Search

For theoretical considerations and for numerical determination of photo lysis rates, knowledge of absorption spectra is essential. This is especially true for chemicalmodels of the atmosphere, as all chemical reactions are driven directly or indirectly by the sun's radiation. Together with the wavelength dependent quantum yields ofthe respective photolysis processes, the absorption spectra govern the photodissociation frequencies. Therefore, these quantities are of highest interest to allatmospheric chemists. Despite the importance of photodissociation processes, very few collections of absorption spectra in the visible and ultraviolet wavelength region are available. Moreover, most of these collections do not give the spectra in their original form, but tabulate selected data points with a rather poor resolution. The collection of gas phase absorption cross sections presented here originates trom the data compiled at the Max Planck Institute for Chemistry used for kinetic purposes and from the collecion used in the authors' atmospheric chemistry models at the Research Center Jülich. It is the aim to present all spectra as they were originally published, regardess of whether errors are obvious or not. Only in the case of typing errors or if corrections were published later, the corrected values were included in this collection. All spectra are presented in the same format to simplify comparison and incorporaion of the spectra into chemical models of the atmosphere. The data presented here should be considered as a preliminary version of a data base of spectra and quantum yields of atmospheric relevant species. It is planed to provide an updated version in the near future, including new entries and possible corrections of the existing files. It is not our intention to give a recommendation at the moment, this may be the subject of aseparate project. There are two volumes : the first treats the spectra of inorganic species, the second the organic compounds. A third volume with liquid phase spectra is planned to be published later. The absorption spectra and the wavelength dependent quantum yields are both temperature dependent. The temperature dependencies in the atmospheric relevant temperature range fram below 200 K to about 300 K have been included, where [...]

For theoretical considerations and for numerical determination of photolysis rates, knowledge of absorption spectra is essential. This is especially true for chemicalmodels of the atmosphere, as all chemical reactions are driven directly or indirectly by the sun's radiation. Together with the wavelength dependent quantum yields ofthe respective photo lysis processes, the absorption spectra govern the photodissociation frequencies. Therefore, these quantities are of highest interest to allatmospheric chemists. Despite the importance of photodissociation processes, very few collections of absorption spectra in the visible and ultraviolet wavelength region are available. Moreover, most of these col/ections do not give the spectra in their original form, but tabulate selected data points with a rather poor resolution. The collection of gas phase absorption cross seetions presented here originates from the data compiled at the Max Planck Institute for Chemistry used for kinetic purposes and from the collection used in the authors' atmospheric chemistry models at the Research Center Jülich. It is the aim to present all spectra as they were originally published, regardess of whether errors are obvious or not. Only in the case of typing errors or if corections were published later, the corrected values were included in this collection. All spectra are presented in the same format to simplify comparison and incorporaion of the spectra into chemical models of the atmosphere. The data presented here should be considered as a preliminary version of a data base of spectra and quantum yields of atmospheric relevant species. It is planed to provide an updated version in the near future, including new entries and possible corrections of the existing files. It is not our intention to give a recommendation at the moment, this may be the subject of a separate project. There are two volumes : the first treats the spectra of inorganic species, the second the organic compounds. A third volume with liquid phase spectra is planned to be published later. The absorption spectra and the wavelength dependent quantum yields are both temperature dependent. The temperature dependencies in the atmospheric relevant temperature range from below 200 K to about 300 K have been included, where [...]

Bei der Beantwortung umweltrelevanter Fragen stellen Modelle der Atmosphäre wesentliche Hilfsmittel dar. Die in der atmosphärischen Forschung verwendeten Modelle bilden das reale Verhalten der Luft in den primitiven Gleichungen ab. Eine dieser grundlegenden Gleichungen ist die Massenkontinuitätsgleichung oder Ausbreitungsgleichung: $\frac{dc}{dt} = \overline{\triangledown}(\overline{u} \cdot c)$+(P-D $\cdot$ c) (1.1) Gemäß dieser Gleichung setzt sich die zeitliche Änderung der Konzentration c einer Luftkomponente aus einem Transport-Term $\overline{\triangledown}$ ($\overline{u} \cdot$ c) und einem Term (P-D·c) zusammen, der die Quellen und Senken und die chemischen Umwandlungen des Stoffes in der Atmosphäre enthält. Aufgrund der additiven Verknüpfung der beiden Terme sind diese in der modellmäßigen Beschreibung leicht zu trennen, und somit können die Parameter der beiden Terme $\overline{\triangledown}$ ($\overline{u} \cdot$ c) und (P-D·c) getrennt berechnet werden. Die Kopplung von Transport und chemischen Reaktionen geschieht in den atmosphärischen Modellen erst im letzten Schritt, der Lösung der Ausbreitungsgleichung (1.1). Eine Unterscheidung der Modelle erfolgt zumeist durch das zugrundegelegte räumlicheGitter und damit durch die Behandlung des Transport-Terms $\overline{\triangledown}$ ($\overline{u} \cdot$ c) (siehe auch GRAEDEL UND CRUTZEN (1994)). Es ist grundsätzlich denkbar, ein einziges Modell zu konstruieren, das es erlaubt, alle Fragestellungen sowohl in räumlicher als auch in zeitlicher Hinsicht zu beantworten. Dieses Modell wäre aber zum einen sehr rechenzeit- und somit auch kostenintensiv und zum anderen würde es eine Fülle von Informationen liefern, die für die Beantwortung der interessierenden Fragestellung keine Bedeutung besitzen. Daher wurden verschiedene Modelle entwickelt, die zwar alle die Massenkontinuitätsgleichung lösen, deren räumliche und zeitliche Maßstäbe aber den zu beantwortenden Fragestellungen angepaßt sind (siehe auch RÖTH (1985)). Der erste Schritt bei der Simulation von gemessenen Konzentrationsverläufen und somit der Untersuchung der interessierenden Fragestellung mit Hilfe eines Modells besteht daher darin, das für den speziellen Zweck geeignete Modell auszuwählen. Diese Auswahl muß sich zum einen an dem Zeitraum orientieren, der simuliert werden soll (z.B. Stunden oder Jahre), und zum anderen an dem zu simulierenden Raum (z.B. ortsfester Meßpunkt in Bodennähe oder ballon- bzw. flugzeuggetragener Meßpunkt). [...]