a contribution to the ENVISAT satellite, which has been launched successfully in March 2002. SCIAMACHY determines the amount and distributions of a large number of atmospheric constituents by measuring Earthshine radiance and solar irradiance spectra simultaneously from the UV to the NIR in various viewing geometries. The scientific goals of the SCIAMACHY mission can only be reached by an instrument having a high spectral and radiometric accuracy and stability. For example, to determine global NO2 concentrations SCIAMACHY measurements need to be sensitive to differential spectral structures down to the order of 10−4. These requirements can only be met by an appropriate instrument design in combination with both on-ground and in-flight calibration and monitoring. This paper gives an overview on the SCIAMACHY calibration and monitoring concept and activities which are essential to ensure the high quality of SCIAMACHY data products throughout the instrument lifetime. Furthermore, first in-flight monitoring results are presented.

The geostationary scanning imaging absorption spectrometer (GeoSCIA) mission: requirements and capabilities

Abstract Instrumentation aboard satellite platforms in Low Earth Orbit (LEO) have been successfully used to measure back scattered and reflected light from atmosphere. Inversion of such observation enable trace gas amounts and distributions in the stratosphere and the troposphere to be derived. LEO measurements are restricted to a specific time at a given location. Contrary to that several tropospheric processes, for example pollution episodes, have a strong diurnal variation and variability or they are masked by the highly variable processes in the troposphere, for example clouds. This obviously defines the need to perform measurements with high spatial and temporal resolution. Measurements of the back scattered and reflected solar light from spectrometers on geostationary platforms enable diurnal variations and variability of constituents to be retrieved at high spatial (25 km × 25 km) and temporal (full Earth disk every 30 min) resolution. The geostationary imaging absorption spectrometer mission GeoSCIA is a concept yielding such data. Details of the mission objectives and requirements will be discussed.