A hierarchical approach for the regionalization of precipitation annual maxima in Canada

• Published in: Journal of Geophysical Research, Washington, DC Washington, DC, 1999-12, Vol.104 (D24), p.31645-31655
• Main Author: Alila, Younes
• Format: Article
• Language: English
• Subjects: Canada; Earth, ocean, space; Exact sciences and technology; External geophysics; Geophysics. Techniques, methods, instrumentation and models
• ISSN: 0148-0227; 2156-2202
• DOI: 10.1029/1999JD900764

The L moments are used in the three stages of regional frequency analysis: the delineation of homogeneous regions, the identification of a regional parent distribution, and the estimation of distribution parameters. Numerical analysis is conducted on 5 min to 24 hours annual rainfall extremes from 375 precipitation gaging stations in Canada. The numerical analysis concluded that Canada could be considered as a single homogeneous region in which the L skewness and L kurtosis display no significant spatial variability. Also, on the basis of mean annual precipitation (MAP), Canada can be divided into climatologically homogeneous subregions, in which the L coefficient of variation is virtually constant. The parent distribution was identified as the general extreme value (GEV), the parameters of which depend on the MAP and storm duration. A hierarchical regional approach is proposed for fitting the identified GEV distribution, where the L skewness, L coefficient of variation, and mean are estimated on a regional, subregional, and single‐site basis, respectively. Monte Carlo simulations indicate that design storms estimated by the proposed hierarchical approach are substantially more accurate than those estimated by the single‐site method. The simulations also demonstrate that the proposed hierarchical approach makes the estimation of design storms at ungaged sites less dependent on the availability of precipitation data.