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The spatial and temporal distribution of point precipitation quantiles representing abnormal moisture conditions over the Colorado River Basin (CRB) is analyzed by means of the Standardized Precipitation Index (SPI), calculated in annual and seasonal aggregations. From a cell-by-cell analysis, the area covered by abnormally wet and dry conditions during the last century shows an inverse relationship with their frequency of occurrence, with frequent events (occurring 80% of the time) in which abnormal conditions cover less than 10% of the basin and infrequent events (occurring 5% of the time) in which abnormal conditions cover around 50% of the basin. During El Ni´┐Żo years, both extremely wet and dry conditions are...
The expected moments algorithm (EMA) [Cohn et al., 1997] and the Bulletin 17B [Interagency Committee on Water Data, 1982] historical weighting procedure (B17H) for the log Pearson type III distribution are compared by Monte Carlo computer simulation for cases in which historical and/or paleoflood data are available. The relative performance of the estimators was explored for three cases: fixed-threshold exceedances, a fixed number of large floods, and floods generated from a different parent distribution. EMA can effectively incorporate four types of historical and paleoflood data: floods where the discharge is explicitly known, unknown discharges below a single threshold, floods with unknown discharge that exceed...