A comparative modeling analysis of multiscale temporal variability of rainfall in Australia
Authors:Samuel, Jos M. Sivapalan, Murugesu
Volume:44
Published:2008
Document Type:Article
Abstract:[1] The effects of long-term natural climate variability and human-induced climate change on rainfall variability have become the focus of much concern and recent research efforts. In this paper, we present the results of a comparative analysis of observed multiscale temporal variability of rainfall in the Perth, Newcastle, and Darwin regions of Australia. This empirical and stochastic modeling analysis explores multiscale rainfall variability, i.e.,ranging from short to long term, including within-storm patterns, and intra-annual, interannual, and interdecadal variabilities, using data taken from each of these regions. The analyses investigated how storm durations, interstorm periods, and average storm rainfall intensities differ for different climate states and demonstrated significant differences in this regard between the three selected regions. In Perth, the average storm intensity is stronger during La Nina a years than during El Nino years, whereas in Newcastle and Darwin storm duration is longer during La Nina a years. Increase of either storm duration or average storm intensity is the cause of higher average annual rainfall during La Nina a years as compared to El Nino years. On the other hand, within-storm variability does not differ significantly between different ENSO states in all three locations. In the case of long-term rainfall variability, the statistical analyses indicated that in Newcastle the long-term rainfall pattern reflects the variability of the Interdecadal Pacific Oscillation ( IPO) index, whereas in Perth and Darwin the long-term variability exhibits a step change in average annual rainfall ( up in Darwin and down in Perth) which occurred around 1970. The step changes in Perth and Darwin and the switch in IPO states in Newcastle manifested differently in the three study regions in terms of changes in the annual number of rainy days or the average daily rainfall intensity or both. On the basis of these empirical data analyses, a stochastic rainfall time series model was developed that incorporates the entire range of multiscale variabilities observed in each region, including within-storm, intra-annual, interannual, and interdecadal variability. Such ability to characterize, model, and synthetically generate realistic time series of rainfall intensities is essential for addressing many hydrological problems, including estimation of flood and drought frequencies, pesticide risk assessment, and landslide frequencies.
Author Information
Corresponding Author:Samuel, JM (通讯作者)，Univ Western Australia, Sch Environm Syst Engn, 35 Stirling Highway, Crawley, WA 6009, Australia.
Reprint Address:Samuel, JM (通讯作者)，Univ Western Australia, Sch Environm Syst Engn, 35 Stirling Highway, Crawley, WA 6009, Australia.
Addresses:[Samuel, Jos M.] Univ Western Australia, Sch Environm Syst Engn, Crawley, WA 6009, Australia; [Sivapalan, Murugesu] Univ Western Australia, Ctr Water Res, Crawley, WA 6009, Australia
E-mail Addresses:sivapala@uiuc.edu