Ulrich Platt

The remote sensing of tropospheric composition from space

Tropospheric Remote Sensing From Space.- Solar Backscattered Radiation: UV, Visible and near IR-Trace Gases.- Thermal Infrared: Absorption and Emission - Trace Gases and Parameters.- Microwave: Absorption and Emission - Trace Gases and Metereological Parameters.- Remote Sensing of Terrestrial Clouds from Space using Backscattering and Thermal Emission Techniques.- Retrieval of Aerosol Properties.- Data Quality and Validation of Satellite Measurements of Tropospheric Composition.- Applications: Satellite Observations of Tropospheric Compostion.- Applications - Data and Models: Synergetic Use of Satellite Retrieved Trophospheric Trace Constituent Distributions and Numerical Modelling.- Conclusions and Perspectives.- Appendices.

Differential optical absorption spectroscopy instrument for stratospheric balloonborne trace-gas studies.

A newly developed UV-visible instrument for differential optical absorption spectroscopic measurements of atmospheric trace gases from balloon platforms is described. Direct solar light at daytime in the near-ultraviolet (320.6-422.6-nm) and the visible (417.6-670.7-nm) spectral ranges can be simultaneously analyzed for the atmospheric column abundances or profiles of O(3), NO(2), NO(3), BrO, OClO, O(4), H(2)O, and possibly other species (HNO(2), IO, CH(2)O). Compared with previously used balloonborne UV-visible spectrometers, the instrument has the superior properties of low mass (42 kg), low power consumption (30 W), decreased spectral drift that is caused by temperature and pressure changes, low detector dark current, and low spectrometer stray light. The three last-named characteristics are achieved by enclosure of the entire spectrometer in a pressurized and thermostated container and by inclusion of separately thermostated photodiode array detectors. The optical setup is simplified to reduce its weight. The spectral stray light is reduced by suppression of the higher-order and zero-order grating reflections by use of light traps and in the UV by addition of a dispersive prism preanalyzer. The major instrumental design characteristics and the instrumental performance as tested in the laboratory and during several stratospheric balloon flights are reported.

Luftverschmutzung in den Städten

Spatestens seit dem VW-Abgasskandal sind Stickoxid-Emissionen in den Fokus offentli- cher Debatten geruckt. Stickoxide sind sehr giftig und ihre Konzen- tration in den Stadten gesundheitsgefahrdend hoch – unter realen Bedingungen liesen sie sich bislang aber nur schwer messen. Heidel- berger Umweltphysiker haben eine innovative Losung fur das Problem.

Den Himmel betrachten, die Hölle verstehen. Telegramm aus dem Inneren der Erde

Im Jahr 1864 beschrieb der franzosische Schriftsteller Jules Verne die Reise zum Mittelpunkt der Erde. In der Realitat ist es den Wissenschaftlern bis heute nicht gelungen, in das geheimnisvolle Innere unseres Planeten vorzustosen. Wir mussen uns mit indirekten Hinweisen begnugen, beispielsweise mit Gasen, die von Vulkanen – den Toren zum Innern der Erde – freigesetzt werden. Die in Vulkanfahnen nachweisbaren Gase erlauben Ruckschlusse auf Vorgange unter der Erdkruste und konnen genutzt werden, um drohende Vulkanausbruche vorherzusagen. Ein neuer Kandidat fur ein praziseres Fruhwarnsystem ist das Spurengas Brommonoxid.

Monocyclic aromatic hydrocarbons measured by differential optical absorption spectroscopy in urban areas (China)

Monocyclic aromatic hydrocarbons are regarded as one of the most important classes of hydrocarbons in the atmosphere since they are a potential risk for human health and play a key role for photochemical smog formation. Differential Optical Absorption Spectroscopy (DOAS) has been widely used for many trace gases monitoring in the atmosphere however he analysis of aromatic compounds is difficult and the spectral structures from interfering absorbers (e.g. O2) should be very careful to separate correctly. This paper describes a spectral evaluation technique of aromatic compounds from DOAS measurement and summarizes the results of field measurements of benzene toluene xylene (BTX) in Chinese cities Beijing (2000) Shanghai (2001) and Hefei (2002). High concentrations of BTX were observed in Beijing and Shanghai whereas low concentrations in Hefei. This study will provide useful information to help understanding air pollution and atmospheric chemistry processes in urban areas ofChina and thereby contributes towards an improved pollution control strategy in Chinese cities.

Individual Reports from TOPAS Contributors

The work accomplished during the period 1990 to 1995 by the three Belgian groups participating in the EUROTRAC-TOPAS project is described. It involved the construction and permanent improvement of two DOAS (Differential Optical Absorption Spectroscopy) spectrometers. One of these is a Fourier transform instrument which was applied to atmospheric measurements in the Visible-UV region for the first time. Long path absorption set-ups were constructed. Software was developped to operate and automate the instruments and specific algorithms were written for the retrieval of concentrations from the atmospheric spectra. Both instruments were validated by participating in two EUROTRAC-TOPAS intercomparison campaigns which gathered instruments from six european countries. Finaly, high resolution absorption cross sections of several atmospherically relevant species were measured in the laboratory.