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首页> 外文期刊>Acta Geophysica Polonica >PHYSICS OF FLOOD FREQUENCY ANALYSIS. Ⅱ. CONVECTIVE DIFFUSION MODEL VERSUS LOGNORMAL MODEL
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PHYSICS OF FLOOD FREQUENCY ANALYSIS. Ⅱ. CONVECTIVE DIFFUSION MODEL VERSUS LOGNORMAL MODEL

机译：洪水频率分析物理。 Ⅱ。对流扩散模型与对数对数模型

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摘要

The similarity between the convective diffusion (CD) model and the log-normal (LAO distributions is shown by comparison of their moment estimates. Both models are tested using annual peak discharges observed at 39 gauging -sections of Polish rivers. The average value of the ratio of the coefficient of skew-ness to the coefficient of variation equals about 2.52, a value closer to the ratio of the CD model than to the gamma or the lognormal model. The likelihood ratio indicates the preference of the CD model over the LN model for 27 out of 39 cases. Applying the maximum likelihood (ML) method, one should take into account the consequences of the wrong distributional assumption on the estimate of moments. In the case of CD, the ML-estimate of the mean is unbiased for any true distribution, which is not the case with the LN model. Moreover the ML-estimate of the two first moments of CD remains asymptotically unbiased if LN is true, while there is small bias in the opposite case. To check the objectivity of our inferences from empirical findings, a simulation experiment was carried out, which comprised gen- crated CD- and LN-distributed samples and both the moment and likelihood criteria for the distribution choice. Its results clearly show that normal hydrological sample sizes are far too small for selecting the true distribution.
机译：对流扩散（CD）模型和对数正态（LAO）分布的矩估计值进行了比较，两者相似，这两种模型均使用在波兰河流39个测量断面观测到的年峰值流量进行了测试。偏度系数与变异系数之比约为2.52，该值更接近于CD模型的比率，而不是与γ或对数正态模型的比率。似然比表明CD模型相对于LN模型的偏好对于39个案例中的27个，应用最大似然（ML）方法时，应考虑错误的分布假设对矩估计的影响；对于CD而言，均值的ML估计是无偏的。如果LN为真，则CD的两个第一矩的ML估计保持渐近无偏，而在相反的情况下偏差很小。根据经验发现得出的结论具有客观性，我们进行了模拟实验，包括生成的CD和LN分布样本以及分布选择的时机和可能性标准。其结果清楚地表明，正常的水文样本量太小，无法选择真实的分布。

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