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Titelaufnahme
- TitelAssessing precipitation mechanisms on Kilimanjaro and Mount Kenya : an idealized modeling study / by Federico Covi
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- betreut von
- ErschienenInnsbruck, November 2016
- Umfangvi, 91 Seiten : Illustrationen, Karten
- Datum der AbgabeNovember 2016
- SpracheEnglisch
- DokumenttypMasterarbeit
- Schlagwörter
- Schlagwörter (EN)
- URN
- Das Dokument ist online verfügbar
- Nachweis
Tropical glaciers have proved to be fundamental in the understanding of the climate behaviour and its change in the tropical mid troposphere, where measurements have been only recently collected. Glaciers on Kilimanjaro and Mount Kenya in tropical East Africa are among the best studied sites in the tropics and their general behaviour is nowadays well understood. The two mountains, located 370 km away from each other, are often considered as typically influenced by the same air masses. Yet, their precipitation patterns and glaciers behaviour differ considerably. This indicates that either different air masses are at play or that precipitation processes are considerably different. The present study aims to investigate the most relevant mechanisms of precipitation over Kilimanjaro and Mount Kenya.
First, in-situ observations and ERA-Interim reanalysis data are used to characterize the atmospheric background conditions during precipitation events at the two mountains. Next, idealized vertical profiles are constructed and used as an atmospheric reference state for simulations with the Weather Research and Forecasting (WRF) model. Two types of model topography are used, a semi-realistic topography constructed from a high-resolution digital elevation dataset (SRTM) and an ideal topography obtained by a parametric formula. A series of sensitivity simulations is carried out with modified topography, atmospheric reference state and surface heat fluxes to asses the dominant factors governing precipitation over the two mountains.
The analysis of atmospheric background conditions confirms the hypothesis that Kilimanjaro and Mount Kenya are locally influenced by the same air mass during precipitation events. Numerical simulations show that the mesoscale circulation over the two mountains is the result of a complex interaction of the large-scale flow with the topography and the surface heat fluxes. Precipitation distribution and magnitude are very sensitive to the orientation of the mountain respect to the large-scale flow. Moreover the precipitation magnitude and the shift upslope, towards the summit, of the precipitation maximum are strongly controlled by the surface heat fluxes. With this, we aim to enhance the climate information from the differently behaving glaciers on the two East African mountains.
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