Trends in Monthly and Annual Total Precipitation in Southern Quebec and Ontario, Canada during 1954-2008

摘要

Drawing upon monthly and annual data, trends in total precipitation in Quebec and Ontario, Canada over the period 1954 - 2008, were analyzed to determine the main periodic components responsible for the trends. New approaches for trend detection and analysis, based on the combined use of discrete wavelet transform (DWT) and the Mann-Kendall (MK) trend test (and MK modified and sequential versions) were used. Although the theory of wavelet transforms has been widely recognized, concomitant use of the DWT and the MK test/sequential MK analysis in detecting trends in the hydrological field has not been extensively explored in Canadian studies. A new criterion, based on the relative error of trend values between the original data and the approximation component of the last decomposition level is used. It is used in the DWT procedure in determining the number of decomposition levels, the type of Daubechies mother wavelet, and the type of extension border. Positive trends were found to be more prevalent, and mainly originated between 1965 and 1970. Application of the DWT and MK tests, indicated that trends in total precipitation over southern Quebec and Ontario are mostly dominated by events of 4 years or less.