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Person: Buchholz, Joachim (Autor) 
Titel: Simulations of physics and chemistry of polar stratospheric clouds with a general circulation model
818.pdf (3.242 KB) PDF
Quelle: Mainz : Univ.
Erscheinungsjahr:    2005
URN: urn:nbn:de:hebis:77-8187
Buch Buch
Weitere Angaben zur Dokumentart:    Dissertation
Sprache: Englisch
Open Access: OpenAccess
Einrichtung: FB 08: Physik, Mathematik und Informatik
DDC-Sachgruppe:    Geowissenschaften
ID: 818  Universitätsbibliothek Mainz
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Abstract: A polar stratospheric cloud submodel has been developed and incorporated in a general circulation model including atmospheric chemistry (ECHAM5/MESSy). The formation and sedimentation of polar stratospheric cloud (PSC) particles can thus be simulated as well as heterogeneous chemical reactions that take place on the PSC particles.

For solid PSC particle sedimentation, the need for a tailor-made algorithm has been elucidated. A sedimentation scheme based on first order approximations of vertical mixing ratio profiles has been developed. It produces relatively little numerical diffusion and can deal well
with divergent or convergent sedimentation velocity fields.

For the determination of solid PSC particle sizes, an efficient algorithm has been adapted. It assumes a monodisperse radii distribution and thermodynamic equilibrium between the gas phase and the solid particle phase. This scheme, though relatively simple, is shown to produce particle number densities and radii within the observed range. The combined effects of the representations of sedimentation and solid PSC particles on vertical H2O and HNO3 redistribution are investigated in a series of tests.

The formation of solid PSC particles, especially of those consisting of nitric acid trihydrate, has been discussed extensively in recent years. Three particle formation schemes in accordance with the most widely used approaches have been identified and implemented. For the evaluation of PSC occurrence a new data set with unprecedented spatial and temporal coverage was available. A quantitative method for the comparison of
simulation results and observations is developed and applied. It reveals that the relative PSC sighting frequency can be reproduced well with the PSC submodel whereas the detailed modelling of PSC events is beyond the scope of coarse global scale models.

In addition to the development and evaluation of new PSC submodel components, parts of existing simulation programs have been improved, e.g. a method for the assimilation of meteorological analysis data in the general circulation model, the liquid PSC particle composition scheme, and the calculation of heterogeneous reaction rate coefficients. The interplay of these model components is demonstrated in a simulation of stratospheric chemistry with the coupled general circulation model. Tests against recent satellite data show that the model successfully reproduces the Antarctic ozone hole.
Verfügbarkeit prüfen:    URN (urn:nbn:de:hebis:77-8187)