An analysis is made of a sample of 732 12-hr rainfall fields forJune to July, 1975-80, to yield a quantitative description and objectiveclassification. Three aspects are examined: (i) how to reduce the in-stability and inhomogeneity in magnitude and distribution of the short-term precipitation fields to facilitate quantitative description; (ii)how to select the characteristic parameters in order to condense thefield quantities and (iii) the objective scattering analysis of different categories of rainfall amount and distribution, using these characteristic parameters. The results are found to be satisfactory.