To retrieve the gamma drop size distribution (DSD) parameters from observed drop spectra, the most common approach is the method of moments (MM). However, the goodness of this method is still disputed. To assess its reliability, the aims of this paper are: (i) estimation of empirical values of rainfall rate (I) and kinetic energy (KE) from DSD measurements collected by a laser‐optical disdrometer; (ii) estimation of gamma DSD parameters by MM and another widespread method, i.e. maximum likelihood (ML); (iii) evaluation of theoretical values of rainfall rate and KE and comparison between these values and measured ones. The novelty of this work is the assessment of both MM and ML using the rainfall intensity measured by the disdrometer as a benchmark, rather than the KE or a statistical test as done in common practice. The assessment of the goodness of the estimates was performed on variables most investigated in soil erosion studies (i.e. I and KE). Results show that smaller error values are associated with ML and that MM does not provide reliable estimations of I. On the other hand, both methods substantially underestimate KE with increasing rainfall intensity.

中文翻译：

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关于用伽马分布dsds建模降雨动能的可靠性*

要从观察到的液滴光谱中检索伽玛液滴尺寸分布（DSD）参数，最常用的方法是矩量法（MM）。但是，这种方法的优点仍然存在争议。为了评估其可靠性，本文的目的是：（i）估算降雨率的经验值（I）和由激光测速仪收集的DSD测量的动能（KE）; （ii）通过MM和另一种普遍使用的方法，即最大似然（ML）估计伽玛DSD参数；（iii）评估降雨率和KE的理论值，并将其与实测值进行比较。这项工作的新颖之处在于，它使用测速仪测量的降雨强度作为基准，而不是像通常做法那样进行的KE或统计检验，来对MM和ML进行评估。对估计的优劣程度的评估是根据土壤侵蚀研究（即I和KE）中调查最多的变量进行的。结果表明，较小的误差值与ML相关，并且MM无法提供I的可靠估计。 另一方面，随着降雨强度的增加，这两种方法都大大低估了KE。