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Statistical downscaling of daily precipitation from GCM output: A Swedish case study
Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences.
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Manuscript (Other academic)
URN: urn:nbn:se:uu:diva-93488OAI: oai:DiVA.org:uu-93488DiVA: diva2:166977
Available from: 2005-09-09 Created: 2005-09-09 Last updated: 2010-01-13Bibliographically approved
In thesis
1. Statistical Downscaling of Precipitation from Large-scale Atmospheric Circulation: Comparison of Methods and Climate Regions
Open this publication in new window or tab >>Statistical Downscaling of Precipitation from Large-scale Atmospheric Circulation: Comparison of Methods and Climate Regions
2005 (English)Doctoral thesis, comprehensive summary (Other academic)
Alternative title[sv]
Statistisk nedskalning av nederbörd från storskalig atmosfärscirkulation : Jämförelse mellan metoder och klimatregioner
Abstract [en]

A global climate change may have large impacts on water resources on regional and global scales. General circulation models (GCMs) are the most used tools to evaluate climate-change scenarios on a global scale. They are, however, insufficiently describing the effects at the local scale. This thesis evaluates different approaches of statistical downscaling of precipitation from large-scale circulation variables, both concerning the method performance and the optimum choice of predictor variables.

The analogue downscaling method (AM) was found to work well as “benchmark” method in comparison to more complicated methods. AM was implemented using principal component analysis (PCA) and Teweles-Wobus Scores (TWS). Statistical properties of daily and monthly precipitation on a catchment in south-central Sweden, as well as daily precipitation in three catchments in China were acceptably downscaled.

A regression method conditioning a weather generator (SDSM) as well as a fuzzy-rule based circulation-pattern classification method conditioning a stochastical precipitation model (MOFRBC) gave good results when applied on Swedish and Chinese catchments. Statistical downscaling with MOFRBC from GMC (HADAM3P) output improved the statistical properties as well as the intra-annual variation of precipitation.

The studies show that temporal and areal settings of the predictor are important factors concerning the success of precipitation modelling. The MOFRCB and SDSM are generally performing better than the AM, and the best choice of method is depending on the purpose of the study. MOFRBC applied on output from a GCM future scenario indicates that the large-scale circulation will not be significantly affected. Adding humidity flux as predictor indicated an increased intensity both in extreme events and daily amounts in central and northern Sweden.

64 p.
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 93
Hydrology, Statistical, Downscaling, Precipitation, Large-scale circulation, PCA, TWS, Weather pattern, Regression, Weather generator, Hydrologi
National Category
Oceanography, Hydrology, Water Resources
urn:nbn:se:uu:diva-5937 (URN)91-554-6344-4 (ISBN)
Public defence
2005-09-30, Axel Hambergssalen, Geocentrum, Villavägen 16, Uppsala, 10:00
Available from: 2005-09-09 Created: 2005-09-09Bibliographically approved

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