The probability distribution of daily precipitation at the point and catchment scales in the United States

Abstract. Choosing a probability distribution to represent daily precipitation depths

is important for precipitation frequency analysis, stochastic precipitation

modeling and in climate trend assessments. Early studies identified the

two-parameter gamma (G2) distribution as a suitable distribution for wet-day

precipitation based on the traditional goodness-of-fit tests. Here,

probability plot correlation coefficients and L-moment diagrams are used to

examine distributional alternatives for the wet-day series of daily

precipitation for hundreds of stations at the point and catchment scales in

the United States. Importantly, both Pearson Type-III (P3) and kappa (KAP)

distributions perform very well, particularly for point rainfall. Our analysis

indicates that the KAP distribution best describes the distribution of

wet-day precipitation at the point scale, whereas the performance of G2 and

P3 distributions are comparable for wet-day precipitation at the catchment

scale, with P3 generally providing the improved goodness of fit over G2.

Since the G2 distribution is currently the most widely used probability

density function, our findings could be considerably important, especially

within the context of climate change investigations.